Natural and Cultural Landscape Evolution During the Late Holocene in North Central Guatemalan

Natural and cultural landscape evolution during the Late Holocene in North Central Guatemalan

Lowlands and Highlands

Carlos Enrique Avendaño Mendoza

A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Graduate Department of Geography University of Toronto

Natural and cultural landscape evolution during the Late Holocene in North Central Guatemalan Lowlands and Highlands

Doctor of Philosophy 2012

Carlos Enrique Avendaño Mendoza Graduate Department of Geography University of Toronto Abstract

Paleoecology has been only in recent decades applied to Mesoamerica; this thesis

provides new records of paleoenvironmental changes in Guatemala. Paleoecological

reconstructions are developed based mainly on pollen in the Lachuá lowlands and

Purulhá highlands of the Las Verapaces Region. For the first time, quantitative vegetation and climate analyses are developed, and plant indicator taxa from vegetation belts are identified. Changes in vegetation are explained partially by elevation and climatic parameters, topography, drainage divides, and biogeography. Pollen rain and indicator plant taxa from vegetation belts were linked through a first modern pollen rain analysis based on bryophyte polsters and surface sediments. The latter contain fewer forest- interior plant taxa in both locations, and in the highlands, they contain higher local pollen content than in the lowlands. These calibrations aided vegetation reconstructions based on fossil pollen in sediment records from the Lachuá and Purulhá regions.

Reconstructions for the last ~2000 years before present (BP) were developed based on fossil pollen from cores P-4 on a floodplain in Purulhá, and L-3, a wetland in Lachuá.

Core P-4 suggests that Mayan populations developed a system of agricultural terraces in a former paleolake-swamp environment, which was abandoned at the time of the Spanish

Conquest (~400 BP). Core L-3 indicates the abandonment of Mayan “Forest Gardens” at the time of the early Postclassic. These gardens likely prevailed during the Classic period

(~300-1100 yrs BP) at the outskirts of the ancient city of Salinas de los Nueve Cerros.

Following abandonment, forest recovery took place for about 800 yrs. Cultural factors are found to be more important in determining vegetation dynamics in this region, since no clear evidence of climate forcing was found. The P-4 and L-3 cores provide likely evidence that Mayan populations were, contrary to other evidence, innovative landscape managers. Scenarios in the Las Verapaces Region have been drastically modified in recent times (e.g. after the European Conquest), as suggested by pollen evidence in the top of both P-4 and L-3 cores, possibly due mostly to modern large scale natural resources exploitation, which represent environmental threats greater than any seen in the last ca. 2000 years.

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Acknowledgments

I deeply thank my supervisor Sharon Cowling for her sincere and wonderful support

during the development of my Ph.D since the very first day I arrived to Canada. She was

there waiting for me in the Toronto International Pearson Airport with a sign that had my name on, I can only say “Muchas gracias eternas”. Thanked is my co-supervisor Sarah

Finkelstein for her marvellous support at the Paleoecology Laboratory of the Department of Geography. I had the honor to be at the start of her Laboratory and see the evolution to what today is: An excellent place to learn and grow.

I thank Prof. Tenley Conway and Prof. Anthony Davis for their helpful comments as part of my Ph.D. Academic Committee. Prof. Juan Carlos Berrio is greatly thanked for his valuable training in tropical paleoecology during field campaign in Guatemala and during my visits to his laboratory at the Department of Geography, Leicester University,

England. I thank his wife Natalia de Berrio for her support too. I thank too the “Los

Juanetes”, a Latin American rock band in the middle of England, for making my visit a nice one. I thank the Guatemalan team, “los COMPAI” and more, that supported me during my field campaign in Guatemala in 2006 and many many more things.

Lachuá National Park and Biotopo del Quetzal Administrations and staff are thanked for supporting my research. I am greatly thankful to forest guards at Lachuá National Park for their support in bryophyte polster and core sampling. I thank Santa Lucia Lachuá

Municipality for support in collecting sediments from Salinas de los Nueve Cerros, especially to Major Pedro Oxom and Family Tun. San Cristobal Verapaz Municipality

Administration and staff are thanked for supporting our research. Fincas Villa Trinidad,

Patal, Chisiguan, and Lesbia Mus and Yolanda Barahona are thanked for their support in collecting sediments.

I thank CONAP, Franklin Herrera, Escuela de Biología –at the Faculty of CCQQ and

Pharmacy –USAC- for the support in acquiring collection and research licenses. As well

I thank staff and members of Escuela de Biología, Faculty of CCQQ and Pharmacy, and

USAC for their support during my Ph.D.

I thank Dr. Gerald Islebe for his support in pollen identification and feedback during my thesis development. Enric Aguilar and Melissa Gervais are thanked for obtaining

Guatemalan climatic information. Joan Bunbury is greatly thanked for the support in creating maps and using CANOCO ©. Dr. Arnoud Boom is thanked for his support during my visit to Leicester University, England (as well, thanks for introducing me more into Asian Cinema). Grace Jeon is thanked for her support in developing Loss-on-ignition measurements for my core samples in the Paleoecology Lab, Department of Geography –

UofT-. The Centre for Global Change Science and their staff, especially Ana Sousa, at the University of Toronto is greatly thanked for enhancing my Ph.D. experience. I thank

Prof. Jock McAndrews and Charlie Turton for their support during my Ph.D.

I thank everybody at the Department of Geography who supported me during my Ph.D. years as a student, especially from the main office at Sidney Smith (esp. Marianne

Ishibashi, Marika Maslej, and Jessica Finlayson). I am very grateful to the Physical

Geography Building (PGB) community who supported and helped me, especially members of Cowling and Finkelstein’s research laboratories. Members of Chen’s,

Diamond’s and Desloge’s laboratories are greatly thanked for their company and support.

I am greatly grateful to Mircea Pilaf for his support since the first day I arrived to PGB and for the conversations in Romanian. I thank the “Geography soccer” community whom I shared many summer, fall, winter, and spring games. Thanked are Maria Johnson and Family for being my Guatemalan-“Chapina”-Canadian Family.

I am grateful to Claudia Avendaño and Knutt Eissermann for providing help and time in finding the source vegetation literature for this study. I am grateful to Maria Elena

Hidalgo “mi Ague”, Carlos Avendaño E., Yolanda Mendoza de Avendaño, Gary

Avendaño, and Hector Bol for providing help during field work. I thank my Family in

Guatemala for their spiritual and moral support: Papa, Mama, Clada, Gary, Abue, Hector,

Ti Lili, Dn. Enrique, Kennes ... This thesis is dedicated to my Family, which has supported me in my entire life in any possible path that I have taken … forever and ever.

Special dedication for Mateo and Belinda, who now have become my triangle of life, joy, and motivation to become a better being. Mateo:

“No llegó la gota carmín, Llegó en su lugar la noticia de su visita, Certidumbres y rumbos no aleatorios, A esta edad, en este lugar, en esta vida… Semilla liberando indicios de luz, Transformando auras, metamorfosis interna, Milagro de la multiplicación de tu rostro en cada rostro, en el niño de la calle, en el abuelo de la esquina, en el rostro del espejo, Bien leí que en tradiciones ancestrales se entiende como la llegada de un maestro, En silencio quiero aprender de ti… Después de años de ser profecía, la epifanía llego esta mañana: reconocer al prójimo como a mi propio hijo… Traes polvo cósmico celestial, soplas tu aliento en mi oído y me revelas el universo”.

Table of Contents Abstract...... ii Acknowledgments...... iv List of Tables ...... ix List of Figures...... x List of Appendices ...... xii Chapter 1: Background Information ...... 1 1.1 Pollen as a Paleoecological Proxy ...... 1 1.2 Climate Variability Over the Holocene ...... 4 1.3 Reconstructing vegetation and landscapes...... 8 1.4 Reconstructing Cultural Landscapes...... 10 1.5 Thesis Objectives and Research Questions...... 13 1.6 Geomorphological and Vegetational Setting of Study Region...... 15 1.7 Cultural History of Study Region ...... 20 Chapter 2 Vegetation Distribution along the Las Verapaces region in North Central Guatemala.... 27 2.1 Introduction...... 27 2.2 Methods...... 30 2.3 Results...... 35 2.4 Discussion...... 47 2.5. Chapter summary...... 54 Chapter 3 Modern pollen rain in the north-central Guatemalan lowlands and highlands...... 56 3.1 Introduction...... 56 3.2 Methods...... 59 3.3 Results...... 64 3.4 Discussion...... 85 3.5. Chapter summary...... 95 Chapter 4 Late-Holocene History of a Highland Floodplain in Las Verapaces, Guatemala...... 98 4.1 Introduction...... 98 4.2 Methods...... 99 4.3 Results...... 103 4.4 Discussion...... 115

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4.5. Chapter Summary ...... 132 Chapter 5 The Lachuá Lowlands Rain Forest in Guatemala: 2,000 yrs of forested landscape?..... 134 5.1 Introduction...... 134 5.2 Methods...... 136 5.3 Results...... 139 5.4 Discussion...... 149 5.5 Chapter summary...... 161 Chapter 6 Conclusions...... 163 6.1 What are the factors that explain vegetation distribution along the Las Verapaces environmental gradient and what taxa can be used as "indicator species"? ...... 164 6.2 Can paleoecological calibrations for fossil pollen be constructed from a comparison of modern pollen rain from surface sediments and bryophyte polsters? ...... 166 6.3 What are the major vegetation changes recorded in the highland core from the Las Verapaces region? ...... 168 6.4 What are the major vegetation changes recorded in the lowland core from the Las Verapaces region? ...... 170 6.5 What is the role of natural variability and cultural factors related to the Maya Civilization in the evolution of landscapes in the Las Verapaces Region? ...... 172 References...... 174 Appendices...... 196

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List of Tables

Table 2.1. Sites included in the Las Verapaces Gradient, providing a total of 23 sampling units (SU) from 9 sites spanning an elevation gradient of 170 to 2532 m asl.

Table 2.2. Indicator plant taxa for the three vegetation belts along the Las Verapaces Gradient, selected from DCA axis scores for species (see text for details).

Table 2.3. Generalist plant taxa for the Las Verapaces Gradient, as determined by DCA axis scores for species (see text for details).

Table 2.4. Disjunctive plant taxa distributed in Lowland Rain Forest and Montane Cloud Forest in the Las Verapaces Gradient generated from DCA axis scores for species (see text for details).

Table 3.1. Pollen types and their % range for bryophyte polsters and surface sediments. Information about vegetation belt, plant habit, and pollen dispersal syndrome is provided.

Table 3.2. Lachuá bryophyte polsters and surface sediments samples.

Table 3.3. Purulhá bryophyte polsters and surface sediments samples.

Table 3.4. Factor Analysis scores for pollen types with highest amount of variance.

Table 4.1. P-4 core stratigraphic sequence.

Table 4.2. Radiocarbon dates, calibrated age ranges from dated sediment from P-4 core of the Cahabón Floodplain, Purulhá

Table 5.1. Radiocarbon dates, calibrated age ranges from dated sediment from P-4 core of the Cahabón Floodplain, Purulhá.

List of Figures

Figure 1.1. Temperature changes in the late Pleistocene and the Holocene inferred from oxygen-18 measurements in Greenland ice core (taken from Dergachev and van Geel, 2004).

Figure 1.2. Location of Guatemala in Central America. Numbers indicate location of meteorological stations.

Figure 1.3. Topographic map of the Las Verapaces Region in Guatemala.

Figure 1.4. Topographic map of study sites in the Las Verapaces Region in Guatemala. Map I= Lachuá lowlands, Map II= Purulhá highlands.

Figure 2.1. Detrended Correspondence Analysis diagram of Las Verapaces sites along the first two DCA axes.

Figure 2.2. Linear regression of Detrended Correspondence Analysis (DCA) Axis 1 scores (raw scores) of indicator plant taxa (A) and sites (B) against elevation values per site of the Las Verapaces Gradient.

Figure 2.3. Linear regression curves for temperature (°C) from meteorological stations from Central and Northern Guatemala.

Figure 2.4. Detrended Correspondence Analysis diagram for the Las Verapaces Gradient sites and climatic variables.

Figure 2.5. A) Indicator (in one vegetation belt) and B) generalist (across two vegetation belts) taxa separated according to their biogeographic origin along the Las Verapaces gradient vegetation belts

Figure 3.1. Location of Guatemala in Central America. Las Verapaces Region is enclosed in rectangle.

Figure 3.2. Pollen diagram from Lachuá and Purulhá based on bryophyte polsters and surface sediment samples.

Figure 3.3. Lachuá pollen diagram based on bryophyte polsters and surface sediment samples.

Figure 3.4. Lachuá DCA Q-mode diagrams of arboreal pollen data with Pinus removal.

Figure 3.5. Purulhá pollen diagram based on bryophyte polster and surface sediment samples.

Figure 3.6. Purulhá DCA Q-mode diagrams based on arboreal pollen and non-arboreal pollen data.

Figure 3.7. Las Verapaces DCA Q-mode diagram AP shared data.

Figure 4.1. P-4 core paleoecological diagram taken from Cahabón River Flooplain.

Figure 4.2. Graph showing depth (cm) vs. calendar age (cal yrs BP) of sediments from core P-4 taken from the Cahabón River floodplain.

Figure 4.3. Principal Component Analysis (PCA) of sampled levels from core P-4.

Figure 4.4. Pollen percentage diagram of P-4 core from the Cahabón River floodplain.

Figure 4.5. Location of the headwaters of the Cahabón River and the floodplain.

Figure 4.6. Principal Component Analysis (PCA) of modern pollen rain samples from Purulhá highlands and fossil samples from core P-4.

Figure 4.7. Principal Component Analysis (PCA) of modern pollen rain samples from Purulhá highlands and sampled levels from core P-4.

Figure 5.1. L-3 core paleoecological diagram taken from a wetland next to Lake Lachuá.

Figure 5.2. Principal Component Analysis (PCA) of sampled levels from core L-3.

Figure 5.3. Pollen percentage diagram of L-3 core from a wetland next to Lake Lachuá.

Figure 5.4. Location of the ancient Mayan city of Salinas de los Nueve Cerros on the banks of the Chixoy River, Alta Verapaz, Guatemala.

Figure 5.5. Principal Component Analysis (PCA) of modern pollen rain samples from Lachuá lowlands and fossil samples from core L-3.

List of Appendices

Appendix 2.1. Indicator, generalist, and disjunctive plant checklist.

Appendix 3.1. Pollen types found in modern pollen calibrations and fossil pollen spectra from cores P-4 and L-3. Associated plant and uses by ancient Mayan populations are shown.

Appendix 4.1. Pollen counts (raw) from P-4 core.

Appendix 5.1. Pollen counts (raw) from L-3 core.

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Chapter 1: Background Information

1.1 Pollen as a Paleoecological Proxy

One of the main objectives of paleoecological research is to reconstruct environmental

changes occuring at different scales of resolution, from global to local scales (Bennington

et al., 2009; Birks, 2005; Hunter, 1998; Willis and Birks, 2006). Many Holocene examples can be cited that demonstrate how natural and cultural factors influence the evolution of landscapes and regions (Berrio et al., 2001; Lorimer, 2001; Muñoz and

Gajewski, 2010; Ye et al., 2010). The likely reason for the emphasis on separating natural from cultural factors relates to our understanding of whether current global environmental trends are due to natural variability, cultural factors, or some combination

(Harris, 2003; Cao et al., 2010).

Vegetation is a fundamental component of ecosystems, landscapes and regions, and has been used widely as a paleoecological indicator (Markgraf et al., 2009; Valsecchi et al.,

2010; Cheng, 2011). Vegetation was chosen as a proxy for landscape evolution because of its intimate relationship with climatic and topographic variability (Clark, 2007;

Davidar et al., 2005; Simona et al., 2009). Vegetation reflects the environmental and/or cultural regimes that control landscapes and regions at different spatio-temporal ranges.

The chosen proxy for vegetation reconstruction is pollen because of its taxonomic specificity and because it reflects processes related to vegetation dynamics (i.e. pollination), in addition to the fact that it has been studied thoroughly and used often for

2 different applications in biogeography, climate change, biome reconstructions, and archaeology (Berrio et al., 2001; Birks and Birks, 2003.; Graham, 2006; Marchant et al.,

2009). The relationship between vegetation and pollen found in depository records, either superficial or sedimentary, is not 1:1 because of the multiple factors that are involved in pollen release, transportation, deposition and preservation (Brown et al., 2007; Bunting et al., 2004; Campbell, 1999; Fægri and Iversen, 1989). It is necessary to understand the relationship between vegetation and pollen collected from depositories, in order to understand pollen representation at modern or past times for a determined landscape and region. Therefore the concept of uniformitarism underlies palynological research: it is assumed that the chosen proxy has had a response in the past similar to its responses to present-day natural and cultural changes (Bradley, 1999).

Vegetation has been closely linked to human history and activities (e.g. agriculture and forestry) because vegetation provides a resource source for multiple needs: timber, fuelwood, medicine, food, and resins (Fuller et al., 2010; Innes et al., 2009; Rokaya et al.,

2010; Weiser and Lepofsky, 2009). Complementary use of archaeological methods helps to broaden our ability to understand human impact on landscapes (Li et al., 2010; McKey et al., 2010; Weiss and Brunner, 2010). Pollen grains (i.e. as micro-botanical remains or microfossils) have been widely used in paleoecology and have become relevant proxies to reveal natural and cultural factors in landscape evolution (Lozano-García et al., 2010;

Scharf, 2010). Changes in pollen composition, pollen abundance, and information related to the presence or absence of specific taxa provide the foundation for paleoecological reconstructions of past environmental change.

Modern pollen spectra have been studied from bryophyte polsters (e.g. mosses and liverworts) and are collected mostly from the interior of non-disturbed forests

(Domínguez-Vázquez et al., 2004). These studies are important in understanding the conditions under which the pollen is deposited; these studies are also necessary for comparisons (i.e. in presence, absence and abundance) between observed pollen signal and surrounding plant taxa. This modern-day calibration process is necessary for the best possible interpretation of the fossil pollen record.

Topography affects energy distribution in landscapes, such as water and wind flows where pollen transportation occurs (Schueler and Schluenzen, 2006; Vogler et al., 2009).

The role of topography in affecting pollen transport, however, is not entirely understood

(Higgins et al., 2003). These processes have mostly studied with respect to maize pollen in terms of cross-pollination in agricultural fields (Klein et al., 2003). On its own, elevation above sea level has an influence on pollen dispersal and deposition because of orographic effects related to patterns of wind circulation (Fægri and Iversen, 1989).

Regionally-dispersed pollen is sensitive to atmospheric conditions, for example, because surface convection (i.e. air turbulence from heating) can raise pollen above the canopy- level, causing long-distance, horizontal transfer until the air parcel eventually cools and descends (Murray et al., 2007), or it encounters a “disturbance” in flow such as a lake basin causing pollen to fall out of the atmosphere (Sugita 1993). Provenance of pollen may also be a source of bias in interpreting paleoecological signals because where sediment is deposited (i.e. lakes, rivers, oceans) and how it is transported (i.e. by wind, water, terrestrial and aquatic animals) is important (Traverse, 1994; Nielsen, 2005). Once

4 pollen grains land on a surface, they will respond to the physical, chemical, and biological processes occurring on the surface, that in turn determine sedimentation and preservation of pollen samples. The understanding of taphonomy and pollen-environment relationship is determinant in pollen analysis, since an important assumption is that the pollen assemblage recorded from a sediment sample is the same as the originally deposited (Twiddle and Bunting, 2010).

The wide ranging applications of pollen analysis in paleoecology have increased the research scope to conservation biology and biogeography. For example, conservation efforts have been directed where plant communities in riparian environments have been identified as relicts (i.e. early Holocene), after studying pollen spectra in sedimentary records found in floodplains (Southgate, 2010). At the geological scale, pollen records have been the basis to explain the evolution of biomes coupled to tectonic processes (e.g. orogeny) based on pollen spectra collected in lakes sediments in the Andes

(Hooghiemstra et al., 2006).

1.2 Climate Variability Over the Holocene

Reconstucting past climate changes is important for explaining roles of external and

internal forcings on the climate system and for predicting future trends. External forcings

on the climate system include changes in orbital parameters of the Earth, and solar variability; internal forcings, by contrast, are related to processes that occur within the

Earth system (e.g. volcanic activity) (Beniston, 2005). The Milankovitch Cycles are important variations in Earth’s orbit, known mostly for their role in promoting the

Pleistocene Ice Ages (Lisiecki, 2010). The parameter of eccentricity (the measure of the shape of the Earth's orbit around the sun) varies on a timescale of ~ 100,000 yrs and contributes to glacial-interglacial cycling (Berger, 1989). The other two Milankovitch parameters are: obliquity (measure of the Earth’s rotation tilt from 22 to 24.8° every 41 ky) that is responsible for the definition of tropical and circum-polar latitudes, and precession of the equinoxes (which cycles on a scale of 19 to 26 ky), which is related to solar insolation variability as a function of the Earth-Sun distance at the moment of the vernal equinox. The interaction of the three Milankovitch parameters is consistent with recorded climatic variability at the multi-millenial timescale, by producing a complex pattern of solar radiation reception on Earth’s atmosphere (Mendoza, 2005). Large-scale biotic processes such as migration and colonization have been affected by these cycles and modern day biogeography has been greatly influenced by the glacial – interglacial cycling of the Quaternary (Erwin, 2009; Kerhoulas and Arbogast, 2010).

At a much smaller time scale, solar variability as evidenced through the sunspot cycles of

11, 22 and 240 years, result in changes in the amount of short wave radiation reaching the

Earth (Rapp, 2010). Decreased occurrence of sunspots is believed to be one of the factors explaining reductions of global temperature (see Little Ice Age below) (Haase-Schramm et al., 2005).

Internal forcing of climate is related to volcanic activity (i.e. tectonics), ocean circulation, and critical changes in the biosphere (marine and terrestrial) and cryosphere (Beniston,

2005). Volcanic activity cools the climate because particulate matter emitted from the

6 eruption changes the Earth's albedo, increasing solar energy reflectance. Ocean circulation patterns affect the climate, such as the associated drop in global temperatures due to a weakening of the thermohaline circulation during the Younger Dryas (ca. 11,000 yrs BP) and Little Ice Age (ca. 300 yrs BP) (Bradley and England, 2008; Helama et al.,

2009). Variability in other circulations could have more regional effects at decadal time scales such as El Niño Southern Oscillation (ENSO) and the North Atlantic Oscillation

(NAO) (Seager et al., 2010). The former is associated to the contraction and expansion of warm waters in the west Pacific, and the latter is believed to account for ca. 50% of variability in sea level pressure on both sides of the Atlantic Ocean. The internal forcing factors have in common that they operate at a sub-millenial time scale.

The explanation of the Holocene climatic variability requires understanding the coupled effects of external and internal forcings. During the last 10,000-12,000 years the

Holocene stands as an epoch of warmth and steady climate, characterized by centennial and millennial-scale alternating of cold and warm periods, superimposed over a long- term trend of first warming and then cooling (Bjune et al., 2004). The onset of the

Holocene climate has been shaped by the cyclical transition from a glacial to an interglacial where the maximum insolation was experienced (~10 ky BP) (Solanki et al.,

2004) (Figure 1.1.). Thereafter four warming maxima, alternated by cold stages, have been deducted from paleoecological data during the intervals: 6700-5700, 4500-3200,

2300-1600, and during 1150-900 yrs BP (the Medieval Climatic Optimum) (Dergachev and van Geel, 2004). Cold Heinrich events (stadials) and Dansgaard-Oeschger warm stages (interstadials) are important factors that are believed to play a role determining

climatic shifts at the millennial scale (Merkel et al., 2010). Millennial to centennial

natural variability modifies macro-regional climatic regimes and therefore more localized

dynamics such as forest humidity and temperature (Jouzel et al., 2007; Popescu et al.,

2010).

Although global climatic synchronicities have been recognized, regional variations play a

critical role in understanding biogeographical patterns found at smaller spatio-temporal

scales (Viau and Gajewski, 2009). Variability in the location of the Intertropical

Convergence Zone (Chiang and Bitz, 2005; Holbourn et al., 2010) and cyclicity of ENSO

(Merkel et al., 2010) are of major importance to understanding climatic variability at

more regional scales in Mesoamerica. Evidence of climatic variability in the Yucatán

Peninsula, is derived from the 206-year period oscillations of oxygen isotopes and

gypsum precipitation from Lake Chicancanab, and possibly related to variation in solar

radiation (Hodell et al., 2001). Similar paleoclimatic patterns have been gathered from

Figure 1.1 Temperature changes along the late Pleistocene and the Holocene inferred from oxygen-18 measurements in Greenland ice core (taken from Dergachev and van Geel, 2004).

8 the Circum-Caribbean, Lake Valencia and the Cariaco Basin in Venezuela, and when combined with the Chicancanab data, aligns with critical processes along major cultural periods (Alley et al., 2003; Hodell et al., 1991; Peterson et al., 1991). Arid events have been associated with cyclic events and include observed droughts between 150 and 250

AD (Pre-Classic abandonment), 750-1050 AD (Terminal Classic Collapse) and 1450 AD

(Post-Classic) (Hodell et al., 2007).

The climate system is currently understood as the product of the coupled interactions between the atmosphere, hydrosphere, lithosphere, cryosphere, and biosphere.

Information provided by paleoclimatic studies provide scientific basis for hypothesis testing of climatic variability in determined locations under different temporal scales of resolution.

1.3 Reconstructing vegetation and landscapes

A large number of vegetation reconstructions based on pollen have been conducted

around the world, spanning time periods from hundred to millions of years ago, and have

provided important information to determine the roles of natural factors in landscape

evolution. Based on changes in pollen composition, it has been possible to identify a high

correlation between tectonic processes of the Andean orogeny of the last 3 million years

(Mya) with altitudinal changes in North Andean biomes (Hooghiemstra and Van der

Hammen, 2004; Torres et al., 2005). In coastal environments, sea level changes at the

multi-millenial scale have been analyzed based on regressive and transgressive phases

9 reconstructed from sedimentary sequences, and have been used in conjunction with pollen information to show an inland-to-coast migration of vegetation (Torrescano and

Islebe, 2006; Gabriel et al., 2009). Milankovitch cycles affect the retreat and advance of glacial ice caps, events that can be recognized in pollen diagrams showing latitudinal tree line oscillations (Kramer et al., 2010). Other periods of natural climatic variability such as the Younger Dryas stadial (cold event) (Kokorowski et al., 2008) and solar cycles are evident in pollen diagrams (Morner, 2010). Pollen from the Arctic specialist Dryas octopetala is used as an indicator of the Younger Dryas because of the increase in distribution and abundance of D. octopetala at this stadial (Joosten, 1995).

In places such as the Mexican Central Highlands and the Lacandon rain forest in Chiapas, evidence of the Maya Terminal Classic (800-900 century AD) drought event has been interpreted based on the increase of Pinus pollen (Almeida et al., 2005; Domínguez-

Vázquez and Islebe, 2008). In contrast, reconstructions from neighboring regions such as the Mexican Sierra Madre Oriental (East-Central Mexico) (Conserva and Byrne, 2002) and Sierra de Los Tuxtlas (Lozano-García et al., 2010) show no evidence of drought and actually indicate slightly moister conditions. Geographical variability in precipitation may be because of orographic effects in topographically complex regions, which creates climatic envelopes at the regional scale. For example, Wendt (1989) proposed the existence of a wet belt across the Gulf of Mexico, Southeast of Mexico, Central

Guatemala, and the Izabal province (Caribbean Guatemalan Coast), which possibly allowed the permanence of hypothesized tropical rain forests pleistocenic refuges.

Data from Los Tuxtlas show evidence of the Little Ice Age (LIA) in the Gulf of Mexico; multi-proxy records indicate wetter conditions around 1500 to 1700 AD (e.g. increased lake levels and increased accumulation rates of pollen of lowland or highland forest taxa)

(Lozano-García et al., 2007; Lozano-García et al., 2010). In contrast, reconstructions based on oxygen isotopes and titanium content from the Yucatán peninsula (Aguada

X’caamal) and the Cariaco basin (respectively) show lower precipitation between 1500 and 1800 AD (Hodell et al., 2005). Climate proxies and the presence of Zea pollen from

Lake Tzib at Quintana Roo, Mexico (Carrillo-Bastos et al., 2010) likely indicate higher precipitation around 1200 AD contrary to what would be expected during the time of the

Medieval Warm Period (MWP) (just before the LIA).

1.4 Reconstructing Cultural Landscapes

Pollen can also be used to reconstruct anthropogenic impacts on landscapes during

different cultural periods, for example, during the early Holocene phase of hunters-and-

gatherers (Kunes et al., 2008). Cultural impacts on the environment are of greater interest

for more recent times, including the transition from nomadic human populations to fully

sedentary communities (Rowley-Conwy, 2009). It is when human groups started to

remain in one area for longer periods of time that we can see a clear anthropogenic signal

in the paleo-record, reflecting the evolution of agriculture as an important modifier of landscapes.

In different culturally important regions around the globe (the Near East, Ganges Delta,

Yellow River watershed), the origins and development of agriculture have been

11 reconstructed based on the first appearance of cereal pollen cultigens. In the case of

Mesoamerica, corn pollen (Zea mays L.) is traced (Zizumbo-Villarreal and Colunga-

García, 2010) whereas in China, the initial presence of rice pollen (Oryza sativa) is used to signify the beginning of agriculture (Fuller et al., 2009). The reconstruction of landscapes histories based on architectural and ceramic remains (i.e. archaeological methods) is complemented with the use of pollen because it can tell a more complete story about an area, including information on landscape management, levels of disturbance, and conservation efforts (Bettis III et al., 2008; Dambrine et al., 2007;

Delhon et al., 2009; Mercuri, 2008).

The magnitude to which anthropogenic activities influence landscapes is a topic of much discussion between researchers (Horrocks et al., 2007; Williams et al., 2010; Yu et al.,

2010; Zhao et al., 2010). Numerous scholarly theories have been derived depending on the type of evidence collected (i.e. paleoecological versus archaeological) and the cultural context in which that evidence is found. On the one hand, ancient cultures have been considered responsible for major modifications to landscapes; involving activities that generally bring upon detrimental societal consequences as a result of natural factors such as soil erosion and resource depletion (Diamond, 2009; McWethy et al., 2009). It has been suggested that anthropogenic activities (particularly changes in land-use) can alter regional climate, such as precipitation (Shaw, 2003; Gill et al., 2007) and therefore could play an interactive role in prolonging periods of drought and/or deepening the magnitude of water stress. From this perspective, anthropogenic activities are considered the critical trigger in the collapse of past societies (Diamond, 2005).

In contrast, past societies can be viewed from the perspective of practicing sustainability of resources in their everyday activities, such as the planting of trees to prevent large- scale erosion of highlands (Smith and Demarest, 2001; Aimers, 2007). From this second point of view, the “collapse” of an ancient civilization has foundations in multi-factorial processes, both anthropogenic and natural (e.g. biotic, abiotic) (Demarest et al., 2004;

Demarest, 2009).

Regardless of how human activity is viewed within ecosystem dynamics, evidence shows an increasing effect of changes in greenhouse gas concentrations in the atmosphere, since the onset of agricultural activities, the introduction of large-scale herding of grazers, and most recently due to the burning of fossil fuels (Olofsson and Hickler, 2008; Brook,

2009). The "Anthropocene", a controversial naming of the latter period of the Holocene, has been defined by the period of over-arching effects of humans on climatic, hydrologic and edaphic cycles (Ruddiman, 2003; Crutzen, 2006).

1.5 Thesis Objectives and Research Questions

1.5.1. Rationale.

The role of natural and cultural factors in the evolution of landscapes within the Las

Verapaces region of north-central Guatemala is the focus of this thesis. Natural and

cultural factors can intermingle or act independently at different spatio-temporal scales

(Clark, 2007; Díaz and Stahle, 2007; Partel et al., 2007; Sarmiento et al., 2008;

Wainwright, 2008). The separation of past cultural and natural processes by using

paleoecological methodology is needed to help provide a solid scientific basis to assess

modern-day impacts of human activities at the global, regional and landscape scales. This

thesis is developed in the Lachuá lowlands and the Purulhá highlands of the Las

Verapaces region, an important location in the Mesoamerican context due to its high

biological and cultural diversity, which nevertheless lacks exploration in paleoecological

terms.

1.5.2. Approach.

My approach involves paleovegetation reconstructions of the Lachuá lowlands and the

Purulhá highlands in the Las Verapaces Region from the Preclassic to modern-day times,

covering the past two millennia. To develop paleo-vegetation reconstructions for the Las

Verapaces Region, it was necessary to first determine the taxonomic composition of

vegetation communities and the altitudinal distribution of vegetation types, including

explanations for their geographical variation (Chapter 2). Since the relationship between the abundance of pollen grains and the abundance of corresponding vegetation is not 1:1,

14 it was necessary to develop the first calibration study of the region by comparing pollen sources such as lake sediments and bryophyte polsters and analyzing the modern pollen rain (Chapter 3). Paleoecological reconstructions were developed based on fossil pollen spectra collected from a core (P-4) from the Cahabón River floodplain at the Purulhá highlands spanning the last ~2390 years (Chapter 4) and a wetland core (L-3), taken adjacent to Lachuá Lake, within the Lachuá lowlands (Chapter 5) spanning the last

~2000 years.

Research Questions. The main research questions addressed in this thesis include:

a) What are the factors that explain vegetation distribution along the Las Verapaces

environmental gradient and what taxa can be used as "indicators"?

b) Can paleoecological calibrations for fossil pollen be constructed from a

comparison of modern pollen rain from surface sediments and bryophyte polsters?

c) What are the major vegetation changes recorded in the two (lowland, highland)

cores from the Las Verapaces region?

d) What is the role of natural variability and cultural factors related to the Maya

Civilization in the evolution of landscapes in the Las Verapaces Region?

1.6 Geomorphological and Vegetational Setting of Study Region

The Las Verapaces region is located in north central Guatemala, encompassing sharp

environmental gradients from the Lachuá lowlands (~170 masl) to the Purulhá highlands

(~2500 masl) (Figure 1.2). In addition to being characterized by environmental gradients,

I also selected the region because of the absence of paleoecological research (Islebe and

Leyden, 2006) despite its importance in both natural and historical cultural diversity. Las

Verapaces is distributed across two Guatemalan provinces: Alta Verapaz and Baja

Verapaz (Figure 1.2 and 1.3). The geological structure of the area is primarily karstic terrain of Cretaceous and Tertiary origin (Alta Verapaz), with metamorphic regions dating from the Lower Paleozoic (Baja Verapaz and Alta Verapaz) (Ortega-Gutiérrez et al., 2007).

1.6.1 Lachuá Lowlands

The Lachuá lowlands are located in a transitional zone between the Petén Lowlands and

the Cordilleran central highlands (Weyl, 1980) and contain one of the last remnants of

Lowland Rain Forest remaining in Guatemala (Figure 1.3) (for vegetation belt

description see results Chapter 2). The site has a protected area, the Lachuá Lake

National Park, which covers approximately 14,500 ha in addition to a surrounding buffer

zone of approximately 28,000 ha (Monzón, 1999). An inventory of Lachuá’s forest

species (as well as other vegetation types) was undertaken within the past 10 years

(García, 2001; Ávila, 2004; Cajas, 2009; Castañeda, 1997), and more recently, a modern pollen reference collection of the thirty most abundant plant species has been collated

(Barrientos, 2006). There is a Lowland Rain Forest remnant (~300 ha) northeast of

Lachuá Lake National Park located in the top of a hill 285 masl in elevation with a series of small ponds known as Tortugas (Tun personal communication, 2006). The remnant is known as Salinas de los Nueve Cerros Regional Park, where an archaeological site of the same name is located.

Geomorphologically, the area contains undulated karstic hills and varied landforms ranging from low- to mid-elevations (170-600 masl) (Avendaño et al. 2007). The Lachuá

Lake is found at the Lachuá Lake National Park; a circular depression (400 hectares) with a depth of 200 m, draining into the lower sedimentary basin of the Chixoy River

(Granados, 2001). Moisture-laden winds from the northwest and east originate from within the Caribbean Sea, creating a mean annual precipitation of approximately 2000-

2499 mm. The rainy season occurs between May and October, with mean annual temperatures between 25.5–28°C (Monzón, 1999).

1.6.2 Purulhá highlands

The Purulhá highlands cover the Cahabón River headwaters, and the Polochic and

Chixoy upper basins, ranging in elevation from 1560-2300 masl (Figure 1.3). Purulhá

contains a main remnant of cloud forest (1044 ha) that is protected under the jurisdiction

of “Biotopo Universitario para la Conservación del Quetzal” (BUCQ) (CONAP, 2000).

This site is underlain by the metamorphic and karstic system of the Sierra Chuacús

mountain range (Weyl, 1980). Moisture-laden Caribbean winds from the east, northeast,

and northwest result in mean annual precipitation around 2092 mm and mean annual

Figure 1.2. Location of Guatemala in Central America. Circle encloses location of the Las Verapaces Region. Numbers indicate locations of meteorological stations. 1= Flores, 2= Puerto Barrios, 3= Las Vegas, 4= Panzos, 5= Cahabón, 6=Papalhá, 7= Cobán, 8= Suiza Continental.

Gulf of Mexico

Caribbean Sea México 1 Belize

2 Guatemala 5 3 7 6 4 Honduras 8

El Salvador Nicaragua

Costa Rica Pacific Ocean

Panama

Figure 1.3. Topographic map of the Las Verapaces Region in Guatemala. Encircled numbers indicate study sites. 1= Lachuá lowlands, 2=Sierra Chinajá, 3= Rio Tinajas, 4= Chelemhá, 5=Tucurú, 6= Tamahú, 7=Purulhá (BUCQ)-, 8= Tactic, 9= Santa Cruz Verapaz. Locations #6 to #9 are part of the Purulhá highlands. Watershed names are indicated in italics.

México

1 La Pasión

Chixoy

1800 m 1000 m 200 m Chinaja Watershed boundary Cahabón 4 9 8 Polochic 6 5 3 7

19 temperatures between 13.9–20.4°C (García, 1998). The rainy and dry seasons occur between June and September and January and April, respectively. The Cahabón River headwaters are located in the municipality of Purulhá town, province of Baja Verapaz, at an elevation of approximately 1570 masl. The Cahabón River floodplain is characterized by the presence of entisols and inceptisols in the low valley sections, surrounded by andisols and ultisols in the surrounding mountains (MAGA, 2001). The floodplain is located close to the upper limit of the Lower Montane Rain Forest (1000-1800 masl), surrounded by valley slopes covered by Montane Cloud Forest (1800-2500 masl in my study region) (for vegetation belts description see results Chapter 2). Local inhabitants from Purulhá town have mentioned of the possible existence in the past of a lake in the environs of the town (Vázquez C. personal communication 2011).

1.6.3. Geographical setting and study design

Vegetation sampling (Chapter 2) of lowland sites took place in separate watersheds: (1) the Chixoy watershed which is composed of mainly Cretaceous-Tertiary marine sediments and Quaternary alluvium, and (2) the Polochic watershed located over a pull- apart type basin containing Quaternary alluvium (Fourcade et al., 1999). Highland sites are located in the upland portions of the Cahabón and Polochic watersheds, which are underlain by Pennsylvanian to Permian eclogitic rocks and gneisses (Ortega-Gutiérrez et al., 2007). Rio Tinajas vegetation sampling sites are located in a sub-watershed that drains into the Polochic Watershed (Tot, 2000).

Modern pollen samples for palynological calibration (Chapter 3) and core samples

(Chapter 4 and 5) were collected in two sites located at both ends of the Las Verapaces elevational gradient (Figure 1.3): (1) Lowland Rain Forests at the Lachuá lowlands in

Alta Verapaz (~ 170 masl), and (2) the Montane Cloud Forest and the transitional vegetation belt at the lower limit at the Purulhá highlands and its environs in Alta and

Baja Verapaz (~ 1400-2000 masl). The Purulhá highlands in our study region represent the highest geographical point.

1.7 Cultural History of Study Region

According to the cultural succession and temporal differentiation for Mesoamerican civilizations such as Olmec, Maya and Aztec (Chase et al., 2009), standardized periods have been defined as the following: 1) Pre-Classic (3000 BC-300 AD), 2) Classic (300 -

900 AD), and 3) Post-Classic (900~1500 AD). These periods are delineated based on critical changes to the political, economic and ceremonial development of Mesoamerican civilizations. The most studied transition includes the end of the Classic Period of the

Maya Lowlands, known as the Terminal Classic Period (Demarest et al., 2004; Demarest,

2006).

Paleoecological studies in the Guatemalan Northern Petén Lowlands (Figure 1.2) have reconstructed environmental changes dating back to the Last Glacial before any human settlement took place in the region (Leyden, 2002), but emphasis has been placed on

Mayan cities that flourished mostly during the Classic Cultural period (300-900 AD)

(Islebe and Leyden, 2006). The heightened interest in this time period occurs mostly

21 because the majority of Classical cities underwent a regional transformation process at the time of the Terminal Classic, largely known as Classic Mayan collapse (Aimers,

2007). Conclusions from some authors indicate that environmental anomalies, such as droughts (Diamond, 2005; Gill et al., 2007), have played a critical role in determining the fate of human societies, sometimes enhanced by human disturbances, which brought together social instability and revolts due to natural resource demise. Contrasting research approaches have concluded that environmental variability could have played more of a secondary role on the transformation of societies, and that intrinsic societal characteristics have a more relevant role in societal collapse (Demarest et al., 2004). This latter approach emphasizes the idea that societies like the Mayan are able to cope with extrinsic disturbances such as environmental extreme events, even when facing intrinsic instabilities that requires substantial societal transformations.

Mesoamerican paleoecological research has provided explanations regarding the role of environmental and societal factors on the shaping of landscapes along both highlands and lowlands. Based on different fossil proxy evidence found in sedimentary records, some lowland locations indicate the occurrence of drastic droughts, which are believed to have had a dramatic impact on the transition between the Classic and Postclassic (900-1000

AD) . On the other hand, at some other locations experiencing possible arid events, there were relatively few cultural changes or negative anthropogenic environmental impacts even when human populations were highest. The Classic-Postclassic transition is delineated mostly as a socio-political and religious transformation, that in some locations promoted total or temporary abandonment of cities, semi-destruction due to warfare,

22 while in other locations, cultural flourishment took place (Demarest, 2009). Evidence indicates that the most dramatic changes to all aspects of the Mayan Culture and the environment occurred during the Spanish Conquest and Colonization (Elliot et al. 2010).

The Spanish settlers brought new diseases that contributed in part to the Mayan population demise, and ultimately the introduction of new economic, political, sociological, and religious systems (Van Buren 2010).

There is an obvious void in the Mesoamerican paleoecological record that must be filled due to the contextual importance of the Las Verapaces region. The Las Verapaces lowlands represent an important geographical transition from the Northern Petén region to the Las Verapaces Highlands, and Southern Maya Area (i.e. Kaminal Juyu, Copán, and

Takalik Abaj) (Rice et al., 1985; Fowler et al., 1989). The lack of paleoecological information for the Las Verapaces Region places this thesis as critical for providing information about the landscape evolution of the last two millennia. Natural and cultural factors have been explored in this thesis to provide a baseline for continuing paleoecological research in this region as well as in neighboring regions in Mesoamerica.

The Lachuá lowlands are located east of the neighboring Petexbatún cultural region where important cities were developed along the Pasión and Chixoy rivers banks

(Demarest, 2006). The Petexbatún region had different political elites that established a succession of Kingdoms, where military control was critical to maintain privileged economic riverine routes. Cancuen, located approximately 60 km east of Lachuá, was an important city since the late Pre-Classic until its abandonment during the Late Classic

(Aimers, 2007). Paleoecological and paleoagronomic evidence from the Petexbatún lowlands indicate that sustainable agriculture and forestry were practiced in succession

(Demarest, 1997). Sustainable management practices likely involved soil conservation to mitigate environmental deterioration with time (Beach and Dunning, 1995; Beach et al.,

2008; Dunning et al., 1997).

At the Lachuá lowlands, the ancient city of Salinas de los Nueve Cerros was established as an important salt producing center along the Chixoy river banks (Figure 1.4) (Dillon,

1977; 1990; Garrido, 2009). There is no direct evidence describing landscape management practices, but it is possible that similar soil ammendment measures observed in the Petexbatún region were also occuring in Salinas de los Nueve Cerros.

Archaeological studies indicate that the economic importance of the Mayan site of

Salinas de los Nueve Cerros was salt production practiced from the Preclassic to Post-

Classic times. At present, population pressure in the Lachuá Region is beginning to encroach on the Lachuá Lake National Park and Salinas de los Nueve Cerros; over the past 50 years, 50% of the forest has been lost to anthropogenic land-use change

(Avendaño et al, 2007). The population generally consists of people from the q’eqchi’ ethnic group who mostly ended up in the region as a result of territorial displacement and colonization projects following the Civil War (Hurtado, 2008).

In order to better understand the cultural processes that were taking place in the Maya

Lowlands, it is critical to concomitantly address the environmental and cultural history of the Maya Highlands. The scarcity of lakes on the one hand explains why highlands (i.e.

Figure 1.4. Topographic map of study sites in the Las Verapaces Region in Guatemala. Map I= Lachuá lowlands, Map II= Purulhá highlands. Bryophyte polsters are indicated in letters and surface sediments in numbers. 1= L1, 2= L2, 3= L3, 4= Sa2 (Salinas de los Nueve Cerros archaeological site and natural reserve), 5=J1, 6= T1, 7= P4, 8= P1, A=samples Ca-Ce, B= samples Ra-Re. Both A and B are located at the Lachuá Lake National Park. C= Samples N1-N10 (“Biotopo Universitario para la Conservación del Quetzal”). Highland archaeological sites: VP=Valpraiso, CH= Chican, CX= Cerro Xucaneb, S= Sulin. National parks are represented as dark grey polygons. Rivers are irregular black thick lines. Lachuá Lake is represented as light gray polygon in map I. Chichoj Lake is represented as light gray polygon in map II. Samples 6-8 are located in the Cahabón River Floodplains. Isolines every 50 m in Map I (lowest point 150 masl, highest point 700 masl). Isolines every 100 m in Map II (lowest point 1400 masl, highest point 2300 masl).

Las Verapaces) paleoecological research lags behind its lowlands counterpart. But on the other hand, this scarcity is related to the main interest of researchers in wanting analyze paleoenvironmental records related to archaeological findings from major Classic Maya centers which were distributed mostly in Mesoamerican lowlands (Anselmetti et al.,

2006; Hillesheim et al., 2005; Wahl et al., 2007). This trend has dominated despite of the importance that the multi-factorial interaction (i.e. political, economical, ceremonial, etc.) lowlands-highlands had for the development of the Maya Civilization during the last

3000 years (Freidel et al., 1993). Nevertheless, recently there has been an increase in addressing paleoecological questions related to highlands environments in Mesoamerica

(Almeida et al., 2005).

There is scarce paleoecological information about highlands landscape management practices, but archaeological investigations indicate that relatively high gradient environmental (e.g. topographic) boundaries promoted the evolution of relatively small

(regional) and well-bounded cultural systems (Sharer and Sedat, 1987). In the Purulhá highlands, there are many minor archaeological sites that range from the Pre-Classic to the Post-Classic, including such sites as Cerro Xucaneb, Chican, Sulin, and Valparaiso

(Figure 1.4) (Arnauld, 1978, 1987; Ichon et al., 1996). In contrast to the lowlands, expansion and alliances of these highland cultural entities was limited in part to constrained communication over mountainous landscapes, and not strictly to economic, social, political and ideological factors (Ichon et al., 1996). Natural trade routes have been traced between lowland and highland archaeological sites that cross mountain ridges and valleys, therefore indicating that commerce and cultural interregional exchange were

26 occurring at this time (Andrews, 1984). It is precisely the connection between disparate regions that was important for the development of the Maya Civilization (Arnauld, 1997).

It is the exchange of socio-political, cosmological and ceremonial knowledge, in addition to landscape management practices, that unifies the Mayan cultural region. Little has been discussed about the Mayan Highlands terminal Classic and the occurrence of city- center collapse (Demarest, 2009). There is need for further investigation about what causes some cities to be abandoned while others to be founded and flourished.

Land-use at the Purulhá highlands during the late-19th century was dominated by coffee plantations, whereas today the area is dominated by a complex mosaic of cattle fields, agricultural crops (mainly corn), and ornamental species. Population density in this highland area (primarily comprising achi, poqomchi’, q’eqchi’, and ladino ethnic groups) is steadily increasing, and has created an ever heightening demand for land for agriculture and urbanization (CONAP, 2000). Following European conquest (ca. 500 yrs BP) socioeconomic and political pressures led to dramatic changes in (1) land-use patterns (i.e. introduction of cash crops and plantations), (2) foreign investment, and (3) displacement of indigenous populations (Van Buren, 2010). More recently, anthropogenic disturbances associated with civil war, strong military rule, colonization, deforestation and pollution related to natural resource extraction (i.e. mining) have contributed to the character of the landscape in the Las Verapaces Region (Hurtado, 2008).

Chapter 2: Vegetation Distribution along the Las Verapaces region in North Central Guatemala

2.1 Introduction

Understanding the controls on vegetation distribution in the tropics will improve predictions of responses to future climate change (Freycon et al., 2010) and help to better determine factors behind centers of high biological diversity ("biodiversity"). Climate is usually considered a first-order control on vegetation type and distribution (Tietjen et al.,

2010); however, other factors such as watershed topography (Bertoldi et al., 2010) and evolutionary history (Vanderpoorten et al., 2010) can also play critical roles in shaping biogeography. Guatemala currently does not have a formal protocol for describing vegetation types or belts based on floristic and environmental criteria, however, the following approaches have been used in the past: (1) qualitative integrations of flora with physiographic and geomorphologic factors (Villar, 1998), (2) quantitative local adaptations of Holdridge Life Zones (De La Cruz, 1982), or (3) qualitative adaptations of classifications from neighboring regions like Mexico (Rzedowski, 2006). More formalized vegetation identification surveys are needed, particularly in light of the fact that Guatemala is located in Nuclear Central America and is home to the Mesoamerican

Tropical Forest Hotspot (Harvey et al., 2008). The Mesoamerican hotspot is renowned for its high vegetation diversity (Knapp and Davidse, 2006), despite being located in an area influenced by humans for over the past 7,000 years (Chinchilla, 1984). Guatemala’s rich

28 biological and cultural complexity highlight the necessity for better understanding the roles of natural and cultural factors in vegetation distribution.

The first research objective is to identify changes in vegetation communities and to delineate boundaries between vegetation belts along an elevational gradient located in the

Purulhá highlands and the Lachuá lowlands of the Las Verapaces region in north central

Guatemala. The names of the vegetation belts applied for Las Verapaces region were adapted and integrated from different vegetation regional studies (Breedlove, 1981; de la

Cruz, 1982; Kappelle et al., 1995; Kappelle, 1996; Domínguez-Vázquez et al., 2004)

(Table 2.1): (a) Lowland Rain Forest below 1000 masl, (b) Lower Montane Rain Forest between 1000 and 1800 masl and (c) Montane Cloud Forest above 1800 masl up to approximately 2500-3000 masl. Other vegetation belts found in neighbouring regions include (de la Cruz, 1982; Islebe and Kappelle, 1994; Islebe and Velázquez, 1994; Islebe et al., 1995) (Table 2.1): (d) Lowland Humid Forest, with less precipitation than the

Lowland Rain Forest, such as in the northern Petén region; (e) Montane Mixed Forest, where the endemic tree Abies guatemalensis is found; (f) Sub-Alpine Forest, being the tree line limit in Guatemalan forests; and (g) Páramo (Alpine bunchgrassland), in the

Sierra de los Cuchumatanes and in the Western Volcanic Chain.

In order to achieve the first research objective a meta-data analysis of different local literature sources has been created, where the distribution of plant taxa within one site or among different sites in the elevation gradient is included. The existence of plant taxa with discrete elevational distributions is responsible for the delineation of vegetation

Table 2.1 Description of vegetation belts found in the Las Verapaces region* and neighbouring regions in Guatemala.

Vegetation Belt Elevation range Mean annual Associated plant taxa (masl) precipitation (mm)

Lowland Humid Forest ~ 0 to <600 ~1100-1700 Alseis yucatanensis, Aspidoderma megalocarpon, Manilkara zapota, Sabal morisiana.

Lowland Rain Forest* ~ 0 to 1000 ~2100-4300 Sapium, Terminalia amazonia, Trema, Ulmus.

Lower Montane Rain ~ 1000 to 1800 ~2000-2500 Alchornea, Croton Forest* draco, Persea schiediana, Rapanea, Myrica.

Montane Cloud Forest* ~1800 to 2500-3000 ~ >4100 Hedyosmum mexicanum, Quercus, Podocarpus oleifolius.

Mixed Montane Forest ~ 2500 to 3000-3100 ~2500 Abies guatemalensis, Alnus, Pinus ayacahuite, P. montezumae, Quercus.

Sub-Alpine Forest ~ 3100 to 3800 ~1100-1800 Alnus, Buddleja, Juniperus, Pinus hartwegii.

Páramo (Alpine ~ >3800 ~1275 Cardamine, Poa bunchgrassland) venosa, Senecio, (Sierra de los Cuchumatanes); Calamagrostris, Luzula, Halencia, Oxylobus, Poa tacanae (Western Volcanic Chain).

30 belts; alternatively, plant taxa that have more continuous distribution create landscape continuums (Kessler, 2000; Hemp, 2006).

The second objective is to evaluate the factors responsible for vegetation distribution and turnover of plant communities along the Las Verapaces region. Three key deriving factors will be examined: (1) elevation and associated changes in climate (i.e. environmental lapse rate), (2) landscape position and topography in drainage divides, and

(3) biogeographic origin (i.e. over geological timescales). The findings from this analysis will also provide a critical baseline from which to conduct palaeoecological research because we can relate fossil pollen spectra to indicator taxa from modern-day vegetation belts. Ultimately, by studying the natural (biotic, abiotic) factors influencing vegetation I can begin to tease apart complex interactions between the natural environment and anthropogenic processes.

2.2 Methods

2.2.1 Compilation of the vegetation database

For areas with few published records, forest inventory databases and unpublished academic theses provide a rich source from which to better understand the biotic and abiotic factors influencing vegetation trends observed across modern-day landscapes

(Kitahara et al., 2009; Veen et al., 2010). Data on vegetation community composition, plant species identification and abundance were collected from multiple sources including silvicultural, ecological and landscape research reports (Table 2.2). Five out of

31 ten of the sources report ecological data using traditional experimental design, including large sample sizes and multiple replicates. Dissertation research conducted by University students in Guatemala was invaluable to the collation of the database. These sources included: (1) four undergraduate theses from Lachuá (Ávila, 2004; Cajas, 2009),

Purulhá (García, 1998), and Chelemhá (López, 2009.), (2) one Master of Science thesis from Sierra Chinajá (Bonham, 2006), and (3) forestry inventories extracted from undergraduate theses for Tucurú (Paz, 2001), Tamahú (Alonso, 1999), Santa Cruz

(Palala, 2000), Tactic (Mollinedo, 2002), and Rio Tinajas (Tot, 2000).

Because six studies only presented qualitative data (presence/absence), sources that had quantitative data (abundances) were transformed to presence/absence to standardize my database. Taxonomic nomenclature was also standardized when necessary and updated

(Gentry, 1982; Smith et al., 2004). In some cases, standardization required retention of genus-level information only, correction of spelling, and revision of taxonomic synonymies. The end result is a matrix showing distributions (presence/absence) of 794 angiosperm taxa across 23 sampling units.

Although I recognize the ecological, biogeographic and economic importance of gymnosperms, I am not incorporating them in my study because in Guatemala little information on their distributions is available outside of a plantation/forestry context.

Therefore, my analysis focuses on exclusively angiosperms.

2.2.2 Creation of climate databases

To create a regional climate database for sites along our selected gradient, I used information from eight meteorological stations located in Central and Northern

Guatemala (Figure 1.1). Data from seven stations at different elevations were collected directly from INSIVUMEH (Volcanology, Meteorology, and Hydrology National

Institute) in Guatemala City, each having temporal coverage from the years 1990-2005 inclusive. From a longer climate database (42 years; 1961-2003) (Aguilar et al., 2005), data from Flores (123 masl) was used for my analysis. Of all meteorological variables available, I selected three temperature variables that best represent both extremes and average indicators of regional climate. The chosen variables include: (1) maximum absolute temperature (TXx) defined as the recorded annual maximum value of daily maximum temperature, (2) minimum absolute temperature (TNn) defined as the recorded annual minimum value of daily minimum temperature, and (3) mean annual temperature

(MAT). Temperature parameters such as MAT have been used to estimate upper limits of low-elevation taxa (Latorre et al., 2006), and TNn and TXx are useful to estimate physiological barriers for plants survival (e.g. drop of temperatures close to overnight frosting and dessication stress related high temperatures, respectively).

2.2.3 Statistical Analysis

A multivariate analysis was run on a total of 794 angiosperm plant taxa from nine sites with a total of 23 sampling units (presence/absence data), to determine the degree of similarity between sites and the relationships between taxonomic assemblages and climate variables. Through a detrended correspondence analysis (DCA) sites were

33 arranged in a diagram along ordination axes to indirectly identify possible underlying environmental gradients (Jongman et al., 1995). The presented DCA diagram presents axis scores transformed into percentages to help visualize the data variability (McCune and Mefford, 2006). I created dendrograms through hierarchical cluster analysis (HCA)

(relative Euclidean distance and Unweighted Pair Group Method Algorithm; UPGMA) of sites with similar taxonomic composition, which were of aid to establish groups of sites in the DCA diagram (Jongman et al., 1995). Where consistent agglomeration of sites was observed through ordination axes and cluster analysis, a vegetation belt was delineated as a correlation of elevation and species composition (Axis scores). The software PC-Ord was used to conduct all statistical analyses (McCune and Mefford, 2006). Plant taxon that presented a unique DCA Axis 1 score were chosen as representative of a particular distribution pattern along the altitudinal gradient, instead of utilizing a group of taxa with the same Axis 1 score. Species scores are known to represent a particular site or groups of sites, as DCA Mode-Q analysis indicates that sites are “centroids” for an assemblage or array of determined species (Jongman et al., 1995). Species and sites scores are known to be illustrative of each other (Chase et al. 2000).

As mentioned earlier, the names of the vegetation belts and their elevation limits were established a priori (Table 2.1): (a) Lowland Rain Forest below 1000 masl, (b) Lower

Montane Rain Forest between 1000 and 1800 masl and (c) Montane Cloud Forest between above 1800 and 2500 masl. Indicator taxa were defined as those found exclusively inside a vegetation belt (i.e. in a discrete elevation range like 1000-1800 masl) whereas generalist taxa are those with a wide distribution that span across one or

Table 2.2. Sites included in the vegetation database of the Las Verapaces region, providing a total of 23 sampling units (SU) from 10 studies spanning an elevation gradient of 170 to 2532 masl. Where indicated, elevation ranges used to calculate average elevations are shown in parentheses. If researchers pooled sampling units (SU) of a site into one vegetation data set, the average elevation was calculated for the site. When sampling units of one site were not pooled, their elevations and corresponding vegetation data were entered directly into our database. If elevation ranges for sampling units were given, the average elevation was calculated. For data type, Q indicates studies that used abundance as measurement and C indicates studies that used presence/absence as measurement.

Source Ávila (2004) Bonham Paz (2001) Alonso Palala Mollinedo Tot (2000) García López (2009) and Cajas (2006) (1999) (2000) (2002) (1998) (2009) Sites Lachuá Sierra Tucurú Tamahú Santa Cruz Tactic Rio Tinajas Purulhá Chelemhá (n=1) Chinajá (n=3) (n=1) (n=1) (n=1) (n=6) (n=5) (n=4) (n=1) SU codes Lach Chin Buena Vista Tam Scruz Tac Tin1 Pur1 Che1 (in bold) (Bvta) Tin2 Pur2 Che2 Cumbre de Tin3 Pur3 Che3 Florida, Tin4 Pur4 Che4 (Flo) Tin5 Pur5 Chelemá Tin6 (Che) Elevation 170 400 (200- 1200 1048 1500 1650 200 (0-400) 1800 1900 (1800- (m asl) 600) 1100 600 (400-800) 1900 2000) 1260 1000 (800-1200) 2000 2100 (2000- 1400 (1200-1600) 2100 2200) 1800 (1600-2000) 2200 2300 (2200- 2200 (2000-2400) 2400) 2466 (2400- 2532) Data Q C C C C C C Q Q Watershed Chixoy Chixoy Polochic Polochic Cahabón Cahabón Tinajas/ Cahabón Cahabón / (see Fig. 1.3) Polochic / Polochic Polochic

35 two neighboring vegetation belts (i.e. from 400 to 1800 masl). I defined disjunctive taxa as those found at two discrete vegetation belts but not in three (i.e. 400 and 1800 masl).

Disjunctive taxa were considered when they were distributed in two non-neighboring elevation belts. I created my plant checklist based on taxa from these three different categories (indicator, generalist, and disjunctive). DCA Axis 1 scores were used as representative of vegetation composition at each of the sites and Axis 1 scores were regressed against elevation.

Indicator, generalist and disjunctive plant taxa were allocated to one of Gentry’s (1982) four paleogeographic categories: (1) Laurasian, (2) Amazonian-centered, (3) Andean- centered, and (4) Miscellaneous. A chi-square contingency table test was run to analyze the relationship between these categories and their corresponding vegetation belts.

Equations were constructed to describe the relationship between elevation and temperature (temporal average for each meteorological station) to determine the lapse rate. To predict the value of the chosen parameters for our study sites according to their elevation, an interpolation was performed for sites located between 2 masl (Puerto

Barrios) and 2100 masl (Suiza Continental) in elevation, and an extrapolation was performed for sites with elevations higher than Suiza Continental.

2.3 Results

2.3.1 Ordination and grouping of sites and plant taxa

A linear regression of the DCA Axis 1 scores of sites and their elevation showed a significant correlation (r2=0.53, p<0.01), and sites were ordered from lowlands to

36 highlands (Figure 2.1 and 2.2). Based on the DCA diagram I identified the three expected vegetation belts according to their elevation and related Axis 1 site scores

(Figure 2.2): (a) Lowland Rain Forest below 1000 masl, (b) Lower Montane Rain Forest between 1000 and 1800 masl and (c) Montane Cloud Forest above 1800 masl. Axis 1 scores of indicator taxa combined against their average elevation, showed a significant correlation to elevation (r2=0.80, p<0.0001; Figure 2.2 A).

2.3.2 Climate-elevation-species relationships

Although there was considerable variation in climatic variables between and within meteorological stations, I found a strong linear relationships between temperature and elevation (r2= 0.65–0.87) (Figure 2.3). Based on these estimations, the environmental lapse rate of temperature is approximately 0.5°C/100 masl, close to the expected theoretical value of 0.6°C /100 masl. Variations in correlations may be due to one, or a combination, of two factors: (1) highly localized weather variability, and (2) insufficient size of climatic data and/or missing data points. Based on my equations of climate parameter by elevation, I could identify temperature ranges associated with each of the three identified vegetation belts.

According to my climate data model for the elevation ranges associated with Lowland

Rain Forest, mean annual temperature (MAT) ranges from 19.9-25.3°C, maximum absolute temperature (TXx) ranges from 32.2-36.1°C, and minimum absolute temperature

(TNn) ranges from 6.8- 12.3°C. For Lower Montane Rain Forest, MAT ranges from 16.7-

19.9°C, TXx ranges from 32.0-33.2°C, and TNn ranges from 5.2-6.8°C. For Montane

Figure 2.1. Detrended Correspondence Analysis diagram of Las Verapaces sites along the first two DCA axes. Sites enclosed by ovals represent groups identified in the Hierarchical Cluster Analysis (HCA). LRF= Lowland Rain Forest sites, LMRF= Lower Montane Rain Forest sites, MCF= Montane Cloud Forest. W= West, E= East.

80 Scruz LRF Tinajas LRF Tam LMRF -W

Tac Tin1

60 Tin2 MCF Purulhá LMRF - E LRF Tin3 Che1 Che Chin Pur1 Che2 Axis 2

40 Lach Pur2 Che3 MCF Chelemhá Pur3 Pur4 Pur5 Che4 Tin4 Tin5 20 MCF Tinajas LMRF -E- E Tin6

Flo

Bvta

0 0 40 80 Axis 1

Figure 2.2. Linear regression of Detrended Correspondence Analysis (DCA) Axis 1 scores (raw scores) of indicator plant taxa (A) and sites (B) against elevation values per site along the Las Verapaces gradient. LRF= Lowland Rain Forest, LMRF= Lower Montane Rain Forest, MCF= Montane Cloud Forest. The dashed square in panel B refers to Tin5 MCF sampling unit.

y=3.85x+243 r2=0.80

y=3.04x+497.2 r2=0.53

Figure 2.3. Linear regression curves of temperature (°C) variables collected from meteorological stations from Central and Northern Guatemala. A) TXx = maximum absolute temperature, B) TNn = minimum absolute temperature, and C) MAT= mean annual temperature. Diamonds represents the mean temporal value for the period reported in the station, and dots represent the temporal variation over the length of the record. MAT is taken from 6 stations, and TXx and TNn from 7 stations (see Figure 1.2. for stations locations).

40 r2 =0.79 38

°C 34

TXx 30

28 26 24

22 30 0 500 1000 1500 2000 2500 Elevation (m) 28 r2 =0.87

°C 24

MAT 22

16 0 500 1000 1500 2000 2500 30 Elevation (m)

25 r2 =0.65

20 °C

15 TNn

0 0 500 1000 1500 2000 2500 Elevation (m) 40

Cloud Forest, MAT ranges from 13.9-16.1°C, TXx ranges from 26.7-30.4°C, and TNn ranges from 4.0-4.9°C.

2.3.3 Role of landscape position and watershed topography

Although elevation appears to be an important factor controlling plant taxa differences between sites, the multivariate analyses show that other factors are important as well. The arrangement of sites along the DCA axes responds possibly to landscape position which was further confirmed through the HCA dendrogram (Figure 2.1). Lachuá and Chinajá are both Lowland Rain Forest sites yet they show a separation on the ordination diagram likely due to topographical factors (i.e. Lachuá flatlands versus Sierra Chinajá).

According to HCA, sampling units from Tinajas watershed were separated according to elevation in the three vegetation belts. Lower Montane Rain Forest sites were separated in two main groups according to their geographical location: east and west. The east group consisted of the Tucurú sampling units and the west group included Tactic, Santa

Cruz and Tamahú sites. The Montane Cloud Forest sites were allocated into sub-groups as a function of their location in three different ridges separated by valleys (Figure 1.2):

Sierra de Las Minas, Sierra Chuacús, and Sierra Yalijux.

2.3.4 Species assemblages and indicator species

Using regression of DCA Axis scores against elevation for each taxon, I sorted the original 794 angiosperm plant taxa into 26 indicator, 20 generalist, and 9 disjunctive plant taxa whose distributions were zonal, continuous and discontinuous (respectively) along the elevational gradient. These categories allowed me to more clearly correlate vegetation

41 with elevation, geographical conditions, and in turn, with climate. The remaining taxa

(739) did not present a unique DCA Axis 1 score, as many plant taxa shared the same score. The identified indicator taxa were related to the elevational range of one of three vegetation belts (Table 2.3). In terms of generalist taxa (Table 2.4) there were 14 taxa common across Lowland Rain Forest and Lower Montane Rain Forest, 11 taxa common across Lower Montane Rain Forest and Montane Cloud Forest, and 2 taxa across all three vegetation belts. Disjunctive taxa (Table 2.5) were distributed in both Lowland Rain

Forest and Montane Cloud Forest.

2.3.5 Biogeographical affinities

There is an increase in Laurasian and Andean indicator taxa, and a decrease in

Amazonian taxa, when moving from Lowland Rain Forest to Montane Cloud Forest

(Figure 2.4). The generalist taxa common to Lowland Rain Forests and Lower Montane

Rain Forests are all Amazonian-centered taxa. Andean-centered and Laurasian generalist taxa are only common between Lower Montane Rain Forest and Montane Cloud Forest

(Figure 2.4). Andean-centered taxa co-dominate the disjunctive taxa with Amazonian- centered taxa, and to a much lesser extent, the unassigned taxa to a particular origin.

According to the chi-square contingency test, the frequencies observed of biogeographic categories along vegetation zones are not at all likely explained by chance (Χ2= 35.00, df

=8, p<0.0001).

2.3.6 Study Limitations: sampling effects

The sites included in this study can be separated into two groups according to their sampling effort: high intensity sampling, representing a detailed collection of plants

(understory, subcanopy and canopy layers) along the spatial variability of an environmental gradient (Purulhá, Chelemhá, Lachuá and Chinajá) and low intensity sampling (Tucurú, Tamahú, Santa Cruz, Tactic, and Rio Tinajas). Many studies indicate that sampling effort is directly related to species richness and diversity (Shen et al.,

2003). Low intensity sampling studies (e.g. mainly focused on forest inventories) are likely to result in the collection of mostly abundant and generalist species than rare and specialist species (Pitman et al., 2001). Most of the generalist plant taxa were found in the

Lower Montane Forest which includes exclusively the low intensity sampling sites

(Figure 2.2b).

The pattern found in the Las Verapaces region could be affected by differences in the research objective of each study, experimental designs, and sampling efforts (Otypková and Chytry, 2006). This limitation is significant to recognize because most of the information on vegetation is in low intensity format for Guatemala (i.e. as it is over the rest of the tropics) (Mathewson, 2006). Nevertheless, after being made aware of the possible caveats and weaknesses, I found that the combination of information from both low and high sampling effort studies allowed me to differentiate three vegetation belts and explain their delineation based on elevation and climate, landscape position and watershed topography, and biogeographic origin (Figure 2.1 and 2.2).

Table 2.3 Indicator plant taxa for the three vegetation belts along the Las Verapaces region, selected from DCA axis scores for species (see text for details). AN= Andean- centered, AMZ=Amazon-centered, LAU= Laurasian.

Vegetation belt Family Biogeographic origin Lowland Rain Forest Genipa sp. RUBIACEAE AN Spondias mombim ANACARDIACEAE AMZ Tabebuia sp. BIGNONIACEAE AMZ

Lower Montane Rain Forest

Cedrela pacayana MELIACEAE AMZ Heliocarpus mexicanus TILIACEAE AMZ Inga sp. FABACEAE AMZ Perymenium grande ASTERACEAE AN Saurauia belisensis ACTINIDIACEAE LAU

Montane Cloud Forest Begonia oaxacana BEGONIACEAE AN Cavendishia guatemalensis ERICACEAE AN Centropogon cordifolius CAMPANULACEAE AN Clethra suaveolens CLETHRACEAE LAU

Erigeron karvinskianus ASTERACEAE AN Fuchsia microphylla ONAGRACEAE AN Lobelia nubicola CAMPANULACEAE AN Miconia aeruginosa MELASTOMATACEAE AN Miconia glaberrima MELASTOMATACEAE AN Ocotea sp. LAURACEAE AMZ Oreopanax liebmanii ARALIACEAE AN Passiflora sexflora EUPHORBIACEAE AMZ Phoradendron sp. LORANTHACEAE AN Psychotria parasitica RUBIACEAE AN Rhynchosia sp. FABACEAE AMZ Styrax argenteus STYRACACEAE LAU Synardisia venosa MYRSINACEAE AN Weinmannia pinnata CUNIONIACEAE AN

Table 2.4 Generalist plant taxa for the Las Verapaces region, as determined by DCA axis scores for species (see text for details). AN= Andean-centered, AMZ=Amazon-centered, LAU= Laurasian.

Vegetation belts Family Biogeographic origin LRF-LMRF

Bursera simaruba BURSERACEAE AMZ Cecropia peltata CECROPIACEAE AMZ Ceiba pentandra BOMBACACEAE AMZ Parathesis vulgata MYRSINACEAE AN Terminalia amazonia COMBRETACEAE AMZ

Virola sp. MYRYSTICACEAE AMZ Vochysia guatemalensis VOCHYSIACEAE AMZ

LMRF-MCF Billia hippocastanum HIPPOCASTANACEAE LAU Brunellia mexicana BRUNELLIACEAE AN Dendropanax leptopodus ARALIACEAE AN

Engelhardtia guatemalensis JUGLANDACEAE LAU

Eupatorium semialatum ASTERACEAE AN Hedyosmum mexicanum CHLORANTHACEAE LAU Liquidambar styraciflua HAMMAMELIDACEAE LAU Myrica cerifera MYRICACEAE LAU Persea donnell-smithii LAURACEAE AMZ

Quercus crispifolia FAGACEAE LAU

Quercus sp. FAGACEAE LAU

LRF-LMRF-MCF Clusia sp. CLUSIACEAE AN Mollinedia guatemalensis MONIMIACEAE AN

Table 2.5. Disjunctive plant taxa distributed in Lowland Rain Forest and Montane Cloud Forest in the Las Verapaces region generated from DCA axis scores for species (see text for details). AN= Andean-centered, AMZ=Amazon-centered, LAU= Laurasian.

Disjunctive taxa Family Biogeographic origin

Clidemia capitellata MELASTOMATACEAE AN Conyza bonariensis ASTERACEAE AN Dendropanax arboreus ARALIACEAE AN Lasciacis divaricata POACEAE Unassigned Matayba oppositifolia SAPINDACEAE AMZ Ocotea eucuneata LAURACEAE AMZ Peperomia cobana PIPERACEAE AN Phoebe sp. LAURACEAE AMZ Pouteria campechiana SAPOTACEAE AMZ

Figure 2.4. A) Indicator (in one vegetation belt) and B) generalist (across two vegetation belts) taxa separated according to their biogeographic origin along the Las Verapaces region vegetation belts (increasing in elevation from left to right) (for indicator taxa Χ2= 35.00, df =8, p<0.0001). LRF=Lowland Rain Forest, LMRF=Lower Montane Rain Forest, MCF=Montane Cloud Forest, AN= Andean-centered, AMZ=Amazon-centered, LAU= Laurasian.

100% A

80%

60% LAU AN AMZ 40%

20%

0% LRF LMRF MCF 100% B

80%

60% LAU AN AMZ 40%

20%

0% LRF-LMRF LMRF-MCF LRF-LMRF-MCF 47

2.4 Discussion

2.4.1 Elevation and climate

Climatic dynamics along elevation is possibly the first-order explanatory factor in understanding modern-day vegetation trends in our study region in Guatemala, as is found with other Latin American countries (Quintana-Ascencio and González-Espinosa,

1993; Gerold et al., 2008) and generally world-wide (Hemp, 2006; Kappelle et al., 1995).

The arrangement of sites along Axis 1 in the DCA diagram shows a clear relationship between floristic composition and elevation (Figure 2.2). Elevation-species interactions are the result of the environmental lapse rate; in other words, changes in climate associated with distance from sea level (Figure 2.3). Temperature data for each vegetation belt generally corresponds to Holdridge’s Life Zones in Guatemala (De La

Cruz, 1982) that are themselves defined mostly as a function of climate. After reviewing information for vegetation belts across Central America and Mexico (Islebe and

Kappelle, 1994; Islebe and Velázquez, 1994), elevation and its correlation with temperature variability is found to be a common factor for differentiation of vegetation belts.

Within a given elevation, my data highlight some unexpected differences in vegetation composition, indicating that maybe broad-scale climatic changes dictated by the environmental lapse rate are only part of the explanation for plant species turn-over through space and time. Studies of tropical forests in Hawai'i (Crausbay and Hotchkiss,

2010), Venezuelan Andes (Cuello and Cleef, 2009) and the Chihuahuan Borderlands

(Poulos and Camp, 2010) indicate that factors such as strong moisture gradients,

48 topography, and incident solar radiation are important to define changes in vegetation.

Lachuá’s dissimilarity to Chinajá (Figure 2.1) within the Lowland Rain Forest belt, for example, may be due to variations in local microclimate. On the one hand, Chinajá vegetation is located in an isolated topographic feature (e.g. approximately 500 m higher than Lachuá) of the relatively flat lowlands of the Chixoy watershed and therefore will likely exhibit a distinct microclimate. On the other hand, Lachuá vegetation is located close to the Sierra Chamá foothills (~170 masl) and therefore exposed to increased moisture due to orographic effects on precipitation. My climate data were unable to capture this climatic variability likely because of the lack of spatial coverage of meteorological stations in this region.

The climatic uniqueness of the Sierra Chinajá and Lachuá has resulted in the presence of some plant taxa distributed normally in higher elevations at the Montane Cloud Forest.

Cloud forest microclimate and niche variability has possibly allowed highland species to establish at locations outside of their expected distributional range, in this case in lower elevations (Table 2.4). These species are found jointly in Chinajá and Lachuá, both at the foothills of Sierra Chamá.

2.4.2 Watershed topography and landscape position

The other Montane Cloud Forest sites (Purulhá and Chelemhá) are most likely differentiated in terms of their location in different mountain ranges: the Sierra Chuacús and Sierra Yalijux, respectively (Figure 1.2). The low altitude mountain passes (valleys) found between Purulhá and Chelemhá may function as a modern-day physical barrier for

49 biological dispersal as montane species would have to migrate below the minimum altitude defining cloud forests (~ 400-1400 masl) to reach to the other side. Alternatively, these valley bottom habitats act as corridors for biota that have adapted physiological tolerances to lower elevation conditions (Schmitt et al., 2010). I believe the separation of

Tinajas 6 site from the other highland sites (Purulhá, Chelemhá) is probably due to the fact that the site's vegetation data are based solely on forest inventories that lack taxonomic specificity. In other words, the underlying explanation for the Tinajas 6 site containing mostly generalist taxa (Billia hippocastanum, Dendropanax leptopodus) for

Lower Montane Rain Forest and Montane Cloud Forest is most likely a reflection of differences in sampling intensity.

Analysis of sites as a function of their watershed location indicates that the landscape position of sampling sites with respect to local relief (topography) may be another important element in explaining plant community composition in the Guatemalan lowlands. The Lachuá and Chinajá Lowland Rain Forest sites are more probably differentiated from their lowland counterpart, Tinajas, because the former sites are found in the Chixoy watershed and the latter in the Polochic watershed (Figure 2.1). These two watersheds are separated by steep highland mountains, the Sierra Chamá and the east portions of Sierra Yalijux. Steep mountain divides may be currently acting as physical barriers to species migrations between adjacent watersheds. Janzen (1967) was the first to recognize the ecological importance of steep elevational (climatic) gradients that tend to be more common in tropical mountain passes than they are in mountainous regions at higher latitudes (i.e. temperate and boreal regions).

DCA results indicate that longitudinal differentiation between western and eastern groups in the Lower Montane Rain Forest correlate in part to topographical differences (Figure

1.2) and according to national descriptive maps (i.e. topographic and climatic), they may also correlate to variations in temperature and precipitation (MAGA, 2004). The latter response could not be tested due to the limitations of my climatic database. In the western group, topography is influenced most by the narrow and higher elevation valleys at the

Cahabón watershed. In the eastern group, topography is characterized as wider and lower elevated valleys located in the Polochic Watershed. The HCA dendrogram indicates that although the Tamahú site is located in the eastern group, because of its geographical proximity to the border of the Cahabón watershed, its vegetation is more similar to the western group’s vegetation community than to that of the eastern group (i.e. an indication of spatial autocorrelation).

2.4.3 Paleogeography and current vegetation biogeography

Analyses of data also indicate a possible role for biogeographic origin in explaining vegetation distribution (Figure 2.4). Amazonian-centered taxa found in Central America occupy ecologically important niches as lowland forest dominants with wide-ranging distributions, and Andean-centered taxa dominate the humid foothills and mid-elevational ranges (Gentry, 1982). Laurasian taxa are important in ecological terms because they are dominant canopy members in montane forests, becoming more dominant as elevation increases (Hammel and Zamora, 1990). In southeastern Mexico, Laurasian taxa were found to increase with elevation, likely as a result of adaptations to climate-related

51 disturbances such as the risk of night frosts and desiccation arising from strong winds

(Quintana-Ascencio and González-Espinosa, 1993).

At this time, however, I believe it is premature to speculate on modern-day vegetation trends in the Las Verapaces region (e.g. Amazonian, Andean, and Laurasian) or in the rest of Guatemala arising from paleoclimate-forest dynamics. Glacial and inter-glacial cycles of the Pleistocene are known to cause mixing of lowland and highland plant taxa

(Hooghiemstra and Van der Hammen, 2004), as well as to create a deterrent (barrier) to vegetation migration between two points on the landscape (Terrab et al., 2008). Both mixing and separation of plant taxa during the Pleistocene could explain the present vegetation pattern found in the Las Verapaces elevational gradient (Figure 2.4). Studies on the population dynamics of Scarabaeoidea (dung beetles) in Guatemala have identified locations within montane cloud forests containing endemics that likely resulted from

Pleistocene paleoclimatology (Schuster, 2006). Because the delineation of Scarabaoidea communities as a function of elevation (Schuster et al., 2000) is very similar to my proposed vegetation belts, it makes the connection to Pleistocene dynamics all that more enticing. Strong similarities and redundancy between flora and fauna distributions are good indications of the importance of historical biogeographic processes in explaining modern-day species distributions (Jones and Kennedy, 2008)

The regional geological history of Guatemala as it relates to mountain building in North and South America may contribute to the explanation of why I have found a combination of plant taxa with different biogeographic origins occupying different ecological niches

(Figure 2.4). Laurasian taxa typical of high elevation locations, for example, are found in highland sites (Sauraia belisensis, Clethra suaveolens). For the most part, generalized vegetation patterns across Central America were laid down in the Miocene period, when

Nuclear Central America was known as Proto-Central America (Raven and Axelrod,

1974; Graham, 1999). Orogenic processes in eastern-southern Mexico and central- southern Guatemala (Padilla, 2007) likely promoted dispersion of Laurasian taxa throughout the newly originated Guatemalan highlands. Amazonian-centered taxa

(Spondias mombin, Tabebuia sp.) dispersed into lowland regions via "island hopping" over the Proto-Antillean Mountain Chain, both before and after the Pliocene closing of the Central American Land Bridge approximately 3 million years ago (My). The physical connection of Central America to South America also facilitated migration of Andean- centered taxa (Oreopanax liebmanii, Weinmannia pinnata) into the foothills and highlands in Guatemala where they currently dominate in the Montane Cloud Forest

(Table 2.3). Migration of Andean-centered taxa occurred sometime after Andean orogenesis, beginning around 5 My BP (Antonelli et al., 2009).

2.4.4 Conservation biology and disjunctive taxa

Montane cloud forests are quickly becoming the focus of international conservation as both their ecological and societal services are now being highly recognized (Vargas-

Rodríguez et al., 2010). Already, indications that cloud forests are experiencing change, whether due directly to humans via land-use change or indirectly through climate change, have been identified in India (Murugan et al., 2009), Mexico (Martínez et al., 2009) and

Central America (Colwell et al., 2008). Models predict that deforestation of lowland

53 rainforest causes a lowering of cloud base heights, in turn promoting reductions in atmospheric moisture in the upper reaches of cloud forest (Nair et al., 2003). From a conservation perspective, this study containing lists of plant species composition in

Guatemalan cloud forests will be important; as it is important to know what species are there now so to have a benchmark from which to ascertain potential species turnover in the future. The fact that some Montane Cloud Forest taxa have been observed at lower altitudes in Purulhá and Chelemhá indicate that Chinajá and Lachuá forests have unique habitat conditions (i.e. canopy microclimate) that have provided a critical refuge for cloud forest plant species.

Andean-centered forest taxa such as Clidemia capitellata (Melastomataceae), Conyza bonariensis (Asteraceae), and Dendropanax arboreus (Araliaceae) that are typically located in the montane cloud forests were also found in lowland rain forests, indicating an important link between both vegetation belts. Other taxa along our montane Chinajá site also include non-plant taxonomic groups such as dung beetles, birds and bats (Bonham,

2006). In some cases the disjunctive pattern that we observed in understory vegetation such as Lasiacis divaricata is more likely the result of insufficient sampling size due mostly to the fact that the forestry surveys were primarily focused on canopy tree species.

Some Amazon-centered plant taxa from the Lauraceae (e.g. Ocotea and Phoebe) family have extended their distribution from typical lowland habitats to high elevation conditions (Chanderbali et al., 2001). Mixing of species increases regional diversity (i.e. gamma diversity) as a response to the presence of multiple habitats (i.e. alpha and beta

54 diversity) each with unique physiographic and ecological features (Emmerson et al.,

2001).

2.5. Chapter summary

In this chapter three vegetation belts have been identified as expected and described in terms of changes in plant communities along elevation. Other factors were found to complementarily explain the relationship plant taxa-elevation, such as variability in climatic parameters (i.e. temperature related), watershed location and topography, and biogeographic origin. A list of 794 angiosperm plan taxa was generated based on the collation of a data base of local vegetation inventories in the Las Verapaces region. This list contains information about the elevation distribution of each taxon in different watersheds according to the location of the vegetation inventory.

Based on a Detrended Correspondence Analysis (DCA), plant taxa with unique scores along ordination Axis 1 were separated according to their distribution in elevation ranges that corresponded three vegetation belts: Lowland Rain Forest (170-1000 masl), Lower

Montane Rain Forest (1000-1800 masl), and Montane Cloud Forest (1800-2500 masl).

The selection of these plant taxa is useful in identifying indicators for each vegetation belt, or for generalists with a wider elevational distribution preference over no more two neighbouring vegetation belts (Tables 2.3 and 2.4).

The application of identifying the correspondence between vegetation belts and indicators and generalist taxa, is to know how to identify in calibration and paleoecological studies

55 the vegetation source of correspondent pollen taxa. Relating the prevalence of different biogeographic origins (Amazonian, Andean, and Laurasian) and plant taxa provides the linkage to understand the ecological characteristics of vegetation belts, which explains to great extent the pollen source area and representations of pollen spectra of a location (i.e. dispersion of pollen depends greatly on dispersal syndromes). In this sense Tables 2.3 and 2.4 are linked to Table 3.1.

Chapter 3: Modern pollen rain in the north-central Guatemalan lowlands and highlands

3.1 Introduction

The correlation of modern pollen rain to landscape features is an important first step in understanding the interpretation of paleoecological pollen signals at either local or regional scales. Defined mostly from Northern Hemisphere paleoecological studies, pollen observed in mid-sized to larger lakes represents mostly regional vegetation, whereas pollen in observed in small basins represents local vegetation. As landscapes become more open in character, the pollen signal from both smaller and larger basins becomes more similar (Conedera et al., 2006; Lynch, 1996; Prentice, 1985). Thus, basin size, range of pollen dispersal, and patterns of vegetation cover are factors that can influence the mix of pollen found at any one sampling location. Moreover, other factors such as topography, atmospheric conditions (i.e. prevailing wind circulation), sedimentation rates and mode of sediment transport (Brown et al., 2008; Bunting et al.,

2004) may also control the mix of accumulating pollen.

In temperate regions (i.e. mid-latitude) it has been found that pollen content from sediments of open basins has a more regional vegetation signal than a local signal, because the pollen source area allows more deposition of wind-dispersed pollen (Fægri

57 and Iversen, 1989). Higher proportions of local vegetation have has been found in pollen collected in forest interior surfaces, such as bryophyte polsters (i.e. moss polsters), where short-distance dispersed pollen (i.e. animal pollinated) is found in greater amounts. Pollen dispersal syndrome directly influences pollen source area and indirectly influences the way pollen grains are trapped in different habitats and reservoirs (Bush and Rivera,

1998). The probability that bryophyte polsters will trap airborne pollen is low relative to sediment samples from mid- and large-sized basins, where the effectiveness of vegetation barriers decreases as distance increases from the shoreline (Conedera et al., 2006; Fægri and Iversen, 1989; Lynch, 1996). Therefore, pollen content is different according to the pollen sources, and in this case pollen signal of bryophyte polsters may indicate which local pollen types are absent from surface sediments (Wilmshurst and McGlone, 2005).

This is of special interest for calibration because surface sediments represent the best analogue for samples collected from cores where fossil assemblages are extracted from and from where landscape evolution is inferred.

The over-arching objectives in conducting this research are two-fold: (1) To quantify the relationship between modern pollen rain and local-to-regional features of the natural landscape in two sites along a north-to-south elevational gradient (i.e. 170 to ~ 2000 masl) in the Las Verapaces region in Central Guatemala (Figure 3.1). The two sites are located at the Lachuá lowlands and Purulhá highlands, in the Lowland Rain Forest belt, and the Lower Montane Rain Forest-Montane Cloud Forest ecotone, respectively (see

Chapter 2). The Las Verapaces region was chosen because of its complex mosaic of biophysical settings (Avendaño et al., 2007, MAGA, 2001) and archaeological sites

Figure 3.1. Location of Guatemala in Central America. Las Verapaces Region is enclosed in rectangle. 1= Lachuá lowlands, 2= Purulhá highlands.

Gulf of Mexico 1

2 México Belize Guatemala

Honduras

Caribbean Sea El Salvador Nicaragua

Costa Rica Pacific Ocean Panama

(Dillon, 1977; Ichon et al., 1996). (2) To provide much-needed data for the Las

Verapaces region, an area that to date is under-explored in terms of modern pollen calibration and paleoecology relative to the number of studies focusing on the northern

Guatemalan lowlands (Binford and Leyden, 1987; Curtis et al., 1996; Hillesheim et al.,

2005; Wahl et al., 2007a). This study represents the second modern pollen rain calibration conducted in Guatemala and is one of the few studies in the Mesoamerica region across Southeast Mexico, Guatemala, Belize and Honduras. For these reasons, this study represents an important contribution for paleoecological study of tropical ecosystems in general.

Specifically, I address the following three research questions: (1) What are the differences between pollen spectra represented in bryophyte polsters and surface sediments? How does the first inform me about the latter? (2) Is the modern pollen rain in bryophyte polsters and surface sediments representative of local or regional vegetation?

(3) Which pollen taxa are reliable indicators of environmental conditions or vegetation zonation along the study gradient?

3.2 Methods

3.2.1 Bryophyte polster pollen sampling

Bryophyte polsters were collected in the interior of minimally-disturbed forest habitats, located far enough inside the forest (more than 250 m) to avoid “edge-effects” (Bush and

Rivera, 1998). Bryophyte polster samples from Lachuá lowlands (hereafter just Lachuá)

60 were taken every 50 m along a 200 m transect in two locations in the interior of forests

(n=10) (elevation ~170 masl) (interior of LLNP) (Figure 1.3). Bryophyte polsters samples from Purulhá highlands (hereafter just Purulhá) were collected along a 2 km transect (10 samples spaced 200 m apart) (elevation ~1700-1800 masl) (interior of

BUCQ) (Figure 1.3). A bryophyte polster sample comprised of the amalgamation of bryophytes cushions found in a 5 m radius, were stored and labeled in plastic Ziploc bags.

3.2.2 Surface sediment pollen sampling

Surface sediments samples of 1.0 cm in length were extracted from cores taken using a

Livingstone corer and stored in plastic Ziploc bags. Lachuá samples are from Lachuá

Lake and Tortugas Ponds; and Purulhá samples from Chichoj Lake and the Cahabón

River Floodplain. Surface sediments from Lachuá samples were collected in three locations (L1, L2 and L3) near the Lachuá lakeshore because the ideal location (lake centre) was too deep to core (200 m) (Figure 1.3). I chose sites that were located away from stream inflow and outflows to minimize disturbance of sediments. Sample L1 was located approximately 2-3 m from the shore, sample L2 approximately 20 m from the shore, and sample L3 was located in a lakeside wetland. Approximately 5 km northeast from Lachuá Lake one extra core was sampled from the Tortugas Ponds shore at Salinas de los Nueve Cerros Regional Park (sample Sa2). The pond is about 200 m in diameter and is completely surrounded by high canopy (40 m) lowland rainforest (Cajas, 2009).

Surface sediments from the Purulhá were sampled in several Fincas (Villa Trinidad,

Patal, and Chisiguan) along the floodplains (600 m to 1 km wide) of the headwaters of

61 the Cahabón River (elevation range 1450-1560 masl), close to the towns of Purulhá

(samples P1 and P4) and Tactic (sample T1) (Figure 1.3). Another sample was taken from a marsh adjacent to the heavily-polluted Lake Chichoj (sample J1) (47.6 ha) near the town of Santa Cruz Verapaz (elevation 1390 masl) (Sánchez, 1994). As much caution as possible was taken in choosing samples from locations where disturbance from incoming rivers, landslides, or human activities was at a minimum.

3.2.3 Identification of pollen source areas

Pollen source area is considered "local" when the plant is reported in the local vegetation inventory, "regional" when the vegetation source is located in a neighboring elevational vegetation belt, and is considered “extra-regional” when the plant is separated more than one vegetation belt (Chapter 2). Since I do not have modern pollen rain samples from the Lower Montane Rain Forest (intermediate vegetation belt between Lachuá and

Purulhá), Lachuá pollen is regional when found in Purulhá because in terms of pollen signal I considered Lowland Rain Forest and Lower Montane Rain Forest closely related, an assumption based on Domínguez-Vázquez et al. (2004) (See Chapter 2 for definition of vegetation belts). Due to their biogeographical affinity, arboreal pollen taxa from

Lachuá are named tropical and from Purulhá they are considered temperate. In the case of

Abies and Alnus, I consider them extra-regional for Lachuá because their plant stands are found two vegetational zones higher, but for Purulhá they are regional. In the case of the widely distributed Pinus, it is an indicator of highland temperate vegetation, independent of its lowland populations (P. caribea). In order to create Table 3.1, identified pollen types corresponding to plant taxa listed in Tables 2.3 and 2.4 were automatically

62 assigned to one or two vegetation belts. When pollen types (i.e. genus) are not found in the latter tables, their allocation to lowlands or highlands vegetation, or a vegetation belt not covered in the Las Verapaces (i.e. due to its location in higher elevation) was based on revision of Latin American pollen and vegetation literature (Gentry 1982, Marchant,

2002; Domínguez -Vázquez et al. 2004).

3.2.4 Modern pollen laboratory work

Samples for pollen analysis were processed under standardized acetolysis procedures to remove organic matter and cellulose, as well as to concentrate pollen grains (Fægri and

Iversen, 1989). Pollen counting was completed on a 200 grain per sample basis when possible, of which at least 100 pollen grains were from arboreal taxa. Pollen concentration was calculated based on the addition of exotic Lycopodium clavatum spore tablets. A total of ten bryophyte polsters and four surface sediments samples were counted in each of Lachuá and Purulhá making a total of twenty (20) bryophyte polsters and eight (8) surface sediment samples.

Pollen grain identification was done using regional and local pollen reference collections obtained from Colombia (Hooghiemstra, 1984), Barro Colorado Island in Panama

(Roubik and Moreno, 1991), Lachuá (Barrientos, 2006) and generally for the Neotropics

(Bush and Weng, 2007). Pollen identification was aided by the Pollen Reference

Collection from the Neotropical Research Unit from the Department of Geography,

University of Leicester, England. Fixed slides were stored in the reference collection at

63 the Paleoecology Laboratory of the Department of Geography at the University of

Toronto (Canada).

3.2.5 Modern pollen rain statistical calibration

The pollen sum included arboreal and non-arboreal taxa, which were identified to family and genus level. Unknowns, spores and aquatics (e.g. Cyperaceae) were not included in the pollen sum (Fægri and Iversen, 1989) and their abundance was measured as a ratio in relation to the total pollen sum calculated per sample. Arboreal pollen (AP) and non- arboreal pollen (NAP) percentages were calculated per site and pollen reservoir

(bryophyte polster and surface sediment) to represent local landscape vegetation cover.

Additionally, for each sample the contribution of pollen provenance (i.e. local or regional) and pollen dispersal syndrome were identified. Dispersal syndrome included the following: (1) zoophilous (animal dispersed), (2) anemophilous (wind dispersed), and (3) ambiphilous (combination of both).

For local analysis at each site, species abundance matrices were built to compare bryophyte polsters and surface sediments. In contrast, for regional analysis a common matrix based on shared taxa between sites was built. Detrended correspondence analysis

(DCA) was used to visualize samples according to similarity of their pollen assemblages and their probable arrangement as a function of environmental gradients (Jongman et al.,

1995). Analysis was complemented with a factor analysis (FA) using Varimax rotation in order to isolate pollen types (factors) that explain the largest amount of variance (with minimal loss of information) (May, 1974). The pollen type’s scores over FA gradients

(named "factors") complemented the explanation of gradients found in DCA axes.

Summary pollen diagrams were plotted based on local and regional analyses. PC-Ord

(McCune and Mefford, 2006) and PAST (Hammer et al., 2001) were statistical packages used for multivariate analysis, and C2 (Juggins, 2003) for building pollen diagrams.

Information on pollen dispersal syndrome per taxon was derived from local vegetation studies (Ávila, 2004; Cajas, 2009; García, 1998).

3.3 Results

56 pollen types were identified at least to family and genus taxonomic level at the Las

Verapaces region (Table 3.1). Pollen types were compared to information presented in

Tables 2.2 and 2.3 in order to link them to corresponding vegetation belt(s). Plant indicator taxa (Table 2.2) correspond to one vegetation belt because of their specificity, while generalist taxa correspond to two belts (Table 2.3). Based on criteria found in bibliographic revisions of Latin American pollen studies, some pollen types were interpreted to represent in general “lowlands” (i.e. Sapotaceae) or “highlands” (i.e.

Urticaceae) vegetation, when they represented more vegetation belts (i.e. Lowland Humid

Forest, see Table 2.1) that the ones covered in the Las Verapaces region vegetation chapter (Chapter 2), or in the case that the pollen type had a wide altitudinal range distribution either in lowlands (i.e. Celtis) or highlands (i.e. Pinus). Pollen types from vegetation belts not found in the Las Verapaces region were collected (see Table 2.1), such as Abies from Montane Mixed Forest, and Alnus from Montane Mixed Forest and

Subalpine Forest belt.

Lachuá species richness is higher than Purulhá (45 pollen types versus 31), with a total of

20 pollen types shared between sites (Figure 3.2). Bryophyte polsters contain higher arboreal pollen (AP) type richness than surface sediments at both locations.

3.3.1 Lachuá modern pollen spectra

AP content is dominant in both bryophyte polsters and surface sediments at Lachuá, and with few exceptions, consists of mostly local provenance and zoophilous taxa (Figure 3.3 and Table 3.2). Once the over-represented Pinus is removed from the AP data matrix, the

DCA diagram shows a general separation between bryophyte polsters and surface sediments along Axis 1, with the exception of surface sediment sample Sa2 which is separated along Axis 2 (Figure 3.4). Sa2 is segregated from other surface sediment samples because its pollen content has the highest abundances of local taxa (Bursera,

Psychotria, Spondias, and Trema) and has the only record of Inga for surface sediments.

Surface sediments are dominated by the local entomophilous Celtis and highland anemophilous Pinus. Sample L2 has the higher abundances of the temperate highland anemophilous Abies and Myrica, and is the only sample that contains local entomophilous Mimosa. Surface sediments at L3 have the highest abundance of Ilex

(highland zoophilous taxon) and some local entomophilous taxa such as Myrtaceae,

Sapium, Solanaceae and Terminalia. The pollen assemblage in sample L1 is a mix of taxa found at sites L2 and L3.

The dominant taxa in bryophyte polsters are the local entomophilous Solanaceae and highland Pinus. Many local entomophilous taxa (e.g. Bombacaceae) are only found in

66 bryophyte polsters (although poorly represented at ~1%). Various local entomophilous

(Brosimum and Terminalia), local anemophilous (Alchornea) and anemophilous temperate (Alnus, Pinus, and Quercus) taxa have a wide representation across both pollen reservoirs.

Asteraceae is similarly distributed in bryophyte polsters and surface sediments; Poaceae is more abundant in the former, and Zea is poorly represented in both (~1%) (Figure

3.3). Trilete spores are consistently more abundant in bryophyte polsters, while monolete spores (with the exception of sample L3) and aquatic pollen are similarly represented across both pollen reservoirs.

3.3.2 Purulhá modern pollen spectra

The AP fraction is higher than non-arboreal pollen (NAP) in bryophyte polsters, and local and anemophilous pollen fractions are higher than regional and zoophilous in both bryophyte polsters and surface sediments (Table 3.3). Local anemophilous Hedyosmum and Quercus are the most abundant AP taxa and are highly represented in bryophyte polsters (Figure 3.5). With respect to AP and NAP combinations, DCA analysis shows a separation between bryophyte polsters and surface sediments along Axis 1 (Figure 3.6).

Some regional taxa are represented in both pollen reservoirs (e.g. highland Alnus, and lowland Celtis). Local (Ilex) and lowland taxa (Alchornea and Myrsinaceae) are found only in bryophyte polsters relative to surface sediments. Temperate taxa abundances, such as Abies, Pinus and the local Myrica, are similar in representation between bryophyte polsters and surface sediments. Sample N4 presents the highest abundance of

Cecropia. Most of lowland taxa (in particular, those with entomophilous dispersal syndrome) were poorly represented in both polsters and surface samples in highlands.

Poaceae is the most abundant NAP type and is more abundantly represented in surface sediments, while Asteraceae (second most abundant NAP type) is similarly represented in both pollen reservoirs. Surface sediment sample P4 is the only sample where the disturbance-related taxon, Alternanthera, is found. Trilete spores are more abundant in bryophyte polsters, while monolete spores and aquatic pollen types are dominant in surface sediments.

3.3.3 Las Verapaces regional modern pollen spectra

Fifteen AP and five NAP taxa are common in both Lachuá and Purulhá (Figure 3.2), with most of these taxa having their highest relative abundance either where plant stands are reported from local inventories, or according to their elevational range of distribution

(Table 3.1). When analyzing shared AP-types, there is a clear separation along DCA

Axis 1 between the bryophyte polsters of Lachuá and Purulhá. Surface sediments are located in the middle of Axis 1 (with some separation along Axis 2) and slightly separated according to their location (Figure 3.7). The exception to this includes samples

L1, Sa2, and P4 surface sediments that are placed closer to their polster counterparts.

Lachuá surface sediment (L3) and Purulhá bryophyte polster (N8) are isolated on Axis 2 because they have the highest values of Ilex, which is neither found in bryophyte polsters at Lachuá or surface sediments at Purulhá. When surface sediments samples are compared at both Lachuá and Purulhá, there is a clear segregation between lowlands and

Table 3.1. Pollen types and their % range in abundance for bryophyte polsters (BP) and surface sediments (SS). Information about vegetation belt, plant habit, pollen dispersal syndrome (DS), and biogeographic origin (Biogeo) is provided, partially based on Table 2.2 and 2.3 (Chapter 2). Z= Zoophilous, W= anemophilous, A= Ambophilous (Z and W). L-BP to H-SS include percent pollen abundances. L= Lachuá lowlands, H=Purulhá highlands. Plant habit codes: T=Tree, S=Shrub, H=Herb. Vegetation belt codes (see Table 2.1): LRF= Lowland Rain Forest, LMRF= Lower Montane Rain Forest, MCF= Montane Cloud Forest, MMF= Montane Mixed Forest, SAF= Sub-Alpine Forest, *= Undefined vegetation belt, ?= Unassigned origin.

Pollen taxa

Genus Family Vegetation belt Habit DS Biogeo L-BP L-SS H-BP H-SS

Acacia Fabaceae Lowlands T-S Z AMZ 2.70 1.61 Alchornea Euphorbiaceae Lowlands T W AMZ 0.8-8.5 1.6-2.6 0.5-2.1 Anthurium Araceae Lowlands H Z AN 10.80 Araliaceae Lowlands S Z AN 0.9 1.60 Arecaceae Lowlands S Z AMZ 1.1-10.9 0.9-3.22 Bignoniaceae Lowlands T Z AMZ 0.8-1.8 Bombacaceae Lowlands T Z AMZ 0.7-1.6 Boraginaceae Lowlands S Z LAU 0.80 Brosimum Moraceae Lowlands T Z AMZ 5.2-20 1.6-4.2 0.6-3.6 Celtis Ulmaceae Lowlands T Z LAU 1.5-20.1 1.6-14.4 0.5-3.1 0.90 Combretaceae/Melastomataceae Lowlands T Z AMZ/AN 0.8-9.1 0.8-1.6 Euphorbiaceae Lowlands T A AMZ 0.9-1.6 1.2-2.6 Fabaceae Lowlands T Z AMZ 1.8-8.1 0.80 Mimosa Fabaceae Lowlands T Z AMZ 0.60 Malpighiaceae Lowlands T-S Z AMZ 1.42 Moraceae Lowlands T W AMZ 1.8-12.1 0.90 0.7-1.1 Myrsinaceae Lowlands T W AN 0.5-6.6

Table 3.1 continued.

Pollen taxa

Genus Family Vegetation belt Habit DS Biogeo L-BP L-SS H-BP H-SS

Myrtaceae Lowlands T Z AN 1.10 4.80 Pachira Bombacaceae Lowlands T Z AMZ 0.8-1.5 Piper Piperaceae Lowlands S Z AMZ 0.9-4.2 0.8-5.3 Psychotria Rubiaceae Lowlands S Z AN 1.1-4.1 4.8-16.7 Rubiaceae Lowlands S Z AN 0.8-6 0.80 1.60 Salvia Lamiaceae Lowlands T-S Z LAU 2.70 Sapium Euphorbiaceae Lowlands T Z AMZ 0.8-0.9 6.50 Sapotaceae Lowlands T Z AMZ 0.8-16.4 0.6-1.7 Solanaceae Lowlands T-S Z AN 0.8-24.1 0.6-9.7 Trema Ulmaceae Lowlands T Z LAU 0.9-3.6 15.80 Ulmaceae Lowlands T W LAU 0.9 Verbenaceae Lowlands H Z ? 0.8-2.3 1.3-6.5

Spondias Anacardiaceae LRF T Z AMZ 0.7-2.3 6.10

Bursera Burseraceae LRF-LMRF T Z AMZ 0.9-3.3 11.40 0.9-1.3 Cecropia Cecropiaceae LRF-LMRF T W AMZ 0.9-8.1 2.50 0.5-56.4 Terminalia Combretaceae LRF-LMRF T Z AMZ 2.7-16.4 0.6-9.7 0.5-1.5 0.70

Table 3.1. continued.

Pollen taxa Genus Family Vegetation belt H DS Biogeo L-BP L-SS H-BP H-SS

Inga Fabaceae LMRF T Z AMZ 0.7-3.4 2.60

Hedyosmum Chloranthaceae LMRF-MCF T W LAU 0.8-1.8 0.80 3.3-31.3 1.2-5.9 Myrica Myricaceae LMRF-MCF S W LAU 0.8-4.1 2.6-42 0.9-10 1.9-6.1 10.3- LMRF-MCF Quercus Fagaceae T W LAU 0.7-8.1 0.8-2.6 60.9 3.1-16.7

Abies Pinaceae MMF T W LAU 0.8-1.5 3.4-9.6 0.7-7 1.2-8.5

Alnus Betulaceae MMF-SAF T W LAU 1.7-9.9 0.6-4.2 0.8-2.2 1.2-1.3

Ericaceae Highlands S W AN 1.7-4.2 Conifer6 Pinaceae Highlands T W LAU 0.8 Pinales Pinaceae Highlands T W LAU 0.7-3.6 0.7 Pinus Pinaceae Highlands T W LAU 9-35.1 1.6-46.6 2.2-16.6 3.7-14.8 Urticaceae Highlands H W AN 2.20

Table 3.1 continued.

Pollen taxa

Genus Family Vegetation belt H DS Biogeo L-BP L-SS H-BP H-SS

Alternanthera Amaranthaceae * H Z ? 0.8-3.2 4.90 Amaranthaceae/Chenopodiaceae * H Z ? 0.9-1.7 0.80 0.5-0.9 0.6-1.3 Asteraceae * H Z AN 1.6-6.9 0.6-4.8 0.8-20.3 11.8-15.9 70.1- * Cyperaceae H AMZ 1.4-7.6 0.8-4.8 0.6-5.1 140.3 Peperomia Piperaceae * H Z AMZ 0.9-3.3 1.7-1.8 Piperaceae * S Z AMZ 0.6-2.6 0.7-0.9 Poaceae * H W ? 1.6-6.5 0.8-1.6 0.9-41.6 14.7-65.6 Polygonum Polygonaceae * H Z ? 1.4-24.5 Zea Poaceae * H W AMZ 0.8-0.9 1.70 0.5-0.9 0.7-1.9 56.1- 18.9- 80.9- * Trilete spores H ? 96.3 89.2 94.9 14.5-45.5 10.8- * Monolete spores H ? 3.7-43.9 81.1 5.1-19 54.5-85.5

Figure 3.2. Pollen diagram from Lachuá and Purulhá based on bryophyte polster (BP) and surface sediment (SS) samples. Ca to Rd Lachuá BP, and Sa2 to L3 Lachuá SS. P1 to J1 Purulhá SS, and N1 to N10 Purulhá BP. + = rare taxa appearing at <1%. AP=Arboreal pollen, FA1=Factor Analysis first component.

Tropical trees and shrubs Temperate trees and shrubs

e ea a rn ra ce smum o ia yo s rse rminalia d ie lch u b A Brosimum B Cecropia Celtis Moraceae Rub Te He Ilex Myrica Quercus A Alnus Pinus AP FA1

Ca Cb Cc Ce Cd BP Lachua Ra Rb Rc Re Rd Sa2 L1 L2 SS Lachua L3 P1 P4 T1 SS Purulha J1 N1 N2 N3 N4 N5 N6 BP Purulha N7 N8 N9 N10

0 0200200204060020 0200 02002040020 02040 0204060 0 0 0204012 36 60 84 108-0.2 0.2 0.5 0.8 1.1 Percent pollen abundance

Figure 3.2. Continued. NAP=Non-arboreal pollen, FA1=Factor Analysis first component.

Herbs Pteridophytes

e cm3) ns/ diacea po 0 grai 0 0 Cheno (x1 / e ion rat era h acea ae cent th e nt n c ae a e raceae con rn e ara era p len 1 lte m oac A A A Ast P Zea Trilete Monolete Cy Pol NAP F

Ca Cb Cc Ce Cd BP Lachua Ra Rb Rc Re Rd Sa2 L1 L2 SS Lachua L3 P1 P4 T1 SS Purulha J1 N1 N2 N3 N4 N5 N6 BP Purulha N7 N8 N9 N10

0 0 020 0204060 0 0204060 02040 03060901201500 120 240 360 480 600 0306090-0.2 0.2 0.5 0.8 1.1 Percent pollen/spore abundance

Figure 3.3. Lachuá pollen diagram based on bryophyte polster (BP) and surface sediment (SS) samples. + = rare taxa appearing at <1%.

Tropical trees and shrubs Temperate trees and shrubs

e ea nus) c ia ia i a r 6 ac naceaeum etaceae / Melastomataceae a aceae as (-P m br ighiaceae r m a er cus 1 liaceae agi sera anaceae minal if r es cacialchorneara recaceaeignoniaceaeomb or rosi ur om abaceae ol oraceaeyrtaceaeachi sychot alvia apiu apot pondier rem on yrica ue bi lnus P CA A A A A B B B B B CecropiaCeltis C F Inga S MalpMimosaM M P P RubiaceaeRubiaceae 1 S 2 S S S T T C HedyosmumEricaceaeIlex M Q A A Pinus A DCA 1 D

Ca Cb Cc Ce

Cd BP Ra Rb Rc Re Rd Sa2 L1 L2 SS L3

0 0 0 0200 0 0 0200200 0200 0 0 020400 0 0200 0 0200 0200 0 0200 0200200 0 0 020020400 0 0 020400 20406080100-1.0 0.0 1.0 2.0 3.00.0 1.0 2.0 3.0

Percent abundance

Figure 3.3. Continued. AP=Arboreal pollen, NAP=Non-arboreal pollen, DCA1= Detrended Correspondence Analysis first axis. Herbs Pteridophytes

ins/cm ra g

ration (x1000 cent en e te n h a naceae nanthera r e e e co r a/C c t n thurium teraceae a le lle lte m n s ipe o erb yperaceaei o AP A A A A PeperomiaP P V Zea C Tr Monole P N

Ca Cb

Cc Ce Cd BP Ra Rb Rc Re

Rd Sa2 L1

L2 SS L3

0 0 0200 0 0 0 0 0 0 02040020400 1632486480048121620 Percent abundance

Table 3.2. Lachuá bryophyte polsters (Ca-Re) and surface sediments (Sa2-L3) samples. Local and highlands (regional and extra-regional) refers to percentages of arboreal pollen (AP) spectra. NAP= Non-arboreal pollen, Z= Zoophilous, W=Anemophilous.

Samples AP NAP Local Highlands Z W

Ca 81 19 78 22 72 28 Cb 100 0 84 16 78 22 Cc 88 12 86 14 84 16 Cd 96 4 72 28 68 32 Ce 86 14 75 25 59 41 Ra 94 6 77 23 68 32 Rb 93 7 42 58 30 70 Rc 90 10 59 41 50 50

Rd 90 10 74 26 67 33 Re 89 11 52 48 30 70 Sa2 92 8 85 15 66 34 L1 91 9 38 62 34 66 L2 98 2 56 44 56 44

L3 87 13 74 26 70 30

Table 3.3. Purulhá bryophyte polsters (N1-N10) and surface sediments (P1-J1) samples. Local, lowlands, and highlands refers to percentages of arboreal pollen (AP) spectra. NAP= Non-arboreal pollen, A=Ambophilous, Z= Zoophilous, W=Anemophilous.

Sample AP NAP Local Lowlands Highlands A W Z

N1 79 21 83 10 7 4 90 7 N2 65 35 82 5 12 1 95 4 N3 86 14 67 25 7 18 77 5 N4 88 12 92 5 3 1 98 1 N5 77 23 75 22 4 15 84 1 N6 49 51 78 14 8 11 84 6 N7 62 38 71 19 10 8 86 5 N8 69 31 82 14 3 2 66 32 N9 83 17 89 5 6 2 95 3 N10946908 2 0946 P1 26 74 55 15 30 10 85 5 P4 41 59 86 5 10 0 95 5 T1 18 82 79 7 14 7 93 0 J1 38 62 72 6 22 4 94 2

Figure 3.4. Lachuá DCA Q-mode ordination diagrams of AP data with Pinus removal. (+) represent bryophyte polsters, and diamonds surface sediments.

Figure 3.5. Purulhá pollen diagram based on bryophyte polster (BP) and surface sediment (SS) samples. + = rare taxa appearing at <1%.

Temperate trees and shrubs Tropical trees and shrubs

ae e ce a e e e cea rbia smum um a alia o ceae rn ra pia n cea in yo ica o o si ia us ales se rm uercus tica n n lch rosim yr e Euph Hed Ilex Myr Q Ur Pi Pi Abies Alnus A B Bur Cecr Celtis MoraceaM Rub T UlmaceaeAP DCA1

N1 N2 N3 N4

N5 BP N6 N7

N8 N9 N10 P1 P4

T1 SS J1

020020400200 0 2040600 0200 0 0 0 0 0 02040600 0 0 0 0 0 16 32 48 64 80 96 0 100 200 300 Percent abundance

Figure 3.5. Continued. AP=Arboreal pollen, NAP=Non-arboreal pollen, DCA1= Detrended Correspondence Analysis first axis.

Herbs Aquatics Pteridophytes

e s/cm3) n cea a podi no (x1000 grai he C tration eae / n c ae eae? e c te conce a ac ceae gonum er ole arantha a y p lete iper ol y ri Am Asteraceae P Poa Ze P C T Mon Pollen NAP

N1 N2 N3 N4

N5 BP N6 N7 N8 N9 N10 P1 P4 T1 SS J1

0 0200 02040600 0200 30 60 90 120 150 0204060020400 120 240 360 480 600 0 306090

Percent abundance

Figure 3.6. Purulhá DCA Q-mode ordination diagrams based on AP and NAP data. (+) represent bryophyte polsters, and diamonds surface sediments

81 and highlands pollen along DCA Axis 1.

At Lachuá, temperate Alnus and Pinus have high abundances in both pollen reservoirs.

Abies is similarly represented in surface sediments from Lachuá and Purulhá, and in bryophyte polsters at Purulhá (Table 3.1). Highland taxa, Quercus and Hedyosmum, are abundant in both bryophyte polsters and surface sediments at Purulhá. Pollen taxon

Myrica has similar abundances in Lachuá and Purulhá (both polsters and surface sediments), with the exception of L2 where Myrica reaches its highest representation.

Cecropia plant stands are found in both Lachuá and Purulhá (i.e. indicator species for disturbance-edge effects) and Cecropia pollen is over-represented in one sample of bryophyte polsters at Purulhá.

Asteraceae and Poaceae taxa have their highest abundances at Purulhá. Poaceae pollen is more abundant in surface sediments than in bryophyte polsters. At both Lachuá and

Purulhá, Amaranthaceae/Chenopodiaceae and Zea are rare (Table 3.1). Alternanthera has similarly low abundances in Lachuá and Purulhá surface sediments. Trilete spores are generally more abundant in bryophyte polsters of Lachuá and Purulhá like in surface sediment samples of Lachuá. In contrast, monolete spores have their highest abundance in Purulhá surface sediments. Aquatics (i.e. Cyperaceae) are likely over-represented relative to the pollen types included in the pollen sum in surface sediments from Purulhá.

Results of factor analysis indicate pollen types that explain the maximum amount of variance along positive and negative trends of the ordination gradients (Table 3.4). For

Lachuá, the variance in positive trend is explained by Pinus and Myrica; with the negative variance trend explained by Solanaceae and Sapotaceae. The trend represented by these groups of pollen taxa, correspond most likely the pollen source area, the former highlands and the latter lowlands. Once Pinus (over-represented) is removed, the following other pollen types explain the variation: (1) Celtis, Brosimum, Terminalia and

Sapotaceae along a positive trend, and (2) Ilex and Trema explains the negative trend. For

Purulhá, the main explanatory taxa are the following: Quercus and Ilex in a positive trend, and Euphorbiaceae and Abies in a negative trend. These two trends in Purulhá may indicate small scale gradients, because apparently they do not reveal an environmental gradient between forest interior (e.g. bryophyte polster) and open landscape (i.e. surface sediment). The main taxa for both Lachuá and Purulhá correspond to the lowlands to highlands environmental gradient: Quercus, Hedyosmum, Asteraceae, and Cecropia along a positive trend, and Celtis and Brosimum along a negative trend.

Figure 3.7. Las Verapaces DCA Q-mode diagram AP shared data. Lachuá surface sediments are indicated by circles, and bryophyte polster samples are enclosed by the continuous line polygon. Purulhá surface sediments are indicated by discontinuous line squares, and bryophyte polster samples are enclosed by the discontinuous line polygon. See tables 3.2. and 3.3 for codes.

Table 3.4. Factor Analysis scores for pollen types with highest amount of variance. + or – indicates direction of magnitude along factors.

Location Taxon Factor 1 Factor 2 Factor 3

Lachuá Brosimum +2.4 Celtis +4.6 Terminalia +1.6 Sapotaceae +1.3 Solanaceae -5.7 Poaceae +6.9 Asteraceae +1.6

Purulhá Quercus +4.3 Ilex +1.0 Euphorbiaceae -0.6 Abies -0.4 Myrica -2 Pinus -3.3 Cecropia +4.4

Las Quercus +5.4 Verapaces Hedyosmum +4.1 Cecropia +1.1 Asteraceae +1.4 Pinus +6.0 Celtis +2.1 Brosimum +1.9 Ilex -1.0 Poaceae +6.9 Asteraceae +1.6 Hedyosmum -0.7

3.4 Discussion

3.4.1 Relevance of dispersal syndrome for pollen assemblages in bryophyte polsters and surface sediment

Taxonomic content, which in turn is tightly correlated with dispersal syndrome and pollen source area, contributes in differentiating bryophyte polsters and surface sediments at both Lachuá and Purulhá (Tables 3.2 and 3.3). Because local plant taxa in Purulhá are mostly temperate and therefore anemophilous (i.e. rich pollen producers), AP spectra are almost entirely local. In an analysis of modern pollen rain where moss polsters were collected in the same sites where vegetation cover was recorded using a Braun-Blanquet scale in the Guatemalan western highlands (2800-3800 masl) and Volcanic Chain (3000-

4000 masl) (Islebe and Hooghiemstra, 1995), pollen spectra showed widespread overrepresentation of anemophilous taxa (e.g. Pinus, Alnus, and Quercus). The explanation is because at these elevations, anemophily is the dominant pollen dispersal syndrome.

Lachuá's AP spectra are more representative of local tropical provinces that contain more zoophilous plant taxa (i.e. poor pollen producers). Islebe and Hooghiemstra (1995) found that in spite that zoophilous pollen taxon poor abundance could under-estimate the local abundance of the plant, their presence correspond well with the elevational vegetation zone associated with the plant itself (e.g. Buddleja pollen found only in the subalpine forest belt at 3400-4000 masl). This is probably because short-distance pollen dispersal results in more accurate representation of local vegetation. Pollen taxa from highlands still contribute in a major way to Lachuá pollen spectra, because highlands pollen is largely more adapted for airbone dispersion than lowlands pollen. On the other hand,

86 representation of lowlands pollen taxa in highlands is minimal because of the poor abilities of lowlands pollen for long-distance dispersal.

Regional analysis of Lachuá data indicates that bryophyte polsters and sediment samples,

L1 (close to lakeshore) and Sa2 (small basin), are similar in that they share at least some percentage of local pollen (Figure 3.4). In general, pollen trapped in bryophyte polsters travels shorter distances from within the surrounding forest (Fægri and Iversen, 1989), and to a much lesser extent, traps pollen that is airborne (i.e. transported great distances) or is the consequence of wind friction created by forest canopy gaps. Sediment sample

Sa2, was collected from a small basin surrounded by high canopy forest; therefore its similarity in pollen signal to bryophyte polsters is not surprising because the surrounding high canopy forest likely acted as a barrier to long-distance dispersal. Despite this, Sa2 shows partial separation from bryophyte polsters when the full AP spectrum is analyzed

(Figure 3.4). Lachuá vegetation analysis shows that the "landscape unit" (i.e. homogeneous biological and geomorphological area) where Sa2 is located (Salinas de los

Nueve Cerros) is different due to its unusual hilly topography within the generally flat landscape of Lachuá. Landscape topography has been shown to influence composition of vegetation communities (Cajas, 2009) and therefore to influence pollen source.

Even though surface sediments samples were not collected from the exact center of the

Lachuá Lake (i.e. ideal sampling location), their long-distance dispersed AP content is sufficient to produce a typical highland signal (15-62%). Local analysis of Lachuá shows a clear separation of both pollen reservoirs once the over-represented Pinus is removed

(Figure 3.4). As with many regions world-wide, Pinus is notorious for overshadowing signals from local pollen taxa (for discussion about Pinus pollen see section 3.4.5).

Because Purulhá’s surface sediments were collected in mid-sized basins located in deforested landscapes, pollen spectra would be expected to have a major regional pollen content (Sugita et al., 1999). Nevertheless, because zoophilous pollen dispersal syndrome dominates, Purulhá’s regional component from the lowland is minimal (zoophilous; 5-

15%) and mostly local (anemophilous; 55-86%) (Table 3.2). The higher content of lowlands pollen in bryophyte polsters in comparison to surface sediments could be explained in terms of differential preservation. Forest interior conditions where bryophyte polsters are found allow for better preservation of pollen (i.e. less dessication under a canopy cover) (Vermoere et al., 2000). Surface sediments from the small basin Chichoj

Lake and Cahabón river floodplain correspond to lentic (still water ecosystem) and lotic

(flowing water ecosystem) environments, respectively (Brown et al., 2007), yet surprisingly their pollen spectra shows a degree of similarity (Figure 3.6). The similarity in pollen collection in lentic and lotic environments is likely due to the energy environments in which the sediments were deposited (i.e. both are low energy floodplains). In addition, their location within a deforested landscape results in overall low AP values.

3.4.2 Influence of land-use change on pollen source

Deforestation rates are currently high in Purulhá highlands, thus the expected high AP sediment signal in basins and lakes surrounded by forest is not possible to be assessed

(e.g. no forest surrounds any possible sediment reservoir candidate for paleoecological research). Despite this limitation, forested conditions should be identified if pollen spectra from sedimentary records are similar to modern pollen spectra from bryophyte polsters (i.e. high AP values). Other studies in tropical highlands with other types of reservoirs have differentiated between forest, grasslands, and open spaces based on different pollen spectra and associated forest taxa contribution (Kennedy et al., 2005;

Olivera et al., 2009).

From Quintana Roo in Mexico, Islebe et al. (2001) analyzed pollen rain from moss polsters along a disturbance gradient which included lowland forest, disturbed forest, and secondary vegetation. The pollen data provided a clear signal for the three vegetation types because they cover large areas in the region, and a list of 15 indicator taxa was selected based on their overall good representation in the pollen spectra. In contrast, bryophyte polsters and surface sediments from Lachuá reflect the local forested condition because of their high AP values (14,500 ha of forest on Lachuá Lake National Park), which is similar to other lowland pollen analyses in the tropics where forest cover conditions are similar (Behling and Negrelle, 2006; Batthacharya et al. 2011). In contrast,

Dominguez-Vásquez et al. (2004) found a dominant allochtonous (i.e. anemophilous) signal in the Lacandon Lowland Rain Forest in Chiapas, Mexico. A greater allochtonous contribution in the Lacandon lowlands pollen spectra may be a response to higher deforestation rates, because as openness increases in landscapes long-distance dispersed pollen input increases (Lynch, 1996; Gaillard et al., 2008; Hellman et al., 2009), which in the case of lowlands scenarios correspond to highlands anemophilous pollen taxa.

3.4.3 Tropical and extra-tropical generalities

The present study and others (Bush and Rivera, 1998; Bush and Rivera, 1991) indicate that it is not possible to generalize pollen differences in bryophyte polsters from surface sediments in tropical regions like it is done for northern temperate and boreal latitudes

(Bush, 1995). In extra-tropical climates of the Northern Hemisphere, generalizations concerning the primary presence of short-distance dispersed pollen in bryophyte polsters and long-distance dispersed pollen in surface sediments are acceptable (Fægri and

Iversen, 1989). Tropical environments are completely different because dispersal syndrome is more important than basin-size generalizations in long- and short-distance dispersal. In tropical lowland environments, for example, short-distance dispersed pollen refers mainly to zoophilous taxa, whereas long-distance dispersed pollen mainly to anemophilous pollen. In contrast, in tropical highland environments short-distance dispersed pollen (i.e. local input) will contain anemophilous pollen. Long-distance dispersed pollen (i.e. regional input) in tropical highland environments will contain pollen from both anemophilous pollen from higher elevations and lowland zoophilous taxa (although not aerodynamically designed, some are transported by upslope winds).

Elevational gradients in the tropics do not conform to generalities made for northern temperate regions (Janzen, 1967).

In three out of four existing modern pollen rain studies for the Maya region (Islebe and

Hooghiemstra, 1995; Islebe et al., 2001; Domínguez-Vázquez et al., 2004), pollen is captured by moss polsters in different scenarios, lowland and highland settings, and all contain an over-representation of long-distance dispersed taxa (anemophilous taxa) and

90 an under-representation of short-distance dispersed taxa (mostly entomophilous taxa).

This in turn interfered with the overall ability to detect typical "regional" versus "local" vegetation signals. Broadly-dispersed tropical and temperate anemophilous taxa in tropical regions, such as the Amazon Forest, reflect a less heterogeneous and diverse landscape. This relationship poses a limitation to differentiating ecosystem types in the pollen record (Bush et al., 2001). To overcome difficulties associated with anemophilous taxa, Gosling et al. (2009) have stressed that more attention should be placed on identifying and differentiating pollen abundances and accumulation rates for ecosystems.

Nonetheless, to achieve this it requires extensive spatial and detailed temporal sampling.

3.4.4 Identifying indicator taxa and vegetation associations

The pollen collection sites represented changes along the elevational gradient from

Lachuá to Purulhá (Figure 3.7 and Table 3.4), as has been found in other pollen studies in Latin America (Weng et al., 2004; Weng et al., 2007). For their study region in

Guatemala, Islebe and Hooghiemstra (1995) concluded that moisture gradients have an important role in explaining variation in pollen assemblages. In an elevational gradient

(from 130 to 1191 masl) in the Chiapas Lacandon Forest in Mexico, modern pollen spectra collected from moss polsters (Domínguez-Vázquez et al., 2004) indicate high overlapping of lowland rain forest and lower montane rain forest vegetation zones, and montane rain forest and pine-oak forest respectively. The majority of pollen types from

Lachuá and Purulhá are generalist since they represent mainly lowlands and highlands vegetation, while few represent a specific vegetation belt (Table 3.1). This representation pattern in the Las Verapaces region is similar to the analysis of Dominguez-Vásquez et

91 al. (2004), which indicates that pollen taxa represent broader and less specific environmental ranges, possibly in response to the taxonomic resolution of genus and family. According to results from Chapter 2 (Table 2.2 and 2.3) a few pollen types can be associated to specific vegetation belts, such as the case of Spondias for Lowland Rain

Forest, and Inga for Lower Montane Rain Forest, and although not part of the Las

Verapaces Region, Abies for Mixed Montane Rain Forest. In a smaller spatial scale,

Batthacharya et al. (2011) were able to differentiate lowlands ecosystem types (i.e. upland, bajo, and riparian forests) in Northeast Belize based on changes in abundance of pollen types in relationship to ecological preferences of the correspondent source plant taxa.

Gradients interpreted from DCA Axes and factor analysis identify indicator taxa for

Lachuá and Purulhá. Pollen from Celtis is associated with Lowland Rainforest in both pollen reservoirs and is known to indicate high canopy transition (medium- to large-size trees) in an early- to mid-succession phase following human disturbance (Marchant et al.,

2002). In Guatemala, plant stands of C. trinervia have been recorded in Lowland Humid

Forest from the Petén (Standley and Steyermark, 1946), an area which receives less precipitation than the Lachuá Lowland Rain Forest (Standley, 1958). Celtis has thus adapted to drier conditions and therefore could be found from lowland vegetation up to lower montane rain forest. Such a trend has already been reported in pollen studies from

Costa Rica (Islebe and Hooghiemstra, 1997). The large tree, Brosimum has similar distribution preferences as Celtis plant stands because it too has been reported in Lowland

Humid Forest (Cascante and Estrada, 2001) (see Table 2.1) and Lowlands Rain Forest

(Chapter 2), such as the lowland rain forests from Lachuá (Table 3.1).

Terminalia pollen is a generalist taxon characteristic of Lowland Rain Forest and Lower

Montane Rain Forest (Chapter 2). I also identify Sapotaceae pollen as representative of

Lachuá Lowland Rain Forest, an observation similarly made in other areas of Latin

America (Marchant et al., 2002). In my study, both Hedyosmum and Quercus indicate

Lower Montane Rain Forest and Montane Cloud Forest vegetation, a distribution also found elsewhere in the tropics (Domínguez-Vázquez et al., 2004). At Purulhá, the values of these two taxa are lower in surface sediments than in bryophyte polsters most likely because of proximity of forest stands to polsters and because in surface sediments, values are diluted by high abundance of non-arboreal pollen (NAP).

The abundance of Quercus in bryophyte polsters (10-61%) is higher than those recorded by Islebe and Hooghiemstra (1995) (3-16%), whom sampled at higher elevations (above

3000 masl) where oak is naturally less abundant (i.e. too cold). Pollen abundances of

Hedyosmum found in bryophyte polsters in the present study (3-31%) are similar to values documented by a study in southern Peru (15-65%), at elevations between 1600-

2000 masl (Weng et al., 2004). In contrast, Islebe and Hooghiemstra (1995) did not find

Hedyosmum pollen at higher elevations (> 3000 masl) in Guatemala. Islebe and

Hooghiemstra (1995) found relatively high concentrations of Abies and Alnus at elevations higher than 3000 masl (30 and 40%, respectively) yet I report a maximum abundance of 10% for both because of their relative absence in forests in my study region

(Chapter 2). Ilex pollen appears to be behaving as an outlier, because it is unclear why this zoophilous highland taxon is as abundant in Lachuá’s surface sediments as in

Purulhá’s bryophyte polsters, and yet is totally absent in Purulhá’s surface sediments.

Differential preservation could in part explain this seemingly odd distribution, but the explanatory mechanism remains speculative. According to Behling et al. (1999), the ecological significance of finding Ilex within a paleoecological context remains uncertain.

Analysis of pollen in bryophyte polsters and surface sediments aided in identifying indicator and generalist plant taxa at Las Verapaces region, showing partially the results from the inventory study of vegetation belts (Chapter 2). Lowland taxa such as Bursera,

Inga, Spondias and Trema, and highland taxon such as Myrica, are reported in current forest inventories (Chapter 2) but they are not statistically relevant in the ordination gradients formed for DCA and Factor Analysis based on pollen in this study.

Nevertheless, they are qualitatively key taxa whose importance remains in their associated presence-absence in the pollen spectra. Weng et al. (2004) have suggested that in order to maximize detecting environmental changes for tropical studies qualitative information such as presence/absence data should become more prominent in palynological studies.

3.4.5 Interpretation of Pinus pollen

Overrepresentation of Pinus taxon is discussed separately because its abundance has to be read carefully due to its high dispersion ability (Bohrerova et al., 2009). The location of the sampling point is therefore critical to understand what Pinus pollen percentages

94 reflect. Pinus is more abundant in bryophyte polsters and surface sediments from Lachuá than from Purulhá possibly because of a mixture of pollen sources from different populations of Pinus species (Figure 3.2). Natural Pinus populations are established in different highland regions around Lachuá, in the northwest at the Chiapas highlands of La

Selva Lacandona (Breedlove, 1981), in the west and southwest at the Sierra de los

Cuchumatanes (Islebe et al., 1995), and Pinus caribea populations north of Lachuá and to the northeast in Belize (Bridgewater et al., 2006). Pinus pollen has been considered as an indicator of highlands vegetation where abundances can reach up to 90-95% (above 2500 masl) which inform me more about larger scale scenarios (i.e. across different regions)

(Islebe and Hooghiemstra, 1995).

Nevertheless, as was found in Chapter 5, Pinus pollen percentages of the last ca. 2000 yrs in Lachuá lowlands have never been as abundant as modern pollen rain analysis shows. High abundance of Pinus pollen in Lachuá may represent the general increasing environmental deterioration of Mesoamerican forests in Southeast Mexico and

Guatemala, because it is known that Pinus is a successful colonizer of disturbed areas. A related factor to be considered is the extensive Pinus plantations established in lowlands and highlands in the recent years in Guatemala as part of governmental reforestation programs (Gaillard, 2003). This probably created a bias in the modern pollen rain

(Behling and Negrelle, 2006), which urges the necessity to develop more modern pollen rain studies in the region. A recent study by Battacharya (2011) in a pine savanna

(characterized by the presence of Pinus caribea and Quercus) shows similar Pinus pollen

95 percentages to the ones found in Lachuá (up to ca. 40%), which possibly explains how

Pinus pollen could reflect local Pinus populations.

One factor that currently precludes geographical discrimination of pollen provenance of

Pinus populations is that highland Pinus species and P. caribea pollen cannot be differentiated because they form part of the same subgenus (i.e. Diploxylon). More palynological work with Pinus and other pollen types (e.g. Combretaceae and

Melastomataceae) is required to overcome these taxonomic limitations in order to identify more accurately pollen source areas, geographical provenance, and ecological preferences.

3.5. Chapter summary

The purpose of modern pollen rain calibrations developed in this chapter is to understand better the meaning of the pollen spectra of surface sediments, as they represent the best analogue for sedimentary records. Calibrations of modern pollen rain of bryophyte polsters and surface sediments from Lachuá lowlands and Purulhá highlands revealed the importance of geographical context and related vegetation. Results from Chapter 2 were the basis to determine pollen source areas of pollen types found in modern pollen reservoirs, as Table 3.1 indicates. The pollen assemblage in Lachuá lowlands is dominantly zoophilous because the associated vegetation is mainly of tropical biogeographic origin (Amazonian and Andean). This is the reason why lowlands pollen is poorly represented in the highlands pollen assemblage, because zoophilous pollen taxa

96 disperse mostly over short distances. On the contrary, because the pollen assemblage in

Purulhá highlands is dominantly anemophilous (adapted for airborne dispersal) and of temperate biogeographic origin (Laurasian), they are relatively more abundant in the

Lachuá lowlands pollen assemblage.

In general terms, surface sediments in Lachuá lowlands have similar pollen spectra than the one found in bryophyte polsters, with the exception that the latter contained higher abundances of forest interior taxa (e.g. Brosimum, Celtis, and Terminalia) and some additional taxa (e.g. Bignoniaceae and Salvia). In the Lachuá lowlands, in both types of depositional environments (polsters and surface sediments), high arboreal pollen content was linked to the high remaining forest cover of the area (ca. 50%). In Purulhá highlands, bryophyte polsters and surface sediments pollen spectra are different due to the fact that the former were collected in forested conditions (e.g. high percentages of

Hedyosmum and Quercus), and the latter in a more open landscape. The non-arboreal pollen content of bryophyte polsters and surface sediments reflected the degree of forest cover where pollen reservoirs were collected, low for the former and high for the latter.

Combined analysis of pollen spectra of Lachuá and Purulhá showed the clearest elevational differentiation when comparing bryophyte polsters, and lesser when comparing surface sediments. The explanation for this pattern could be that surface sediments from Lachuá lowlands have a significant representation of highland pollen, which needs careful attention when interpreting fossil pollen spectra.

The application of modern pollen rain calibration from bryophyte polsters and surface sediments is developed in the following chapters on the paleoecology of Lachuá lowlands and Purulhá highlands. Data matrices of modern pollen rain from both types of pollen reservoirs are compared with fossil pollen assemblages from different levels in the cores

L-3 in Lachuá lowlands and P-4 in Purulhá highlands. These comparisons are the basis for determining analog or non-analog environmental conditions along the temporal frame covered in each core. Pollen types included in Table 4.4 were relevant in developing paleoecological reconstructions in Chapter 4 and Chapter 5. The contributions of

Chapter 2 and Chapter 3 in understanding the importance of the relationships between geographical context, vegetation biogeography, environmental conditions, and pollen spectra resulted in better interpretations of the paleoecology of Lachuá lowlands and

Purulhá highlands.

Chapter 4: Late-Holocene History of a Highland Floodplain in Las Verapaces, Guatemala

4.1 Introduction

Sedimentary records from lakes and peat deposits are one of the most relied upon tools for paleoecological research, in part because aquatic environments are generally more stable (i.e. continuous accumulation through time) and less disturbed than riverine environments (Larsen and Macdonald, 1993; Birks, 2005; Brown et al., 2007). In circumstances where lacustrine and peat deposits are rare, records from floodplains, terraces and alluvial fans have been instead studied (Cheng, 2011; Gandouin et al., 2006;

Gandouin and Ponel, 2010). Paleoenvironmental information retrieved from river floodplains can reflect in some cases floodplain communities, and to a lesser degree upland vegetation communities (Solomon et al., 1982; Xia et al., 2002; Zazula et al.,

2006). Regional pollen however, is generally represented in floodplain sedimentary cores

(Qinghai et al., 1996). Floodplain sedimentary records offer a unique opportunity to study the paleoecology of high energy systems (i.e. riparian plant communities) as well as their successional dynamics related to flood events (Pokorny et al., 2000) and disturbances such as fire (Gagnon, 2009).

It was the objective of my study to retrieve fossil pollen spectra from the headwaters of the Cahabón River floodplain in the Las Verapaces highlands region of central

Guatemala (Figure 1.2 and 1.3). Due to the dominant karstic geology of the Las

Verapaces region (Fourcade et al., 1999), aquatic ecosystems are mostly dominated by sinkholes or “cenotes” where sediments are minimal to non-existent. Only a few small lakes have been reported in the region as most have been either naturally drained through karstic bedrock or anthropogenically disturbed (Castañeda, 1995). This study represents the first paleoecological study (spanning the past ~2,400 years) of a region located in a floodplain environment in highland Mesoamerica. Archaeological studies indicate the existence of numerous small Maya centers in the Las Verapaces (i.e. Carcha, Sakajut,

Chican, Pasmolon) (Arnauld, 1978; Arnauld, 1987; Arnauld, 1997; Sharer and Sedat,

1987) that date from the Pre-Classic through to the Spanish Conquest.

The research goals of the following study are twofold: (1) to reconstruct the paleoenvironmental history of a river floodplain located in the Las Verapaces highlands for the past ~2400 years, with methods based on pollen and loss-on-ignition (LOI) analysis, and (2) to make regional comparisons between other records in Mesoamerica, with special emphasis on highland ecosystems. This research builds on previous highland studies of vegetation biogeography (Chapter 2) and modern pollen calibrations

(Chapter 3).

4.2 Methods

4.2.1 Core Sampling and Laboratory Work

With the use of a Livingstone Corer, I extracted a ~1.5 m core (labeled as P-4) on the north side of the Cahabón River headwaters floodplain (Figure 1.3). The location of my

100 core was cautiously selected in order to avoid any disturbance from modern hydrological modifications on the Cahabón River floodplain, landslides on the slopes or incoming or outflowing rivers. Coring was stopped once it became impossible to continue due to stiffness of sediments.

The top centimeter of P-4 core was separated for modern pollen rain calibration (Chapter

3), and the rest was wrapped in aluminum foil and enclosed in a PVC pipe. A 1 ml subsample was taken every 5 cm along P-4 core. Sub-samples were stored in Ziploc bags, and the core’s stratigraphy was qualitatively described. After proper labeling, the core and the subsamples were stored in a cold room.

According to the Department of Geography Protocol (No. 010) of the University of

Leicester, samples were pre-treated overnight with pyrophosphate, followed by standard acetolysis procedure and heavy liquid separation with the use of bromoform (Fægri and

Iversen, 1989). Exotic Lycopodium spore tablets were added as markers to calculate pollen concentration. Pollen counting was completed to 200 grains per sample when possible (Lytle and Wahl, 2005). Pollen sum included arboreal and non-arboreal taxa that were identified to family and genus level. Unknowns, spores and aquatics (Cyperaceae) were not included in the pollen sum (Fægri and Iversen, 1989) and their abundance was measured as a ratio in relationship to the total pollen sum per sample.

Arboreal pollen (AP) and non-arboreal pollen (NAP) percentages were calculated to represent local landscape vegetation cover. The Loss of ignition (LOI) protocol used at

101 the Paleoecology Laboratory of the University of Toronto (Heiri et al., 2001) was applied for each subsample where pollen was analyzed (see above), to calculate the organic

(550°C), inorganic (950°C), and silicate (% left) contribution to the sediment sample

(estimated 2% error in the measurement). Only the LOI at 550°C is presented and referred as "LOI". A bulk sample from the bottom level (145 cm in depth) of core P-4

(Purulhá) was radiocarbon dated to estimate the time span of the core, and three additional samples (25, 50 and 70 cm in depth) were dated to develop models of sediment accumulation rates. Dates were calibrated through the use of the IntCal04 curve from

CALIB 6.0 (Stuiver et al., 2005).

4.2.2 Core data analysis

Pollen counts were tabulated for pollen types and core levels (sub-samples), including for the surficial level, for comparison with the modern pollen rain data presented in Chapter

3. Arboreal and non-arboreal pollen types were included in the pollen sum, excluding aquatics (e.g. Cyperaceae), pteridophytes spores, and unknowns. For pollen concentration, all counts were included. Principal component analysis (PCA) (Shi, 1993) was performed with the statistical package PAST (Hammer et al., 2001) to describe changes of pollen spectra along the core including common and rare taxa (Figure 4.3). A second PCA was done (Figure 4.6) for the comparison of fossil pollen spectra of sampled levels of the P-4 core and modern pollen spectra from bryophyte polsters and surface sediments from Purulhá highlands (Chapter 3). The software C2 (Juggins, 2003) was used to construct a stratigraphic diagram (based on depth measured in cm and calibrated time scale) (Figure 4.1) according to the information on vegetation belts and pollen types

102 presented in Table 3.1. Vegetation belts included in Figure 4.1 are Lower Montane Rain

Forest-Montane Cloud Forest and Mixed Montane Forest (see Table 2.1 and Table 3.1), which comprised the sum of the percentages of Hedyosmum, Myrica and Quercus; and

Abies and Alnus, respectively. Complementary information for stratigraphic diagrams

(Figure 4.1 and 4.4), included relative abundance of arboreal (temperate trees and shrubs) and non-arboreal pollen content, aquatics, pteridophytes spores, LOI (loss-on- igition), sedimentation rate, and PCA axes scores. The stratigraphic diagram was divided into a priori zones according to cultural periods defined for Mesoamerica (i.e. see

Introduction, section 1.7).

Equations for sedimentation rates were calculated based on sediment thickness (in cm) per number of years between two identified dates. An analysis based on nine regional studies from Mexico and Central America and our data spanning the Preclassic to colonial times (Almeida et al., 2005; Carrillo-Bastos et al., 2010a; Conserva and Byrne,

2002; Dull et al., 2010; Figueroa-Rangel et al., 2008; Islebe and Hooghiemstra, 1997;

McNeil et al., 2010; Wahl et al., 2006) was performed to compare our calculated sedimentation rates with values found in other Mesoamerican highland and lowland sites.

A total of 65 levels (radiocarbon dates) from the nine sites were included in my analysis, which were allocated into elevation and cultural period categories. The sites used in this regional comparison were placed into groups according to elevation: 0-500 m (n=20),

500-1000 m (n=16), 1000-2000 m (n=9), and 2000-3100 m (n=20); and cultural periods:

Preclassic (n=26), Classic (n=10), Postclassic (n=13), and Colony (n=3). Levels that cover Pleistocene (n=4) and Archaic times (n=9) (5000-10000 yrs BP) were excluded

103 from my analysis. Based on non-parametric boxplots (Tukey, 1977; Hyndman and Shang,

2010), P-4 sedimentation rate values were plotted in order to explore if they behaved as outlier values for the groups were they belonged. The analysis was complemented with a

Kruskal-Walis test to test the coherence of created elevation and cultural period groups

(Kruskal and Wallis, 1952). P-4 sedimentation rate values are located in the 1000-2000 m ranges, and across four cultural periods (Preclassic, Classic, Postclassic, European conquest and Colonial Guatemala).

4.3 Results

4.3.1 Stratigraphical description

The P-4 sediment core is characterized by an alternation of different tones of gray fine grained sediment from the base at 144 cm up to 30 cm in depth (Table 4.1). Brown fine grained sediment are found in between 30 and 5 cm depths, and dark brown organic matter in the top 5 cm. LOI values steadily increase from 9 to 13% between the Late-

Preclassic and Late-Classic period (144-45 cm in depth) (Figure 4.1). At the time of the

Terminal Classic and onset of the Postclassic, there is a decrease in LOI to 9% (45-40 cm core interval). A two-fold increase in LOI to 16% occurs during the next 300 years; LOI values remain high (15-22 %,) during the Colonial to present-day cultural period.

4.3.2 Chronological control and sedimentation rates

The oldest age of 2390 yrs BP (all ages are reported as calibrated years before 1950 AD) corresponds to sediments at the bottom of the core (144 cm in depth). Subsequent

104 radiocarbon analyses indicate ages of 2060 yrs BP at 70 cm, 1510 yrs BP at 50 cm, and

150 yrs BP at 25 cm (Figure 4.2) (Table 4.2). There are two critical inflection points in the age-depth curve, at 70 cm of depth, and above 25 cm of depth (Figure 4.2).

According to such a pattern, different periods of changing sedimentation rates (i.e. changing of energy at time of deposition, sediment type, or source area) can be postulated.

The lower phase from 2390 yrs BP until 2060 yrs BP (144-70 cm core interval) records a relatively rapid sedimentation rate of 0.22 cm yr-1 (corresponding cultural period of the

Late Preclassic to Terminal Preclassic). The next phase, which includes dates from 2060 until 1510 yrs BP (70-50 cm core interval), has a marked reduction in sedimentation rate to 0.036 cm yr-1 (corresponding cultural period of the late Preclassic to the middle

Classic). The following phase includes dates from 1510 until ~150 yrs BP (50-25 cm core interval) and has an even more marked reduction in sedimentation rate to 0.018 cm yr-1

(corresponding cultural period of the middle Classic to end of the Postclassic, and the start of Colonial Guatemala). The upper phase, from ~150 yrs BP to modern-day (25-0 cm core interval) shows a relative increase in sedimentation rate to 0.17 cm yr-1 (cultural period of Colonial Guatemala).

The sedimentation rates found for P-4 core (0.22, 0.036, 0.018, and 0.17 cm yr-1) are not outliers in the groups they belonged according to elevation and age (Figure 4.3). There is no statistically significant difference in rate of sediment accumulation among the sites in the regional comparison when they are divided by cultural period (Kruskal-Walis H=,

105 p>0.01); and in relation to elevation, ranges 500-1000 and 1000-2000 m ranges are considered a group, and 0-500 and 2000-3100 m another group (Kruskal-Walis H= 32.87, p<0.01). The exploration of sedimentation patterns and differences in relationship to environmental and cultural factors needs further discussion in the future, but is beyond the scope of this thesis.

4.3.3 Description of pollen diagram

The variability found along the first factor of principal component analysis (PCA1) and the first component of factor analysis (F1) (Figure 4.1), corresponds to the pollen zones that were identified a priori based on cultural periods. According to trends in the PCA

Axis 1 analysis, the main variability in pollen assemblages occurs as a function of changes in abundance of Asteraceae (Figure 4.4). PCA Axis 2 scores are linked to variation in the dominances of Pinus and Alternanthera, Quercus, Poaceae and

Polygonum, alternating with dominance of Amaranthaceae/Chenopodiaceae (Figure 4.4).

The presented pollen diagram (Figure 4.5) is based on common and rare taxa identified to at least to the level of genus or family. Tropical lowlands pollen taxa are extremely rare and do not show a clear trend in the P-4 core. Pollen zones were closely related to the four cultural periods identified to our region: Pre-Classic, Classic, Post-Classic, Colonial and modern-day Guatemala. For the core interval between 144 and 90 cm (representing the period from 2390 to 2150 yrs BP) there was no pollen or spore preservation.

106

Table 4.1. P-4 core stratigraphic sequence.

Stratigraphy of core P-4 taken from the Cahabón Floodplain, Purulhá

Depth (cm) Description

0-5 Dark brown organic material 5-30 Light brown organic material 30-32 Dark gray fine grained sediment 32-39 Medium gray fine grained sediment 39-44 Bright gray fine grained sediment 44-49 Medium gray fine grained sediment with oxide (red) spots 49-86 Brown-greyish fine grained sediment 86-93 Dark gray fine grained sediment 93-105 Medium gray fine grained sediment 105-111 Dark gray fine grained sediment 111-119 Bright gray fine grained sediment 119-144 Bright grey-green fine grained sediment with black laminations

Table 4.2. AMS radiocarbon dates, calibrates age ranges from dated sediment from P-4 core of the Cahabón Floodplain, Purulhá highlands. Bold numbers in brackets are the calibrated dates. All radiocarbon dated material is from bulk samples.

Depth (cm) Lab No 13C/12C 14C yrs BP Age range 2σ and Median Age (in brackets) (cal yrs BP)

25 Beta-281243 -24.6 150±40 42-(151)-284

50 Beta-281244 24.3 1510±40 1313-(1394)-1517

70 Beta-281245 -24.3 2060±40 1926-(2029)-2133

144 GrA-40112 --- 2390±35 2341 –(2422)- 2683

107

Zone 1: Pre-Classic (2390-1650 yrs BP)

Pollen is preserved starting at 2150 yrs BP (90 cm). This zone is characterized by a dominance of non-arboreal pollen (78-90%) consisting mostly of Asteraceae (48-76%); with Asteraceae remaining at high values (55%) until the end of the Postclassic. Other non-arboreal taxa include Poaceae (1-17%), Amaranthaceae/Chenopodiaceae (4-21%) and Zea (1-3%) which remain at relatively low to medium values throughout the zone.

Cyperaceae (27-80%), Polygonum (0-4%), trilete spores (6-23%) and Monolete spores

(0-14%) all reach their minimum values in this zone. Pinus is present at intermediate values (3-11%), similar to Hedyosmum (0-6%) and Quercus (1-8%), with Myrica reaching its maximum abundance (0-5%) in the entire core. Regional taxa for the modern-day Cahabón floodplain, Abies and Alnus, are not present at this time.

Zone 2: Classic (1650-1240 yrs BP)

This zone has relatively decreasing pollen abundances of Pinus (4-6%), Hedyosmum (1-

3%), Myrica (0-3%) and Quercus (0-4%). Alnus (1%) and Malphigiaceae (2%) make their first appearance along the core. Non-arboreal pollen dominates this zone (87-89%), once again consisting mainly of Asteraceae (46-71%). In comparison to Zone 1, Poaceae

(6-29%), Polygonum (0-9%), Cyperaceae (60-165%), and trilete spores (9-48%) increase in abundance, while Amaranthaceae/Chenopodiaceae (4-9%) decrease. Zea (0-4%) and monoletes spores (4-17%) have similar values across Zone 1 and Zone 2.

108

Zone 3: Post-Classic (1240-420 yrs BP)

Total arboreal pollen shows a subtle decrease to between 5 and 13%; comprising mainly

Pinus (2%), Hedyosmum (2-6%), Quercus (1-2%), Alnus (0-1%) and Malphigiaceae

(1%). Myrica is absent. Similar to Zone 2, Asteraceae is the dominant taxon (55-56%) showing only small variations in concentration between the zones. Other taxa that show small decreases in concentration include Poaceae (4-16%), whereas Cyperaceae (19-

20%) decreases the most substantially. Amaranthaceae/Chenopodiaceae (1-25%), trilete spores (22-112%) and monolete spores (47-97%) all show an increase in abundance.

Polygonum (3-5%) and Zea (3-5%) abundance remains the same across the previous zone to Zone 3.

Zone 4: Colonial to modern-day Guatemala (420 yrs BP-Present)

This zone is characterized by a co-dominance of Pinus and Asteraceae with maximum values at 30 and 35%, respectively. It is only at the most recent time that Pinus shows a modest decrease (to 12%). In general, Quercus shows stability with low values (~1%) along most of the core. Whereas Pinus shows decrease in the uppermost sample, Quercus shows an abrupt increase (18%). Abies (modern-day regional species; Chapter 4) appears for the first time in this zone, with a trend towards increasing abundance through time

(i.e. from 0 to 4% by the top of the core). The observed three-fold increase in arboreal pollen (from between 10-22% to between 32-49%) is due to increased presence of Pinus,

Quercus and Abies. Hedyosmum shows relatively stable presence (2-7%) at the start of the zone, and then begins to decrease (2%) towards the modern-day time. Myrica (0-3%)

109 and Alnus (0-1%) show a similar pattern where their populations are relatively stable in the lower sections of the core, then begin to decrease towards the upper part of the core.

By the onset of Colonial Guatemala, Asteraceae begins to show a sharp drop in dominance (17-36%) showing even a lesser value at the present (13%) (Chapter 3). Zone

4 shows Cyperaceae increasing to its maximum value (from 49 to 226%), followed by a sharp decrease to (58%) in the upper-most sample. In contrast, Polygonum shows a steady and gradual increase (2-17%) until the modern day (26%). Poaceae shows an increase in abudance to its peak (4-26%) during this zone, but right at present day, the abundance of Poaceae returns to values more characteristic of previous zones (16%).

Amaranthaceae/Chenopodiaceae shows small decreases (3-13%) towards present day, a pattern also observed for trilete spores (10-36%) and monolete spores (10-32%). At the start of Zone 4, Zea abundance begins to decrease (0-1%) but then begins to recover (2%) near present day. The most significant pollen signal in this zone is the first appearance of the disturbance indicator, Alternanthera (1 - 11%). According to the PCA ordination

(Figure 4.4), the major division in the core in terms of the pollen assemblages is between the Guatemala zone and pre-Guatemala zones.

110

Figure 4.1. P-4 core paleoecological diagram taken from Cahabón River Flooplain. AP = Arboreal pollen; LOI550 = Loss on ignition at 550°C (expressed as % of dry mass); PCA1 = Axis 1 scores from principal components analysis. Sedimentation rate is shown in cm/yr. Mayan cultural periods are shown. The Guatemala zone represents modern day Republic of Guatemala. Vegetation belts are composed of pollen indicator taxa (see Table 3.1 and section 2.4.3 for calculations). LMRF= Lower Montane Rain Forest, MCF= Montane Cloud Forest. ) /cm3 rains g t 0 00 es 1 (x For ion /yr) ane trat nt en (cm ) o e M nc cm s rat 1 n co ed e I 550 h ( ix erb Pinus LMRF-MCFM H AP Poll LO Sed. PCA Cal yrs BP Dept 0

10 100 Guatemala 20

350 30 600 Postclassic 850 40 1100 1350 50 1600 Classic 1850 60 70

2100 80

100 Preclassic 110

120

130 2350 140 020400200 0 204060801000 102030405004812160816240.00.10.20.3-80 0 80 160 Percent abundance

111

Figure 4.2. Graph showing depth (cm) vs. calendar age (cal yrs BP) of sediments from core P-4 taken from the Cahabón River floodplain, as determined by 4 radiocarbon dates (black diamond symbols, see Table 4.2). Asymmetric bars indicate ±2σ in cal. yrs.

2500

2000

1500

1000 Calendar age (cal yr BP) yr Calendar age (cal 500

0 20 40 60 80 100 120 140 Depth (cm)

112

Figure 4.3. Sedimentation rate (cm/yr) values from elevation ranges (masl) across Mesoamerica, as determined from a regional comparison from nine published studies (65 radiocarbon samples). Small squares= outliers.

113

Figure 4.4. Principal Component Analysis (PCA) of sampled levels from core P-4. PCA1= First principal component, PCA2= second principal component. PC= preclassic levels, C=classic levels, PT=postclassic levels, G= Guatemala zone, modern= surface sediment (0-1 cm) for core P-4.

G3 G1 10

PT3 PC1 PC5 G4

PT2PT1 PC6

PCA2 -32 -16 16 PC4 C1 PC3 C2 C3 PC2

-10

C4 Modern

-20

PCA1

114

Figure 4.5. Pollen percentage diagram of P-4 core from the Cahabón River floodplain. Rare taxa appearing at <1% are indicated by a "+" symbol. .

Temperate trees and shrubs Herbs Tropical trees and shrubs Aquatics Pteridophytes

ae eae e ac podi tomatac

Cheno / Melas / eae a e e m hac her aceae mu um cea te P m) nea a et eae n e B c a cus ant e ( ic nant s br tac rs dyos er ies aceae er a rser lti m lygo pera let recaceae yr inus b lnus mar o lt e lchor rosimumu e o yr o y i onol P A H Ilex MalphigiaceaeM Qu P A A Asteraceae A P A Z A B B C C M P C Tr M A Cal y Depth 0

10 100 Guatemala 20

350 30 600 Postclassic 850 40 1100 1350 50 1600 Classic 1850 60 70

2100 80

100 Preclassic 110

120

130 2350 140 20 20 40 20 40 60 80 20 20 20 0200 50 100 150 200 250 0 30 60 90 120 0 24487202040 Percent abundance

115

4.4 Discussion

4.4.1 Ancient lacustrine-like conditions at the floodplain?

The development of the Cahabón River Floodplain at 2390 yr BP is characterized by a relatively higher sedimentation rate than in the present, which based on other studies in similar types of settings, could mean a higher energy regime related to fluvio-lacustrine

(river to lake transition) environments (Figure 4.1). A range of 5-9% for LOI during this time period (2390 until 2170 yrs BP) at P-4 core is similar to what was recorded in the environments of a paleolake that once existed in the basin of Bogota from the late-

Pliocene through the Pleistocene (Torres et al., 2005). LOI values around 10% found in lacustrine conditions indicate the provenance of the sediments mainly from swampy environments. It is possible that core P-4 is located at what was once a swamp (i.e. light gray fine grained sediments) in the remnants of a lacustrine environment (Shuman, 2003).

The location of core P-4 corresponds to the headwaters of the Cahabón River watershed, at the top of a plateau where the drainage divide is located (Figure 4.6). The relatively flat terrain and the location of the floodplain are factors that may help explain the existence of a paleolake, but nevertheless particle size analysis is needed to permit more conclusive inferences. The fine grained sediments suggest a location with low energy and not close to a main channel where sediments are in general coarse-grained (Bridge,

2003). In the Bogota Basin swamp environments with fine grained sediment in a fluvio- lacustrine hydrological context with LOI values from around 10% (Torres et al., 2005), are interpreted as episodes of high rates of bioturbation due to high levels of biological activity in organic-rich mud. This in turn may help to explain the absence of pollen grains observed in our P-4 core during this time (144 to 90 cm) as a result of bioturbation

116 disturbance. Further exploration about the possible existence of formerly paleolacustrine conditions in the floodplain is needed (e.g. particle size analysis), because our speculation is greatly based only on the Torres et al. (2005) study.

An alternative explanation for the absence of palynomorphs in the lower section of the core could be that this was a period of rapid sedimentation due to increased erosion or flows in the river, either due to natural (e.g. higher precipitation due to a wetter climate, or any other related hydrological changes) or cultural factors (e.g. increased erosion due to deforestation), preventing in the end the accummulation and deposition of pollen and spores into the sediments. The absence of palynomorphs in the lower section of the core makes it difficult to infer what the vegetation cover could have been during this time period (2390 until 2150 yrs BP). Although differences exist, sedimentation rates from the bottom (Preclassic period) and the top (Guatemala zone) belong to higher ranges (0.22 and 0.17 cm yr-1), which suggests that sedimentary conditions may have been relatively similar. In this area today, economic human activities have resulted in a high deforestation rate leaving most of the floodplain valley floor and slopes with scarce vegetation cover (MAGA, 2006). By analogy, the same low vegetation cover could be inferred for the beginning of our core; however, there is insufficient evidence to indicate whether or not the cause of low vegetation cover was due to natural or cultural circumstances. Nevertheless, a cultural cause may help explain the high sedimentation rate caused from slope erosion into the floodplain (Thieme, 2001; Charlton, 2008). The first Preclassic agriculturalists in Mesoamerica have been associated with evidence of the highest rates of soil erosion and degradation in the region, mainly due to the

117

Figure 4.6. Cahabón River Floodplain. The core P-4 is located in the headwaters of the Cahabón River (running eastwards). Rivers are irregular black thick lines. Dark grey polygons represent natural reserves (mainly Montane Cloud Forest). Archaeological sites are indicated by circles: VP= Valparaiso, CH= Chican, CX= Cerro Xucaneb, SL=Sulin. See Figure 1.4 for elevation references.

VP CX

P‐4 SL

118 trial and error of people learning the consequences of land-use change (Beach et al.,

2006).

The lower-most pollen sample in the P-4 core (at 90 cm) shows a low percentage of arboreal pollen and high values of herbs. The bottom of P-4 core could be indicating intense land use change and conversion to agricultural uses (e.g. Zea and Cyperaceae).

The inferred lacustrine swampy environment was probably disturbed at this time, as a slight increase in LOI (9 to 13%) possibly represent land use modifications in the floodplain. The fact that pollen appears simultaneously strengthens the possibility that

LOI increase is due to the floodplain stabilization.

4.4.2 Evolution of Mayan land management at the Cahabón Floodplain

The accompanying changes in fluvial parameters may have been influenced by

(culturally-induced) hydraulic management of the floodplain (i.e. leading to the presence of fine-grained sediments that are darkin in colour and higher in organic matter) (Table

4.1, see interval 49-86 cm). Approximately 340 years after the first appearance of pollen in P-4 core (2040 yrs BP), the sedimentation rate decreases several-fold (from 0.22 to

0.036 cm yr-1), possibly indicating that early Mayans evolved along this time some form of soil conservation practice that helped to decrease rates of soil erosion. It is possible then that progressive agriculturally-related fallow debris may have increasingly influenced the slight increase of LOI from 9 to 13% during those three centuries. Changes in PCA1 values suggest that vegetation dynamics reflect approximately the conditions in the riparian zone before the sedimentation rate decreased, in between the end of the

119

Preclassic and start of the Classic (Figure 4.1). For many years, archaeologists have shown evidence that the early Mayans incorporated terraces and raised fields in their agricultural management plans, ultimately leading to reduced soil erosion over the time the region was in agricultural use (Beach, 2003; Beach et al., 2009). Raised fields were useful in modulating soil-water conditions, where channels in between the field functioned to regulate water tables resulting in permanent flooded conditions (e.g. rise in water table) (Turner and Harrison, 1981; Scarborough, 1991; Beach et al., 2011). The sedimentation rate in core P-4 remained relatively low for roughly 1600 years (e.g. from

0.036 to 0.018 cm yr-1), until the end of the Postclassic period, when presumably dispersion of Mayan populations resulted in abandonment of established agricultural plots.

Arboreal components (Hedyosmum, Myrica, and Quercus) from Lower Montane Rain

Forest (i.e. located most likely along the valley bottom) and Montane Cloud Forest (i.e. located most likely along the valley slopes) may be an indication of recovery from agricultural disturbance, since their presence in the floodplain environment increases towards the late-Preclassic (i.e. rising 3 to 11%). The first appearance of Zea pollen during the late-Preclassic with values lower than 1% supports the development of agriculture in the floodplain, because generally Zea pollen disperses close to its source

(McNeil et al., 2010). Progressive increment in Zea pollen percentages greater than 1% suggest possibly that agriculture was developing in a wider area along the floodplain and more intensively, as has been reported in other Mesoamerican locations (Wahl et al.,

2007). Currently the major land use at the floodplain is cattle pasture with some

120 agricultural plots (personal observation). This is reflected in modern pollen rain (Chapter

3) where values of Zea pollen are higher in surface sediments (>1%) than in bryophyte polsters (<1%) (Figure 3.5), because the latter were collected in forest interiors far away from the floodplain (ca. 5 km). PCA ordination of modern and fossil AP pollen spectra shows how bryophyte polsters do not overlap with sediments over PCA1, while modern surface sediments overlap with Preclassic, Classic, and Postclassic sediments because possibly the landscape was similar in openness (Figure 4.7). Analysis of multiple cores along the study site (e.g. Cahabón Catchment) will in the future allow a more complete view of the evolution of the floodplain.

Present day AP values range from 16 to 32% which corresponds to the current deforested and open landscape at the Cahabón River Floodplain, but with scattered forest remnants in the valley slopes (Figure 3.5 and Figure 4.8). In comparison the 11% arboreal content at the late-Preclassic could be signalling even less presence of continuous forest cover, and more open shrubland near the floodplain, most likely on valley slope environments.

Pollen abundance below 5% for Myrica throughout the core supports this hypothesis (van der Hammen and Hooghiemstra, 2003). Approximately 90 ky yrs BP, higher abundance pollen values (around 30%) at Lake Fuquene in Colombia indicate the presence of

Myrica shrub forest surrounding the lake. In the Las Verapaces region today at elevational ranges from ~1400-2000 masl, Myrica pollen is an indicator of open landscapes and humid grounds (Marchant et al., 2002) (i.e. 2-6% in surface sediments, see Chapter 3) which are similar to the values observed during the Preclassic (i.e. 1-4%).

In west-central Mexico today, montane forest taxon Quercus has remained non-dominant

121 in the pollen record, even when it has maintained a stable presence during fully-forested conditions (Figueroa et al. 2008), but in this case, the presence of Myrica pollen throughout the core supports a more open structure vegetation.

The existence of an open environment during the late-Preclassic is highly supported by the presence of Asteraceae pollen, a disturbance-related family of vegetation. Asteraceae pollen dominates the floodplain until the end of the Postclassic when agriculture ceased.

Other pollen taxa that indicate localized disturbance include Amaranthaceae

/Chenopodiaceae and Poaceae. The latter pollen types have opposing patterns of maximum values (r = -0.52 p = 0.02), possibly related to different phases of post- agricultural vegetation succession. Present day Poaceae pollen has greater values in the floodplain (16 to 66%) than in the past (3 to 28%), evidence for the current major land use as pasture lands (e.g. grasses). Lower present day values of Asteraceae (<16%), support the idea that land use was different in the past (e.g. agriculture) (Figure 3.5 and

4.7). The floodplain could have exhibited high water table levels until the middle-Classic

(supported by a change in PCA1 values in Figure 4.5), since low values of Cyperaceae indicates flooded environments (e.g. deep waters). Although Cyperaceae represents azonal vegetation of aquatic environments, it has been found that its preferred establishment conditions are from shallow waters at shore locations in lakes and floodplains, but not deep waters (Van’t Veer and Hooghiemstra, 2000). The increase of water table and periodic floodings in the floodplain could be the result of Mayan hydraulic management that included the production of canals, water reservoirs, and raised fields for agriculture (Beach, 2003). A rise in water table may have precluded the

122 successful colonization of other aquatic plants that prefer shallower shore conditions such as Polygoynum and members of the Apiaceae, Juncaceae and Typhaceae families (Berrio et al., 2002). Another explanation for the decrease in Cyperaceae involves removal related to anthropogenic use and management (Macia and Balslev, 2000). Ordinations including NAP modern data show that similarly high percentages of Cyperaceae are found both during the late-Classic and modern times, possibly because both time periods are characterized by minimal minimum hydraulic or agricultural management, and therefore flooding events (Figure 4.7). Archaeological work in the floodplain is needed in order to be more conclusive about the existence of such agricultural structures.

Analysis of quantity and size of macroscopic and microscopic charcoal throughout the core will complement hypotheses on the use of the site for Mayan agriculture.

Pinus values from the Preclassic are lower than at present, suggesting the presence of an agricultural regime during the Preclassic period on the floodplain. Pinus is generally one of the first trees to colonize open areas and is traditionally appreciated as a pioneer species in vegetation succession (Conserva and Byrne, 2002). The fact that Pinus does not ever seem to increase in abundance could be evidence that Pinus was under Mayan management (i.e. fuelwood and ceremonial uses), which prevented its colonization in agricultural fields and environs (e.g. valley slopes). During the Preclassic, Classic, and

Postclassic, the floodplain generally remains an agricultural center, characterized by surrounding open landscapes with isolated shrubby patches of Myrica interspersed throughout the environment. Some minor changes in arboreal content, however, may be signalling small regional changes in landscape structure.

123

Figure 4.7. Principal Component Analysis (PCA) of modern pollen rain samples from Purulhá highlands and sampled levels from core P-4. Triangles represent bryophyte polster modern samples, diamonds are modern surface sediments, and (+) are sedimentary records.

124

Arboreal pollen values gradually increase through to the late-Preclassic (from 12 to 18%), probably due to a decrease in agricultural activity associated with the Mayan Preclassic collapse (Arnauld, 1987; Dahlin et al., 1987). According to modern pollen calibration

(Chapter 3), Poaceae pollen may be highly represented (i.e. less than 20%) in the background signal from continuous forest because it is always found in low values.

Cyperaceae and Polygonum (notably successful in shallow water shore environments) increase at the transition, likely as a result of lowering water-table levels on the floodplain caused by temporary abandonment of strict water management practices (PCA

1 values slightly increase). It has been observed in Pacific Ocean coastal pollen records in

Guatemala that as mangroves decrease due to environmental changes (sea level drop

5500 yrs BP), aquatic plants such as Cyperaceae increase (Neff et al., 2006). In the floodplain Asteraceae values decrease as the temporary and partial halt to large-scale agriculture allows colonization from other herb species. Amaranthaceae-Chenopodiaceae pollen increase at this time indicating onset of secondary succession on some but not all plots as Zea pollen remains present at this time. From the onset of the Classic until the end of the Postclassic period, arboreal pollen values once again decrease, likely due to a reestablishment of large-scale agricultural practices in the floodplain.

125

4.4.3 Classic-Postclassic transition and its effects on floodplain management

Based on the apparent absence of Zea pollen in the P-4 core at the transition between the

Classic and Postclassic period, it is likely that large-scale agriculture is temporarily locally abandoned (reflected as an abrupt change in PCA1 values). From the anthropogenic point of view, absence of Zea pollen in Copán at the Classic-Postclassic transition has been interpreted as a temporary abandonment of local agricultural land and as temporary migration to nearby locations, and not necessarily a complete abandonment

(McNeil et al., 2010). However, this reconstruction has to be cautiously interpreted since

126 the Classic-Postclassic transition samples have relatively low pollen concentration in P-4 core (Figure 4.1).

Recognizing that the Classical period in my study has few samples, careful interpretation is needed when reconstructing the floodplain scenarios at this time. However, pollen evidence indicates that possibly the start of the Classic (1780-1510 yrs BP) is characterized by the stable abundance of agriculturally-related pollen (Zea). This possibly determined the concomittant increase of Asteraceae that ecologically replaces (i.e. successfully out-competes) Amaranthaceae /Chenopodiaceae. Towards the end of the

Classic (late-Classic to Terminal Classic, 1510-1240 yrs BP), Cyperaceae increases markedly which suggests a possible abrupt drop in the water-table level of the floodplain

(i.e. because Cyperaceae is extremely successful in shallow water environments) due to temporal abandonment of hydraulic management of agricultural terraces and raised fields.

This agricultural interruption is overlain by a background signal of decreasing arboreal pollen. Geological and geomorphological analyses (e.g. particle size analysis) of the floodplain will allow in the future a more complete reconstruction of the fluvial dynamics at the headwaters of the Cahabón River.

An arid climate event associated with an increase in solar activity is identified around ca.

1200 yrs BP by Hodell (2007) using stable isotope and lithological evidence from Lake

Punta Laguna in the Yucatán Peninsula. Titanium evidence, used as a proxy for the strength of the hydrological cycle, taken from the Cariaco Basin in Venezuela suggests that this drying event was widespread as three centennial periods of reduced rainfall were

127 reconstructed at that site for ~1190, 1140, and 1090 yrs BP (Haug et al., 2003). The P-4 core could be interpreted as indicating that agricultural practices were abandoned at the floodplain possibly related to a drought related event. A decrease in LOI values from 12 to 9% at the Classic-Postclassic transition (60 cm depth) could suggest a slight decrease in organic matter contribution to overall sedimentation. This decrease in LOI is supported by increments in percentages of Cyperaceae and Poaceae (PCA1 values), as both expand when water table lowers.

However, the occurrence of a drought is not likely for the Cahabón River Floodplain, as this lowering in the water table could be due to cultural management (e.g. abandonment of agricultural terraces) since the percentages of Cyperaceae and Poaceae at the Classic-

Postclassic transition are similar to present day when no drastic drought has been registered (Figure 4.7). It is possible that agricultural practices were temporarily transferred to a different location along the floodplain as a regular practice, as suggested by pollen reconstructions by McNeil (2010) for Rio Amarillo in the Copán Valley

(Honduras). Analysis of stable oxygen isotopes is needed to permit more conclusive inferences about drought occurrences in the Las Verapaces highlands.

Climate as a causal element for the Mayan collapse during the terminal Classic is still a contentious issue (Aimers, 2007; Powell, 2008). Agriculture at the Cahabón floodplain during the Classic-Postclassic transition may have been temporarily abandoned (i.e. as

Zea pollen absence suggests) but the reappearance of Zea pollen during the Postclassic indicates that agriculture is likely re-established. The recovery of agricultural activities at

128 the floodplain seems to contradict theories postulating a complete and widespread collapse of Mayan societies across Mesoamerica (Arnauld, 1988; Borgstede and Mathieu,

2007). On the other hand, if the temporary disappearance of Zea represents a counting artefact for P-4 core, continuous agricultural activity is supported during the Classic-

Postclassic transition. However, changes in other pollen taxa (e.g. Aquatics and

Asteraceae) during this transition support temporally local abandonment of the Cahabón floodplain.

The hypothetical abandonment of the floodplain at this transitional period (Classic-

Postclassic) allowed a change in vegetation succession to take place, possibly due to a halt in hydraulic management operations which led water levels to decrease abruptly. By the time that agriculture is re-established at the Postclassic (indicated by the reappearance of Zea pollen), Cyperaceae reaches the lowest values (from 138 to 29%) as an indication of a higher water-table related to artificial flooding (e.g. deeper waters). The marked decrease in sedimentation rate from 0.036 to 0.018 cm yr-1 during the Postclassic supports the continuity of soil conservation practices in the Cahabón floodplain (Figure 4.1), although possibly with less complex hydraulic management (i.e. less water volumes in channels). A two-fold increase in LOI (9 to 16%) suggests secondary vegetation succession taking place at the floodplain environs (i.e. increase of organic matter input), as pollen from Asteraceae and Amaranthaceae/Chenopodiaceae increase temporarily at this time. Cyperaceae is being replaced by trilete spores (increase from 42 to 107%) and monolete spores (increase from 18 to 41%). Based on modern day calibration (Figure

3.5), the former may indicate for the Postclassic a temporary forest recovery (i.e.

129 scattered forest remnants) because trilete spores may represent tree fern taxa found in forested environments (e.g. tree ferns from Cyatheaceae family) (Van’t Veer and

Hooghiemstra, 2000), while the latter supports disturbance due to landscape management.

Archaeological evidence from the terminal Classic in the Maya highlands at Las

Verapaces indicates a vigorous creativity and imagination at the ceramics production level (Arnauld, 1987), which possibly means that although activities at the urban centers may have not halted nor declined, they may have temporarily at the agricultural centers, such as the Cahabón floodplain.

4.4.4 European conquest and possible climatic variability

The end of the Postclassic is clearly characterized by a change in pollen assemblages in the P-4 paleoecological record (over 270 yrs, during the period 420 to 150 yrs BP) (PCA1 values show a marked change). A critical increase in sedimentation rates (from 0.018 to

0.17 cm yr -1) may be indicating that soil conservation practices have been abandoned and that agriculturally-related structures such as terraces have been removed. According to historical documents from Catholic Dominic Missionaries (Godoy, 2006), approximately eight cities (e.g. including Cobán and Purulhá) in the Las Verapaces region were located along the Cahabón Floodplain, all established in a 30-year period from ca. AD 1544 to

1574. This 30-year period falls within the 400-year period characterized by the decrease of Zea pollen as a result of the onset of the European Conquest (~400 yrs BP). Due to decreasing water-table levels on the floodplain, Cyperaceae once again becomes a dominant pollen type, trilete spores decrease possibly due to diminishing forest cover, and monoletes spores maintained relativey high values due to high levels of disturbance.

130

Asteraceae co-dominates with the disturbance related taxon Alternanthera (Marchant et al., 2002), which appears for the first time along the core. Although not an exotic species in Latin America (i.e. found in Amazonian pollen records dating to 8 ky BP), the presence of Alternanthera is related to abrupt land-use change, abandonment of traditional agricultural practices in the floodplain and the installment of different

European management regimes (i.e. Colonial period and modern times) (Behling et al.,

2001).

A critical change in land management at the time of the European conquest is supported by other patterns observed in the P-4 core. Increases in Hedyosmum pollen may show development (succession) of the lower montane and montane forest during the 16th century, while Quercus pollen decreases temporarily (close to 1%). It is possible that selective forest management is being practiced, because while Quercus is extracted for timber and fuelwood (Ramírez-Marcial et al., 2001; Ramírez-Marcial, 2003),

Hedyosmum stands appears to have been left unaffected based on P-4 pollen record.

Pinus pollen increases several-fold during this time period and this could be explained by the fact that Pinus is a pioneer in disturbed conditions (Richardson, 2000). Similarly, based on pollen records, pioneering colonization by Pinus has been suggested during the same period at Laguna Azteca in Central Mexico (Conserva and Byrne, 2002). On the other hand, in a 4200-yr paleoecological study at Sierra Manantlan Biosphere Reserve in the West-Central Mexican highlands, under low to null human disturbance, Pinus colonization responded positively to intervals of aridity (Figueroa-Rangel et al., 2008).

During the 20th century until the present, Pinus pollen decreases (reflected in a change of

131

PCA1 values) (Figure 4.1) probably due to extraction of pine trees for timber use, and because of land use change in the floodplain to cattle pastures and agriculture, which are now a more serious threat for forest species conservation than climate change (van

Zonneveld et al., 2009).

Indicator pollen type from higher elevation (mixed montane forest) Abies briefly appears for the first time in the sedimentary record at the onset of the European conquest (422 yrs

BP), and remains present until the 20th century (Figure 4.1). Appearance of Abies in the

P-4 pollen record matches approximately solar minima events experienced at the time of the Little Ice Age ca. 300-400 yrs BP (Helama et al., 2009). A Mesoamerican regional drop in temperature, associated with drier conditions has been identified in sedimentary records from the Yucatán lowlands (Hodell et al., 2005, 2007), and lakes Zempoala and

Quila in Central Mexican highlands (Almeida et al., 2005). On the other hand, in Lago

Verde, Los Tuxtlas in Mexico (Lozano-García et al., 2010) humid conditions 300-400 yrs

BP promoted an increase in abundance of pollen of upland vegetation. Core P-4 and other highland pollen records may support differential effects of the Little Ice Age cooling event, in general terms increasing aridity in the lowlands and increasing humidity in the highlands. Temporary decreases of Abies and Myrica pollen (~300-100 yrs BP) are possibly explained by increases in regional and local timber harvesting and land clearing by Spanish colonizers, respectively (Islebe and Hooghiemstra, 1995; Andersen et al.,

2006). Land clearing at the Cahabón valley slopes, led possibly to Myrica’s niche occupation by Pinus. Despite of the currently deforested landscape conditions (~60% forest removal) at the Cahabón floodplain, there seems to be an increase at present in

132 pollen indicative of the Montane Cloud Forest and Mixed Montane Forest vegetation belts, possibly due to recent conservation efforts (CECON, 1999; Jolon-Morales, 2007).

4.5. Chapter Summary

Changes in fossil pollen spectra in the P-4 core from the Cahabón River Floodplain corresponded to transitions between Mayan cultural periods and the start of the European conquest (ca. 350 yrs BP). The geographical location of the headwaters of the Cahabón

River, where the P-4 core was collected, fulfills geomorphological conditions for the possible existence of a paleolake in the plateau where currently the floodplain exists. LOI values (ca. 10%) and the non-preservation of pollen support the paleolake explanation.

Agricultural practices are inferred from the appearance of pollen, which is mainly non- arboreal (e.g. Asteraceae and Zea), together with slight increases in LOI values (>10%) and low values of Cyperaceae pollen (which prefers shallow water in shore environments). Based on this evidence it is believed that Mayan agriculture was developed during the transition from lacustrine to floodplain conditions. Sedimentation rates on the floodplain decreased many-fold ca. 360 yrs after the first pollen appearance, which is possibly evidence for the development of agricultural terraces that eventually dimished and controlled locally soil erosion.

During ca. 2000 yrs of agriculture there is evidence of a temporal abandonment of agriculture in the floodplain during the Classic-Postclassic transition, because temporarily

Zea pollen disappears, Cyperaceae and Poaceae pollen increase (e.g. less flooding of

133 terraces), and LOI slightly decreases (12 to 9%). Effects of the occurrence of the known

Mesoamerican megadroughts are not obvious in the floodplain record presented here, since the temporary increase of indicators of dryer conditions (e.g. Cyperaceae and

Poaceae) have values similar to current ones according to modern pollen rain calibrations when no droughts are registered. The appearance of Abies pollen in sedimentary record at the end of the Postclassic ca. 350 yrs BP could be an evidence of regional cooling conditions related to the Little Ice Age cold event.

Agriculture re-establishment during the Postclassic (e.g. Cyperaceae and Poaceae pollen decrease, and Zea pollen reappears) is completely halted by the European conquest, as evidence of disturbances is registered in the sedimentary record, including: abrupt increase of sedimentation rates (0.018 to 0.17 vm yr-1), appearance of disturbance related pollen taxa (e.g. Alternanthera), increase of Cyperaceae pollen due to change in land use

(e.g. lower water table for non-agricultural land use, such as cattle pastures), and increase of Pinus pollen; Pinus colonizes areas that have been cleared for timber extraction and the development of European colonies. The major change in the sedimentary record is related to environmental disturbances after the European conquest over ca. 300 yrs, never seen before in 2000 yrs of history.

134

Chapter 5: The Lachuá Lowlands Rain Forest in Guatemala: 2,000 yrs of forested landscape?

5.1 Introduction

Along the banks of the Chixoy River at the foothills of the Sierra Chama and south of the

Petén Lowlands, there was a city known as Salinas de los Nueve Cerros (Figure 1.2 and

1.3). It was located in a unique landscape, at the intersection between highlands and lowlands, and was a city known to play an important role as salt producer since Preclassic times. The city epicentre is located around the Tortugas and Nueve Cerros hills, where salt extraction took place from an exposed salt dome (Andrews, 1983; Woodfill, 2012).

The city is located close to the floodplain of the Chixoy River, a likely location for agricultural activity. Salinas de los Nueve Cerros probably reached its climax during the late-Classic and was abandoned during the Postclassic; its abandonment was likely in response to the reduced important of salt production during the Terminal Classic, when major cities no longer required large quantities of salt (Arroyo, 1994). Perhaps due to its reliance on salt as an economic resource, the surrounding forest was likely less disturbed than cities that relied on large-scale agriculture. Scientific expedition reports dating to the the 16th century, indicate that the area around Salinas de los Nueve Cerros was likely covered in dense and continuous forest. By ca. 1950, the region still had a forest cover close to 100%, although currently it has decreased to ~50% (Avendaño et al., 2007).

135

Archaeological studies indicate that land use intensity (i.e. agriculture) increased towards the epicentres of Mayan cities (Johnson et al., 2007), leaving outskirts with less urban development, however in some locations urban and rural land use intensity was similar

(Beach et al., 2009). Agriculture was developed using a variety of strategies, such as stone boxes, terraces, swidden techniques (i.e. slash and burn), including crop rotation and forest management (e.g agroforestry) (Demarest, 2005). Agroforestry involved the combination of agriculture and management (silviculture) of beneficial trees (e.g. food, medicines, tools, construction, ceremonial), in a strategy that imitated forest structure and distribution patterns, in the so-called Maya forest gardens (Ford and Nigh, 2009; Ross,

2011). Silviculture was probably more intense than agriculture in furthest points from city epicentres as population density decreased.

The overall objective of this study is to examine a sediment record spanning 2000 years from a wetland located next to Lake Lachuá, approximately 5 km southwest from Salinas de los Nueve Cerros and within the Lake Lachuá National Park. This region is of interest because it lies in a transition zone between the lowlands and highlands of Mayan occupation and has not yet been studied. The Lake Lachuá National Park is currently the last remnant of tropical rain forest in the Franja Transveral del Norte region. The past 60 years has seen much disturbance of natural forests due to (1) colonization of displaced populations, (2) introduction of export cash crops, and (3) most recently oil exploration.

Since this region has a rich history of human-environment interactions spanning pre-

Hispanic to post-Colonial times, I expect that most changes to vegetation will have some

136 relation to human land management and not to climate change. Calculations of the approximate age of the existing remnants of tropical rain forest at Lake Lachuá National

Park should enrich discussions of forest conservation, in particular, the baselines necessary for successful conservation of biological diversity.

5.2 Methods

5.2.1 Core Sampling and Laboratory Work

With the use of a Livingstone Corer, I extracted a ~0.5 m core from the Lachuá Lowlands in a wetland located at the northeast section of the Lachuá Lake (labeled as L-3), at approximately 10 m from the shore (Figure 1.3). The location of L-3 core was cautiously selected in order to avoid any disturbance from modern hydrological modifications, landslides or incoming or outflowing rivers. Coring was stopped once it became impossible to continue due to stiffness of sediments.

The top centimeter of each core was separated for modern pollen rain calibration

(Chapter 3), and the rest was wrapped in aluminum foil and enclosed in a PVC pipe. A 1 ml sub-sample was taken every 2.5 cm along L-3 core. Sub-samples were stored in

Ziploc bags, and the core’s stratigraphy was qualitatively described. After proper labeling, the core and the subsamples were stored in a cold room.

According to the Department of Geography Protocol (No. 010) of the University of

Leicester, samples were pre-treated overnight with pyrophosphate, followed by standard acetolysis procedure and heavy liquid separation with the use of bromoform (Fægri and

137

Arboreal pollen (AP) and non-arboreal pollen (NAP) percentages were calculated to represent local landscape vegetation cover. The Paleoecology Laboratory Loss of ignition

(LOI) protocol from the University of Toronto (Heiri et al., 2001) was applied for each subsample where pollen was analyzed (see above), to calculate the organic (550°C), inorganic (950°C), and silicate (% left) contribution to the sediment sample (estimated

2% error in the measurement). Only the LOI at 550°C is presented and referred as "LOI"; it is expressed as percent of dry mass In the L-3 core, a bulk sample from the lowest level

(47.5 cm in depth) and one additional sample (22.5 cm in depth) were radiocarbon dated to develop models of sediment accumulation rates. Dates were calibrated through the use of the IntCal04 curve from CALIB 6.0 (Stuiver et al., 2005).

5.2.2 Core data analysis

Pollen counts were tabulated for pollen types and core levels, including for the surficial level, for comparison with the modern pollen rain data presented in Chapter 3. Arboreal and non-arboreal pollen types were included in the pollen sum, excluding aquatics (e.g.

Cyperaceae), pteridophytes spores, and unknowns. For pollen concentration, all counts

138 were included. Principal component analysis (PCA) was performed with the statistical package PAST (Hammer et al., 2001) to describe changes in pollen spectra along the core including common and rare taxa. The software C2 (Juggins, 2003) was used to construct a stratigraphic diagram (based on depth measured in cm and calibrated time scale) based on relative abundance of arboreal (temperate trees and shrubs) and non-arboreal pollen types, aquatics, pteridophytes spores, LOI (loss-on-igition), sedimentation rate, and PCA axes scores. The stratigraphic diagram was divided into zones according to cultural periods defined for Mesoamerica (i.e. see Introduction, section 1.6).

An analysis based on nine regional studies and my data (Mexico and Central America) spanning the Preclassic to colonial times (Almeida et al., 2005; Carrillo-Bastos et al.,

2010a; Conserva and Byrne, 2002; Dull et al., 2010; Figueroa-Rangel et al., 2008; Islebe and Hooghiemstra, 1997; McNeil et al., 2010; Wahl et al., 2006) was performed in order to compare my calculated sedimentation rates with values found in other Mesoamerican highland and lowland scenarios. The sites used in this regional comparison were placed into groups according to elevation (0-500 m, 500-1000 m, 1000-2000 m, and 2000-3100 m) and cultural periods (Preclassic, Classic, Postclassic, and Colony), to determine if the sedimentation rates in core L-3 were expected or outlier values for the groups to which they belonged (see section 2.4.3 for further explanation). The analysis was complemented with a Kruskal-Walis test to test the coherence of created elevation and cultural period groups. The sedimentation rate values for core L-3 are compared to other sites in the same elevational range (0-500 m), and across four cultural periods.

139

5.3 Results

5.3.1 Stratigraphic description

The L-3 core is composed mostly of a homogeneous dark peat with some fine-grained inorganic inclusions and scattered wood fragments, with no clear stratigraphic differentiation. Wood fragments are identified along the core at different depths.

LOI values found at the bottom of the L-3 core are characteristic of wetland environments (~ 80-90%), with variability in LOI observed along the core likely being representative of human activity during known cultural periods of the Maya (Figure 5.1).

LOI between 47.5-45 cm core interval decreases gradually from 92 to 86%, during the late-Preclassic period (i.e. core time interval 1835-1750 yrs BP). At the Preclassic-Classic transition, LOI values decrease once again from 86-85% to 79% in approximately a span of 90 years (time interval 1750-1580 yrs BP). LOI values remain relatively stable (75-

81%) for the remainder of the Classic period (1580- 1070 yrs BP). There is a notable decrease in LOI values down to 68% shortly after the Classic-Postclassic transition (~90 yrs), but as it stands as a single point, it should be carefully interpreted. Decreasing LOI indicates a relatively reduced contribution of organic matter into the sediment. During the

Postclassic and European Conquest-Colonization, LOI values remain stable around 82-

86%.

140

Table 5.1. AMS radiocarbon dates, calibrates age ranges from dated sediment from P-4 core of the Cahabón Floodplain, Purulhá. Bold numbers in brackets are the calibrated dates. All radiocarbon dates material is from bulk samples.

Depth (cm) Lab. No 13C/12C 14C yrs BP Age range 2σ and Median Age (cal yrs BP)

22.5 Beta-281242 -27.8 990±40 795-(902)-964

47.5 GrA-40111 --- 1835±30 1705-(1773)-1864

5.3.2 Chronological control and sedimentation rates

The oldest age of 1835 yrs BP corresponds to sediments found at the bottom of the L-3 core at a depth of 47.5 cm (Table 5.1). The second date taken from the core is 990 yrs BP and is found at a depth of 22.5 cm. The depth versus age model is very close to linear (r2=

0.99) although significance of this relationship will be tested when more radiocarbon dates are obtained. Based on the L-3 chronological model, a relatively slow accumulation rate of 0.026 cm yr-1 is observed, a value similar to the slow sedimentation rates observed in the P-4 core (0.018 and 0.036 cm yr-1) during the time of Mayan agricultural management of the Cahabón floodplain (see Chapter 4). The accumulation rate found for the L-3 core (0.026 cm yr-1) is not an outlier in the groups they belonged according to elevation and age (Figure 4.3). For further information about regional Mesoamerican analysis of sedimentation rate values, see section 4.3.2.

141

Figure 5.1. L-3 core paleoecological diagram taken from a wetland next to Lake Lachuá. AP = Arboreal pollen (%); LOI550 = Loss on ignition at 550°C; PCA1 and PCA2= Axis 1 and 2 scores from principal components analysis. Mayan cultural periods are shown. The Guatemala zone represents modern day Republic of Guatemala. Pollen concentration (x1000 grains/cm3).

Herbs Pteridophytes

3) /cm s in a gr

(x1000

tration n e s nc ) o P heno ete B cm C l es aceae s ( 1 2 h a/ et len c yr m ea ono yper OI ol CA CA al ept AsteraceaePoaceaeA Z M Tril C L P P P C D 0

200 5 Guatemala

400 10

600 15

800 Postclassic 20 1000 25

1200 30

1400 35 Classic

40 1600

45 Preclassic 1800

0 0 0 0 02448720 163248640 0 204060801000 50 100 150 -24 -12 0 12 24 -12 -4 4 12 20 Percent abundance

142

5.3.3 Description of pollen diagram

The variability found along the first and second axes of my principal component analysis

(PCA1 and PCA2) is consistent with the a priori pollen zones based on Mayan cultural periods (Figure 5.2). Based on PCA1, primary variability is explained by a change in vegetation composition from Solanaceae to Combretaceae/Melastomataceae, where

Solanaceae dominates from the late Preclassic until the Classic-Postclassic transition, and then is replaced by Combretaceae/Melastomataceae (which in turn dominates until 100 years ago). There are other secondary changes in vegetation succession observed in

PCA1 that are explained below (see pollen zones). PCA2 is governed mostly by variability in regional and local pollen rain, more specifically, by Ilex and a group of tropical pollen types (e.g. Terminalia, Sapium), respectively.

I present in the pollen diagram common and rare taxa identified at least to genus and family (Figure 5.3). Zones were closely related to four cultural periods: Terminal Pre-

Classic, Classic, Post-Classic, and Colonial to modern-day Guatemala. The two bottom levels represent the Terminal Preclassic, where the Preclassic-Classic transition had no pollen content. The non-arboreal pollen contribution is relatively low overall in the L-3 core (<10%).

143

Figure 5.2. Principal Component Analysis (PCA) of sampled levels from core L-3. PCA1= scores along first principal component axis, PCA2= scores along second principal component axis. PC= preclassic levels, C=classic levels, PT=postclassic levels, G= Guatemala zone, Modern= represents surface sediment (0-1 cm).

144

Zone 1: Terminal Preclassic (1835-1750 yrs BP)

Information about vegetation from the Terminal Preclassic comes from the second last level, since both the bottom and the Preclassic-Classic transition levels contain no preserved pollen. Despite the fact that the bottom level at 1835 yrs BP has no preserved pollen, the highest LOI value (92%) at L-3 core is observed at this level, and may be related to a higher vegetation cover in the wetland (i.e. less opened-up landscape).

Possibly oxidation processes at both levels due to temporarily dessication (e.g. lower water levels) resulted in null preservation of pollen.

Solanaceae dominates the pollen assemblage from this single sample dating to the

Preclassic (32%) to the late-Classic, with other taxa such as Alchornea and Spondias co- dominating at ~5%. Other tropical taxa such as Psychotria, Combretaceae

/Melastomataceae, Bursera, Rubiaceae and Terminalia are present at lower values (1-

7%); while Arecaceae, Brosimum, Caesalpinaceae, Celtis, Malphigiaceae, Myrtaceae,

Pachira, Sapium, Sapotaceae, and Trema are absent when compared to modern samples.

At 1750 yrs BP (end of the Preclassic), the temperate taxon Myrica co-dominates with

Solanaceae at 26% and shows a positive correlation for the rest of the core. Regional taxa

Pinus and Quercus are present at intermediate values (6 and 4%, respectively), Alnus and

Hedyosmum at low values (1%), and Hyeronima and Abies are absent during this period.

In fact, Hyeronima, Abies and Alnus are regularly absent at locations along the core.

Although Ilex is at low values (2%) in this period, it will soon become an important taxon for explaining variability along the core.

145

Figure 5.3. Pollen percentage diagram of L-3 core from a wetland next to Lake Lachuá. + = taxa appearing at <1%. Mayan cultural periods are shown. The Guatemala zone represents modern day Republic of Guatemala.

Tropical trees and shrubs Temperate trees and shrubs

e a ceae um ea i a naceae P c as tria pi s m) nal o igi a aceae B c aceae i h bacaceae cu s m ph ser es A1 yr olana yrtaceae lchorneaubi pondi er syc al ur apot iper rema om aesal edyosm bi P C epth ( S Comb/Melas M A R S T SapiumP ArecaceaeM B S P Celtis BrosimumT B C Ilex H HyeronimaMyrica Quer Pinus A Alnus A P PCA2 Cal D 0

200 5 Guatemala

400 10

600 15

800 20 Postclassic

1000 25

1200 30

1400 35 Classic

40 1600

45 Preclassic 1800

02040020400200 0 0 0 0 0200 0 0 0 0 0 0 0 0 0 0200 0 0200 0200 0 0 20406080100-24 -12 0 12 24 -12 -4 4 12 20 Percent abundance

146

Non-arboreal pollen contribution is low (4%) and is characterized by Asteraceae and

Poaceae pollen. Cyperaceae is present at intermediate values (3%) and only increases significantly at the end of the Classic and in modern times (8%). Monolete and trilete spores show relatively intermediate values (34 and 23 %, respectively) during the late-

Preclassic.

Zone 2: Classic (1750-1070 yrs BP)

Although Solanaceae dominates during the Classic (32%), it shows a subtle decreasing trend (down to 25%) up to the Terminal Classic (1070 yrs BP) when it is replaced by

Combretaceae/Melastomataceae. Combretaceae/Melastomataceae experiences a decrease in abundance during the middle Classic (from 9 to 6%), but progressively increases towards the Terminal Classic (18%). Some arboreal taxa decrease in abundance at the

Terminal Classic, behaving similarly to Solanaceae. These taxa include Alchornea (8-

5%), Psychotria (16-1%), and Rubiaceae (5-2%). Myrtaceae increases during the Classic

(15-4%) and abruptly decreases at the Classic-Postclassic transition or shortly thereafter.

The regional taxon Ilex (9-3%) follows a similar increasing and abruptly decreasing trend.

Regional taxa, Myrica and Pinus, show a decreasing trend from the onset of the Classic towards the Postclassic. Alnus appears during the early-Classic (1%) and slightly increases at the Classic-Postclassic transition (~2%). Other arboreal taxa are scarcely present, although Arecaceae, Bursera, Celtis, Malphigiaceae, Sapotaceae and Trema appear in minor abundances during the Classic. Herb species (Asteraceae and Poaceae)

147 and Cyperaceae are also scarce until the Classic where they appear in minor abundance.

Zea appears only once in a very low abundance (1%) during the early-Classic, and reappears (~2%) continuously until the modern period (110 yrs BP). Abundances of monolete spores are relatively low, while trilete spores have their maximum relative values during this period. Both show a sharp peak at the Classic-Postclassic transition (as they did during the late-Preclassic).

Zone 3: Postclassic (1070-440 yrs BP)

Solanaceae (~22%) and Combretaceae/Melastomataceae (~23%) co-dominate during the early Postclassic, and then the former progressively decreases until the present.

Combretaceae/Melastomataceae has a bell shaped dominance curve during the

Postclassic, reaching a maximum (33%) at the middle-Postclassic (770 yrs BP).

Following Combretaceae/Melastomataceae decreases until the late-Postclassic (22%), remaining nevertheless as dominant taxon during cultural period. Other arboreal tropical taxa such as Myrtaceae, Alchornea, Rubiaceae, and Spondias are present at low and intermediate values (2-14%) without showing a stable pattern. Some arboreal taxa,

Terminalia, Sapium, Malpighiaceae and Psychotria, are consistently present in the core but at lower values (1-4%). The remaining arboreal taxa, such as Arecaceae,

Bombacaceae, Bursera, Celtis, Sapotaceae and Trema, are present in few levels at low values (~1-3%) as they are during the Classic period. Brosimum pollen is present at low values (~1%) for the only time in the L-3 core.

148

Temperate taxa like Myrica, Quercus and Pinus are generally less abundant during the

Postclassic. In contrast, Ilex shows an abrupt increase during the early Postclassic

(represented by a change in PCA2 values), although overall it generally maintains intermediate values throughout the core. Hyeronima reappears and increases during the

Postclassic (1-4%), whereas Alnus reappears and remains relatively stable (1-2%) during the Postclassic. Herbs and Cyperaceae maintain a similar pattern from the Classic and are not abundant (<4%). Monolete spores gradually increase during the Postclassic, while trilete spores decrease markedly in abundance.

Zone 4: Colonial to Modern Guatemala (440 yrs BP-Present)

Solanaceae and Myrtaceae maintain intermediate values (7-12% and 4-13%, respectively) in the last ca. 400 yrs. Combretaceae/Melastomataceae increases at the onset of the

Colonial period (from 22-32%) and then decreases towards the present (15-6%).

Alchornea, Rubiaceae, and Spondias show a decreasing tendency towards the present (ca.

7 to 1%), whereas Terminalia, Sapium and Psychotria show an increasing trend towards the present (ca. 2 to 9%). Tropical arboreal taxa like Bursera, Sapotaceae, Celtis, and

Malpighiaceae are present at low values (<2%). Trema slightly increases its abundance up to the present-day (1 to 2%).

Ilex, Pinus and Myrica progressively increase towards the present-day (~ 3 to 15%), whereas Hyeronima stays stable until it disappears from the modern-day sediments. Alnus is present only at low values (~1%) during the Colonial period and then disappears, and

Quercus slightly increases towards the present-day (1 to 3%). Asteraceae and Cyperaceae

149 maintain low values at 2-5% and 1-8%, respectively. Poaceae begins at a low value and decreases at the present. Zea appears for the second time ca. 110 yrs BP. Monolete and trilete spores disappear at 220 yrs BP and then monolete spores show an abundance peak

110 yrs BP and trilete spores present their lowest relative values.

5.4 Discussion

5.4.1 Role of cultural management and vegetation succession

Pollen information from our L-3 core is likely supporting the existence of Mayan forest

management practices close to Lachuá Lake at the outskirts of Salinas de los Nueve

Cerros (Figure 5.4). Pollen of arboreal taxa that have been identified as important tree species to the Maya (e.g. Psychotria, Spondias, Terminalia) have been found in L-3 core, in addition to high arboreal pollen percentages (as much as 80% or more abundance) that reflect a densely-forested portion of the landscape. At the Classic-Postclassic transition, vegetation succession likely reflected cultural activities. For example, dominance of

Solanaceae pollen in L-3 core from the Preclassic to the Classic indicates managed forest because this pollen type is an indicator of shrubs and small trees taxa of secondary succession (e.g. Cestrum, Lycianthes, Lycium) (Marchant et al., 2002). Some of these taxa had economic use (e.g. Capsicum, Solanum). The eventual dominance of trilete spores over monolete spores is possibly indicative of progressive successful forest management since the former benefits from lower levels of disturbance, as modern pollen calibration from Lake Lachuá National Park suggests that trilete spores are indicators of closed canopy forest (Figure 3.4 and Figure 5.5). Monolete spores were found in lower

150

Figure 5.4. Location of the ancient Mayan city of Salinas de los Nueve Cerros on the banks of the Chixoy River, Alta Verapaz, Guatemala. Blue shaded area represents current known maximum spatial extension of Salinas de los Nueve Cerros (Woodfill 2011). Gray polygon represents Lachuá Lake National Park. Irregular black lines represent rivers. Inverse dark triangle represents L-3 core location next to Lachuá Lake (light gray polygon). Figure modified from Dillon (1977) and Woodfill (2011).

151 abundances in forest interior conditions according to modern pollen calibrations (Figure

3.4).

Salinas de los Nueve Cerros was a key salt producing center for many important Mayan cities including the Petexbatún and Tikal kingdoms, and remained so until the end of the

Classic (Wright, 2005; Bachand, 2010). Decreasing Solanaceae pollen during the

Postclassic could be reflective of city abandonment (as reflected by a change of PCA1 values, Figure 5.1), where all major economic activities including cropping, selective tree extraction and forestry ceased to occur due to a drop in the economic importance of salt demand from larger cities facing major societal transformations (e.g. Tikal). The process of abandonment at the Classic-Postclassic transition has been identified in neighbouring Mayan cities of the Petexbatún Region, which is the location where it is believed the Terminal Classic so called collapse started (Demarest, 2006).

Once forest management was possibly halted by the Classic-Postclassic transition, vegetation succession was allowed to occur naturally, eventually resulting in dominance of old-growth forest species such as Combretaceae/Melastomataceae (e.g. Combretum)

(Marchant et al., 2002) as seen in the L-3 core. Trends in pollen abundance within the

L-3 core support this hypothesis. Combretaceae/Melastomataceae pollen has also been shown to increase at the onset of the Postclassic in other sites nearby, including Laguna

Naja (800 masl) located in the Mexican Lacandon Forest (Domínguez-Vázquez and

Islebe, 2008). The shift in Combretaceae/Melastomataceae dominance took approximately 200 years after the onset of the Postclassic (PCA1 values notably reflect

152 change), wherein populations remained dominant for the next ca. 600 years, only decreasing first 400 yrs BP and then abruptly during the last 150 yrs BP.

Information from our L-3 core strongly supports the possible existence of Maya forest

gardens located at the outskirts of the city-centre, Salinas de los Nueve Cerros. I found

pollen from taxa known to be planted by the Maya, including Terminalia, Spondias,

Psychotria, Myrtaceae, Rubiaceae, Sapotaceae, Arecaceae; and used by the Maya for

fuelwood, construction material, medicines, food (i.e. fruit, nuts), as well as latex

extraction (Ross and Rangel, 2011). The L-3 core contains these taxa in high abundance

during the Classic period, the heyday of Maya civilization (Schele and Freidel, 1990;

Freidel et al., 1993). Mayan gardens were planted so that the overall structure mimicked the horizontal and vertical dimensions of a natural forest (Ford and Nigh, 2009). When agroforestry likely ceased during the Classic-Postclassic transition, changes are recorded in the L-3 core among the preferred Mayan garden tree species; some of them declined abruptly and others disappeared for a short period. Nevertheless most of forest garden taxa observed in the L-3 core persisted through Postclassic and Colonial times. The occurrence of a detectable vegetation structure reflecting the composition of Mayan forest gardens has been found elsewhere in ancient Mesoamerican sites (Ford, 2008;

Ross, 2011).

Forestry management may have been successful in reducing soil erosion, as stable LOI values in the L-3 core suggest a continuous forest cover close to the wetland. Other lowland and highland Mesoamerican locations have generally had similar sedimentation

153 rates as was found for L-3 core (Islebe and Hooghiemstra, 1997; Figueroa-Rangel et al.,

2008; Carrillo-Bastos et al., 2010), which is relatively slow (0.026 cm yr-1) and consistent

with forested conditions surrounding the wetland that prevent high inputs of eroded

materials into the peat. In tropical regions, LOI values above 75% (and even as low as

20%) have been traditionally described as containing wetland-marsh environments

(Berrio et al., 2002; Torres et al., 2005).

During the early-Postclassic when silvicultural practices were probably abandoned in

Salinas de los Nueve Cerros, LOI abruptly decreased from 78 to 68% indicate decreasing

organic matter contribution into the sediment load. Diminishing LOI values are probably

explained by decreasing organic matter contribution (i.e. increase of clastic material to

sediment load) (Shuman, 2003), due to deforestation as a consequence of temporary

forest gap openings. Similar patterns have been found in ancient peatlands in Georgia near the Black Sea, where aeolian input increases in the sediment load due to more open landscape conditions (de Klerk et al., 2009). The LOI decrease at this single level

(Classic-Postclassic transition) in L-3 core has been reported in a core from Laguna

Tamarindito in the Petexbatún region, with a drop from ca. 85 to 60% (Dunning et al.,

1998). Around the time of the city abandonment, changes in pollen abundances (from disappearance to reduced values) of forest garden species in Core L-3 indicate a probable abrupt increase in the extraction of valuable plant taxa (i.e. during socially unstable transitional times). Monolete spores abruptly increase possibly reflecting temporary invasion of forest gaps. Shortly after (~ 100 years later), LOI increases to values above

80%, indicating forest recovery wherein late-successional tree taxa such as

154

Combretaceae/Melastomataceae begin to dominate the pollen record. In the literature regarding the neotropics, the problem of separating Melastomataceae (e.g. Clidemia for lowlands and Miconia for highlands) (see Tables 2.1 and 2.3) from Combretaceae (e.g.

Combretum) pollen taxa has been discussed (Marchant et al., 2002), but it is believed that possibly the former could be in higher abundances during early forest succession and progressively replaced by the latter as succession develops (Pascarella et al., 2007).

Nevertheless, the Combretaceae/Melastomataceae pollen type has been found to be representative of mature forests and seasonally inundated forest in Belize (Bhattacharya et al., 2011) and South America (Gosling et al., 2009), such as the forest that surrounded the wetland where Core L-3 was collected up until ca. 100 yrs BP when disturbances related to salt extraction increased (Figure 5.3) (Dillon, 1979).

5.4.2 Baseline for forest conservation at Lachuá lowlands region

Co-dominance of pollen from Combretaceae/Melastomataceae and Solanaceae lasted for

approximately 200 yrs after the Classic-Postclassic transition (PCA1 values remain

relatively constant), likely indicating that some economic activities such as silviculture

and salt production remained, but soon began to decrease gradually up to the complete

abandonment of Salinas de los Nueve Cerros. Salinas de los Nueve Cerros is believed to

have been inhabited by scattered populations after its abandonment because its name

appears in colonial historical documents dating from 1625 AD (Godoy, 2006). It is

registered in such documents that salt extraction by Europeans started around 1626 AD,

which matches the decrease in Combretaceae/Melastomataceae (Figure 5.3, ca. 500 yrs

BP) probably due to related natural resources extraction in the nearby area (e.g. timber).

155

Salinas de los Nueve Cerros was identified as a critical location for salt production, an economy that the Conquistadors felt they needed control to “pacify” local inhabitants.

Salt extraction was suspended for ca. 100 yrs due to local revolts, and resumed in the early 1700’s until the 20th century (Dillon, 1979; Woodfill, 2012).

Despite continued activity at the Salinas salt mine, the surrounding vegetation shows

signs of recovery (ca. 300 yrs BP) because the pollen record is dominated by

Combretaceae/Melastomataceae. Similar pollen taxa were found to increase in abundance

during the Postclassic in the nearby tropical rain forest region of the Mexican Lacandon

Forest (e.g. Combretaceae /Melastomataceae and Myrtaceae) (Domínguez-Vázquez and

Islebe, 2008) and in the less humid Mirador Basin in Northern Petén (i.e. Combretaceae

/Melastomataceae) (Wahl et al., 2006). Forest in Lachuá environs likely remained

without intense anthropogenic management for approximately 800 yrs after its

abandonment during the Postlassic (PCA1 values remain relatively stable until ca. 150

yrs BP, Figure 5.1). Nevertheless, relatively low values of trilete spores and higher

values of monolete spores (McNeil et al., 2010), suggest some degree of disturbance.

Arboreal pollen from Combretaceae/Melastomataceae, Myrtaceae, Alchornea, Rubiaceae,

and Spondias that can tolerate low disturbance regimes begin to show decreases in

abundance during the last 150 yrs BP. On the contrary, Solanaceae benefit from

intermediate disturbance regimes as L-3 pollen pollen record indicates an increase, more

similar to what is found in modern times in bryophyte polsters (Figure 5.5). The present

day pattern of Solanaceae and Combretaceae/Melastomataceae pollen (Figure 3.3) could

156 be associated with the fact that the Lachuá Lake National Park was recently established

(1974 AD) (Monzón, 1999), so most likely the forest is still recovering from recent disturbances occurring during the 20th century. Forest structure that prevailed from 770-

100 years BP changed dramatically during the 20th century, due to economic activities

that involved natural resources extraction, including salt production, oil prospecting

during the 1970’s, 1980's and 2000's, and arrival of displaced populations since the

1950's (Avendaño et al., 2007).

The remnant of tropical rain forest protected currently at Lake Lachuá National Park

(14,500 ha area) since the mid 1970’s is possibly more similar to the one that prevailed

during Classic times when forest gardens dominated land use at the outskirts of Salinas

de los Nueve Cerros (Figure 5.1 and 5.3). Present day PCA1 values are similar to PCA1

values during the Late Classic, suggesting similar disturbance levels.

A baseline to return to a “healthier” forest status (e.g. restoration) before recent

disturbances in the Lachuá environs could be considered to be the forest condition that

prevailed for approximately 800 years after Salinas de los Nueve Cerros was abandoned.

However, the core L-3 time span does not provide any reference for whether this 800-

year condition has an analog at earlier times before the Preclassic colonization at Lachuá.

The previous forest condition composed mostly of forest gardens lasted approximately

600-700 years was maintained under silvicultural principles which required deep

knowledge to imitate forest structure (Gomez-Pompa, 1991; Pyburn, 1998; Fedick,

2010). Although current arboreal composition is similar to the one from the Classic

157

Figure 5.5. Principal Component Analysis (PCA) of modern pollen rain samples from Lachuá lowlands and sampled levels from core L-3. (+) represent bryophyte polsters modern samples, triangles are modern surface sediments, and inversed filled triangles are sedimentary records.

10 PCA2

-32 -16

-10

-20

PCA1

158 period, silvicultural practices are at the moment not being used and therefore current forest management and disturbances may be leading forest into a new equilibrium state with no previous analog (Whitehouse, 2010).

5.4.3 Lachuá Lowlands in the context of Mesoamerican Holocene paleoecology

The location of the L-3 core at the intersection between lowlands and highlands is

important in order to cross-correlate Mesoamerican regional paleoecology (Islebe and

Leyden, 2006) (Figure 3.1). The Lachuá lowlands are located in a wet (high

precipitation) zone that extends from Izabal at the Guatemalan Caribbean coastline to the

Uxpanapa region in the Gulf of Mexico; this contrasts with the much lower rates of precipitation in the Yucatán Peninsula and the Petén lowlands (Imbach et al., 2010). The high precipitation in this zone is believed to have been consistent in the long term

(Wendt, 1989), because it is hypothesized that partly due to resultant wetter conditions, relicts (refugia) of tropical rain forest species were held during the last glacial cycle of the Pleistocene.

For Mesoamerican sites located outside the zone of high precipitation, a series of droughts occuring throughout the late Holocene (i.e. related to either insolation variability or migration of the Intertropical Convergence Zone) have been found to match important transitional cultural periods in Mesoamerica (i.e. Mayan Terminal Classic, the

Toltecs, the Aztecs and Spanish Conquest). These periods of drought have also been correlated with extensive measurements from Cariaco Basin in Venezuela that also show periods of low rainfall. Late-Holocene sites that indicate signs of drought in the paleo-

159 record are located in Central Mexico (Stahle et al., 2011), Northern and Southern

Yucatán Peninsula (Hodell et al., 2001; Carrillo-Bastos et al., 2010), and the Petén region in Guatemala (Islebe and Leyden, 2006; Gill et al., 2007). Changes in vegetation inferred from our L-3 sediment core do not support continued periods of droughts, because at levels in the L-3 core where droughts are expected to be observed, there are no changes in abundance of NAP pollen that could benefit from dryer conditions, such as Asteraceae,

Poaceae, and Amaranthaceae /Chenopodiaceae (Leyden et al., 1998; Wahl et al., 2006;

Wahl et al., 2007). Nevertheless, more high resolution exploration is needed in future studies in the Lachua region, since temporal resolution of the L-3 core may not be adequate to detect decade-long droughts that have been reconstructed for some sites in the Mesoamerican lowlands.

The time of major variability within the pollen composition from L-3 core is at the

Classic-Postclassic transition (PCA1 values cross the zero threshold which indicates opposing trends) and indicates culturally-driven dynamics and not natural climate forcing

(Figure 5.1 and 5.3). The changes in vegetation composition reflected in the L-3 core are likely directly related to cultural management of Mayan forest gardens. Non-arboreal taxa that tend to indicate occurrence of droughts (i.e. Asteraceae or Poaceae) do not show consistent increases at the time of cultural transitional periods (Wahl et al., 2006). Pollen and LOI information from the L-3 core both support a paleoclimate hypothesis of no extended periods of drought, an observation that may be explained by the site's location in the Izabal to Uxpanapa "wet belt". Other locations in this wet belt in Mexico have shown evidence of humid conditions during expected dry conditions, such as the

160

Terminal Classic droughts in Laguna Atezca (Conserva and Byrne, 2002), and during the

Little Ice Age in Los Tuxtlas (Lozano-García et al., 2007). The use of other proxies, such as oxygen isotopes, is needed in order to develop more conclusive inferences about the occurrence of droughts in the Lachuá lowlands and nearby Petexbatún region.

There is considerable controversy surrounding the hypothesis that heavy deforestation by the Mayans directly led to drying microclimate and ultimately the demise of Mayan civilization. In contrast, evidence is surfacing from Copán in Honduras that indicates that the low disturbance effects of the Mayan environmental management regime (Beach et al., 2006) did not always lead to deforestation effects sufficient to have catalyzed the

Mayan Collapse (Fedick, 2010; McNeil et al., 2010). LOI values from core L-3 indicate that possibly the management of Mayan forest gardens did not have a negative impact on the environment, since wetland conditions were maintained in the region over centuries.

Nonetheless, further sedimentological analysis is needed to support our interpretations.

Forest management at Salinas de los Nueve Cerros did not result in a deforested landscape, not even during its phase of maximal development during the Terminal

Classic. This is in stark contrast for Petén cities like Tikal where evidence for deforestation is prevalent (Lentz and Hockaday, 2009) and supported by pollen data and other proxies from different authors (Islebe and Leyden, 2006). To further support the

"no deforestation" hypothesis, sediment cores should be taken from the Salinas de los

Nueve Cerros city epicentre and nearby locations to differentiate between urban versus rural land use change and correlating environmental impacts. More site-specific approaches like the one applied in this study are likely more appropriate to

161 paleoecological-archaeological research because geographical heterogeneity is generally considered more relevant in explaining cultural and environmental idiosyncrasies

(Aimers, 2007; Emery and Thornton, 2008; Beach et al., 2009; Demarest, 2009) than assuming homogeneous responses across large expanses of landscapes and regions

(Powell, 2008).

5.5 Chapter summary

The fossil pollen spectra from the L-3 core indicate three major phases along ca. 2000 yrs in the environs of the Lachuá Lake at the outskirts of Salinas de los Nueve Cerros. The first phase spans over ca. 700 years of development of Mayan forest gardens (i.e. forestry practices) mainly during the Classic, to its eventual abandonment at the Classic-

Postclassic transition ca. 1100 yrs BP. Main pollen taxa related to forest management and economic uses are Solanaceae (related possibly to medium disturbance levels), and

Bursera, Myrtaceae, Sapium, Spondias, and Terminalia, respectively. The effects of registered regional droughts at the Classic-Postclassic transition are discarded because pollen taxa associated to dryer conditions (e.g. Poaceae and Cyperaceae) show no significant increases relative to what is registered in the modern pollen rain.

The second phase is related to an increase in percentages of Combretaceae

/Melastomataceae pollen at the onset of the Postclassic, and to its eventual dominance in the fossil pollen spectra during the next ca.700 years. Combretaceae/Melastomataceae pollen in the L-3 core sedimentary record is associated with the prevailing forest conditions after Salinas de los Nueve Cerros was abandoned due to a cease in major salt

162 production at the end of the Classic. The Mayan forest garden pollen “signal” is maintained during the remains of this second phase until recent times (ca. 150 yrs BP) as modern pollen rain calibration from L-3 core suggests. A minor drop in

Combretaceae/Melastomataceae pollen abundance ca. 500 yrs BP may be indicative of the reactivation of salt production by European settlers, which may have disturbed the forests at some degree since Solanaceae pollen abundance remains relatively constant since then (ca. 10%). An increase in monolete and a decrease in trilete spores support the changes observed in Combretaceae/Melastomataceae and Solanaceae pollen.

The recent phase dates back ca. 150 yrs when a decrease in Combretaceae

/Melastomataceae pollen percentages suggests an increase in the salt production by

European colonists in the region, and probably the extraction of other natural resources

(e.g. timber). In general terms, disturbance levels observed during the last 150 yrs in the region are similar to the one observed during the Classic period according to PCA (which reflect changes in abundance and composition of pollen spectra). The main difference between recent times (150 yrs BP) and the Classic period, is that in the latter forest management was well planned under complex forestry principles.

163

Chapter 6:

Conclusions

164

6.1 What are the factors that explain vegetation distribution along the

Las Verapaces environmental gradient and what taxa can be used as

"indicator species"?

Indicator plant taxa which had discrete distribution allowed me to delineate three

vegetation belts, which represent changes in vegetation communities along the Las

Verapaces elevational gradient in the Central Guatemalan Highlands and Lowlands:

Lowland Rain Forest, Lower Montane Rain Forest, and Montane Cloud Forest.

Generalist taxa smoothed the delineation of vegetation belts because of their continuous

distribution, and montane taxa that were distributed in lowlands informed me of the existence of montane-like habitats beyond their expected elevation range (disjunctive taxa).

The collation of unpublished vegetation inventories was effective as it was possible to identify explanatory factors, such as elevation which in combination with temperature variability (based on a temperature database) are the main criteria for vegetation belt delineation. Other factors such as landscape position in topographically-controlled drainage divides, and biogeographic origin provided complementary explanations.

Landscape position within a watershed and topographic variability (i.e. geomorphology and underlying bedrock controls) influence vegetation distribution through their relationship with dispersal processes and localized microclimate (physical and

physiological barriers). Patterns in the distributions of plant taxa along the Las Verapaces

gradient possibly reflect in part the biogeographic origin of taxa. Plant biogeography

165 integrates vegetation responses (i.e. physiological tolerances) to variability in elevation and climate, with local relief determining whether or not an area is acting as a dispersal corridor or barrier.

Iti is hoped that the research approach used in this study of the Las Verapaces gradient serves as a model for future research in other parts of Guatemala as well as neighboring regions in Mesoamerica. With future climate change and enhanced anthropogenic disturbance of natural landscapes, there is a growing need for baselines from which to compare future changes in vegetation communities. The present study contributes to this objective. Moreover, the categorization of indicator, generalist and idiosyncratic taxa permit more efficient and rigorous analysis of other meta-data bases, enabling better decisions about conservation priorities and design.

166

6.2 Can paleoecological calibrations for fossil pollen be constructed from a comparison of modern pollen rain from surface sediments and bryophyte polsters?

In tropical regions, pollen spectra found in pollen reservoirs depend mainly on the

geographical location (i.e. lowlands or highlands) as it determines vegetation type and

related pollen production and dispersal mechanisms. Biogeographic origin of plants from

the highlands is mainly temperate or Laurasian, and therefore the major pollen dispersal mechanism is anemophily; lowland plants have mainly zoophilous pollen dispersal syndromes, because their origin is tropical or Amazonian. In spite of the fact that anemophilous pollen can reach longer distances, analysis of bryophyte polsters from the lowlands shows that zoophilous and local pollen taxa have in general a higher input than in surface sediments, where zoophilous and anemophilous inputs are generally more even. Pollen input in surface sediments and bryophyte polsters from highlands is dominantly local and anemophilous, while input from lowlands due to wind transporation is minimal. In general, some pollen taxa present in bryophyte polsters are “silent” in surface sediments, because the former contains more pollen types from forest interiors

(i.e gravity and trunk space components, Faegri and Iversen, 1989).

Pollen spectra from small basins could have a higher local pollen input (especially if surrounded by a high dense canopy vegetation) than mid to large sized basins (less barrier effect from surrounding vegetation). Based on the collected information, it is believed that if surface sediments are collected in a landscape that is forested to a large degree,

167 their pollen assemblages would be comparable to those found in bryophyte polsters from forest interiors (i.e. high arboreal pollen content).

A preliminary modern pollen rain calibration has been developed in this study between vegetation and bryophyte polsters and surface sediments, as a means to understand better the pollen signal from the latter as it represents the best analogue for fossil pollen spectra found in sedimentary records. The present calibration study is important because it covers an unexplored important region in Guatemala; these data can be linked to the northern

Petén lowlands, and the Las Verapaces lowland and highlands, with the rest of

Guatemala and Mesoamerica in terms of palynological and paleoecological analyses.

168

6.3 What are the major vegetation changes recorded in the highland

core from the Las Verapaces region?

Paleoecological methods based on pollen and loss-on-ignition, aided in the reconstruction

of the paleoenvironmental history of the Cahabón river floodplain for the past ~2400 years. At the oldest date reported for the P-4 core (2390 yrs BP), possible ancient lacustrine-like conditions are reconstructed for the floodplain, specifically a shoreline environment where due to high rates of decomposition and oxidation, pollen absence is explained. Initial agricultural exploration by Mayan populations at these earlier times during the Preclassic could explain the higher sedimentation rate (0.25 cm yr-1) which

decreases (0.017 cm yr-1) once land management techniques minimized soil erosion. The

P-4 pollen record indicates agricultural activities (e.g. Zea and Asteraceae presence) at

the Cahabón river floodplain almost uninterruptedly for ca. 1700 yrs. One possible

explanation is that agriculture is interrupted first, temporarily at the Classic-Postclassic

transition (e.g. Terminal Classic) without having a significant impact on the culturally-

established floodplain dynamics; and later, completely at the European conquest and

colonization (e.g. Asteraceae pollen decrease), which marked a dramatic change in the

local vegetation dynamics (e.g. Pinus colonization) and floodplain sedimentation regime

(increase from 0.017 to 0.17 cm-1).

Nevertheless, in this mainly culturally driven sequence of vegetation changes, the

appearance of Abies, a higher elevation pollen taxon at the time of the “Little Ice Age”

(300-400 yrs BP), indicates the possibility of some vegetation change in response to

169 decreased solar activity, as seen in other locations in Mesoamerica (Lozano-García et al.,

2010). The linkage between lowering of water table and climatic forcing, such as the occurrence of a drought at the Classic-Postclassic transition is temporarily discarded, because Cyperaceae and Poaceae percentages increase to similar values observed in present day when no major droughts are registered. Most likely temporary abandonment of floodplain terraces for agriculture explains a possibly lower water table, since maintenance is responsible of resultant water level rising. Recorded droughts in

Mesoamerica in particular for the Terminal Classic are not regionally synchronous, since there are locations with no clear evidence of droughts such as in the Las Verapaces highlands. However, more exploration is needed in this region to have a more conclusive explanation about the existence of an agricultural centre in the Cahabón River floodplain.

Paleoecological exploration of highland environments in Mesoamerica is expanding, the relevance of connections between lowland and highland Maya chiefdoms in cultural evolution are better understood. In the face of non-existent lacustrine environments in

Las Verapaces highlands, such as it is in many geographical locations globally, paleoecological analysis of riverine sediments in this study strengthens the use of alternative reservoirs of paleorecords as a means to reconstruct natural and cultural evolution of past landscapes.

170

6.4 What are the major vegetation changes recorded in the lowland core from the Las Verapaces region?

The examination of a ca. 2000-year paleorecord indicates that vegetation changes in the

Lachuá region could be closely related to the history of the Mayan city of Salinas de los

Nueve Cerros. The L-3 core location holds the history of land management that took place at the city's outskirts, where high abundance of pollen belonging to beneficial trees taxa (e.g. Myrtaceae and Spondias) indicates that forest gardens could have been the dominant land use. Cultural management of forest gardens determined vegetation succession during the Preclassic and Classic cultural periods; these systems remained mainly in a secondary succession stage, as indicated by the dominance of Solanaceae pollen. At the Terminal Classic when the abandonment of Salinas de los Nueve Cerros started, later succesional vegetation stages take place as inferred from

Combretaceae/Melastomatacae pollen co-dominance to an eventual complete dominance for ca. 800 years after abandonment. It is not until ca. 150 yrs BP that vegetation changes once again probably in the face of a different disturbance regime that involves major natural resource extraction. In this case, Solanaceae pollen increases and pollen of

Combretaceae/Melastomataceae decreases.

Landscape evolution in the Lachuá lowlands over the development of Salinas de los

Nueve Cerros, including the Guatemalan colonial period, is determined mainly by cultural factors. At the resolution level applied for the L-3 core, there is no clear evidence of local occurrence of droughts reported elsewhere in Mesoamerica, especially at the

171

Classic-Postclassic transition. Changes in vegetation are believed to be more a response to the abandonment of cultural management practices (i.e. forestry) and not to occurrence of droughts since pollen benefited by drier conditions showed no change in their abundances (e.g. Poaceae). Nevertheless, more high resolution paleoecological analysis with more proxies (e.g. oxygen isotopes) is needed in future studies in the Lachuá region to test hypotheses related to decade-long droughts in Mesoamerica.

It is critical to recognize vegetation succession in the long term, and not only analysis based on forest cover percentage calculations because it may lead to unrealistic interpretations in conservation biology (e.g. AP values). Despite the fact that arboreal pollen percentages indicate that at the physiognomic level, Lachuá lowlands landscape forest cover remains at values above 80% for ca. 2000 yrs, vegetation succession indicates dynamics related to different management and disturbance regimes. The question related to “What is natural?” is important to answer in order to understand landscape natural and cultural variability and to incorporate it into conservation management practices aided by paleoecological analysis.

172

6.5 What is the role of natural variability and cultural factors related to the Maya Civilization in the evolution of landscapes in the Las Verapaces

Region?

Las Verapaces Region is located at an important transitional region between the Northern

Lowlands and the North Central Highlands in Guatemala. The pollen record of the last

ca. 2000 yrs BP has not shown any evidence of vegetation dynamics (i.e. succession)

driven by climate variability, especially at the time of the hypothesized droughts at the

Terminal Classic or Early Postclassic. Reduction in precipitation at that time period has been hypothesized as caused by alterations in the latitudinal migration of the Intertropical

Convergence Zone (ITCZ), or ultimately by an increased aridity effect as a consequence of intense land clearing, agricultural activities and high rates of deforestation, respectively. Contrary to the latter hypothesis, Las Verapaces landscapes have an important multi-centennial cultural imprint of successful Mayan management. Pollen records indicate in on one hand the existence of agriculture at the Cahabón River

Floodplain, with possible soil conservation practices that led to the successful establishment of an agricultural center (i.e. low sedimentation rates); and on the other hand, a Mayan forest garden at the outskirts of Salinas de los Nueve Cerros in the Lachuá region. In these scenarios, cultural factors possibly played an important role in the

evolution of landscapes, coupled with the influence of relatively climatic stable

conditions. Regarding natural factors, the lowlands to highlands gradient in the Las

Verapaces is located in a high precipitation and humidity envelop (i.e. known as the

173

Uxpanapa wet belt), a fact that contributes to its climatological stability, and thus in part to its enormous biological diversity.

However, more exploration is needed in the Las Verapaces Region, in terms of collecting longer Holocene records to examine landscape evolution at a longer temporal scale.

Inclusion of locations inside and outside of the “Uxpanapa wet belt” in future studies in the Mesoamerican region will provide basis to explain thoroughly landscape evolution.

Inclusion of more paleoecological proxies (e.g. oxygen isotopes and macro and microscopic charcoal) in future studies will enhance the understanding and the possibility of testing hypotheses related to landscape evolution in terms of natural and cultural factors.

Pollen records, LOI measurements, and sedimentation rates examined in this thesis provided key information to support the idea that sustainable anthropogenic management, if well planned, could enhance natural resources conservation. Lessons learned from the paleoecology of the lowlands and highlands in the Las Verapaces include understanding the negative effects that the European conquest and colony had on landscape dynamics through drastic natural resource extraction. Even in the face of climatic and environmental stable conditions, non-planned, non-measured and non-sustainable natural resources management represents a threat to the conservation of biological diversity and cultural legacies.

174

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Appendices

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Appendix 2.1. Indicator, generalist, and disjunctive plant checklist.

Plant Taxa Axis 1 2466 2300 2200 2200 2100 2100 2000 1900 1900 1800 1800 1650 1500 1400 1258 1106 1048 1000 1000 600 400 200 170

Spondias mombin 109 Tabebuia sp. 176 Genipa sp. 226 Inga sp. 257 Saurauia belisensis 264 Heliocarpus mexicanus 265 Cedrela pacayana 266 Perymenium grande 268 Weinmannia pinnata 363 Miconia aeruginosa 365 Oreopanax liebmanii 373 Psychotria parasitica 390 Centropogon cordifolius 436 Cavendishia guatemalensis 437 Jocotillo 440 Fuchsia microphylla 445 Indicator Taxa Indicator Miconia glaberrima 445 Styrax argenteus 452 Lobelia nubicola 466 Synardisia venosa 479 Clethra suaveolens 498 Phoradendron sp. 500 Erigeron karvinskianus 526 Passiflora sexflora 527 Begonia oaxacana 555 Ocotea sp. 557 Rhynchosia sp. 655

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Appendix 2.1. continued. Idiosyncratic refers to Disjunctive Taxa.

Che4 Che3 Tin6 Pur5 Che2 Pur4 Pur3 Pur2 Che1 Pur1 Tin5 Tac Scruz Tin4 Che Flo Tam Bvta Tin3 Tin2 Chin Tin1 Lach Axis 1 2466 2300 2200 2200 2100 2100 2000 1900 1900 1800 1800 1650 1500 1400 1258 1106 1048 1000 1000 600 400 200 170

Vochysia guatemalensis 153 Terminalia amazonia 168 Bursera simarouba 172 Ceiba pentandra 190 Parathesis vulgata 199 Cecropia peltata 244 Virola sp. 245 Dendropanax leptopodus 269 Mollineda guatemalensis 308 Billia hippocastanum 312 Engelhardtia guatemalensis 317 Brunellia mexicana 330

Generalist Taxa Persea donnell-smithii 333 Liquidambar styraciflua 337 Clusia sp. 368 Hedyosmum mexicanum 384 Quercus sp. 395 Quercus crispifolia 442 Myrica cerifera 512 Eupatorium semialatum 549

Dendropanax arboreus 135 Lasciacis divaricata 156 Ocotea eucuneata 277 Phoebe sp. 293 Matayba oppositifolia 315 Peperomia cobana 336 Pouteria campechiana 338

Idiosyncratic Taxa Clidemia capitellata 430 Conyza bonariensis 499

199

Appendix 3.1. Pollen types found on modern pollen calibrations and fossil pollen spectra from cores P-4 and L-3. Associated plant taxa and uses by ancient Mayan populations are shown. Information about vegetation belt (VB) is provided based on Table 2.2 and 2.3 (Chapter 2). * indicate know usage by modern Mayan populations.

Pollen taxa

VB Genus Family Associated plant taxon/taxa Uses

Acacia Fabaceae Acacia spp. Medicine, forage, construction Alchornea Euphorbiaceae Anthurium Araceae Food, ornamental, forage, Araliaceae Dendropanax arboreus medicine

Arecaceae Acrocomia mexicana Food Attalea cohune Food, construction, medicine Chamaedora spp. Food Lowlands Cryosophila stauracanhta Construction. medicine Sabal morrisiana Construction

Bignoniaceae Tabebuia rosea Medicine, timber, ornamental Bombacaceae Ceiba pentandra Medicine, timber, ritual Quararibea Food Pseudobombax Ritual

Boraginaceae Cordia sp. Food, medicine

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Appendix 3.1. continued

Pollen taxa VB Genus Family Associated plant taxon/taxa Uses

Brosimum Moraceae Brosimum alicastrum Food, medicine, forage, ritual Celtis Ulmaceae Celtis iguanaea Food Combretaceae Combretum Melastomataceae Clidemia Euphorbiaceae Cnidoscolus aconitifolius Food Manihot esculenta Food, medicine Fabaceae Lonchocarpus castilloi Ritual Pachyrhizus erosus Food

Phaseolus lunatus Food Mimosa Fabaceae Mimosa spp. Medicine, fuel

Lowlands Malpighiaceae Byrsonima crassifolia Food, medicine, apiculture Moraceae Castilla elastica Latex Pseudolmedia spuria Food Myrsinaceae Myrsine sp. Myrtaceae Psidium guayaba Food Pimienta dioica Food Pachira Bombacaceae Pachira aquatica Food, medicine, construction

Piper Piperaceae Piper amalago Medicine Psychotria Rubiaceae Psychotria chiapensis Medicine Rubiaceae Alseis yucatanensis Wood Hamelia axillaris Medicine

201

Appendix 3.1. continued Pollen taxa VB Genus Family Associated plant taxon/taxa Uses

Salvia Lamiaceae Salvia coccinea Sapium Euphorbiaceae Sapotaceae Crysophyllum mexicanum Food, medicine

Manilkara zapota Food, medicine, latex Pouteria campechiana Food

Lowlands Solanaceae Solanum Food, medicine, forage, ritual Cestrum Medicine, ornamental Capsicum Food Trema Ulmaceae Trema micrantha Food Ulmaceae Ornamental, fuel, forage, Verbenaceae Vitex gaumeri construction

Spondias mombin, S. LRF Spondias Anacardiaceae purpurea, S. radlkoferi Medicine, construction, food

Bursera Burseraceae Bursera simaruba Medicine, ritual Burseraceae Protium copal1 Ritual LRF- LMRF Cecropia Cecropiaceae Cecropia sp. Medicine, timber Terminalia Combretaceae Terminalia amazonia Construction

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1 Important plant for ancient and modern Maya, but not found in the pollen record. Appendix. 3.1. continued. Pollen taxa VB Genus Family Associated plant taxon/taxa Uses

LMRF Inga Fabaceae Inga spp.

Hedyosmum Chloranthaceae Hedyosmum mexicanun Food LMRF- MCF Myrica Myricaceae Myrica cerifera Medicine*

Quercus Fagaceae Quercus sp. Fuel

MMF Abies Pinaceae Abies guatemalensis

MMF- Alnus acuminata, Alnus Betulaceae SAF A, jorullensis

Arbutus sp,Cavendishia Ericaceae guatemalensis Conifer6 Pinaceae Ritual Pinales Pinaceae Ritual Pinus Pinaceae Pinus caribaea, P. oocarpa Ritual

Highlands Urticaceae Phenax, Pilea, Urera, Urtica Medicine

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Appendix 3.1. continued

Pollen taxa Genus Family Associated plant taxon/taxa Uses

Alternanthera Amaranthaceae Alternanthera sp. Amaranthaceae Amaranthus Food Chenopodiaceae Chenopodium ambrosioides Food Asteraceae2 Medicine* Cyperaceae Cyperus esculentus Food Eleocharis caribaea Peperomia Piperaceae Piperaceae Poaceae Food Polygonum Polygonaceae Food Zea Poaceae Zea mays Food Trilete spores Microgramma lycopodioides, Monolete spores Acrostichum aureum Food

2 Uncertainty about native plant taxa

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Appendix 4.1. Pollen counts (raw) from P-4 core.

POLLEN TYPE P4 P4-1 P4-2 P4-3 P4-4 P4-5 P4-6 P4-7 P4-8 P4-9 P4-10 P4-11 P4-12 P4-13 P4-14 P4-15 P4-16 P4-17 P4-18 Abies 4531080000000000000 Alnus 0011011001100100000 Hedyosmum 67101641213114114673240 Ilex 0000000000000001000 Myrica 2510130002143365511 Pinus 11 72 54 62 56 53 21 1 7 4 6 8 6 12 9 4 9 14 17 Quercus 179512261214111543674 Alternanthera 54113021200000000000000 Amaranthaceae/Chenopodiaceae 0 13 11 13 10 29 5 15 13 17 10 6 23 22 14 18 14 15 21 Asteraceae 12 45 77 59 50 60 138 44 88 81 62 83 83 88 111 139 145 162 151 Poaceae 15 21 29 10 56 8 5 2 8 41 11 12 5 10 4 11 16 29 7 Zea 2010105300344512201 Alchornea 0200000000000000100 Arecaceae 0450020037001003311 Brosimum 0001100000000100000 Bursera 1000000000000000000 Combretaceae/Melastomataceae0003000001000000002 Celtis 1000000000000000000 Malphigiaceae 0000020010000100000 Myrtaceae 0001000000000000000 Pollen sum 101 222 217 206 206 208 202 70 128 172 99 135 142 156 157 194 210 237 205 Cyperaceae 54 159 452 458 462 471 150 20 176 270 63 90 58 48 62 109 74 158 76 Polygonum 25359848835130162215740 Trilete 20 26 46 64 50 56 83 75 54 19 16 27 15 34 23 10 28 43 23 Monolete 24 35 19 141 46 67 22 29 23 9 8 7 13 17 8 15 13 5 7

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Appendix 5.1. Pollen counts (raw) from L-3 core.

POLLEN TYPE L3‐0L3‐1L3‐2L3‐3L3‐4L3‐5L3‐6L3‐7L3‐8L3‐9L3‐10 L3‐11 L3‐12 L3‐13 L3‐14 L3‐15 L3‐16 L3‐18 Abies 010100000000000000 Alchornea 1 41314128 910117 61010716166 8 Alnus 000122043112300121 Arecaceae 4104314631200032130 Bombacaceae 110101111010003100 Brosimum 000001100000000000 Bursera 034001430311221117 Caesalpinaceae 020000110000000010 Celtis 200020311100200720 Combretaceae/Melastomataceae7196163434851653845211610811181311 Hedyosmum 000000100001000112 Hyeronima 008545814500001000 Ilex 21 16 17 19 17 15 17 12 7 37 9 13 9 9 11 5 9 3 Malphigiaceae 210455466132321010 Myrica 1071091355113661481621341842 Myrtaceae 9 10 27 8 20 28 11 12 13 9 12 18 22 20 18 7 1 0 Pinus 75605311641010710494189 Piper 400030000000000000 Psychotria 76683583521469173213 Quercus 414024000305304016 Rubiaceae 14412104131062276710532 Sapium 1163476544001032110 Sapotaceae 000322212222435120 Solanaceae 15 10 20 14 21 24 13 29 37 44 30 39 37 27 45 46 43 51 Spondias 341119121697730335547 Terminalia 846555342605211212 Trema 300010011001012010 Amaranthaceae/Chenopodiaceae000000000100000000 Asteraceae 464354314421121112 Poaceae 143784226344250865 Zea 020000000000000100 Cyperaceae 11219216543513241525 Pollen sum 125 126 201 195 200 196 198 200 166 201 114 153 143 132 186 198 140 161 Monoletes 248757807254563031645026181216165510 Triletes 326108388948975363251163821