The Effect of Site Selection on the Growth of Dipteryx Panamensis in Timber Plantations in Costa Rica and Panama

Faculty of Forest, Geo and Hydro Sciences: Institute of Forest Growth and Forest Computer Sciences

The effect of site selection on the growth of Dipteryx panamensis in timber plantations in Costa Rica and Panama

by Fabian Schmidt

A thesis submitted in partial fulfillment of the requirements for the degree Master of Science in Tropical Forestry and Management

Faculty of Forest, Geo and Hydro Sciences University of Technology, Dresden, Germany

Date of Submission: 30. September 2009 Scientific supervisor: Prof. Dr. rer. silv. habil. Heinz Röhle Institute of Forest Growth and Forest Computer Sciences University of Technology, Dresden, Germany

Co-supervisor: Dr. rer. silv. Hubertus Pohris Institute of International Forestry and Forest Products University Technology, Dresden, Germany

Local advisor: Dr. Olman Murillo Instituto Tecnológico de Costa Rica, Cartago, Costa Rica

Lending admitted / not admitted

Dresden, September 2009

TABLE OF CONTENTS

TABLE OF CONTENTS ...... i ABSTRACT ...... iv ACKNOWLEDGEMENTS ...... v LIST OF ABBREVIATIONS ...... vi LIST OF FIGURES ...... vii LIST OF TABLES ...... viii LIST OF EQUATIONS ...... ix 1. INTRODUCTION ...... 10 1.1 Research justification ...... 11 1.2 Research objectives ...... 12 1.3 Research questions ...... 13 2. LITERATURE REVIEW ...... 14 2.1 Species information ...... 14 2.2 Almendro in timber plantations ...... 16 2.3 Agroforestry and carbon forestry using Almendro ...... 19 3. METHODOLOGY ...... 21 3.1 Study area ...... 21 3.2 Description of the sample plots ...... 22 3.3 Data collection ...... 23 3.4 Data analysis ...... 24 3.5 Growth modeling ...... 28 3.6 Stand height curves ...... 29 3.7 Site classification ...... 31 4. RESULTS ...... 33 4.1 Growth of Almendro in Costa Rica and Panama ...... 33 4.1.1 Site group 1, CR ...... 33

4.1.2 Site group 2, CR ...... 34

TABLE OF CONTENTS

4.1.3 Site group 3, CR ...... 35

4.1.4 Site group 4, CR ...... 38

4.1.5 Site group 5, CR ...... 42

4.1.6 Site group 6, CR ...... 44

4.1.7 Site group 7, PA ...... 46

4.1.8 Site group 8, PA ...... 50

4.1.9 Site group 9, PA ...... 52

4.2 Stand characteristics of Almendro plantations ...... 53 4.2.1 Stem diameter distribution ...... 54

4.2.2 Stand height curves ...... 56

4.3 Growth dynamics of Almendro ...... 58 4.3.1 Mean annual increment of Almendro ...... 59

4.3.2 Top height growth ...... 60

4.4 Preliminary site indices for Almendro ...... 61 4.5 Top-height projections ...... 63 5. DISCUSSION ...... 66 5.1 Data basis ...... 66 5.2 The effect of site selection ...... 68 5.2.1 Site index calculation and top height projection ...... 70

5.2.2 Frequency of site index classes ...... 71

5.2.3 Promising regions for Almendro plantations ...... 73

5.3 Silviculture ...... 73 5.3.1 Initial spacing and stand density ...... 74

5.3.2 Thinning and pruning ...... 75

5.4 Timber production on Almendro plantations ...... 77 5.5 Carbon forestry ...... 79

TABLE OF CONTENTS

5.6 Agroforestry ...... 81 5.7 Limitations of the present study ...... 83 5.8 Recommendations ...... 83 6. CONCLUSION ...... 84 BIBLIOGRAPHY ...... 85 APPENDICES ...... 94 Appendix 1 - Detailed information on sampled Almendro plantations ...... 94 Appendix 2 - Stand diameter distribution ...... 95 Appendix 3 - Stand height curves ...... 98 Appendix 4 - Estimated Parameter values ...... 102 Appendix 5 - Photos ...... 104 EIDESSTATTLICHE ERKLÄRUNG ...... 108

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ABSTRACT

Plantation forestry is of high importance in both Central American countries, Costa Rica and Panama, who promote the establishment of timber plantations through government incentive programs. While most plantation companies plant exotic tree species such as Teak (Tectona grandis), local farmers tend to prefer native species, which are often better adapted to low intensity management and poor soils. More and more companies also start to diversify their product portfolios by using native species. The potential of native tree species is enormous, but research is often site-specific and little is known regarding their long term performance on timber plantations. This lacking knowledge about the silviculture and performance on a multitude of sites, endangers the future of native tree species in timber plantations.

One very promising native tree species that is planted across Costa Rica and Panama is Almendro (Dipteryx panamensis), a keystone rainforest species and premium hardwood on local timber markets. To address the research questions how the species develops over time, how the site affects the growths and to identify promising regions for Almendro plantations, growth records from 36 plantations, some of which have been agroforestry systems, were collected and analyzed. Developments and stand characteristics of all plantations were described and differences between climate zones became evident.

Performance in the Atlantic lowlands of Costa Rica was the greatest and high rainfalls, lower elevations and soils with good drainage favor the growth of Almendro, whereas the growth was restricted in dry climates, elevations higher 500 m and on poorly drained soils.

A preliminary site classification was developed, using five site index classes to describe the growth of Almendro on different sites and a specific top height growth model was designed for several plantations to validate these trends. Additionally, provisional recommendations for silvicultural treatments were given and the potential of Almendro for carbon forestry and agroforestry systems was assessed.

ACKNOWLEDGEMENTS

First of all, I want to thank my supervisors Prof. Dr. Heinz Röhle and Dr. Pohris from the University of Technology Dresden, Germany for their guidance and support from the early ideas until the final thesis. Dr. Olman Murillo from the Instituto Tecnológico de Costa Rica in Cartago has guided me through the Costa Rican world of forestry, which I’m more than grateful for. The passion for Almendro connected us from the moment we first met and I still remember our fruitful discussions about native species research and tropical forestry in general. I would like to express my sincere gratitude to Dr. Klaus Römisch for his patient assistance and comments about statistics, growth modeling and site classification, and Luis Ugalde for his professional suggestions and training in MIRASILV.

During my quest for Almendro plantations in Costa Rica and Panama many people crossed my way and I am so grateful for their practical support, technical inputs, suggestions and encouragement. Without them, this thesis would never have been possible. As this thesis made use of information that was generated by many plantations owners and scientists across Costa Rica and Panama, they receive my utmost appreciation. In Costa Rica, particularly to Adrian Delgado (Precious Woods), Rolando Camacho, Herster Barres (RTT), Guillermo Navarro, Tamara Benjamin, Marvin Hernandez, Oscar Sanabria (CATIE), Orlando Vargas, Ronald Vargas, Bérnal Matarrita, Deedra McClearn (OTS – La Selva), Daniel Piotto, Florencia Montagnini (Yale University), Carlos Sandi, Raul Paniaqua, Ricardo Russo (EARTH), Juan Pablo Jaramillo Castaño (Los Tucanes). In Panama to Jefferson Hall, Michiel Van Breugel (PRORENA) and all my colleagues from ForestFinance, especially Yaels Camacho.

I am indebted to Dr. Marvin Castillo, Andres Castillo and Silke Berger for their valuable field assistance. Finally, I want announce my greatest respect to Lucia Rodriguez (ITCR) for waking my passion for native tree species research when I first worked in Costa Rica in 2007.

Financial support from the “DAAD - Deutscher Akademischer Austausch Dienst” and logistic support from ForestFinance is gratefully acknowledged.

LIST OF ABBREVIATIONS

AGCL Age class CATIE Centro Agronómico Tropical de Investigación y Enseñanza CFS CarbonFix Standard CITES Convention on International Trade in Endangered Species of Wild Fauna and Flora

CO2 Carbon dioxide COSEFORMA Cooperación en los Sectores Forestales y Maderero CR Costa Rica DBH Diameter at breast height EARTH Esucela de agricultura de la region tropical humeda ITCR Instituto Tecnológico de Costa Rica MAI Mean annual increment MINAE Ministerio de Ambiente y Energia (Costa Rican ministry of environment and energy) m.a.s.l Meters above sea level OTS Organization for Tropical Studies PA Panama PRORENA Proyecto de Reforestación con Especies Nativas RTT Reforest the tropics Inc. SHC Stand height curve SI Site index SIGR Site group

LIST OF FIGURES

Figure 1: Map of the study area ...... 22 Figure 2: Stand diameter distribution in “Santa Cecilla” ...... 54 Figure 3: Stand diameter distribution in “Buenos Aires” ...... 55 Figure 4: Stand diameter distribution in “La Bomba” ...... 55 Figure 5: Stand diameter distribution on the “Canadian Trial” ...... 56 Figure 6: Fitted Michailoff stand height curves. “Cope San Juan”...... 57 Figure 7: Fitted Michailoff stand height curve and observed values. “Canadian Trial” ...... 57 Figure 8: Fitted Michailoff stand height curve for D. panamensis in “San Juan” in a mixed species plot together with A. hunsteini, E. deglupta and S. macrophylla...... 58

Figure 9: MAI in top height (h50) of D. panamensis in timber plantations ...... 59

Figure 10: MAI in top diameter (d50) of D. panamensis in timber plantations ...... 60 Figure 11: Top height development of D. panamensis over age ...... 61 Figure 12: Site index curves for 5 different site qualities in CR and PA ...... 63 Figure 13: Top height growth projection in comparison with site index curves ...... 65 Figure 14: Fitted Michailoff stand height curves for D. panamensis, “Pampanillo” ...... 101

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LIST OF TABLES

Table 1: List of own measurements and data sources for growth data prior 2009 ...... 24 Table 2: List of age classes, their ranges and frequencies ...... 25 Table 3: List of site groups and their attributes...... 25 Table 4: Growth of Almendro in SIGR 1 ...... 34 Table 5: Growth of Almendro in SIGR 2 ...... 35 Table 6: Growth of Almendro in SIGR 3, AGCL 3 ...... 36 Table 7: Growth of Almendro in SIGR 3, AGCL 3 ...... 38 Table 8: Growth of Almendro at “La Selva”, SIGR 4, AGCL 3 ...... 40 Table 9: Growth of Almendro for “EARTH” and “Los Tucanes”, SIGR 4, AGCL 2 and 3 ...... 42 Table 10: Description of the species mixtures on “Hacienda Las Delicias”, SIGR 4...... 43 Table 11: Growth of Almendro in SIGR 5, AGCL 2 and 3 ...... 44 Table 12: Description of the species mixtures in “Mulas” and “San Juan”, SIGR 6...... 45 Table 13: Growth of Almendro in SIGR 6, AGCL 2 ...... 46 Table 14: Growth of Almendro on the PRORENA plots “Las Lajas “, SIGR 7, AGCL 1 ...... 47 Table 15: Growth of Almendro on the PRORENA plots “Liquid Jungle Lab “, SIGR 7, AGCL 1 48 Table 16: Growth of Almendro on the ForestFinance plantations, SIGR 7, AGCL 2 ...... 49 Table 17: Growth of Almendro in “Los Santos”, SIGR 8, AGCL 1 ...... 51 Table 18: Growth of Almendro in “Rio Hato”, SIGR 8, AGCL 1 ...... 52 Table 19: Growth of Almendro in SIGR 9, AGLC 1 ...... 53 Table 20: Cross table with the number of available growth records at certain age ...... 67 Table 21: Frequency of site index classes and age classes in each site group ...... 72 Table 22: Proposed thinning regime for Almendro in timber plantations ...... 78 Table 23: Overview and characteristics of Almendro plantations in Costa Rica ...... 95 Table 24: Overview and characteristics of Almendro plantations in Panama ...... 95

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LIST OF EQUATIONS

Equation 1: Volume calculation ...... 27 Equation 2: Basal area calculation ...... 27 Equation 3: Chapman - Richards function ...... 29 Equation 4: Petterson - height curve function ...... 30 Equation 5: Michailoff - height curve function ...... 30 Equation 6: CarbonFix equation ...... 80

INTRODUCTION

1. INTRODUCTION

Forest scientists worldwide recommend the use of native tree species for reforestation- and restoration projects. It is said that native tree species generally have better site adaption, better survival rates and fewer pests. They are also better adapted to low input forestry that is often practiced by local farmers, in contrast to exotic species, which require more intensive production systems and are regularly used by reforestation companies (Butterfield and Fisher, 1994; Butterfield, 1995; Haggar et al., 1998; Jiménez et al., 2002).

The immense biodiversity of native tree species especially in Central America provides a resource to fill other production niches if a wider range of production systems is considered such as agroforestry, mixed plantations or fuel wood lots (Wishnie et al., 2007). However, relatively little information exists regarding the performance of these native trees on timber plantations and as a result this knowledge gap still hinders the implementation in reforestation schemes, for both famers and companies, on a larger scale.

Usually exotic species are preferred because of existing markets, good seed availability and better scientific knowledge about the growth and management of these species (Butterfield and Fisher, 1994; Butterfield, 1995). Likewise, forestry in Costa Rica and Panama is dominated by the use of exotic species such as Teak (Tectona grandis) or Melina (Gmelina arborea). Fortunately, research institutes in Costa Rica like the “Instituto Tecnológico de Costa Rica” (ITCR), the “Centro Agronómico Tropical de Investigación y Enseñanza” (CATIE), the “Esucela de agricultura de la region tropical humeda” (EARTH) or projects like the “Proyecto de Reforestación con Especies Nativas” (PRORENA) in Panama, have been studying a variety of promising tree species native to Central America.

For some native tree species such as Pilon/Zapatero (Hyeronima alchorneoides), Roble Coral/Amarillo (Terminalia amazonia) or Pochote/Cedro espino (Bombacopsis quinata) research is quite advanced and publications are available.

INTRODUCTION

As a result, forest management schemes were developed for these species, which facilitates their use on timber plantations.

1.1 Research justification The variety of native tree species is enormous due to the vast biodiversity in tropical countries, yet little is known about some very promising trees or research outcomes are very site specific (Butterfield and Fisher, 1994; Butterfield, 1995; Haggar et al., 1998; Aguilar and Condit, 2001; Piotto et al., 2003; Wishnie et al., 2007).

One of these “unknown” species is Almendro (Dipteryx panamensis), which was selected for this research for several reasons. The valuable timber is very dense and resistant to decay, it also captures a high amount of carbon dioxide in the tree´s biomass (Redondo-Brenes and Montagnini, 2006; Redondo-Brenes, 2007). In addition Almendro plays a vital role in Neotropical ecosystems as an keystone species that provides food and shelter to endangered species and other forest fauna (Bonaccorso et al., 1980; Flores, 1992; Monge- Arias et al., 2003).

Almendro holds great potential for the production of valuable timber on timber plantations and the reduction of green house gases in the atmosphere, while contributing to biodiversity protection and in the best scenario even reduced deforestation. This species has been studied since the beginning of native tree species research in Costa Rica and Panama. Over the past 25 years experience has been gathered on sample plots in natural forests and scientific plantations. Nevertheless, most studies regarding the performances of Almendro on plantations have been conducted within a relatively small geographic range, thus making it difficult to extrapolate the results to areas with different climates.

This study will connect research that had formerly been limited to a small geographic range, to derive growth predictions, which are valid for most parts of Costa Rica and Panama. These finding can help to secure and increase the income from Almendro timber plantations through improved forest management practices, while the general promotion of the species

INTRODUCTION

Almendro might stimulate the establishment of new Almendro plantations thus relieving some pressure from natural old growth forests. Many plantations have been established by local farmers who dedicated small portions of their farms to plantation forestry with mostly native species (Haggar et al., 1998; Piotto et al., 2003; Streed et al., 2006). The majority of farmers did not receive any training in intensive plantation forestry and knowledge about the best management is lacking for native tree species, such as Almendro. Gathering data about long-term performance of Almendro under varying management regimes is necessary to reduce investments risk for farmers and other plantation owners (Piotto et al., 2003).

Through the development of a site classification, using site indices, based on data from plots in both Costa Rica and Panama, forest managers will be able to classify and project stand growth of their Almendro plantations.

It is likely that in the long run the demand for tropical hardwood produced on plantations, will exceed supply and thus tropical hardwood plantations will have to produce an increasing volume during the coming decades. If the good market potential is not realized the opportunity to substitute wood and non-wood products will be lost (Varmola and Carle, 2002), but through proper site-classification and the development of forest management schemes the wood production of timber plantations can be optimized.

To realize the potential of timber plantations, it is of highest importance to know as much as possible about the commercial tree species. Consequently, studying how species like Almendro perform on a multitude of sites is the next logical step in the ongoing development of tropical forestry.

1.2 Research objectives From numerous sites in Costa Rica and Panama data on actual tree growth was measured and carried together to see if and how site selection of Almendro plantations influences the growth performance. In both countries past measurements were kindly provided from plantation owners and subsequently analyzed.

INTRODUCTION

As past and present research outcomes had been mainly valid for a small geographic range, primarily the Atlantic lowlands of Costa Rica (Wishnie et al., 2007), the creation of time series of the growth of Almendro for different climates based on own measurements and existing, sometimes unpublished datasets, is the main objective of this study.

From these findings a site classification is developed through site index curves. Wherever possible, growth projections will be developed using predictive modeling techniques and finally, silvicultural regimes and possible yield of mature Almendro will be discussed together with the species´ potential for production systems, such as carbon forestry and agroforestry.

1.3 Research questions

- How does Almendro develop over time? - How does the site affect the growth of Almendro? - Which are the most suitable regions for Almendro plantations?

LITERATURE REVIEW

2. LITERATURE REVIEW

2.1 Species information Almendro (Dipteryx panamensis) is a large canopy-emergent tree and rainforest keystone species that occurs from Nicaragua to Colombia in the tropical wet- and moist forests all along the Atlantic coast (Flores, 1992). The species belongs to the family Fabaceae (Leguminosae), sub-family Papilionoidae and is internationally known as “Almendro” or “Tonka Bean tree”. Local names are diverse and depend on the region, although “Almendro” is the most common name (Costa Rica, Nicaragua, Panama, and Colombia). Other names include “Almendro de montaña” (Northern Atlantic zone of Costa Rica, Panama), “Almendro amarillo”, “Almendrón” and “Eboe” (Bribri; indigenous tribe in Costa Rica). This species is also referred to as Coumarouna panamensis Pitt., Dipteryx oleiforma Benth. as well as Oleiocarpon panamensis (Pittier) Dweyer (Vozzo, 2002; Cordero et al., 2003).

The species naturally exists along a precipitation- and temperature gradient from 24°C to 30 °C in mean annual temperature and 3500 – 5500 mm mean annual rainfall (Vozzo, 2002, COSEFORMA, 1999), while the vertical distribution ranges from 20 – 500 m.a.s.l (Jiménez et al., 2002; Cordero et al., 2003).

Canopy-emergent trees like Almendro frequently appear in densities less than 1 adult tree per hectare (Clark and Clark, 1987; Hanson et al., 2006; Hanson et al., 2008). Some regions however support higher densities like the border region of Costa Rica and Nicaragua where densities approach 2 adult trees per hectare (Chun, 2008), or parts of the “Corredor biológico Río San Juan-Estación Biológica La Selva“, with the highest density ever recorded of 4 trees per hectare (Chaverri and López, 1998).

Almendro naturally grows on alluvial or sandy soils and occasionally on soils with an acid and clay profile (Flores, 1992) with pH-values ranging from 4 to 5.5 (Vidal-Riveros, 2004).

LITERATURE REVIEW

Environmental conditions that support high densities of Almendro appear to be soils of the Humult, Aquent, and Tropept‐Aquept sub-order (Chun, 2008).

The height of Almendro trees can reach a maximum of 50 m and diameters of up to 1.5 m. Individuals may live close to 300 years with a theoretical maximum age of 654 years, as found by Fichtler et al. (2003) based on 14C dating and tree ring counts.

Almendro trees have vertical lenticels on their reddish-brown and smooth bark and the stem develops ample basal roots, but seldom buttresses. Branches are ascendant and the crown is semispherical, consisting of alternate, pinnated leaves with 10 to 20 stippled leaflets, opposite, and sub-opposite alternative (Flores, 1992; COSEFORMA, 1999; Jiménez et al., 2002). Bright purple flowers appear with the beginning of the rainy season in late May and flowering lasts until late August, with peak blooming occurring in mid‐July (Perry and Starrett, 1980), although these blooming patterns vary among regions (Arnáez and Moreira, 1995). Immature fruits are green and turn brownish when ripe. The fruits are pods 6 to 8 cm long, 4 to 5 cm wide, and 2 to 3 cm thick, encapsulating seeds ranging from 4.5 to 6 cm long, 3 to 3.5 cm wide, and 1 to 1.6 cm thick. The fruits and seeds are consumed by many animals, highlighting the keystone function of Almendro (Mills et al., 1993; Ruiz et al., 2005). Bonaccorso et al.(1980) recorded sixteen species of mammals and Flores (1992) observed around 100 species of birds feeding on its fruits and seeds. The critically endangered great green macaw (Ara ambiguus), of which less than thirty breeding pairs remain in Costa Rica (Chassot et al., 2009), is among the associated fauna that depends on Almendro not only as a food source, but moreover as nesting site (Monge-Arias et al., 2003; Madriz-Vargas, 2004; Ruiz et al., 2005; Hanson et al., 2006). Boddiger (2003) summarized the conflicts and ongoing great green macaw conservation efforts in Costa Rica.

Almendro is not only famous for its high ecological value, but mostly because of its economic value. The very durable and medium-textured wood rates high in mechanical resistance and has a brown-yellow sapwood and yellow-red heartwood. With wood densities between 0.83 and 1.09 g/cm3 (Vozzo, 2002; Carpio Malavassi, 2003) this species is considered extremely

LITERATURE REVIEW heavy and valuable, reaching the highest wood prices on local markets (Rodriguez and Chaves, 2008). The wood is difficult to saw due to its weight, density and crystalline deposit content, hence commercial exploitation of Almendro could not start before the 1980s when improved saws and milling technology had been introduced (Flores, 1992; Butterfield, 1995). It is used for floorings, bridges, railroad ties, boats, marine construction, handicrafts, veneers, industrial machinery, sport implements, springboards and agricultural tool handles (Jiménez et al., 2002; Carpio Malavassi, 2003). Finally, Almendro is appreciated for its excellent wood, but as one of the prettiest trees in the forest, Almendro with its purple flowers has also great potential for use as an ornamental tree. Moreover, indigenous people benefit from the medical use of parts of the tree, and its nutritious seeds are supposed to taste delicious when roasted (Standley, 1937)

Almendro was once a widespread species, but suffered severely from habitat destruction and timber extraction. In Costa Rica and Nicaragua this species is listed as an Appendix III species by CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES, 2008). Furthermore, the Costa Rican ministry of environment and energy (MINAE, Ministerio de Ambiente y Energia) completely banned the exploitation and extraction of Almendro from natural forests in September 2008 (Ávalos, 2008). Since that time, the Costa Rican wood industry mainly processes Almendro from Nicaraguan sources.

2.2 Almendro in timber plantations Research on native tree species for timber plantations in Costa Rica and Panama is relatively young. Some 24 years ago, in 1985 the first experimental plots using Almendro were established by the “Organization for Tropical Studies” (OTS) in La Selva, Sarapiqui, Costa Rica. In the 1990´s more research projects followed, such as the “Cooperación en los Sectores Forestales y Maderero” (COSEFORMA) project in the northern zone of Costa Rica, and in 1991 the EARTH University in Guácimo also included Almendro in their research. Shortly later the “Comision de Enlace para el Estudio de Especies Forestales Nativas de la Zona Norte y Atlantica” was founded in 1992 to coordinate and support the research of

LITERATURE REVIEW native species in Costa Rica (Müller, 1993). Mora-Chacón (2002) has documented a complete history of native species research in Costa Rica.

Only native species with the highest priorities for commercial plantations have been selected for investigations and Almendro was included for its resistant and durable wood. In contrast to other timber species, which only have national markets, Almendro was also selected because of its potential as timber export (Müller, 1993).

Native species research in Panama was for the most part carried out by the Smithsonian Institute and first research outcomes for Almendro on plantations were published by Condit in 1993. Since 2001, the joint “Native Species Reforestation Project” (PRORENA) between the Smithsonian Tropical Research Institute and the Yale School of Forestry is coordinating ongoing research on trees native to Panama. Like in Costa Rica, Almendro was included in native species research projects in Panama, because of its high commercial value (Ugalde Arias and Gómez Flores, 2006).

Before the early 90´s, native species were not been recommended for commercial reforestation programs as up to date information did not exist, but since this time many of the identified research gaps have been filled. Information about seed sources, species site requirements and silvicultural management are available for numerous native species. Despite the great potential of Almendro determined long ago, the situation is completely different. Neither silvicultural management schemes nor general growth models or site classifications exist for Almendro.

Information for the first stages of plantation establishment such as the treatment of seeds (González, 1999) or nursery seedling growth exist (Russo and Sandí, 1995). Also, studies about the initial growth behavior were published for Costa Rica (Butterfield, 1995) and Panama (Wishnie et al., 2007).

LITERATURE REVIEW

A few growth reports for older Almendro plantations were published, such as the growth in mixed and pure plantations in humid tropical Costa Rica (Petit and Montagnini, 2006); the growth characteristics on farms in humid lowlands of Costa Rica (Piotto et al., 2003) and in silvopastoral systems (Montagnini et al., 2003); performance, growth equations and rotation ages in mixed and pure plantations in the humid neotropics (Petit and Montagnini, 2004); the effects of thinning for pure- and mixed plantations with Almendro (Piotto et al., 2003); the response to reforestation strategies on abandoned farmland in Panama (Hooper et al., 2002); and the performance of native species and preference of farmers in Costa Rica and Nicaragua (Piotto et al., 2003).

A comprehensive study about the growth behavior of Almendro took place on the COSEFORMA plots in the Northern Zone of Costa Rica. These findings were published by Delgado et al. (2003). Growth results after 11 years for three different sites (humid Ultisol, very humid Ultisol and very humid Inceptisol) were presented along with a growth model to predict diameter and height-growth based on the Schumacher model. His results indicated that after 11-years Almendro performed the best on sites with an Ultisol soil profile. However, the rotation time of D. panamensis is assumed to be 25 to 35 years according to Petit and Montagnini (2004), while Montagnini et al. (2003) estimate a rotation period of 22 to 32 years. Through third-degree polynomial regression analysis growth equations for a number of native tree species in the Atlantic lowlands of Costa Rica were developed (Petit and Montagnini, 2004), but the growth of Almendro was to premature for extrapolative modeling, hence only interpolative equations in the form of second-degree polynomials were assigned to this species. Finally, model projections of Almendro are limited to 11-years Delgado et al. (2003) and 12-years Petit and Montagnini (2004), thus covering only half of the predicted rotation time and both models are not suitable for extrapolations.

Several publications, which are focusing more on the general effects of timber plantations than on silviculture, mention Almendro as well. Many authors (Fisher, 1995; Parrotta et al., 1997; Carnevale and Montagnini, 2002; Butler et al., 2008) emphasize that timber plantations of indigenous tree species can support secondary forest succession by improving

LITERATURE REVIEW soil conditions, attracting seed-dispersal agents, and providing shade necessary for understory growth.

Also leaf litter decomposition and mulch performance of Almendro have been described (Byard et al., 1996) as well as the direct effect of Almendro on soils (Montagnini and Sancho, 1994; Montagnini, 2000). Almendro is a leguminous tree, although Montagnini (200) could not find any N-benefits, which can perhaps be ascribed to missing Nodulates on the roots. However, higher levels of K were found under plantations of Almendro in a trial at La Selva, Sarapiqui in the Atlantic lowlands of Costa Rica (Montagnini, 2000), underlining the direct effect that timber plantations can have on soils.

2.3 Agroforestry and carbon forestry using Almendro Various authors highlight the potential of Almendro for agroforestry systems and carbon forestry projects.

It has been established that Almendro is a useful tree for agroforestry systems, (Haggar et al., 1998; Haggar et al., 2003), referring to crop-tree combination with Pineapple (Ananas spp.). Montagnini et al. (2003) described growth characteristics of Almendro in silvopastoral systems, an agroforestry system where the production of livestock and trees takes place on the same land-unit (Klopfenstein et al., 1997). Because of its open crown architecture, Almendro builds a relatively translucent canopy that produces only moderate shade, thus allowing the simultaneous growth of crops like pineapple, cacao and other cash or forage crops. With its good timber quality and high economic value, Almendro can generate extra income for local farmers and may therefore be a good choice for many kinds of agroforestry systems.

Besides the production of timber, or timber in combination with crops and cattle in agroforestry systems, timber plantations provide additional environmental services, such as carbon sequestration (Montagnini and Porras, 1998; Shepherd and Montagnini, 2001; Montagnini and Nair, 2004). Therefore, timber plantations in tropical countries, like Costa

LITERATURE REVIEW

Rica or Panama, have been proposed as one feasible option to offset emissions to mitigate climate change. Through photosynthesis carbon dioxide (CO2) is fixed in the biomass of the tree and sequestered in the key components of forest ecosystems, both as aboveground biomass and belowground biomass (Montagnini and Porras, 1998).

Almendro has been identified as the best option and most promising species for long term carbon sink reforestation projects in Costa Rica (Redondo-Brenes and Montagnini, 2006; Redondo-Brenes, 2007). The study results indicate that fast-growing species accumulate more carbon in the short-term (less than 10 years), but in the long-term slower growing species such as Almendro accumulate more carbon due to different growth-patterns and their high specific wood gravity.

METHODOLOGY

3. METHODOLOGY

3.1 Study area Investigations covered timber plantations in the two Central American countries Costa Rica and Panama. The majority of sample plots (68%) were located in Costa Rica, in particular in the Atlantic lowlands of Costa Rica.

Panama with 77.382 km² has a greater land surface than Costa Rica (51.100 km²), but the climatic conditions in Costa Rica and Panama are broadly similar. These countries belong to the Neotropics and their climate is mostly tropical and in few parts subtropical. Due to considerable relief within these two rather small countries, significant climate diversity over relatively short distances can be discovered. Both countries have a central mountain range and border two oceans. The Caribbean side is usually more humid than the Pacific side and temperatures are lower at higher elevations. The numerous vegetative regimes contribute to the country’s biodiversity and are often a direct result of elevation differences and associated temperature and precipitation patterns. Still, two seasons can be distinguished, the dry season from early December through late April and the wet season from late April until the end of November.

Both countries are, as part of the isthmus between North- and South America, geologically young, diverse and important in the context of geological history (Webb, 1991). Soils are frequently derived from volcanic rocks (Palka, 2005). In Costa Rica 43 soil types are found and in Panama 38 soil types, Inceptisols and Ultisols among the most common ones (Fao- Unesco, 1990; Mata-Chinchilla, 1991).

Kapp (1999) provides a comprehensive summary of the climatic, geographic and edaphic conditions of both countries and described their forestry sectors. The forestry sector is generally more developed in Costa Rica, even if the total plantation area is bigger in Panama.

METHODOLOGY

3.2 Description of the sample plots A total number of 131 sample plots, covering different physiographic, edaphic and climatic conditions in both Costa Rica and Panama, were included in this study. Most of them were permanent sample plots (PSPs), but 9 temporary sample plots (TSPs) were established on plantations without any sample plots or on plantations where the original PSPs could not be located anymore. 19 PSPs were abandoned and were re-measured for this study after identifying the original tree numeration. Depending on the actual stocking, these sample plots had been variable in size, mostly of rectangular shape and few circular ones. The sample plots contained generally 25 trees or more. The northernmost sample plot was on the plantation “Santa Cecilla” (11°11’N, 85°43’W) at the border of Costa Rica and Nicaragua and the southernmost, “Soberania”, in the Panama Canal Region.

Figure 1: Map of the study area. Black dots indicate Almendro plantations included in this study.

Sample plots were distributed from 45 m.a.s.l up to 950 m.a.s.l and covered a precipitation gradient from 1110 mm to 4500 mm.

Past land-use on plantations had been largely pasture and dominant soil types where either Ultisols or Inceptisols. In both Costa Rica and Panama, the seed planting material originated from identified Almendro seed trees in natural forests. Almendro plantations in Costa Rica

METHODOLOGY were by and large established with seeds from identified seed trees in the Sarapiqui and Guácimo region in the Atlantic lowlands and in Panama from seed trees in the Panama Channel region (Butterfield, 1995; Russo and Sandí, 1995; Wishnie et al., 2007).

Plantations were typically established in 3 x 3 m spacing, few in 2 x 2 m spacing and some individual ones 4 x 4 m, 5 x 5 m up to 6 x 6 m. The mixed Almendro plantations were frequently spaced asymmetrical, such as 3 x 5 m or 3 x 4 m.

Plantation establishment normally included manual weeding and cleaning in the first years, however sometimes also Glyphosphat was used to remove competing vegetation. Management was concentrated primarily on the establishment, but silvicultural intervention like thinning and pruning did not take place in most of the plantations.

3.3 Data collection Growth data from 36 timber plantations, scattered in Costa Rica (26) and Panama (10), was collected from March 2009 until the end of May 2009. Overall, this study covers a total of 131 sample plots as mentioned before.

Wherever necessary and possible, stands had been re-measured either on existing PSPs or on newly established TSPs. All plots were mapped using a GPS handheld (Garmin - GPSmap 60Scx) and altitude was measured with the device´s barometric altimeter. Recordings were taken of diameter at breast height (DBH) and the total tree height (h). The diameter was measured with diameter tape, but on a few plantations (<20%) a caliper was used. Tree heights were measured using a clinometer (SILVIA - Clino Master). For 8 plantations, only a representative amount of tree heights (+/- 25) could be collected due to time constraints. For these plantations, missing tree heights have been generated using the Michailoff- function, see chapter 3.6.

For the creation of growth series, scientists and plantation owners provided their growth records as Excel files, for years prior to 2009. These Excel files were then processed with the

METHODOLOGY software MIRASILV 3.2 (Sistema de manejo de información sobre recursos arbóreos en el componente de silvicultura) to clean and organize the data for analysis (including more than 22000 measurement records). MIRASILV was developed at CATIE under the supervision of Ugalde (2003). MIRASILV was used for a plausibility check of all records, and accordingly negative growth records and outliers were excluded before starting the data analysis. A list with detailed description of all plantations can be found in Annex 1.

Table 1: List of own measurements and data sources for growth data prior 2009

Country Institution Data source # of plantations CR OTS – La Selva Own measurements + external 3 CR ITCR / COSEFORMA Own measurements + external 7 CR RTT External data 3 CR CATIE External data 5 CR EARTH Own measurements + external 4 CR PRECIOUS WOODS External data 1 CR LOS TUCANES External data 1 PA FOREST FINANCE Own measurements + external 6 PA PRORENA External data 6

3.4 Data analysis The methodology had to be adapted to account for the fact that the data sets provided originated from heterogenic plantations in terms of site, age, initial spacing and silvicultural management. Various forest mensuration methods were used on all plantations and the provided data set were not always consistent.

All plantations were clustered into 9 site groups (SIGR) and 3 age classes (AGCL), based on their location and age. The SIGRs were then numbered from north to south and east to west.

METHODOLOGY

Table 2: List of age classes, their ranges and frequencies

Age class Range # of Plantations in CR in PA 1 <8 years 17 12 5 2 8-16 years 13 8 5 3 >16 years 6 6 -

The classification of SIGR in Costa Rica incorporated biotic units, soil types, geology, life zones and relief (Ortiz and Cordero, 2008), whereas in Panama the grouping was based on Isohyets, Isotherms and elevation (Hydromet, 2009) due to different data availability.

Table 3: List of site groups and their attributes.

STGR Annual precipitation # of dry Elevation Dominant soil # of Nr. (mm) months* (m) type** plantations COSTA RICA 1 2000 - 2500 3 - 4 <400 Ultisol 3 2 2500 - 3000 1 - 2 <200 Inceptisol 2 3 3000-4000 1 <200 Ultisol 6 4 4000-5500 0 <200 Inceptisol 8 5 3000-3500 0 - 1 300 - 400 Inceptisol 3 6 2500-3000 0 600 - 1000 Ultisol 4 PANAMA 7 3000-3500 2 - 4 <200 Ultisol 7 8 <2000 4 - 6 <300 Alfisol 2 9 2000 – 3000 2 <200 Ultisol 1

* Months with less than 100mm rainfall ** Detailed information about soil types in Panama could not been obtained, as a country wide soil type mapping never took place. The used information for Panama originate from the Harmonized World Soil Database (Fischer, 2008). Soil data from the Digital Atlas de Costa Rica was used for all sites in Costa Rica (Ortiz and Cordero, 2008)

Data analysis was then conducted using MIRASILV v.3.2., the Statistical Package for Social Science (SPSS, Version 16) and Microsoft Excel 2007 (Harris, 1998).

METHODOLOGY

Stand parameters for each plot and plantation were calculated, such as mean diameter (dg), mean height (hg), top diameter (d50), top height (h50), basal area (G) and Volume (V). For plantations with more than one sample plot, average values from all sample plots were calculated. All stand parameter where finally extrapolated to hectare values. To illustrate the availability of trees with diameters suitable for commercial use, diagrams of the stand diameter distribution were drawn using a 2 cm scale. These diagrams are also supposed to illustrate the great variety of Almendro stand scenarios.

The methodology aimed to harmonize all measurement records and to present stand parameters, which allow a comparison between sites and management schemes. This would have not been possible when using mean values, which are in general strongly influenced by stand management schemes. Therefore, primarily top height and top diameter are presented in the results chapter instead of mean height and mean diameter. With these top values, the potential of Almendro plantation can be expressed independently from insufficient management interventions.

To save time and money, several plantation owners measured representative tree heights and generated tree heights for the rest of the stand using stand height curves (SHC). This approach had to be adopted also for the calculation of the top height, the average total height of a specified number of the thickest trees in a stand.

Top height (h50) and top diameter (d50) were calculated for the 50 strongest trees, as it was assumed that at the end of the rotation age no more than 200 Almendro trees per hectare remain on a plantation. Teak (Tectona grandis) plantations in Costa Rica normally yield 120 to 185 final crop trees according to Bermejo et al. (2004). In this case, 100 trees would represent more than half of all trees, thus not representing the strongest ones.

As mentioned before, stand-height curves were used to calculate the top height (h50). For that reason, the quadratic-mean diameter of the largest 50 trees, the top diameter (d50), was entered into the Michailoff-function (see Chapter 3.6.) to estimate the corresponding top

METHODOLOGY height. Similar approaches are adopted in New Zealand and the UK to avoid subjective selection of the tallest trees (Brack, 2000). Dominant height (hdom) could not be taken into account, hence not all tree heights were measured on all plantations, but in very young plantations where no diameter values were available, the dominant height had to be used instead of the top height, thus representing the mean height of the 50 tallest trees per hectare.

For tree volume (V) and basal area (G) calculation the following formulas were used:

Equation 1: Volume calculation

Where: V = tree volume, d = DBH, h = measured tree height and f = form factor* *As no species specific form factor is available for Almendro, a form factor of 0.45 was assumed.

Equation 2: Basal area calculation

Where: G = tree basal area and d = DBH

The respective hectare values were then calculated as the sum of all single tree values.

After the calculation of all stand characteristics, the following steps were taken:

- Development of stand height curves, using the Michailoff-function, see chapter 3.6. - Creation of site index curves based on the top height/plantation age ratio using the Chapman - Richards function (chapter 3.7) - Projection of top-height growth for one rotation period of 25 years, using the Chapman - Richards function (chapter 3.5)

METHODOLOGY

3.5 Growth modeling

Reliable estimates of wood production are fundamental for sustainable forest management on any forest level. These forecasts of growth and yield depend on silvicultural practices, estimates on site productivity and the models used.

The evolution of growth modeling started with “static” growth models at the beginning of the 18th century. They had the form of basic yield tables and were rather simple growth predictions, only valid for pure-, even-aged stands, on particular sites under standardized silvicultural treatments (Alder, 1980; Tesch, 1981).

A substantial change in growth and yield determination began around 1935 when statistical techniques where applied on growth data and growth formulas evolved that were able to project growth for many situations (Tesch, 1981).

Nowadays, some forest growth models are more “dynamic” and not only able to predict future yield, in addition they even allow forest managers to explore several silvicultural options, like forest simulators in Germany, such as SILVA (Pretzsch et al., 2002) or BWinPro (Nagel et al., 2002). Growth models form a continuum from yield tables to single tree models (Leary, 1991) and their development over the last 200 years had been profoundly described by Tesch (1981) and Skovsgaard and Vanclay (2008).

Nevertheless, the situation in tropical countries is exceptional as advanced growth modeling is relatively rare. Only a few provisional yield tables and some growth models exist, and generally only for widely used commercial species like Teak (Tectona grandis), Eucalyptus spp. or Pinus spp.. In Costa Rica and Panama, growth models are available for exotic species such as Teak (Bermejo et al., 2004; Perez and Kanninen, 2005) and for few native species (Somarriba et al., 2001; Cordero et al., 2003), but as mentioned in chapter 2.2, no reliable growth models that are applicable on various sites exist for Almendro.

METHODOLOGY

Numerous growth functions, able to describe plant growth processes, are available (Bredenkamp and Gregoire, 1988; Garcia, 1988; Zeide, 1993). The Chapman-Richards function (Richards, 1959) embodies commonly used growth functions such as monomolecular, Gompertz, and logistic equations and has been widely applied in forestry due to its flexibility, accuracy, and meaningful analytical properties (Pienaar and Turnbull, 1973; Shifley and Brand, 1984; Yuancai et al., 1997; Zhao-gang and Feng-ri, 2003).

The Richards function has been used as well in this study to develop growth curves of top- height growth.

Equation 3: Chapman - Richards function

Where: H = height, a = upper asymptote, t = time, and b, c, d = parameters

Further aspects of growth modeling have been described by many authors (Vanclay, 1992; Vanclay, 1995; Vanclay, 1997; Vanclay and Skovsgaard, 1997).

3.6 Stand height curves Stand height curves represent the correlation between tree height and DBH in a forest or timber plantation. In a scatter diagram with the measured DBH on the X-axis and the measured height on the Y-axis the correlation between the two variables (DBH and height) is visualized in a point cloud, which can be fitted to a stand height curve either graphically or mathematically. The mathematical methods follow the “least squares method” and a variety of equations have been proposed to fit height curves (Schmidt, 1967), each suited to different forest types, stand ages and structures.

METHODOLOGY

The shape of the curve changes with the development and growth stage of the stand, indicating the following (Brack, 2000; Kramer and Akça, 2002):

- Steep sloped curves indicate a young stand, which is still sorting out dominance. - Shallow or flat slope may indicate a mature to over-mature stand, or a stand modified by thinnings. - A right-hand-side of the curve that is relatively high indicates a good site.

As the nature of the curve changes with age, no single method is likely to be satisfactory for all situations.

For this study the Michailoff and Petterson equations (Michailoff, 1943; Kramer and Akça, 2002) were used to fit the observed values to a curve. Especially the Petterson function is suitable for all-aged stands with wide diameter class dispersion, like the unthinned Almendro plantations in Costa Rica and Panama.

Equation 4: Petterson - height curve function

Where: h = (predicted) tree height, ao, a1 = regression coefficients, d = diameter at breast height

However, the Michailoff-function showed better fit for most of the Almendro stands and was therefore used in this study.

Equation 5: Michailoff - height curve function

Where: h = (predicted) tree height, ao, a1 = regression coefficients, d = diameter at breast height

Measuring the height of all trees in a stand is time consuming and therefore stand height curves were used to predict the height of trees where only the height of a representative

METHODOLOGY limited number of trees was measured. This was the case for the 2009 measurements on seven plantations from the COSEFORMA project (“Los Almendros”, “Buenos Aires”, “Cope San Juan”, “Montealegra”, “E. Romero”, “O. González”, “O. Rodriquez”) and the plantation “Santa Cecilla”. The determination of tree heights through this method is facilitated by the relative strong stochastic relationship between the DBH and tree height for each tree species in a stand.

Besides, the Michailoff height curve function was used to determine the top height for the 50 strongest trees in all stands, as described in chapter 3.4.

3.7 Site classification Forest yield determination and site classification were ever closely linked, as on some sites, forests grew better than on others. Differences of soil conditions (e.g. fertility, drainage), climate (rainfall and temperature patterns) and topography (e.g. altitude, slope) are reflected in tree performance, requiring an evaluation of these site varieties to be able to give reliable forecasts of growth and yield (Vanclay, 1992). Various sites classifications exists, such as site index, site quality, and site class or site productivity. An uncomplicated method for site classification is a visual assessment of the site quality into relative classes (i.e. good, poor). Site class is a more objective classification into a number of classes and site productivity is a general term for the potential of a certain tree species to produce timber. The most common way to assess the site quality is the site index, but as for site quality and site class it is an approximate measure of the true site productivity (Vanclay, 1992). For a review of the history and basic principles of site classification see Skovsgaard and Vanclay (2008).

The productive capacity of the site affects both the volume of timber production per hectare and the age of maximum mean annual increment (MAI) culmination. Good sites take a shorter time to reach MAI culmination age and produce more timber as compared to poor sites (Pandey, 1987). Besides the influence on growth factors, site selection also affects

METHODOLOGY susceptibility to forest pest. Planting trees on unsuitable sites favors a high probability of pest outbreaks (Speight and Wylie, 2001).

In the tropics, direct methods to determine the productive potential, such as quantifying climate, soil or indicator plants, are rather uncommon; instead site indices (SI) are used to determine site classification. The site index (SI), is represents the stand top height at a specific age, and is often estimated using a top height-age curve. Although true site productivity may not be fully represented by SI, SI is the most widely accepted and probably the most simple method for estimating site productivity (Sharma et al., 2002).

The top-height is widely accepted as site productivity indicator for even-aged forests as it is little influenced by silvicultural interventions, given that thinnings are not from above (Brack, 2000; Evans and Turnbull, 2004). Trees used in the estimation of site index should rank among the upper social classes and top heights represent those leading trees, thus being a very stable height-based indicator of site productivity (Skovsgaard and Vanclay, 2008; Kramer and Akça, 2002; Sharma et al., 2002; Vanclay, 1992).

Growth models allow foresters to locate the equivalent top height-age curve to classify and project the growth of their stands, based on measured top height and known age of a stand (Avery, 1994). Because of its flexibility, the Chapman-Richards equation is often used to model this top-height growth pattern. This study makes use of this equation for similar reasons, see Chapter 3.6.

Site indices exist for few species in Costa Rica and Panama, such as Tectona grandis (Bermejo et al., 2004; Perez and Kanninen, 2005), Cordia alliodora (Somarriba et al., 2001), Bombacopsis quinata (Cordero et al., 2003) or Terminalia amazonia (De los Santos-Posadas et al., 2006).

RESULTS

4. RESULTS

In this chapter, growth records from all plantations in each site group are presented and stand characteristics for selected plantations are described. Subsequently the top-height growth dynamics of Almendro are illustrated for all development phases (young-, medium and older plantations). Site indices are developed on the basis of the top height growth, together with growth projections of top height for one rotation period.

4.1 Growth of Almendro in Costa Rica and Panama

4.1.1 Site group 1, CR In the north-easternmost region of this study, bordering Nicaragua, three commercial Almendro plantations (all AGCL 1) were visited. The plantations are located in the climatic transition zone between the dry climate of the Pacific lowlands and the wet Atlantic lowlands climate. With annual rainfall ranging from 2000 - 2500 mm and 3 - 4 dry months, the climate is the driest in comparison to all other site groups in Costa Rica.

“Santa Cecilla” is managed by the Swiss based tropical forests management company Precious Woods (http://www.preciouswoods.com). The plantation is mainly stocked with Teak (Tectona grandis) and native species have been typically planted on a trial basis, except for Pochote (Bombacopsis quinata), the most frequently used native species for commercial purposes on their plantations.

A small patch of 2 ha, 110 m.a.s.l, was reforested with Almendro in 2001 on flat terrain. The spacing was 3 x 3 m and two thinnings have been conducted so far. 120 trees per hectare were removed in 2006 and another 200 trees per hectare in 2008. The thinnings have not been from below as one could expect for this stage of plantation development. During both thinnings, trees of the upper classes were removed, as well as trees on the sample plot, which were used for exemplary height measurements (chapter 3.6).

RESULTS

Two more plantations were situated in this site group, but on higher elevations between 300 to 400 m.a.s.l. These educational plantations are owned by a scientist working at CATIE, who is demonstrating multiple use forestry, primarily with native species. Overall, more than 50 different native species are planted on these plantations and some of them in agroforestry systems, along with Cacao (Theobroma cacao) and Vanilla (Vanilla planifolia). On the plantations “Orosi” and “Cacao”, Almendro was planted basically in line plantings in- between a great number of various native species.

Growth data was provided and subsequently analyzed. Table 4 shows the growth of Almendro in this site group.

Table 4: Growth of Almendro in SIGR 1

d50 h50 G V Stocking Plantation Years Months (cm) (m) (m² ha-1) (m3 ha-1) trees ha-1

1.6 19 4.3 3.5 0.7 1.0 920 2.6 31 7.1 6.7 1.7 4.4 900 3.6 43 10.2 9.0 3.6 13.0 900 Santa Cecilla 4.7 56 13.3 11.5 6.3 29.6 900

5.6 67 15.5 11.7 8.0 40.0 780 6.8 81 16.1 15.6 9.3 61.4 780 7.8 93 18.2 16.0 9.8 66.8 580 3.0 36 5.3 5.6 0.5 0.9 542 Orosi 4.0 48 8.0 7.1 0.9 2.4 542 4.0 48 6.0 5.8 0.4 0.8 667 Cacao 5.0 60 8.8 7.1 0.7 2.2 333

4.1.2 Site group 2, CR A short dry period of 1 - 2 month, annual rainfalls of approximately 3000 mm and Inceptisols as dominant soil type are characteristic for this site group. In a 4-year old agroforestry system (“Tamara AFS”), where Almendro was planted together with Cacao (Theobroma

RESULTS cacao) and Banana (Musa spp.) in a 12 x 12 m spacing, high initial growth rates were observed of 1.9 m per year in top height and 2 cm in mean DBH (2.3 cm per annum for d50). Compared to the other Almendro plantation in the same site group (“Montealegra”: 18 years old, 3 x 3 m spacing), the agroforestry system showed faster initial diameter growth, but slower height growth. The plantation in “Montealegra” was managed as silvopastoral system and reached equal values around two years later.

Table 5: Growth of Almendro in SIGR 2

d50 h50 G V Stocking Plantation Years Months (cm) (m) (m² ha-1) (m3 ha-1) trees ha-1 Tamara AFS 3.8 46 8.6 7.1 0.3 0.9 69 2.1 25 4.2 4.0 0.6 0.8 1111 3.1 37 7.3 5.8 1.6 3.3 1100 4.1 49 9.4 8.6 3.0 9.3 1100 5.1 61 10.2 10.3 3.8 14.5 1089 Montealegra 6.1 73 11.8 11.1 5.0 20.8 1033

7.1 85 13.6 12.7 5.8 27.4 967 8.1 97 13.9 13.1 6.2 30.6 956 11.1 133 16.9 16.8 9.5 61.0 867 18.4 221 22.0 18.2 11.7 76.3 700

4.1.3 Site group 3, CR Site group 3 contains the greater part of the Almendro reforestations that had been established during the COSEFORMA project. The COSEFORMA project was a German – Costa Rican development project between the German Technical Cooperation and local forest authorities, promoting sustained and efficient use of forest resources.

RESULTS

Table 6: Growth of Almendro in SIGR 3, AGCL 3

d50 h50 G V Stocking Plantation Years Months (cm) (m) (m² ha-1) (m3 ha-1) trees ha-1 2.0 24 3.8 3.7 0.7 1.0 1100 3.0 36 5.4 5.0 1.6 3.1 1100 4.0 48 7.1 6.3 2.7 6.9 1100 5.0 60 9.6 9.1 5.2 19.5 1100 Oscar Rodriquez 6.0 72 11.0 10.9 6.5 29.9 1089 7.0 84 12.8 12.5 7.1 37.1 956 8.0 96 13.7 13.3 8.1 45.4 956 11.0 132 16.8 14.5 11.0 65.4 956 18.4 221 22.7 19.7 12.0 94.1 667 2.8 34 3.5 3.5 0.1 0.1 1067 3.8 46 5.4 5.3 0.3 0.4 1044 4.8 58 8.7 7.3 1.4 3.2 1022 5.8 70 10.6 8.8 2.3 7.0 1000 Los Almendros 6.8 82 12.8 9.7 3.8 13.6 944 7.8 94 13.9 10.8 4.8 20.0 944 10.8 130 19.9 13.4 8.8 45.3 919 18.4 221 28.7 20.7 15.1 117.1 889 1.8 22 3.9 4.3 0.4 0.6 1111 2.8 34 6.6 6.8 1.5 3.6 1100 3.8 46 8.4 9.0 2.7 8.9 1100 4.8 58 11.0 11.7 4.5 19.3 1089 Cope San Juan 5.8 70 12.1 13.9 5.2 26.4 1078 6.8 82 13.6 15.2 6.4 35.8 1044 7.8 94 14.4 15.3 7.1 41.2 1044 10.8 130 18.0 18.7 10.0 71.4 989 18.4 221 23.4 22.3 14.4 126.3 956

RESULTS

In early 1990, reforestations with native species were initiated on private farmland in the northern zone of Costa Rica, with funds from the COSEFROMA project. Soils in this site group belong to the Ultisol order and annual rainfall fluctuates around 3000 mm.

All experimental plantations were planted in 3 x 3 m spacing on former pasture land and have similar management histories (cleaning and weeding in the first years, no thinning). The three plantations “Edwin Romero”, “Olman González” and the plantation “Buenos Aires” were established in 1994, thus belong to AGCL 2. The others were planted in 1990 (“Cope San Juan”, “Los Almendros” and “Oscar Rodríquez”) and respectively belong to AGCL 3. More detailed descriptions of all plantations can be found in Delgado et al. (2002).

All plantations were established on private farmland in cooperation with local farmers. Some of them used the reforested area for cattle crazing, so that three plantations (“Los Almendros”, “Edwin Romero” and “Olman González”) can be considered as a silvopastoral systems. For a general description of silvopastoral systems see Klopfenstein (1997). “Cope San Juan” supported the highest total stand volume, as 965 trees remained on the plantation after 18 years. Mean diameter (dg) was respectively the lowest, but trees the highest (h50), when compared to the other plantations of the same site group.

The highest top diameter (d50) of 28.7 cm was observed in “Los Almendros“. Considering h50, “Cope San Juan” ranked first, “Los Almendros” second and “Oscar Rodriquez” third.

From the three younger plantations, Buenos Aires had the largest diameter and biggest height values. Mean diameter (dg) in Buenos Aires was the largest in this site group and exceeded the values of the older plantations. Plantation “Edwin Romero” performed better than “Olman González”. For the whole site group basal area (G) was the highest on the plantation “Edwin Romero”. With 850 trees per ha and a total standing volume (V) of 121.7 m³/ha, V in “Edwin Romero” was only 4.6 m³/ha lower compared to the plantation “Cope San Juan”, which was three years older and had the highest standing volume of the site

RESULTS group. The lowest current stocking of 590 trees/ha was observed on plantation “Olman González”.

Table 7: Growth of Almendro in SIGR 3, AGCL 3

d50 h50 G V Stocking Plantation Years Months (cm) (m) (m² ha-1) (m3 ha-1) trees ha-1 1.3 16 2.8 2.8 0.2 0.2 1111 2.3 28 6.4 6.0 1.4 3.0 1070 3.3 40 8.1 7.6 2.4 6.8 1056 Buenos Aires 4.3 52 10.4 9.5 4.2 15.4 1056 7.3 88 16.1 12.5 9.0 45.5 1043 14.8 178 24.2 20.9 13.8 115.4 617 1.3 16 4.3 4.3 0.7 1.2 1029 2.3 28 6.4 6.3 1.7 4.1 1029 3.3 40 9.4 9.1 3.7 12.4 1015 Edwin Romero 4.3 52 10.2 10.0 4.5 16.9 1015 7.3 88 14.9 14.8 9.4 57.7 933 14.8 178 21.0 20.1 16.1 121.7 850 1.3 16 2.0 2.4 0.0 0.0 1084 2.3 28 4.4 4.8 0.5 0.8 837 3.3 40 6.9 6.8 1.2 3.0 741 Olman González 4.3 52 8.2 7.7 1.7 5.1 700 7.3 88 14.2 11.5 5.0 22.3 700 14.8 178 19.5 16.5 7.5 48.1 590

4.1.4 Site group 4, CR This site group covers the Atlantic lowlands of Costa Rica. The region is characterized by high annual rainfalls of 4000 to 5500 mm and soils of better productivity, such as Eutropepts or Dystropepts. Most soils under Almendro in this site group however, belong to the Ultisol

RESULTS order. One commercial plantation (“Los Tucanes”) and seven scientific plantations are part of SIGR 4.

Numerous publications are available for this climatic zone as the major part of research on Almendro was conducted in this region, yet most of the scientific plantations did not receive constant silvicultural management.

Still, groundbreaking information about the performance of Almendro in natural forests . (Clark and Clark, 1987; Fichtler et al., 2003; O'Brien et al., 2008) and on timber plantations (Montagnini and Sancho, 1994; Butterfield, 1995; Stanley and Montagnini, 1999; Carnevale and Montagnini, 2002; Petit and Montagnini, 2004; Petit and Montagnini, 2006; Redondo- Brenes and Montagnini, 2006) were gathered especially, on the sample plots in the research station La Selva (10°26’N, 86°59’W), managed by the Organization for Tropical Studies (OTS). The mean altitude of the mostly flat terrain is 50 m, mean annual temperature is 24 °C and the mean annual rainfall amounts 4000 mm. The “Canadian Trial” and “Montagnini” plots were established on deep, well-drained and stone free Fluventic Dystropepts derived from volcanic alluvium with pH values below 5. Sample plot “J. Haggar” was established on Ultisols. For a in depth description of the soils of the research station La Selva see Sancho and Mata (1987).

The oldest reforestation in Las Selva using Almendro was established in 1985 as part of the TRIALS project (Butterfield and Fisher, 1994). This plot (“Canadian Trial”) was planted with 49 Almendro trees in 2 x 2 m spacing and the plot descriptions and early growth results can be found in Butterfield (1995). After 24 years, 14% of the originally planted Almendro trees survived. Seven trees remained on the plot (sample plot size: 196 m²), thus representing 357 trees per hectare. The measured mean DBH (dg) was bigger 30 cm and the tree in the highest diameter class (d50) measured 39.6 cm. Basal area (G) was 27.6 m²/ha and total stand volume 410 m³/ha. All trees were straight and of good form. Measured heights until the first branch, the commercial height, averaged 14.2 m.

RESULTS

Based on the observations from this plot, the rotation age for Almendro was assumed to be 25 years as this species can produce a target diameter of over 30 cm in this period. This assumed rotation age resembles the assumptions from Petit and Montagnini (2004).

Table 8: Growth of Almendro at “La Selva”, SIGR 4, AGCL 3

d50 h50 G V Stocking Plantation Years Months (cm) (m) (m² ha-1) (m3 ha-1) trees ha-1 Canadian Trials 24.0 288 39.6 33.7 27.6 410.0 357 Jeremy Haggar 14.8 178 29.9 23.9 19.1 188.3 500 2.3 28 5.8 5.8 1.7 3.7 1860 3.3 40 9.1 9.1 5.0 17.4 1786 4.3 52 11.6 11.3 5.8 26.5 1131 Montagnini 6.8 82 16.1 16.5 7.3 46.0 833 (Thinned) 7.9 95 17.5 18.4 10.4 72.0 833 9.9 119 18.7 19.0 11.3 84.4 670 17.6 211 25.1 29.3 18.2 196.6 1094* 2.3 28 6.1 6.5 2.0 4.5 2068 3.3 40 9.4 9.4 5.4 19.0 2024 4.3 52 12.1 12.4 8.1 38.3 2024 Montagnini 6.8 82 16.1 16.0 11.7 67.5 1994 (Unthinned) 7.9 95 18.7 17.2 14.0 85.0 1994 9.9 119 21.1 18.6 12.1 84.4 863 17.6 211 21.3 25.9 27.2 260.4 1875* *These values originate from TSPs and will be discussed in Chapter 5.1.

Growth on the “Montagnini” and “J. Haggar” plots was measured as well. For the “Montagnini” plots older growth data was available for almost 10 years of one thinned and one unthinned block.

Trees on the “J. Haggar” plot were planted in 4 x 4 m spacing and in 2 x 2 m on the “Montagnini” plots. The original permanent sample plots could not be found anymore as the

RESULTS tree numeration was not visible anymore. Therefore, temporary sample plots had to be established, although their size and amount were limited due to time constraints and difficult access.

Some 50 km away from La Selva, four Almendro plantations on the campus (10°12’N, 83°37’W) of the EARTH University (Esucela de agricultura de la region tropical humeda) were measured on temporary sample plots as well. These plantations were established for investigations, commercial timber production and carbon sequestration. Some of the Almendro plantations help to offset green house gas emissions of the University´s vehicle fleet and the city of Rotterdam, the Netherlands. Since 1991 more than 400 hectares have been reforested with native species on the campus of the EARTH University (Russo, 2002).

The terrain on the EARTH campus is flat at a mean altitude of 90 m.a.s.l. Mean annual temperature is 26 °C and annual precipitation fluctuates around 3400 mm. The mainly alluvial soils were derived from sediments and volcanic rocks.

“La Bomba”, the oldest plantation planted 17 years ago, was established in 3 x 3 m spacing and management was primarily focused on the early years after plantation establishment. Weeding and tending in the first years was not followed by a regular thinning regime, typical for all other Almendro plantations at the EARTH University. Stem numbers at “La Bomba”, were almost the same as on the seven years younger, but thinned “Montagnini” plot in La Selva at an age of ten years. Trees with DBH smaller 5 cm were found together with trees greater 30 cm in DBH, indicating the large range of tree diameters. Early growth data for this stand was published by Russo (2002). Growth data for all “EARTH” plantations is given in table 9.

The mean DBH of the medium aged plantation “Y-Griega” (9.3 years, AGCL 2, initial spacing: 3.5 x 3.5 m) was with 17.5 cm, 0.5 cm smaller than on the eight years older plantation “La Bomba”, which had a higher initial stocking density.

RESULTS

One temporary sample plot was established on the plantation “Puente Hamaca”, on flat terrain in close proximity of a river. The measured spacing was 4 x 4 m and mean DBH was bigger than on the slightly younger plantation “Tiro al blanco”, which was established with an initial spacing of 3.5 x 3.5 m.

Table 9: Growth of Almendro for “EARTH” and “Los Tucanes”, SIGR 4, AGCL 2 and 3

d50 h50 G V Stocking Plantation Years Months (cm) (m) (m² ha-1) (m3 ha-1) trees ha-1 La Bomba 17.3 208 28.6 23.1 17.6 151.2 691 Y-Griega 9.3 112 21.4 16.3 13.1 86 544 Tiro al blanco 4.6 55 12.8 12.3 5.6 28.7 663 Puente Hamaca 4.8 58 16.9 14.4 3.1 19.6 180 Los Tucanes 1 4.8 58 14.3 12.5 5.9 28.3 556 Los Tucanes 2 4.1 49 13.3 12.4 3.8 18.0 556

Data was also provided for “Los Tucanes”, the easternmost Almendro plantation in Costa Rica (09°98´ N, 83.17’ W). This commercial Almendro plantation was established in 2004 at an altitude of 175 m.a.s.l., on land that was formerly used for a timber plantation. After the harvest of Eucalyptus (Eucalyptus spec.) and Laurel (Cordia alliodora), the land was replanted with Almendro in a 3 x 4 m spacing.

On both sample plots, few Laurel trees remained, which overtopped the newly planted Almendro trees. Almendro plots were planted at two different times, thus they are considered separately even if management and spacing are the same. In the 9 months older plot “Los Tucanes 1”, the top diameter was 1 cm bigger than in the younger plot “Los Tucanes 2”.

4.1.5 Site group 5, CR Mixed species Almendro plantation for carbon sequestration and timber production have been established by the applied research organization Reforest the Tropics (RTT) on the northern foothills of the Turrialba Mountains.

RESULTS

In cooperation with local farmers, RTT is planting new tropical forest with donations from US sponsors to offset US-generated carbon dioxide (CO2) emissions. At present RTT balances the

CO2 emissions of over 50 US sponsors on a total number of 9 farms in Costa Rica (http://reforestthetropics.org).

Data from three sample plots was provided for their “Hacienda Las Delicias“ (10°12’ N, 83°37’ W), 5 km away from the EARTH University (SIGR 4). Mean annual rainfall of 3414mm was similar, although elevation was higher (mean altitude 320 m.a.s.l.) and mean annual temperatures lower (21°C).

Table 10: Description of the species mixtures on “Hacienda Las Delicias”, SIGR 4.

Mohegan ConCol CMEEC Trees Spacing Trees Spacing Trees Spacing Species Species Species /ha* (m) /ha* (m) /ha* (m) D.panamensis 625 4 x 4 D.panamensis 339 4 x 6 D.panamensis 354 4 x 4 A. hunsteini 312 4 x 8 A. hunsteini 749 4 x 8 A. hunsteini 578 4 x 4 E. deglupta 78 8 x 16 S.macrophylla 78 8 x 16 *Tree numbers per ha at last measurement in March 2009.

RTT is planting Almendro in pure plantations and mixtures with native species, such as Mahogany (Swietenia macrophylla) and exotic species, such as Klinkii pine (Araucaria hunsteini) and Eucalyptus (Eucalyptus deglupta). The mixtures are explained in table 10 and respective growth data for the forests in which the Connecticut College (“ConCol”), the Connecticut Municipal Electric Cooperative (“CMEEC”) and the Mohegan Tribe of Uncasville

Connecticut (“Mohegan”) balance their CO2 emissions are given in table 11.

RESULTS

Table 11: Growth of Almendro in SIGR 5, AGCL 2 and 3

d50 h50 G V Stocking Plantation Years Months (cm) (m) (m² ha-1) (m3 ha-1) trees ha-1 7.3 88 20.1 14.2 4.7 27.7 339 CONCOL-00 8.1 97 21.6 17.6 5.7 40.1 339 2.3 28 - 4.4 - - 380 3.3 40 7.2 6.6 0.7 1.7 367 4.3 52 10.4 8.0 1.4 4.5 362 CMECC 5.2 62 13.3 10.0 2.5 10.4 354 6.3 76 15.8 12.2 3.8 19.4 357 7.3 88 17.9 14.1 4.8 28.5 354 8.3 100 18.7 15.9 5.2 34.3 354 0.8 10 - 1.1 - - 563 1.8 22 4.4 4.9 0.4 0.7 617 2.8 34 7.0 6.7 1.1 2.9 605 MOHEGAN 3.7 44 9.3 8.9 2.1 7.4 602 4.7 56 11.7 11.0 3.3 14.4 602 5.8 70 13.9 13.1 4.6 24.3 594 6.8 82 16.0 15.9 5.5 34.9 582

4.1.6 Site group 6, CR In the highlands of Costa Rica near the town of Turrialba (9°38’ N, 83°38’ W), Almendro plantations were established by RTT and the Centro Agronómico Tropical de Investigación y Enseñanza (CATIE).

Typical for this region are a distinct season with warmer temperatures from May to November and a colder season from December to March. Mean annual temperatures are 22.5 °C and mean annual precipitation 2645 mm. The plantations “Mulas”, “CACTU” and “Las Peñas” were situated on CATIE´s experimental Farm, 600 m.a.s.l. and one plantation (“San Juan”) was established at 942 m.a.s.l., on hilly terrain that was formerly used as a dairy farm.

RESULTS

Soils in San Juan had good drainage and higher nutrient levels, while CATIE´s experimental farm was formerly used for sugarcane production and soils were depleted, had poor drainage and soils exhibit high water tables during the rainy season (Cuenca, 2009). Table 12 explains the species mixtures and in table 13 all growth records for this site group are listed.

Table 12: Description of the species mixtures in “Mulas” and “San Juan”, SIGR 6.

Mulas San Juan Trees Species Spacing (m) Species Trees /ha* Spacing (m) /ha* D.panamensis 360 5 x 5 D.panamensis 325 5 x 5 A. hunsteini 280 4 x 8 A. hunsteini 255 4 x 8 E. deglupta 40 10 x 20 E. deglupta 30 10 x 20 S.macrophylla 50 10 x 20 S.macrophylla 50 10 x 20

*Tree numbers per ha at last measurement in March 2009.

Performance of Almendro was better on the site in “San Juan” and very poor in “Mulas”. In the mixed system in “Mulas”, Almendro grew inferior to all other species. Height growth in “San Juan” differed and Almendro ranked second after E.deglupta.

Two more plantations of Almendro exist on CATIE´s experimental farm. They have never been measured, as growth was lacking and the replanting with another tree species is already planned. These plantations were visually assessed and average tree heights were below 3 m.

Overall, the performance of Almendro in this site group was inferior, when compared with all other site groups in Costa Rica.

RESULTS

Table 13: Growth of Almendro in SIGR 6, AGCL 2

d50 h50 G V Stocking Plantation Years Months (cm) (m) (m² ha-1) (m3 ha-1) trees ha-1 CACTU 7.6 91 8.9 5.8 1.1 2.4 486 Las Peñas 6.0 72 4.6 4.2 0.6 1.1 400 1.7 20 - 1.8 - - 360 2.7 32 - 3.2 - - 360 Mulas 4.8 58 5.7 4.8 0.4 0.7 360 5.6 67 6.9 5.5 0.6 1.3 360 6.6 79 8.2 5.8 0.8 1.9 360 1.5 18 2.5 2.4 - - 350 2.4 29 3.8 - - - 350 San Juan 4.6 55 8.3 7.2 0.7 1.8 335 5.4 65 9.9 8.9 0.9 3.0 330 6.4 77 11.9 9.9 1.3 5.0 325

4.1.7 Site group 7, PA The northernmost site group in Panama is classified by annual rainfall over 3000 mm and covers the eastern part of the Chiriquí province and western part of the Veraguas province. Five Almendro plantations, managed by the German forest investment company ForestFinance (http://www.forestfinance.de/index.php?id=80&L=1) and one site of the PRORENA project are situated close to the village Las Lajas (81°53’ W, 8°15’N), some 8 km away from the Pacific Ocean. Another site (“Liquid Jungle Lab”) of the PRORENA project was located near the small village Pixvae, in the Veraguas province.

Mean altitude of the plantations in Las Lajas is 50 m.a.s.l., mean annual temperature 26.7°C and annual rainfall ranges between 3000 to 3500 mm with a distinct dry period of 4 months from January until April. Rainfall and mean annual temperature are in the same range at the

RESULTS

Liquid Jungle Lab, but soils were Nitisols, which are considered to be among the most productive soils of the humid tropics (WRB, 2007).

Table 14: Growth of Almendro on the PRORENA plots “Las Lajas “, SIGR 7, AGCL 1

d50 h50 G V Stocking Plantation Years Months (cm) (m) (m² ha-1) (m3 ha-1) trees ha-1 0.2 2 - 0.4 - - 1111 1.2 14 - 1.4 - - 1111 Las Lajas - B19 2.0 24 2.8 3.4 0.1 0.1 703 4.8 58 4.7 5.9 0.2 0.4 388 0.3 4 - 0.6 - - 1111 1.2 14 - 1.4 - - 963 Las Lajas - B20 2.1 25 2.5 3.5 0.1 0.1 944 4.8 58 5.7 6.4 0.6 1.4 537 0.3 4 - 0.4 - - 1111 1.2 14 - 1.8 - - 796 Las Lajas - B21 2.1 25 3.6 3.8 0.2 0.3 796 4.8 58 11.8 9.1 2.2 8.0 537

PRORENA plots always followed the management scheme (e.g. spacing of 3 x 3 m) as described by Wishnie et al. (2007). Blocks at the “Liquid Jungle Lab” represent topographical units (B1: lower terrace; B2: slope; B3: upper terrace), although in “Las Lajas” the terrain is flat on all plantations. On the “Liquid Jungle Lab” plots, top height growth was the best in block 1 (B1) that resembled a lower terrace, while height growth in the blocks on the slope or upper terrace was inferior.

The three blocks of the PRORENA project in “Las Lajas” are situated in ForestFinance plantations, but were not actively managed by ForestFinance. Top height on the PRORENA plots in Las Lajas varied considerably and was the highest in Block 21 (B21) with 9.1 m at age 4.8 years and the lowest in block 19 (B19), where trees were around 3 m smaller at the same age.

RESULTS

Table 15: Growth of Almendro on the PRORENA plots “Liquid Jungle Lab “, SIGR 7, AGCL 1

d50 h50 G V Stocking Plantation Years Months (cm) (m) (m² ha-1) (m3 ha-1) trees ha-1 0.2 2 - 0.5 - - 1093 Liquid Jungle Lab - B1 1 12 1.6 2.2 - - 722 2 24 3.4 4.0 0.3 0.4 722 0.2 2 - 0.5 - - 1111 Liquid Jungle Lab - B2 1 12 1.9 2.3 0.1 0.1 1111 2 24 4.1 3.1 0.6 1.0 1019 0.2 2 - 0.5 - - 1111 Liquid Jungle Lab - B3 1.0 12 1.9 2.3 0.1 0.1 1093 2.0 24 4.1 3.1 0.6 1.0 1074

Management on the ForestFinance plantations was more profound than on all other Almendro plantations.

This company uses predominantly native species and aims to create functional forest ecosystems. As part of their ecological forestry techniques not all of the existing vegetation is removed, during the establishment of the plantations. Valuable old-growth trees remain on the plantations and grasses are removed only in the planting lines, but not in-between the planting rows, like on most of the conventional timber plantations. On the plantations “Los Monos” and “Pampanillo” organic fertilizer was applied in the first 3 years. This fertilizer contained chicken droppings, rice husks, saw dust and ash.

Trees were planted in small blocks or sometimes single-lines, in pure and mixed stands. In “Los Monos”, Almendro was planted in a pure block with 6 x 6 m spacing. In “Los Rios 1” and “Los Rios 2” tree were spaced 5 x 5 m, while the spacing in “Los Rios 3” was 4 x 5 m. In “Pampanillo” data was collected on a PSP in a mixed block, containing Almendro planted in a 3 x 5 m spacing together with Bombacopsis quinata. In a second block in Pampanillo, which was pure and planted 5 x 5 m, another TSP was established.

RESULTS

Table 16: Growth of Almendro on the ForestFinance plantations, SIGR 7, AGCL 2

d50 h50 G V Stocking Plantation Years Months (cm) (m) (m² ha-1) (m3 ha-1) trees ha-1 1.5 18 5.0 7.3 0.4 1.0 350 2.5 30 6.3 7.5 0.7 2.2 350 3.5 42 9.3 9.4 1.4 5.6 350 Los Monos 5.5 66 11.8 11.3 2.4 11.3 350 7.6 91 17.2 15.0 4.9 30.1 350 9.5 114 20.1 16.9 6.7 47.1 350 12 144 24.0 21.0 9.1 78.9 350 2.5 30 4.4 5.0 0.3 0.5 5 3.6 43 6.0 6.3 0.4 1.0 425 Los Rios 1 5.7 68 8.8 9.1 1.1 3.6 425 7.8 94 12.2 11.9 2.4 11.5 425 10 120 15.0 14.5 3.6 20.6 400 3.5 42 3.2 4.1 0.1 0.1 350 5.3 64 4.7 5.4 0.2 0.4 350 Los Rios 2 6.8 82 7.8 7.7 0.5 1.6 300 8.8 106 9.8 9.6 0.8 3.0 300 2.5 30 1.5 1.9 0.0 0.0 475 4.3 52 2.2 2.6 0.1 0.1 450 Los Rios 3 5.8 70 4.3 5.6 0.2 0.5 375 7.8 94 6.6 7.1 0.6 1.7 375 9.8 118 9.9 12.6 1.3 6.5 375 4.5 54 3.2 5.8 0.1 0.3 400 6.3 76 13.7 9.6 3.0 11.9 400 Pampanillo (3x5) 7.6 91 17.3 14.3 5.4 31.6 400 12 144 24.5 20.8 7.4 65.1 225 Pampanillo (5x5) 11.9 143 23.1 13.1 11.7 66.2 495

RESULTS

Both plots had been established in 1997, but Almendro in the pure plot had larger crowns and generally lower tree heights. The difference in top-height to the mixed plot with a denser spacing was 7 m while the top-diameters rather similar.

In the widest spacing of 6 x 6 m in “Los Monos” however, trees were the highest. These trees grew in a wide spacing, but ground competition was high in the early years, due to surrounding vegetation, such as bushes and grasses. Trees were liberated when surrounding vegetation started to suppress the trees´ growth

Based on a rapid visual soil assessment it can be said that soils in “Los Monos” were sandy loams, with good drainage, low stone content and high organic matter content. In “Pampanillo” soils had been clayey, organic matter content was lower and drainage appeared to be lower on the plot with 5 x 5 m spacing compared to the plot with 6 x 6 m spacing.

Negative border effects were observed in all plantations in Los Rios, as the surrounding trees often were Terminala amazonia, which mostly grew higher than Almendro. No thinning of these trees took place and growth of Almendro was therefore hindered in some cases.

4.1.8 Site group 8, PA This site group with the overall driest climate, an annual rainfall of less than 2000 mm, contains the two experimental plantations “Rio Hato” and “Los Santos” from the PRORENA project.

The driest site of this present study is the plantation “Rio Hato” at the Pacific coast of Panama. This region has a distinct dry period of 6.7 dry months per year and an annual rainfall of 1107 mm. Soils are shallow, nutrient poor and variable in texture, generally sandy or silty clays (Wishnie et al., 2007).

RESULTS

“Los Santos” is the second driest plantation of this study, 5.2 dry months and a mean annual rainfall of 1946 mm. Soils are tropical Alfisols with high concentration of P, Ca and Mg and rich compared to all other PRORENA plantations (Wishnie et al., 2007).

Table 17: Growth of Almendro in “Los Santos”, SIGR 8, AGCL 1

d50 h50 G V Stocking Plantation Years Months (cm) (m) (m² ha-1) (m3 ha-1) trees ha-1 1.3 16 - 1.4 - - 630 1.9 23 2.1 2.2 0.1 0.1 370 Los Santos - B7 3.2 38 4.4 4.6 0.3 0.6 370 4.0 48 5.6 6.2 0.5 1.1 352 5.8 70 6.2 6.9 0.6 1.8 352 1.3 16 - 1.6 - - 481 2.0 24 2.2 2.6 0.1 0.1 407 Los Santos - B8 3.3 40 4.8 5.2 0.4 0.7 407 4.3 52 6.0 6.7 0.6 1.6 407 1.2 14 - 1.5 - - 722 2.3 28 2.8 2.9 0.2 0.2 703 Los Santos - B9 3.1 37 5.1 5.2 0.5 1.0 500 4.3 52 6.8 6.7 0.9 2.4 500

Mortality of “Rio Hato” was extremely high and after 6 years only 56 trees per hectare remained in Block 4. In Block 5 and 6 all trees died before, indicating that Almendro in “Rio Hato” does not perform well. The overall growth was better in “Los Santos” and mortality was lower in comparison to “Rio Hato”.

Nevertheless, with a mortality that reached more than 50% after 4 years, this site cannot be considered suitable for Almendro.

RESULTS

Table 18: Growth of Almendro in “Rio Hato”, SIGR 8, AGCL 1

d50 h50 G V Stocking Plantation Years Months (cm) (m) (m² ha-1) (m3 ha-1) trees ha-1 1.3 16 - 1.0 - - 870 1.9 23 - 1.6 - - 667 Rio Hato - B4 3.1 37 - 1.7 - - 278 4.3 52 - 1.9 - - 203 5.8 70 - 1.5 - - 56 1.0 12 - 0.9 - - 704 2.0 24 - 1.1 - - 333 Rio Hato - B5 3.2 38 - 1.3 - - 92 4.3 52 - 1.1 - - 37 1.1 13 - 0.9 - - 778 Rio Hato - B6 2.0 24 - 1.3 - - 352 3.3 40 - 0.8 - - 19

4.1.9 Site group 9, PA The PRORENA sample plots in the Soberania National Park, located in the Panama Channel Region, form site group 9. Soberania is the only plantation on the Caribbean side of Panama. Soils in this region belong to the Ultisol order and the climate is characterized by 4.1 dry months per year and 2226 mm mean annual rainfall.

Top height development was better than in SIGR 8 and comparable to the development in SIGR 7, although mortality was high compared to all other sites as around 50% of all trees died in the first 6 years. Only SIGR 7 had a higher mortality. Reasons for this high mortality could be ground competition with exotic grasses that have invaded abandoned agricultural lands in the Panama Channel Region for decades. Soberania has not been farmed for 10 years and was dominated by the exotic invasive grass Saccharum spontaneum that aggressively competes with regenerating tree seedlings preventing natural forest regeneration (Wishnie et al., 2007).

RESULTS

Table 19: Growth of Almendro in SIGR 9, AGLC 1

d50 h50 G V Stocking Plantation Years Months (cm) (m) (m² ha-1) (m3 ha-1) trees ha-1 1.0 12 - 1.2 - - 926 2.0 24 3.3 3.4 0.3 0.4 907 Soberania - B1 3.3 40 5.7 6.7 0.6 1.4 556 4.2 50 7.0 8.0 0.9 2.5 537 5.8 70 9.3 8.7 1.3 4.1 537 1.0 12 - 1.1 - - 741 2.0 24 2.8 3.1 0.1 0.1 741 Soberania - B2 3.0 36 5.1 5.2 0.4 0.8 556 4.3 52 7.1 9.6 0.8 2.4 556 5.8 70 10.9 9.5 1.4 4.8 481 1.1 13 - 0.9 - - 777 2.0 24 2.1 2.3 - 0.04 722 Soberania - B3 3.3 40 3.5 3.9 0.2 0.3 537 4.3 52 4.9 5.5 0.3 0.6 500 5.8 70 7.4 7.2 0.6 1.6 500

4.2 Stand characteristics of Almendro plantations Stand characteristics on all 36 Almendro plantations were very diverse, due to the heterogeneity of the stands. Spacing and management varied, consequently the number of stems per hectare and their respective diameter distribution differed even in plantations of the same age. For every site group, characteristic plantations from mostly AGCL 2 and 3 were selected. For Panama, only site group 7 can be presented as plantations in all other SIGR were too young.

Few plantations, which demonstrate the great variety in stem diameter distribution and have similar spacing, are described in the following chapter 4.2.1 and Appendix 2. Their respective stand height curves are presented in chapter 4.2.2 as well as in Appendix 3.

RESULTS

4.2.1 Stem diameter distribution The only stand that received regular thinning was “Santa Cecilla” in SIGR 1 (figure 2). With an age of 7.8 years it still belongs to AGCL 1, but for the demonstration of the effect of thinning it is shown below.

Figure 2: Stand diameter distribution in “Santa Cecilla” with 7.8 years, 3 x 3 m spacing, regular thinning, SIGR 1, AGCL 1

In two thinnings, 120 trees per ha were removed in 2006 and another 200 trees per hectare in 2008, as described in chapter 4.1.1.

Trees of the smaller diameter (6 - 14 cm) classes are rare and more than half of the total stems per hectare present at age 7.8 ranges in diameter classes greater 14 cm. The total range of all DBH’s covered 12 cm.

It should be emphasized that thinning of Almendro plantations can result in 40 trees per hectare with diameters in-between 18 to 20 cm after less than 8 years.

“Buenos Aires” in STGR 3 (figure 3) is unthinned and covers a DBH range of 20 cm (6 - 26 cm) at age 14.8. After half of the assumed rotation time of 25 years has passed already, more than 40 trees with DBH’s smaller 6 cm can still be found. These trees have no commercial value. On the other hand, 41 trees of the largest diameter class (24 – 26 cm) are present in “Buenos Aires” as well.

RESULTS

Figure 3: Stand diameter distribution in “Buenos Aires” with 14.8 years, 3 x 3 m spacing, no thinning, SIGR 3, AGCL 2

The widest diameter range was found in “La Bomba” in SIGR 4 (figure 4). With an age of 17.3 years, 30 trees per hectare were smaller 6 cm, while 30 other trees measured 30 cm in DBH. A similar situation was found in “Cope San Juan” (SIGR 3, age 18.4, see Appendix 2). The dominant diameter class in “La Bomba” was the range 10 to 12 cm with 120 trees.

Figure 4: Stand diameter distribution in “La Bomba” with 17.3 years, 3 x 3 m spacing, no thinning, SIGR 4, AGCL 3

The oldest plantation of this study, the “Canadian trial”, has been established in a 2 x 2 m spacing and showed the following DBH distribution after 24 years without any thinning interventions.

RESULTS

Figure 5: Stand diameter distribution on the “Canadian Trial” with 24 years, 2 x 2 m spacing, no thinning, SIGR 4, AGCL 3

DBH of all trees was larger 20 cm and 102 trees with DBH’s between 38 and 40 cm are available on such sites with little management.

4.2.2 Stand height curves Stand height curves (SHCs) have been developed to describe the stand structure, in particular the relationship between diameter and height growth of selected Almendro plantations.

Diameter and height were plotted in a scatter diagram and fitted to a SHC using the Michailoff function (chapter 3.7). Parameter estimates and statistical data for all SHC are listed in Appendix 3.

Steep curves in young ages indicate rapid height growth, but because of the retention of a low numbers of small individuals, older curves rather showed an “extension” than a “shift” to the right. In thinned stands, where smaller individuals are normally removed, curves shift more to the right while moving up with increasing age.

“Cope San Juan” is a typical example of a plantation of AGCL 3 in SIGR 3. The stand development from age 2.8 until age 18.4 is illustrated below.

RESULTS

Figure 6: Fitted Michailoff stand height curves. “Cope San Juan”, 18.4 years, 3 x 3 m spacing, no thinning, SIGR 3, AGCL 3

Figure 7: Fitted Michailoff stand height curve and observed values. “Canadian Trial”, 24 years, 2 x 2 m spacing, no thinning, SIGR 4, AGCL 3

RESULTS

The typical near flat and linear behavior of SHC for old plantation was observed on the oldest Almendro plantation of this study. The fitted Michailoff curve and observed values are shown in figure 7.

How SHC develop on poor sites became apparent in “San Juan” in SIGR 6 in figure 8. The diagram was adapted for better clarity, as the SHC lie on top of each other. Height growth and diameter growth for most of the smaller trees was arrested and only a small number of dominant trees grew in diameter and height, thus extending the SHC to the right without shifting up. The arrows in the diagram mark the range of the SHC at different ages.

Figure 8: Fitted Michailoff stand height curve for D. panamensis in “San Juan” in a mixed species plot together with A. hunsteini, E. deglupta and S. macrophylla, age 6.5 years, 5 x 5 m spacing, no thinning, SIGR 6, AGCL 1

Stand height curves for all other SIGR are listed in Appendix 3.

4.3 Growth dynamics of Almendro The growth pattern of Almendro was analyzed by focusing on the MAI in top height and top diameter. Often MAI refers to stand mean values or volume per hectare, but in the present

RESULTS study the resulting values would not have allowed a comparison between the Almendro plantations as they all had different silvicultural management schemes, initial spacing and current stocking, see chapter 3.3.

4.3.1 Mean annual increment of Almendro Figure 9, indicates the fast initial growth that Almendro can achieve. Trees of the highest diameter class are able to grow in average up to 3 m in top height per year, in the first 5 years after planting. This rapid development slows down until age 10 from which the MAI in top height ranges in-between 1 to 2 m/year. The oldest plantation of this study (“Canadian

Trial”) had a MAI in h50 of 1.4 m/year.

Figure 9: MAI in top height (h50) of D. panamensis in timber plantations across CR and PA

This growth pattern seems to be similar to the top diameter development (figure 10). MAI in d50 is also accelerated in the first years and slows down until age 10. Top diameter growth can reach up to 3.5 cm/year at age 4.8, for example on the plantation “Puente Hamaca” in SIGR 4 and 1.7 cm/year at age 24 on the “Canadian Trial”. However, one needs to bear in mind that dominating influences for diameter growth are stocking, spacing and thinning (Evans and Turnbull, 2004).

RESULTS

Figure 10: MAI in top diameter (d50) of D. panamensis in timber plantations across CR and PA

4.3.2 Top height growth Most growth records originated from younger plantations (AGCL 1) and only few are currently available for plantations of AGCL 2 or 3. The mean age of all growth records was 8.8 years, which is rather low considering a rotation time of 25 years.

Still, trends in growth are obvious and based on these observed values lines can be computed to represent the data.

On one hand, sites can be classified based on the observed top height / age relation (chapter 4.4) and on the other hand the observed trend in top height growth can be projected for a certain period to see how the top height might develop, for example until the end of a rotation period as demonstrated in chapter 4.5.

In figure 11, measured top heights of all plantations are plotted against age

RESULTS

Figure 11: Top height development of D. panamensis over age

4.4 Preliminary site indices for Almendro For the classification of Almendro plantations as well as to improve yield estimations, site indices were derived through statistical curve-fitting procedures. This approach is called the “guided curve method” and for the development of anamorphic top height curves the Chapman - Richards function (Equation 3) was used. Based on the observed top-height values, the index age was set to 15 years and five site index – classes in 2 m intervals were defined after the visual assessment of trends in the observed top heights, see figure 11.

Each site index class covers a range of 1.99 m, e.g. the highest class (SI 25) covers the range from 24 to 25.99 m of top-height at index age 15, and accordingly SI 17 covers the range 16 to 17.99 m.

RESULTS

Close to the index age, top height measurements with a distinctive increment were available. Accordingly, the Chapman-Richards model was constrained that predominant height equals the observed top height values at the previously defined index age.

First, using the Microsoft Excel Solver function, the parameter c was estimated after transposing the Chapman-Richards equation accordingly (model 1). Once the coefficients c and d are known, the Chapman-Richards equation can directly predict the site index curves at a given age. Therefore, the previously estimated parameter c was inserted in model 2 to receive parameter d to guide the curve through a second point. The site index curves were then guided at age 10 and index age 15 by setting parameter t to 15 and using the previously calculated parameter d at age 10 (d10), from model 2. The respective SI - curve were then calculated with model 3.

Model 1:

Where: Hi = top height at index age, h1 = presumed top height at age 10, h2 = presumed top height at rotation age 25 and c = parameter

Model 2:

Where: dt = parameter d at age t (guiding point was set at age 10, thus t=10), h1 = presumed top height at age 10, h2 = presumed top height at rotation age 25 and c = parameter

Model 3:

Where: t= index age 15, dt = parameter d at age 10 (calculated with model 2), h1 = presumed top height at age 10, h2 = presumed top height at rotation age 25 and c = parameter

RESULTS

For example, the curve for SI-17 was calculated with the equation below:

Parameter estimates and attributes of all preliminary Almendro site index curves are listed in Appendix 4. The resulting site index curves, together with all top-height measurement of each plantation are illustrated below:

Figure 12: Site index curves for 5 different site qualities in CR and PA

Most of the observed values are covered by the range of the site index curves, yet some top heights range below the lowest SI-class (SI-17) and above the highest SI-class (SI-25)

4.5 Top-height projections Projections of top height to a rotation length of 25 years were developed using the Chapman - Richards model (Equation 3), to show how Almendro plantations might develop until the

RESULTS end of a rotation period and to compare their trend with the site index classes. Most of the Almendro plantations were too young for predictive modeling or did not have a sufficient amount of consecutive measurements. Therefore, only the growth of plantations in AGCL 3 could be projected. These plantations were situated in SIGR 3 and 4 and the resulting growth projections were then compared with the previously developed site index curves.

It became necessary to constrain the model parameters a and b in order to converge on a proper solution. The model did not return a solution of 1 in each case for parameter b, causing curves to start in different points. Parameter b was for that reason constrained to equal 1 and additionally parameter a was constrained to be equal or smaller than 40 to obtain realistic growth projections on the long run (see chapter 5.2.1). All model parameters of the growth functions for the six plantations of AGGR 3 are listed in Appendix 4.

Projections for all plantations showed polymorphic-nondisjoint curves indicating the rapid top height growth in the first years that began to reduce after 10 to 15 years. The plantation “Oscar Rodriquez” showed reduced top height growth already after 5 years and finally reached the same top height like the plantation “Los Almendros” at the end of the rotation period. Overall, projected growth for “Los Almendros” was the lowest.

Plantations from SIGR 4 grew better than plantations from SIGR 3 according to the projections. The “Montagnini” plantation, where a thinning trial took place, developed the best. The unthinned areas of this scientific plantation outperformed the thinned areas in the first 7 years, until a shift in top height growth took place. From that point, top height growth of the thinned areas was clearly higher in the following years and the difference between the projected top height of thinned and unthinned areas at the end of the rotation period was almost 5 m, according to the projections.

RESULTS

Figure 13: Top height growth projection in comparison with site index curves for six plantations in AGCL 3

In comparison to the site index curves, two plantations ranked in the lower classes, two in the middle and two in the upper site index classes. The curve of the “Montealegra” plantation reflected the development of site index class 21 almost exactly.

However, other plantations seem to follow the development of the site index curves in the first years and deviate later on. As a consequence they typically switch to the next lower site class. “Cope San Juan” even started in SI 25, switched in-between year 5 to 10 to SI 23 and ended finally in SI 21.

Nonetheless, all projected top height curves stayed in the respective site index class they had at index age 15.

DISCUSSION

5. DISCUSSION

In this chapter, the presented results are critically discussed in reference to other studies. This present study is of explorative character and therefore comparison is drawn to tropical forest ecology and other commercial timber species, as no publications exist regarding Almendro in older timber plantations. As a final point, limitations of the study are identified and further recommendations for future research are given.

5.1 Data basis Through the monitoring of Almendro plantations in Costa Rica and Panama, important information about the growth of this tree species was generated by both plantation owners and scientist. For this study a vast data pool was established based on these existing, but also on new datasets. However, measurement data originated from plantations that were treated and monitored in various ways. The data pool was prepared for data analysis as described in chapter 3.3, yet even after removing false values and outliers, some unclear developments occurred on few timber plantations, which could not be verified afterwards.

PSPs could not be restored in some cases and the established TSPs did not succeed in describing the stand density in two cases, in particular on the “Montagnini” plantation, leading to unreliable volume values from these plots. Moreover, in the provided dataset of the same plantation, an unrealistic drop in the stocking took place at age 9.9 from 1994 to 863 trees per hectare. This event would comply with a sudden mortality of more than 50% and does not match the density per hectare of 1875 trees / ha-1 that was recorded personally on a TSP in 2009, almost 9 years later.

It also needs to be mentioned that border effects were observed on PSPs, especially on plantations where small pure patches of Almendro had been mixed with other species in blocks or lines, such as the Los Rios plantations in Panama, SIGR 7. Positive border effects were filtered out during the data preparation phase, but negative border effects have not been excluded from the data set as they seem to be common in Almendro line mixtures or

DISCUSSION small sized block mixtures, where no thinning interventions of the surrounding stands have taken place.

To give details about the great variety of the underlying data set a statistical analysis (regression and correlation) was tried, but overall sample size and the distribution of the measurements was suboptimal as most of the plantations were too young, thus not allowing a precise statistical description of variations or influencing site factors for the whole dataset. Data for young Almendro plantations in particular at 2 years of age, was exceptionally frequent, as shown in table 20. Using a reference age of 2 years for statistical comparisons would not have made any sense. Total number of measurements for each age and precipitation group is given in the following cross-table.

Precipitation Group Age 1000 – 1999 2000 – 2999 3000 – 3999 >4000 N (mm) (mm) (mm) (mm) 0 6 3 6 0 15 1 6 3 9 1 19 2 7 7 13 3 30 3 7 6 10 3 26 4 7 6 11 4 28 5 1 5 12 1 19 6 3 7 9 0 19 7 1 2 9 3 15 8 1 2 9 2 14 9 0 0 2 0 2 10 0 0 3 2 5 11 0 1 3 0 4 12 0 0 3 0 3 15 0 0 2 2 4 17 0 0 1 0 1 18 0 1 3 2 6 24 0 0 0 1 1 Total 39 43 105 24 211 Table 20: Cross table with the number of available growth records at a certain age in different precipitation groups across CR and PA

DISCUSSION

The situation was similar with other site parameters, such as soil type and altitude.

Furthermore, site factors could not be assessed locally on every plantation. Local precipitation values from “Santa Cecilla” in SIGR 1 (annual rainfalls of 3649 mm in the period from 2002 until 2006) for example, were significantly higher than shown in climatic maps of Costa Rica (Ortiz and Cordero, 2008), where annual rainfall of 2000 - 2500 mm is given for this region. Soil data as well originated from general maps, thus not having the precision and accuracy of local soil samples.

5.2 The effect of site selection Regional distinctions of top height growth have been observed and site index calculations, the analysis of mean annual increment in top height growth, as well as observed mortality indicate the effect that site selection can have on the growth of Almendro.

The influence of the site was already apparent when comparing MAI values of plantations in different SIGRs in AGCL 1. The h50 MAI in the plantation “Mulas” in SIGR 6 for example was

0.8 m/yr at age 6.6, while the “Montagnini” plantation in SIGR 4 had a h50 MAI of 2.4 m/yr at age 6.8. In the latter case, top height growth was more than three times higher as in the plantation “Mulas”. Also mortality indicated the effect of site selection, like on the PRORENA plantations “Rio Hato” and “Los Santos” in drier regions of Panama (annual rainfall below 2000 mm, SIGR 8) as described in chapter 4.1.8. For older plantations in AGCL 2 and all plantations in AGCL 3, the site index curves can be used to determine the site quality since plantations do not switch the site class anymore once they reached the index age of 15 years, as described in chapter 4.5.

In line with other publications (Pyke et al., 2001) it can be said that tropical forests show clear patterns of spatial organization along environmental gradients, predominantly precipitation. In addition, geologic and edaphic conditions can override the effect of precipitation in some cases, such as acidic soils or excessively drained limestone substrates (Pyke et al., 2001).

DISCUSSION

These factors need to be considered for the tree species selection before plantations get established. By not doing so, plantations might not return the investment. Predictive modeling and site classification, to select the best land for plantations, can have a major influence on plantation profitability according to Evans and Turnbull (2004).

Almendro naturally exists in areas with mean annual rainfall ranging from 3500 to 5000 mm and in altitudes from 20 to 500 m.a.s.l, as mentioned in chapter 2.1. In particular plantations in SIGR 6 and 8 have been established outside this natural range of Almendro and especially these plantations performed the poorest. SIGR 6 was higher than 600 meters and SIGR 8 was characterized by annual rainfall lower than 2000 mm. In other site groups with annual precipitation from 2000 to 3000 mm where the altitude corresponded with the natural range, Almendro performed well, e.g. in SIGR 1 and 2 at the edge of the geographic range of Almendro, or SIGR 7 with annual rainfall greater than 3000 mm on the Pacific site of Panama, where Almendro naturally does not occur frequently.

Based on this observation it can be said that Almendro needs at least 2000 mm rainfall per year to grow satisfactorily and results from regions with lower rainfalls do therefore not represent the species potential. Whereby, in tropical regions the distribution of the rainfall probably might be more important than the actual amount (Vanclay, 1992).

Effects of the soil cannot be assessed as soils have not been sampled for each plot and soil data originated from large scale soil type mapping, not allowing an accurate comparison between sites. Most of the plantations were established on Ultisols and the few plantations, which were established on other soil types, were subject to other influences such as soil compaction due to grazing. Delgado et al. (2003) compared the growth of Almendro on soils of the Ultisol and Inceptisol order and highlights that Almendro performed the best on sites with an Ultisol soil profile. However, based on the general characteristics of the soil types it can be argued that plantations of Almendro grow best on richer soils with good drainage in general, for instance the Fluventic Dystropepts in La Selva (SIGR 4). Anyhow, Almendro showed good results on poorer soils with high acidity such as Ultisols. This can be considered

DISCUSSION a great advantage over exotic species, such as Tectona grandis, which need fertile soils to perform well (Butterfield, 1994).

Taking the natural distribution of Almendro into account, Chun (2008) stated that environmental factors exists that predict high densities of Almendro in natural forests, such as elevations between 45 – 125 m.a.s.l and soils of the Humult, Aquent, and Tropept suborder. It can be assumed that Almendro plantations will thrive well on these sites as well.

5.2.1 Site index calculation and top height projection It has to be remembered that the growth observations, which were used for the development of the site index curves, covered a wide range of sites, but plantations were very heterogenic, young and not evenly distributed along every SIGR. Some SIGRs for instance contained only young plantations of AGCL 1. According to the data set it would make sense to set the index age to an earlier age, as many observations are available, but index age 15 was chosen instead for of several reasons.

Brack (2000) notes that for the selection of the index age, the index age should be greater than eight years as factors of the site have to express themselves. Accordingly, a good criterion for the selection is 2/3 of the rotation age and the selected age of 15 is close to this criterion (Brack, 2000). Other publications made use of index age 15 as well, such as Cháves and Mora (2002), who additionally compared their site index model for Bombacopsis quinata on plantations in the Guanacaste Region of Costa Rica with the one of Navarro (1987), who used the index age 10 for the same species and region. The comparison showed that site index curves, developed with such a young index age of 10 years, tend to overstate the overall growth as they project the increased height growth in young stands for the entire rotation period. For the same reason, top height projections in chapter 4.5 were only developed for plantations in AGCL 3.

Publications from e.g. De los Santos-Posados et al. (2006) underline the limitations that the Chapman-Richards function can have. They used the function to produce height growth

DISCUSSION curves for Terminalia amazonia in Costa Rica and discovered that the model shows good statistical fit, but overestimated the height development at the intermediate age range of 12 to 20 years.

Nevertheless, given its flexibility, the Chapman-Richards model was also used to create the site index curves for Almendro and in accordance with other publications (Montero et al., 2001; Somarriba et al., 2001; Montero and Kanninen, 2003; Bermejo et al., 2004; Upadhyay et al., 2005), the “guided curve method” was used. This approach is wide spread in tropical forestry and site index curves for other commercial tree species in Costa Rica and Panama were developed by the same method.

Apart from limitations of the developed site indices given by varying management practices and seed sources, deviations from the predicted growth pattern may occur due to: - Climatic fluctuations - Changes in atmospheric nitrogen deposition - Elimination of dominant heights due to disease or thinning

All site quality indices and growth projections should be validated as soon as stands of AGCL 1 have reached age 15, because significant differences in their development are not foreseen. It might become necessary to develop another set of site-index curves that is able to describe their growth dynamics.

As a final point, it must be mentioned that more sophisticated models are used in temperate forests of industrialized countries, but they have not found their implication in tropical forestry yet (Sloboda, 1972; Zeide, 1993; Pretzsch, 2009), see chapter 3.5.

5.2.2 Frequency of site index classes The preliminary site indices were used to associate the last observed top height of each plantation with a particular site index class. Overall, site index class 19 was the most frequent, followed by SI 17 and SI 25.

DISCUSSION

The frequency of site index classes and age classes in every SIGR is given below:

Table 21: Frequency of site index classes and age classes in each site group

AGCL Frequency of site index classes SIGR 1 2 3 SI-17 SI-19 SI-21 SI-23 SI-25 1 3 - - - 1 1 1 - 2 1 1 - 1 - 1 - - 3 - 3 3 2 2 2 - - 4 4 2 4 - - 1 2 7 5 1 2 - - - - - 3 6 4 - - 3 1 - - - 7 6 - - 3 3 - - - 8 3 - - 1 2 - - - 9 6 6 - 3 5 2 2 - Total frequency of SI-classes 13 14 7 5 10

The table shows that it is impossible for most of the SIGRs, to classify their suitability for Almendro plantations, if the classification is solely based on the site index classes. On the one hand, a clear trend in site index class distribution can be observed only in SIGR 4, 5 and 9 and on the other hand, most plantations were too young to associate them with a particular site index class, as young plantations tend to switch to the next lower site index class while maturing, see chapter 4.5. A trend that was also observed for Tectona grandis in Trinidad, where height growth equivalent to that of site class I at 5 years of age, dropped to site class II as it grew older (Lamb, 1957).

Though significant height/age relationships may not be causal, defining them still assists the prediction of growth on similar sites and therewith aids rational decision-making on land suitable for reforestation projects (Evans and Turnbull, 2004).

DISCUSSION

5.2.3 Promising regions for Almendro plantations Taking all observations, such as MAI in the first years, mortality and the assigned site index classes for all plantations in AGCL 3 into account, recommendations for regions suitable for Almendro plantations, can be derived.

Performance of Almendro was clearly the best in the Atlantic lowlands of Costa Rica, in particular SIGR 4 and 5. Also the northern zone of Costa Rica (SIGR 2 and 3), the Pacific – Atlantic transition zone (SIGR 1) as well as the wet Pacific region in Panama (SIGR 7) showed good results. The suitability of Soberania (SIGR 9) is given, when considering the top height growth and natural distribution of Almendro in this region, but the high mortality levels on the other hand, indicate that this site is not suitable for Almendro. Reasons for the poor performance of Almendro on this site could be the presence of Saccharum spontaneum, which aggressively competes with regenerating tree seedlings (Hooper et al., 2002; Wishnie et al., 2007; Joo Kim et al., 2008). Balderrama and Chazdon (2005) summarized that Almendro seedlings and sapling have generally a high survival rate and can survive in shade, gaps and sunny sites, but Hooper et al. (2002) proved in a trial in Saccharum spontaneum grasslands, that Almendro can be outcompeted if the grass is not mown, shaded or treated with herbicides.

Besides suitable regions, unsuitable regions for Almendro plantations were identified as well. In particular regions above 500 m.a.s.l (SIGR 6) and regions with annual rainfalls below 2000 mm (SIGR 7). These findings are in line with other publications (Cordero et al., 2003), in which dry climates, elevations higher 500 m and poorly drained soils were described as limiting factors for Almendro.

5.3 Silviculture The stand development showed a great variety, when comparing the different management schemes of Almendro plantations in Costa Rica and Panama. Factors that affect the increment are the internal conditions of the tree species (genetic and physiological), external conditions (the site) and the management, of which the most important effects on the

DISCUSSION growth in plantations are determined by initial spacing and silvicultural treatments such as thinning and pruning (Brack, 2000; Evans and Turnbull, 2004). All of these factors differed in Costa Rica and Panama, and in most cases the management can be improved to enable Almendro, to fully unfold its potential and to produce a mix of tree sizes for sawn timber, veneer or poles.

At the time when most of the Almendro plantations were established, commercial seeds were unavailable (Butterfield, 1995). Seeds have been sourced from identified seed trees growing in natural forests in different regions of Costa Rica and Panama, and thus did not undergo any genetic improvement or strict selection process based on experience in timber plantations or seed orchards. Chun (2008) found four separate Almendro subpopulations, solely in the proposed “San Juan - La Selva Biological Corridor” in Costa Rica and correspondingly it can be assumed that the genetic variability of Almendro grown in timber plantations is immense due to numerous seed trees in Costa Rican and Panamanian rainforests.

The external factors affecting the growth were already discussed in chapter 5.2 and particular focus to the silvicultural management is given in the following chapters 5.3.1 and 5.3.2.

5.3.1 Initial spacing and stand density The observed stand density on all plantations, best explains the differences in growth as lower density plantations yielded higher DBH, total height and tree volume in most of the cases.

Some studies have shown a relationship between the maximum number of individuals that can occupy a site and the average size of the individuals (Smith et al., 1997). This natural basal area effect was also described by Pienaar and Turnbull (1973), who stated that even- aged stands with initial stocking above a certain limit, converged towards identical stand basal area, determined by the capacity of the site.

DISCUSSION

On the “Canadian Trial” (SIGR 4), where the initial spacing was 2 x 2 m and no management took place, 357 trees per hectare were found, representing the natural basal area of this site at 24 years of age (chapter 4.1.4). The existing trees were of good form, as they first had to grow in height to outcompete surrounding trees and could not develop any lower branches, because of high ground competition in early years. Finally, the surviving trees did then succeed in building up descent crowns even after heavy competition over a long period of time, which could be explained by the fact that Almendro belongs to the canopy emergent layer in Neotropical rainforests. Tropical ecologist emphasize that these canopy species, usually have a high juvenile survival and a large increase in growth rates when exposed to high light levels (Turner, 2001). Nevertheless, information on crown and stand characteristics in response to initial spacing are not available for Almendro, but have been published for widespread commercial tree species, for example Eucalyptus nitens (Pinkard and Neilsen, 2003).

Top diameter on the “Canadian Trial” was close to 40 cm and it can be assumed that the commercial value of this scientific plantation is high, also due to good form and a commercial height over 14 m.

Nevertheless, through managing a plantation diameter growth can be increased, the wood quality improved and rotation cycles shortened, thus increasing the overall financial yield of the plantation (Lamprecht, 1986; Piotto et al., 2003; Evans and Turnbull, 2004). Only by performing intensive and timely silvicultural interventions, success in the management of plantations of tropical tree species can be achieved (Kanninen et al., 2004).

5.3.2 Thinning and pruning One thinning trial in the Atlantic lowlands of Costa Rica included Almendro (Piotto et al., 2003) with the results that thinning in pure- and mixed stands does have positive effects all in all. Diameters were larger, mean total height and basal area per tree were higher, but stand volume and stand basal area were lower in thinned plots compared to unthinned plots. Although, thinning may lead to losses in wood volume, the loss of volume is generally

DISCUSSION compensated by superior wood quality and value (Espinosa et al., 1994). Other authors showed that if the plantation density is not reduced crown recession, reductions in diameter growth and increases in height/diameter rations are the result. Even reduction in height growth, including dominant height, can appear within a short period of time (Galloway et al., 1996).

According to Evans and Turnbull (2004), thinning would help to: - Reduce the number of trees to have more space for the development of the remaining ones, thus encouraging diameter growth to reach a usable size sooner - To remove trees of poor form (crooked, forked, etc.) to concentrate future increment on the best trees - Favor the most vigorous tress of good form, which will make up the final crop - Provide an intermediate financial return from sale of thinnings

Even delayed thinnings can favor the growth, as shown for Vochysia guatemalensis, Hyeronima alchorneoides, Terminalia amazonia, and Calophyllum brasiliense in native species plantations in Costa Rica (Jacobs et al., 2005).

This study did not assess single tree quality, but visual observations showed that Almendro tends to low bifurcation if spacing is too wide, especially if trees are planted in line mixtures. Lower spacing and timely pruning interventions could help to obtain better tree form. It was observed that Almendro mostly builds branches with included bark. To assists the healing of the pruning scar, the pruning cut should be done according the attachment of the branch as described by Dujesiefken and Stobbe (2002). Finally, pruning has to be considered together with the initial spacing and thinning regime (Evans and Turnbull, 2004). On the long run, a pruning regime similar to the one for Tectona grandis (Víquez and Pérez, 2005) should be developed for Almendro as well.

DISCUSSION

The benefit of silvicultural management is evident and based on the own observations on timber plantations across Costa Rica and Panama, provisional management recommendations will be given for three management scenarios.

The good performance of Almendro in mixed species plantation and the general advantages of species mixtures such as diversified timber products, increased biodiversity and soil protection were described by several authors (Petit and Montagnini, 2004; Petit and Montagnini, 2006; Redondo-Brenes and Montagnini, 2006), but given the great number of possible species mixtures, recommendations are only given for pure plantations.

5.4 Timber production on Almendro plantations Almendro outsells every other tree species on the Costa Rican timber market (Rodriguez and Chaves, 2008; Grethel and Norman, 2009), but the situation on the Panamanian timber market is unclear, because of unavailability of data on timber prices. Wood prices for Almendro in Costa Rica however exhibit a steady increase and are not as susceptible to heavy fluctuations like the prices for Teak (Grethel and Norman, 2009). Up to the present day, timber from Almendro plantations has never been sold, as plantations did not receive any commercial thinnings or intermediate- or final harvests. The high prices in Costa Rica are obtained for Almendro from natural forests and it is not certain, what prices Almendro from timber plantation will achieve on local or international timber markets in the near future.

A first provisional silvicultural regime, with the main goal of producing high quality timber for different uses, such as poles, sawn timber and veneer was developed for Almendro. The focus is therefore on maximum tree growth and tree quality, instead of maximum volume growth as in carbon forestry projects, see chapter 5.5. All recommendations are given based on Evans and Turnbull (2004), growth records, own observation and in line with other publications (Jiménez et al., 2002; Cordero et al., 2003; Piotto et al., 2003; Kanninen et al., 2004; Perez and Kanninen, 2005; Víquez and Pérez, 2005).

DISCUSSION

Almendro plantations should be established with an initial spacing of 3 x 3 m, thus resulting in 1111 trees per hectare. A selective thinning method is recommended, following the proposed thinning regime (table 22).

Table 22: Proposed thinning regime for Almendro in timber plantations

Stocking** Intervention Age Thinning rate* Intensity Potential products Before After 1st thinning 3-4 20% 1111 889 Light poles 2nd thinning 8-9 30% 889 622 Moderate poles/ sawn timber 3rd thinning 14-15 40% 622 249 Heavy sawn timber 4th thinning 19-20 50% 249 124 Very heavy sawn timber/ veneer

* % of the standing trees, ** trees / ha-1

In the first thinning dead, diseased, suppressed and trees of poor form should be removed in-between age 3 and 4. This thinning should be followed directly by a low pruning up to a height of 3 m in order to obtain a high amount of knot free timber on the lowest stem section. Pruning should include all trees to improve the overall timber quality.

The first light thinning and the low pruning should then be followed by a moderate second thinning from below at age 8 to 9, where suppressed and sub-dominant trees should be removed. If markets are available also co-dominant trees may be removed additionally. Afterwards, a second pruning should be conducted up to a height of 6 meters. By implementing a medium pruning the value of all trees is increased once more as trees that will be removed in the next thinning, might already have diameters suitable for sawn timber.

At age 14 to 15 trees can be pruned for the third time. The thinning should be heavy as the plantation reaches an age where marketable tree sizes are very likely. All sub-dominants and co-dominants trees can be removed in a thinning from below. If the removal of some dominant trees does not result in permanent gaps, thinning can go more into the crowns to

DISCUSSION remove some dominant trees for commercial uses. After that, the selection and marking of future crop trees can take place.

The last thinning at age 19 to 20 should be very heavy and result in a stand that consist only in trees of best form, with good crowns, well spaced and evenly distributed over the plantation. Future crop trees should be liberated in this last thinning to concentrate the growth on the best trees, before the final harvest can take place at age 25.

This proposed management scheme for Almendro has to be validated in the field and should be optimized through thinning trials were different intensities are tested. For the beginning, it should be sufficient to improve the quality of Almendro plantations in Central America.

5.5 Carbon forestry The main goal of planted carbon forestry systems is the sequestration of a maximum amount of CO2, which can be achieved through focusing management and silvicultural interventions on maximum stand volume growth (Read et al., 2001). Tree form and quality are of importance if timber revenues should be generated, but a low-input conservation approach is assumed for the development of recommendations for pure carbon forestry projects using Almendro.

All assumptions and calculations are based on the methodology of the CarbonFix Standard* (CFS). This ex-ante standard enables plantation owners to generate verifiable offsets, which can be traded on international voluntary carbon markets (Hamilton et al., 2009).

Other carbon standards are available as well, but the CFS is considered the one assuring the highest quality of the generated offsets (Kollmuss et al., 2008).

*The standard (Version 3.0) can be directly downloaded on the following webpage: http://www.carbonfix.info/chameleon//outbox/public/189/CarbonFix_Standard_v30.pdf?PHPSESSID=4bo1l5c5 pbh5gj88g93ed1p832

DISCUSSION

The CFS offers two calculative options to determine the future CO2-fixation, depending on the applied silvicultural methods. These silvicultural options are selective harvesting, conservation forest or rotation forestry. The calculations of the future CO2-fixations are based on the mean stand volume during the first rotation period in case of rotation forestry and the equilibrium stand volume in case of selective harvesting or conservation forests.

Recommendations given in chapter 5.4 are valid for the rotation forestry approach, but as mentioned earlier, the conservation forests approach is assumed for pure carbon forestry projects, meaning that no interventions are supposed to take place.

For the achievement of maximum stand volume growth in conservation forests, the initial spacing is of high importance (Evans and Turnbull, 2004) and a spacing of 2 x 2 m is therefore recommended. No thinnings are suggested as thinnings tend to decrease the total volume, while increasing the single tree quality (Piotto et al., 2003; Evans and Turnbull, 2004).

This proposed management regime resembles the development on the “Canadian Trial”, as the observed results indicate that after 24 years 356 trees can grow on one hectare with a total stand volume of 410 m³/ha. The predefined calculation method for the amount of sequestered carbon is part of the CFS and would result in 755 t CO2/ha when using the numbers from the “Canadian Trial”.

The CFS provides conservative standard values if no scientific data is available. In the case of Almendro, standard values were used for the biomass expansion factor and the root to shoot ratio. Carbon fraction is 0.5 and C to CO2 conversion factor is 3.6666 according to the standards´ definition.

Equation 6: CarbonFix equation

Where: TWB = total woody biomass, V = stem volume, BEF = biomass expansion factor, WD = wood density,

CF = carbon fraction, CCF = C to CO2 conversion factor, RSR = root to shoot ratio.

DISCUSSION

This formula is an easy to use approach for the estimation of total woody biomass, above- and belowground. It is evident in this formula that high wood densities are a driving force for high carbon uptake, as described by e.g. Redondo-Brenes (2007).

The results for Almendro on the “Canadian Trial” can be compared deliberately with data from unthinned Teak plantations in Panama (Kraenzel et al., 2003). Above – and belowground biomass was measured for 20 year old plantations and total carbon storage was estimated to be 351 t C/ha. However, the soil stored the biggest amount of carbon, but tree carbon storage averaged 120 t C/ha, which would equal a total amount of stored CO2 of

440 t CO2/ha, when applying the specified C to CO2 conversion factor set by the CFS.

5.6 Agroforestry The present study includes growth records from Almendro in agroforestry systems as well (see chapter 4.1.2 and 4.1.3). Almendro was frequently used in silvopastoral systems and observations indicate that the species has great potential for agroforestry systems of various kind. Observed growth in silvopastoral systems was slower than in plantations, which have not been grazed, but with proper silvicultural management (thinning and pruning) diameter growth and tree quality in silvopastoral systems can be encouraged. Almendro commonly sheds leaves in dry periods and allows in general the penetration of high amounts of light to the forest ground, thus making it an optimal species for the use in agroforestry systems (Haggar et al., 1998; Haggar et al., 2003; Montagnini et al., 2003). Thinnings might help to even increase this amount of light, to maintain proper light levels beneath a stand, for deliberately growing other crops or provide vegetation for grazing. Thinning or harvesting Almendro could supplement farmers´ income when prices for the crops or cattle are low and intermediate returns are desired (Somarriba, 1992).

Given the natural distribution of Almendro and the fact, that Almendro does not perform well on higher elevations, the use of this species can only be recommended for lowland agroforestry systems, such as tree crop combinations with cacao (Theobroma cacao), pineapple (Ananas spp.) or silvopasture and not for crops that are normally grown in higher

DISCUSSION elevations, such as coffee (Coffea spp.) or highland silvopastoral systems (Beer, 1987; Beer et al., 1997; Dagang and Nair, 2003; Haggar et al., 2003; Montagnini et al., 2003).

Finally, carbon sequestration could also be a possible benefit in agroforestry systems (Montagnini and Nair, 2004) and the CFS for instance would even allow the generation of tradable carbon offsets in silvopastoral systems.

DISCUSSION

5.7 Limitations of the present study Some limitations have been already discussed in the previous chapters, but the main limitations are listed below:

- Most of the plantations were too young for a proper statistical correlation of site factors and site factors, such as the soil were not assessed locally on all plantations - Permanent sample plot design was insufficient in some cases - Site index curves, growth projections and silvicultural recommendations are based on data from only few older plantations any many young ones. All plantations had inappropriate management and overall growth might therefore be understated.

5.8 Recommendations Based on observations and results from Almendro timber plantations across Costa Rica and Panama, the following recommendations can be given:

- The immediate implementation of silvicultural management schemes for all stands, especially thinning and pruning to obtain trees of good form and large diameters - Continuation of all measurements on all plots and reactivation of unmanaged permanent sample plots to collect data about the performance of Almendro in different growth stages, spacing, and mixture under various site conditions - Establishment of thinning trials for early interventions and delayed thinnings - Establishment of pruning trials to develop a pruning regime - Assessment of the tree competition and crown development (measurement of the trees position on plots as well as measurement of crown parameters) - Development of a species specific form factor - Development of biomass expansion factors and root to shoot ratios

CONCLUSION

6. CONCLUSION

The superb wood quality of Almendro pays the highest prices on local timber markets and using this fine hardwood especially for floorings, furniture or heavy construction is widespread. The wood that is processed in Costa Rica originates from Nicaraguan rainforests, as the logging of Almendro is banned in Costa Rica since 2008. With diminishing supply from natural forests, Almendro grown on plantations will gain importance. These plantations have the potential to lower the pressure on natural forest resources if management is optimized. In the best scenario high levels of biodiversity and endangered species like the great green macaw (Ara ambiguus) can be protected and preserved for future generations.

In the present study data on long-term growth of Almendro in plantations in various climatic zones of Costa Rica and Panama was collected. Preliminary findings showed that Almendro plantations developed the best in Atlantic lowlands of Costa Rica and good performance was achieved in regions that are characterized by a climate with annual rainfall greater 2000 mm and elevations below 500 m. Almendro also grew well on poor soils and showed good performance in silvopastoral systems.

Through site classification, growth modeling and the creation of provisional silvicultural regimes, a starting point for further improvements of the management of Almendro plantations was set by this study.

As current plantations mature, silvicultural knowledge under local conditions should increase, if research and monitoring is continued on existing sample plots. It is of highest importance to reactivate abandoned permanent sample plots and to implement thinning on all plantations, to gain knowledge about the long-term growth and the reaction of Almendro to thinnings. Through these activities and the establishment of new sample plots, the results from this study can be verified and further developed.

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APPENDICES

Appendix 1 - Detailed information on sampled Almendro plantations

Number Dominant Initial Institution Plantation SIGR of plots AGCL spacing Canadian Trial 1 4 3 2 x 2 m OTS - La Selva Haggar 1 4 2 4 x 4 m Montagnini 18 4 2 2 x 2 m Oscar Rodriquez 4 3 3 3 x 3 m Montealegra 4 2 3 3 x 3 m Los Almendros 4 3 3 3 x 3 m ITCR / Cope San Juan 4 3 3 3 x 3 m COSEFORMA Edwin Romero 1 3 2 3 x 3 m Olman González 1 3 2 3 x 3 m Buenos Aires 1 3 2 3 x 3 m CMECC 4 5 2 4 x 4 m RTT CONCOL-00 2 5 2 4 x 6 m MOHEGAN 4 5 1 4 x 4 m CACTU 4 6 1 3 x 3 m Las Peñas 1 6 1 3 x 3 m CATIE Las Mulas (RTT) 1 6 1 5 x5 San Juan 2 6 1 5 x5 Tamara AFS 1 2 1 12 x 12 m La Bomba 2 4 3 3 x 3 m Y-Griega 1 4 2 3.5 x 3.5 m EARTH Tiro al blanco 1 4 1 3.5 x 3.5 m Puente Hamaca 1 4 1 4 x 4 m Precious Woods Santa Cecilla 1 1 1 3 x 3 m Cacao 4 1 1 4 x 4 m G. Navarro Orosi 9 1 1 4 x 4 m Los Tucanes Los Tucanes 2 4 1 3 x 4 m

APPENDICES

Table 23: Overview and characteristics of Almendro plantations in Costa Rica

Number of Dominant Institution Plantation SIGR Initial spacing plots AGCL Liquid Jungle Lab 9 7 1 3 x 3 m Rio Hato 9 8 1 3 x 3 m PRORENA Soberania 9 9 1 3 x 3 m Las Lajas 9 7 1 3 x 3 m Los Santos 9 8 1 3 x 3 m Los Monos 97 1 7 2 6 x 6 m Los Rios 1 2 7 2 5 x5 m ForestFinance Los Rios 2 1 7 2 5 x5 m Los Rios 3 1 7 2 4 x5 m Pampanillo 2 7 2 5 x5 m; 3 x 5 m

Table 24: Overview and characteristics of Almendro plantations in Panama

Appendix 2 - Stand diameter distribution

Stand diameter distribution for “ Cope San Juan”, 18.4 years, no thinning, 3 x 3 m spacing, SIGR 3

APPENDICES

Stand diameter distribution for D. panamensis in a mixed species plot together with A. hunsteini, “ConCol”, 8.1 years, no thinning, 4 x 6 m spacing, SIGR 5

Stand diameter distribution for D. panamensis in a mixed species plot together with A. hunsteini, “CMECC”, 8.3 years, no thinning, 4 x 4 m spacing, SIGR 5

Stand diameter distribution for D. panamensis in a mixed species plot together with A. hunsteini, E. deglupta and S. macrophylla, “San Juan”, 6.5 years, no thinning, 5 x 5 m spacing, SIGR 5

APPENDICES

Stand diameter distribution for “Los Monos”, 12 years, no thinning, 6 x 6 m spacing, SIGR 7

Stand diameter distribution for “Pampanillo”, 11.9 years, no thinning, 5 x 5 m spacing, SIGR 7

Stand diameter distribution for D. panamensis in a mixed species plot with B. quinata, “Pampanillo”, 12 years, no thinning, 5 x 3 m spacing, SIGR 7

APPENDICES

Appendix 3 - Stand height curves

Fitted Michailoff stand height curves for “Santa Cecilla”, SIGR 1

Fitted Michailoff stand height curves for “Buenos Aires”, SIGR 3

APPENDICES

Fitted Michailoff stand height curves for “J. Haggar” with observed values, SIGR 4

Fitted Michailoff stand height curve for “La Bomba” with observed values, SIGR 4

APPENDICES

Fitted Michailoff stand height curve for D. panamensis, “CMECC”, SIGR 5

Fitted Michailoff stand height curve for D. panamensis with observed values, “CONCOL”, SIGR 5

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APPENDICES

Fitted Michailoff stand height curves for “Los Monos”, SIGR 7

Figure 14: Fitted Michailoff stand height curves for D. panamensis, “Pampanillo”, SIGR 7

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APPENDICES

Appendix 4 - Estimated Parameter values

Plantation Age R² a b Sum of least squares Sampled trees 1 0,43 3,853912121 -2,356908027 4,12 78 2,3 0,83 9,095444759 -4,215977709 16,34 74 3,3 0,92 11,27458549 -4,745733111 14,64 77 Buenos Aires 4,3 0,80 12,97154668 -4,804472409 49,36 77 7,3 0,67 14,92544283 -4,694847191 154,84 77 14,8 0,90 30,36284524 -10,56895767 21,53 11 Canadian Trial 24 0,98 35,04232114 -3,155333474 4,16 7 3,3 0,84 9,459949302 -4,161450134 40,51 135 4,3 0,81 10,96552761 -5,145008512 70,12 135 CMECC 5,2 0,61 12,43454353 -4,712923607 169,03 136 6,3 0,64 14,64202281 -4,628358969 180,29 137 7,3 0,67 16,69260261 -4,766946843 205,62 136 8,3 0,48 20,32593057 -6,141946701 794,38 136 CONCOL 7,3 0,46 16,65947672 -5,222655425 252,22 64 8,1 0,53 23,20447389 -7,648951101 520,44 65 1,8 0,63 8,85612637 -4,208595152 8,10 49 2,8 0,86 12,55067033 -5,397150404 29,84 97 3,8 0,84 14,87100375 -5,525583647 53,04 98 4,8 0,79 18,51352662 -6,353061865 108,78 98 Cope San Juan 5,8 0,68 22,01301218 -6,738789723 262,27 97 6,8 0,76 23,17276213 -6,994102617 196,17 94 7,8 0,72 21,19839349 -5,97426213 199,71 94 10,8 0,62 25,79567891 -7,078052712 374,17 89 18,4 0,11 26,47077248 -5,380519031 27,85 10 J. Haggar 14,8 0,83 30,09154572 -8,585385826 45,75 8 La Bomba 17,3 0,89 35,10798114 -13,62425784 94,44 25 1,5 1,00 20,10721905 -6,025172417 1,43 13 2,5 0,49 11,36652347 -3,862622168 20,63 14 3,5 6,33 13,1346891 -4,46804204 0,80 14 Los Monos 5,5 0,68 16,75146229 -6,01897672 18,79 14 7,6 0,62 20,27287996 -6,750115341 24,11 14 9,5 0,74 22,97832475 -7,730528932 17,63 14 12 0,66 28,61688328 -8,837494901 38,45 14 4,5 0,72 5,601035534 -0,671132027 3,36 16 Pampanillo 6,3 0,77 11,80555215 -4,739939678 8,02 16 7,6 0,72 19,35761987 -6,918161441 17,34 16 12 0,34 26,79694279 -7,798224422 26,51 9

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APPENDICES

Plantation Age R² a b Sum of least squares Sampled trees 1,6 0,04 2,741401887 -0,568569864 2,69 11 2,6 0,87 8,961041486 -3,554859312 0,81 10 3,6 0,67 11,57137015 -4,212509914 2,22 10 Santa Cecilla 4,7 0,69 13,73261204 -3,972315888 3,25 10 5,6 0,50 12,08893732 -2,389334412 2,99 10 6,8 0,72 19,01150194 -4,539678496 7,67 10 7,8 0,71 18,88008319 -4,542115395 4,01 7 1,5 0,79 13,62941014 -6,065471266 1,37 27 San Juan 4,6 0,91 12,2610103 -6,027137096 18,76 63 5,4 0,91 15,13156374 -6,782467572 29,28 63 6,4 0,89 15,13156374 -6,782467572 45,55 63 Parameter estimates of the stand height curves fitted with the Michailoff – function (in alphabetical order)

Parameters Site indices SI - 17 SI - 19 SI - 21 SI - 23 SI - 25 C 0,07280059 0,06888142 0,06106933 0,05857689 0,05651072

dt 1,38945024 1,18520384 0,99967262 0,88578144 0,79501365

h1 12 14 16 18 20

h2 30 32 35 37 39

Hi at index age 17 19 21 23 25

Hi at rotation end 23.5 25.3 27.4 29.3 31.2

Parameter estimates and attributes of the preliminary Almendro site index curves

Parameter estimates Plantations SSR* a b c d Los Almendros 32,8931169 1 0,05697188 1,09214275 1,36872872 Cope San Juan 40 1 0,03454887 0,6798233 11,3553863 Montealegra 40 1 0,0222607 0,63735647 8,66314029 O. Rodriquez 40 1 0,02914949 0,75988554 8,4894628 Montagnini - Thinned 40 1 0,07078486 0,96047437 4,47393735 Montagnini - Unthinned 32,5106876 1 0,07971772 0,84208541 2,29128769 *SSR: Residual sum of squares

Used parameter values for the Chapman - Richards top height growth model

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APPENDICES

Appendix 5 - Photos

Picture 1: The commercial Almendro plantation “Santa Cecilla” in SGGR 1, 7.8 years

Picture 2: The COSEFORMA plot “Montealegra“, 18.4 years, SIGR 2

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APPENDICES

Picture 3: Silvopastoral system with Almendro, “Olman González”, 14.8 years, SIGR 3

Picture 4: The oldest Almendro plantation, “Canadian Trial”, 24 years, SIGR 4

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APPENDICES

Picture 5: Almendro in mixed plantations of RTT, “ConCol”, 8.1 years, SIGR 5

Picture 6: Mixed Almendro plantation in the highlands of Turrialba, “Mulas”, 6.6 years, SIGR 6

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APPENDICES

Picture 7: Almendro in the ForestFinance plantation „Pampanillo”, 11.8 years, SIGR 7

Picture 8: Remnant Almendro trees on a pasture close to Sarapiqui, SIGR 4

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