FluxLetter

The Newsletter of FLUXNET Vol. 2 No. 4, December, 2009

Highlight FLUXNET site Highlighting Site: Santa Rita Creosotebush Santa Rita Creosotebush by Shirley A. (Kurc) Papuga

Compared to other areas which in the timing, frequency and tridentata (hereafter referred to In This Issue: receive greater annual precipita- magnitude of precipitation as Larrea) already inhabited the tion, dryland carbon uptake is events will have important eco- southwestern United States by highly sensitive to precipitation hydrological consequences. the Last Glacial Maximum inputs (Huxman et al., 2004). Critical to predicting and under- (Duran et al., 2005). Now, Lar- FLUXNET site: The amount of precipitation in standing the implications of these rea is pervasive in three North Santa Rita Creosotebush Papuga (Kurc) S……...……...Pages 1-4 drylands is small; therefore, climatic changes is a better un- American deserts: the Mojave, dryland depend on derstanding how dryland vegeta- the Sonoran, and the Chihua- Correspondence: pulses of moisture, i.e. small tion responds to and uses water huan, even though they differ in New Investments in the Austra- resources. topography, climate, and histori- pulses that primarily trigger lian Flux Network microbial activity and evapora- cal background. While Larrea Eamus D……………………Page 5-7 tion or large pulses that provide Introduction to Larrea triden- typically forms extensive mono-

tata. typic stands, they are greatest in moisture to support photosyn- FLUXNET young scientist: thesis and transpiration. Most In the arid to semiarid areas of density in the Chihuahuan De- Aline Jaimes …………….….Pages 8-9 global climate models predict North America, a drought toler- sert with decreasing density to changes in the intra-annual vari- ant plant Larrea tridentata domi- the west (Barbour, 1969). A Research: ability of precipitation (Knapp et nates the landscape, extending ploidy gradient also occurs in Semiarid ECohydrological al., 2008). Given the average from Nevada, United States this species from east to west: Array – SECA (“creosotebush”) to Hidalgo, generally speaking, the Chihua- Scott RL, Jenerette GD, Huxman TE annual precipitation in drylands ………………..……....….Pages 10-12 globally is expected to decline Mexico (“gobernadora” or huan populations are diploid, the

(e.g. Seager et al., 2007), changes “hediondilla”) (Figure 1). Larrea Sonoran populations are Lateral versus vertical car- tetraploid, and Mojave popula- bon fluxes in Baja California, tions are hexaploid; higher ploidy Mexico races are believed to be an adap- Escoto-Rodriguez M, Smith SV, Bullock SH………………..Pages 13-15 tation to increased aridity and/or higher temperature (Hunter et al., 2001). This unusual poly- CO2 fluxes in semi-arid sites on carbonate substrates ploidy is likely to have been a located in southeast Spain major factor in expansion in Serrano-Ortiz P, Pérez Sánchez-Cañete range of Larrea throughout the E, Domingo F, Were A, Villagarcía L, and Kowalski AS………...... Pages 16-18 20th century (Duran et al., 2005). Larrea is a repeat-blooming, New Mexico elevation gradi- ent evergreen shrub, with a C3 pho- Litvak M, and Fox, A…...... Pages 19-21 tosynthetic pathway. With no defined trunk, it typically reaches heights of 1 to 1.5 m, but has been found to stretch as high as Figure 1: Distribution of creosotebush in North America and the location of the Santa Rita 4 m. Both inverted-cone and Creosotebush tower site at the northern boundary of the Santa Rita Experimental Range in southeastern Arizona. Image by Michelle Cavanaugh. Page 2

Santa Rita Creosotebush

of Larrea were to change, would all depths) with no caliche layer, a reduction in cover and subse- to at least 1 m. Long term quent exposure of records from the SRER archives strengthen feedback to local (http://ag.arizona.edu/SRER/ and regional climate? data.html) suggest that the SRC flux station area receives aver- Site Description. age annual precipitation of 330 As of February 2010, a full two mm, half occurring in July years of flux observations will through September with mon- have been made at the Santa soon rains and the other half Rita Creosotebush (SRC) occurring from December tower site (Figure 3) located through February with winter about 30 miles south of Tucson and spring rains. within the boundaries of the Unique long-term measure- Santa Rita Experimental Range ments at the SRC tower site

Figure 2: Close up view of Larrea leaves and flowers. Photo by Shirley Papuga. (SRER) in southeastern Arizona, include continuous measure- United States (Figure 1). The ments of soil moisture at multi- hemispherical canopies have illustrating the drought tolerant SRER is bounded at its southern ple depths in multiple profiles been identified, the architecture shrub provides a dependable and eastern borders by the all down to 1 m. Additionally, suggested to facilitate functional resource in an unpredictable Santa Rita Mountains. Since at three digital “game” cameras, water and nutrient accumulation environment (Minckley et al., least 1904 (Figure 4), Larrea has on a time-lapse setting, are below the shrub (DeSoyza et al., 2000). The spherical fruit, pea- been the dominant species near monitoring the daily phenologi- 1997; Whitford et al., 1997). sized and densely covered with the very northern boundary of cal activity of the Larrea, such as The bifoliolate leaves of Larrea fuzzy white hairs, eventually the SRER where the SRC tower green up and flowering, within are opposite, with two asymmet- splits into 5 pieces, each contain- site is located (UTM: 0515177, footprint of the flux tower. rical oblong leaflets joined at the ing a single seed. Moisture, 3530284) at an elevation of base, measuring about 1 cm long temperature, and soil conditions about 950 m. Some Research Highlights. and 3 to 4 mm wide (Figure 2). are all thought to play a role in Total canopy cover at the SRC We have seen that the depth of The odorous resin that coats the ability of Larrea seeds to tower site is 24% (14% Larrea moisture reservoirs is largely these leaves has been shown to germinate. and the other 10% a combina- associated with the nature of promote water use efficiency, Over the last century, the area tion of annual grasses, annual precipitation events in dryland deter herbivores, and screen dominated by Larrea in North herbaceous species, and cacti). ecosystems (Kurc and Small, ultra-violet radiation (Meinzer et America has increased, and is Soil crusts are also prevalent 2004; Kurc and Small, 2007). al., 1990). This resin, secreted associated with coincident land throughout the site. The height Soil moisture pulses at the by a glandular epidermis of the degradation during that time of the average Larrea is 1.7 m, surface follow most storms stipules, is a complex mixture of (Grover and Musick, 1990). with an average of 24 stems while deep soil moisture pulses phenolics, saponins, terpenoids, Therefore, the management of about 10 mm in diameter. are less frequent. In fact, sur- wax esters, partially o- cattle grazing and fire has been Thus, Larrea at the SRC tower face soil moisture decreases methylated flavones and fla- modified to minimize shrub en- site are larger than many en- rapidly following rainfall events; vonols (Gonzalez-Coloma et al., croachment. Yet, widespread countered in the southwestern the best fit exponential time 1994), which can be extracted Larrea offers a predictable re- United States. Additionally, constant is less than 3 days for medicinal and industrial uses source in an otherwise unpre- insect galls – potentially an (Kurc and Small, 2004). Likely, (Arteaga et al., 2005). Flowers dictable and harsh environment. indication of plants with mini- this surface moisture is only of Larrea are solitary, axillary, For better or for worse, climatic mal water stress (Waring and available to shallow rooted and perfect, about 2 cm wide changes that will temperature Price, 1990) – are common on plants, if they are able use the (Figure 2). More than 120 bee and precipitation patterns are the Larrea at this site. moisture before it is quickly species have been found on the likely affect the distribution of Soil at the SRC tower site is lost to evaporation. flowers of creosotebush, 21 of Larrea in the region. How resil- sandy loam (~ 65% sand, ~ 24% Because evaporation and respi- which are Larrea specialists; ient is Larrea? If the distribution silt, ~ 11% clay, averaged over ration should be more influ- Page 3

Santa Rita Creosotebush

tion (E) and soil moisture at press). This digital image- A several depths. ET was best derived greenness showed that correlated with soil moisture at the green-up of creosotebush is 37.5 cm (deep soil moisture). driven by deep soil moisture, At this depth, T and soil mois- just as for transpiration and net ture were also most strongly carbon uptake. We also show correlated. On the other hand, that carbon uptake in Larrea E was best correlated with soil ecosystems is correlated with, moisture at 2.5 cm (surface soil and may be able to be predicted moisture). Given these statis- using, image-derived greenness, tics, undoubtedly large rainfall suggesting that this inexpensive events or closely spaced small tool has the potential to play a rainfall events are critical to the large role in developing a better healthy structure and function spatial understanding of the of these Larrea ecosystems. carbon dynamics of shrub- Finally, we recently processed a dominated drylands. year of images from our time- The dependence of Larrea on B lapse digital cameras to derive deep soil moisture is evident daily greenness at the SRC from our research. Still, more tower site (Kurc and Benton, in work is necessary to under-

Figure 3: Side view of the Santa Rita Creosotebush tower site (a) Photo by Shirley Papuga. An overhead view of the Santa Rita Creosotebush tower site (b) Photo by Mark Heitlinger.

enced by soil moisture near the carbon uptake (Kurc and Small, surface than by deep soil mois- 2007). Because carbon uptake ture, we break the soil profile and transpiration are inextricably into two regions: surface soil linked, this suggests that semiarid moisture (< 20 cm) and deep grasses and shrubs are only able soil moisture (> 20 cm). A re- to use soil moisture to photo- gression of net ex- synthesize when the water has

change of CO2 (NEE) versus infiltrated deep enough into the evapotranspiration (ET) per- profile to be uninfluenced by formed for four cases at a semi- evaporative demand. arid grassland and shrubland: (1) This is further supported in dry surface, wet deep; (2) wet shrubs by a recent sap flow surface, dry deep, (3) wet sur- study (Figure 5) at the SRC face, wet deep, and (4) dry sur- tower site (Cavanaugh et al., in face, wet deep revealed a strong review). Linear regressions negative correlation for case (1), were performed between ET, corresponding to periods of net transpiration (T), and evapora- Figure 4: Map of vegetation distribution at the Santa Rita Experimental Range in 1904, copy of original from the thesis of: L.A. Mehroff, University of Arizona, 1955. Page 4

Santa Rita Creosotebush

References summer monsoon season, central NM. Water Resources Research, 40 Arteaga, S., Andrade-Cetto, A. (W09305). and Cardenas, R., 2005. Larrea triden- tata (Creosote bush), an abundant Kurc, S.A. and Benton, L.M., in press. plant of Mexican and US-American Digital image-derived greenness links deserts and its metabolite nordihy- deep soil moisture to carbon uptake in droguaiaretic acid. Journal of Ethno- a creosotebush-dominated shrubland. pharmacology, 98(3): 231-239. Journal of Arid Environments (Ecohydrology of NAM). Barbour, M.G., 1969. Age and space distribution of desert shrub Larrea- Kurc, S.A. and Small, E.E., 2007. Soil divaricata. , 50(4): 679-&. moisture variations and ecosystem- scale fluxes of water and carbon in Cavanaugh, M., Kurc, S. and Scott, R., semiarid grassland and shrubland. in review. Evapotranspiration parti- Water Resources Research, 43(6). tioning in semiarid creosotebush dominated ecosystems: Meinzer, F.C., Wisdom, C.S., Gon- implications of soil moisture control zalezcoloma, A., Rundel, P.W. and on shrubland transpiration. Ecohydrol- Shultz, L.M., 1990. Effect of leaf resin ogy. on stomatal behavior and gas-exchange of Larrea-tridentata (DC) Cov. Functional DeSoyza, A.G., Whitford, W.G., Ecology, 4(4): 579-584. MartinezMeza, E. and VanZee, J.W., 1997. Variation in creosotebush Minckley, R.L., Cane, J.H. and Kervin, (Larrea tridentata) canopy morphology L., 2000. Origins and ecological conse- in relation to habitat, soil fertility and quences of pollen specialization among associated annual plant communities. desert bees. Proceedings of the Royal American Midland Naturalist, 137(1): Society of London Series B-Biological 13-26. Sciences, 267(1440): 265-271.

Duran, K.L., Lowrey, T.K., Parmenter, Seager, R. et al., 2007. Model projec- R.R. and Lewis, P.O., 2005. Genetic tions of an imminent transition to a diversity in Chihuahuan Desert popula- more arid climate in southwestern tions of creosotebush North America. Science, 316(5828): (Zygophyllaceae : Larrea tridentata). 1181-1184. American Journal of Botany, 92(4): 722 -729. Waring, G.L. and Price, P.W., 1990. Plant water-stress and gall formation Gonzalez-Coloma, A., Wisdom, C.S., (cecidomyiidae, asphondylia spp) on Sharifi, M.R. and Rundel, P.W., 1994. creosote bush. Ecological Entomology, Figure 5: An example of a heat balance sap flow used at the Santa Rita Creosote- Water and nitrogen manipulations of 15(1): 87-95. bush tower site which was constructed in the laboratory. Insulation and weather protection the desert shrub larrea-divaricata would complete the installation of this instrument. Image by Shirley Papuga. subsp tridentata (Zygophyllaceae). Whitford, W.G., Anderson, J. and Journal of Arid Environments, 28(2): Rice, P.M., 1997. Stemflow contribu- stand the implications of climate 139-146. tion to the 'fertile island' effect in change for this important and contact: creosotebush, Larrea tridentata. Journal Grover, H.D. and Musick, H.B., 1990. of Arid Environments, 33: 451-457. pervasive dryland ecosystem and Shirley A. (Kurc) Papuga Shrubland encroachment in southern its interactions with ecosystems [email protected] New Mexico, U.S.A.: an analysis of processes in the Ameri- throughout southwestern North can Southwest. Climatic Change, 17: America. As such, this same School of Natural Resources and the 305-330.

Larrea ecosystem has also been Environment Hunter, K.L. et al., 2001. Ploidy race University of Arizona distributions since the Last Glacial selected as the core site for Maximum in the North American Domain 14 within National Eco- Tucson, AZ 85716 desert shrub, Larrea tridentata. Global Ecology and Biogeography, 10(5): 521- logical Observatory Network 533. (NEON). Please contact me for Huxman, T.E. et al., 2004. Precipitation further information or to partici- pulses and carbon fluxes in semiarid pate in our research efforts. and arid ecosystems. Oecologia, 141 (2): 254-268.

Knapp, A.K. et al., 2008. Conse- quences of more extreme precipita- tion regimes for terrestrial ecosys- tems. Bioscience, 58(9): 811-821.

Kurc, S. and Small, E., 2004. Dynamics of evapotranspiration in semiarid grassland and shrubland during the Page 5

Correspondence New Investments in the Australian Flux Network Derek Eamus

As many of you will know, Aus- and soil moisture content (top 1 ingly little ecophysiological or one-hour drive from Alice tralia has a flux network m) between wet and dry season, ecohydrological work, and no Springs in Central Australia. (OZFLUX) that has been in tree water use is highly conser- flux measurements have been Mean annual rainfall for this site existence for many years. In- vative, showing minimal variation undertaken in these regions. is 277 mm but this statistic is too deed, I think the first co- across season. Since those early As part of the Australian Federal broad to be of much value. The variance data for Australia were days, more flux sites have been Government’s increase in fund- annual minimum and maximum measured in 1997 in the North- added, notably in Victoria, the ing for nationally important re- rainfall is 82 and 783 mm respec- ern Territory of Australia, in the Australian Capital Territory and search, $542 million dollars was tively. Over the past 60 years, all wet-dry tropics at a savanna site tropical Queensland. All three of made available (over 2004 – months have at some stage re- (Hutley et al. 2002, 2001; Eamus these sites are situated in tall (> 2011) through the National ceived zero rain but on average et al 2001). This site receives 30 m) wet (>1000 mm annual Collaborative Research Infra- each month receives some rain, between 1500 mm and 2500 mm rainfall) closed . However, structure Strategy to develop ranging on average from 4.2 to of rain each year in each 5 most of Australia is arid or semi- and fund national research infra- 73.1 mm per month (O’Grady et month long wet season. Despite arid, receiving less than 500 – structure projects. One of the al 2009). However, maximum the huge change in rainfall, VPD 600 mm annual rainfall. Surpris- initiatives funded in this program monthly rainfall recorded is 357 was the Terrestrial Ecosystem mm – yes, in March 2000, the Research Network (TERN). rainfall exceeded the long-term annual rainfall for Alice. Mean Terrestrial Ecosystem Re- daily potential evaporation rates search Network (TERN) range from 4 mm to 13 mm. The TERN initiative is designed Central Australia has been ex- to provide a nationally consistent periencing some of the most approach to collecting and man- rapid rates of climate warming aging time-series datasets across on the continent, especially since Australian landscapes and invest- 1950 (Box et al 2008). The only ment from NCIRS to the TERN prominent mesoscale meteoro- will assist in establishing a na- logical feature that affects the tional, collaborative infrastruc- region is the passage of subtropi- ture that will facilitate enhanced cal cold fronts that develop in ecosystem research. One part of the late spring, before summer the NCRIS investment in TERN precipitation pulses initiate is to provide funding for addi- (Beringer and Tapper 2000). tional flux sites across Australia These cold fronts develop at and to provide a centralised data night and generate profound management, data quality assur- effects on the partitioning of ance and data storage/ energy fluxes, often generating dissemination facility. moisture pulses into the canopy from aloft. The new Alice Springs flux Vegetation in this region tends site to be dominated either by Acacia One of the new sites currently shrubland (to 4 m height) Acacia being established as part of the open woodland (taller) or exten- new TERN funding is located sive modified grasslands used in Figure 1: The author inspects a fine example of Acacia aneura (mulga) growing at a site approximately 150 km north of Alice Springs in central Australia. Page 6

Australian Flux Network

Figure 2: Acacia aneura (mulga) is a dominant woody species across much of the arid interior of Australia. To Aboriginal people of Australia, mulga is a much used food source with edible seeds. the cattle industry. It is our * What is the daily, seasonal and *How will climate change, warm- intent to put the flux tower over annual carbon and water budget *How do shaded and inter- ing, and variability affect carbon, Acacia shrubland, which contains for the Acacia shrubland? canopy spaces vary in evapora- water, and energy fluxes, as well a seasonal grass understory. The tion-induced enrichment of deu- as the penetration of spring cold 18 LAI at the site is low (ca 0.5), *What are the response-times terium and O? fronts? and situated in a landscape of and patterns of response to sand swales. In addition to the pulses of rain? *What attributes of Acacia makes A key activity that the ecohy- gold standard it so resilient to this environ- drology research lab at UTS is system, we shall install our new *Can we distinguish different ment? undertaking is to take multiple- small aperture scintillometer at ecohydrological types amongst site EC data and to use these the same site to compare the species in the different patterns *What is the rate of deep drain- data to improve on the Austra- two methods in their estimation of response to pulses of rain? age of water (groundwater re- lian standard land surface ex- of surface energy budgets. charge) and how is this related change model (CABLE). The Key questions we wish address *How does soil respiration and to the size of the rainfall event Alice Springs site will be one of include the following: the understory pattern of water and antecedent soil moisture many sites we shall use in this use and C uptake compare with content? CABLE model development the overstory? project. CABLE, like all such Page 7

Australian Flux Network

models, has representations of photosynthesis, transpiration and surface energy balances at land- scape scales. However, it has major limitations in its accurate representation of landscape function for much of the conti- nent. By combining data assimila- tion methods, remote sensing of land surface processes and at- tributes, and CABLE model de- velopment we intend to provide a more accurate assessment of land surface- ex-

changes of CO2, water and en- ergy. One the first steps in this will be to improve the represen- tation of the link between stomatal conductance and soil and atmospheric water content.

contact: Derek Eamus [email protected]

University of Technology Sydney

Figure 3: Alongside dry river beds majestic River Red Gums (Eucalyptus camaldulensis) can be found, even in aird zone central Australia. Page 8

Highlight Young Scientist Aline Jaimes

My name is Aline Jaimes. I am in micrometeorology. I think that mental Range (JER) in southern that will join the Ameriflux net- from the city of Xalapa, Ve- interdisciplinary science allows a New Mexico (See figure 2). The work and a common use field racruz, located on the east coast researcher to integrate and build JER is managed by the US De- and cyber infrastructure that will of Mexico. After receiving my on many amazing and well estab- partment of Agriculture Agricul- advance capacities for examining BSc. in from Universidad lished areas of knowledge to tural Research Service and is land-atmosphere interactions Veracruzana, I pursued a MSc in address some of the most press- part of the Jornada Long Term and spatio-temporal scaling of Baja California - one of the most ing environmental challenges we Ecological Research Program, ecosystem structure and func- beautiful places in Mexico sur- are facing - like climate change. which has been active since 1982 tion in desert shrublands. Our rounded by Desert and Ocean. I My career goal is to be able to (http://jornada-www.nmsu.edu/). activities are funded through a studied physical and biological study, understand, and communi- Dr Kris Havstad, Dr Deb Peters National Science Foundation interactions focused on marine cate findings related to complex (USDA-ARS, Jornada Experimen- CREST (Centers for Research primary productivity and environmental process to other tal Range, Las Cruces, New Excellence and Technology) mesoscale structures researchers, the general public Mexico) have been extremely award granted to UTEP to de- (geophysical turbulence) at the and decision makers. I hope that helpful in accommodating our velop the Cyber-ShARE Center entrance of the Gulf of Califor- my research will someday be needs on the JER and Dr Al of Excellence nia. This was program jointly used to make more informed Rango’s remote sensing team has (www.cybershare.utep.edu). The managed between the North- decisions regarding the manage- been kind enough to fly their Cyber-ShARE Center gives me west Center of Biological Re- ment of our natural resources. Unmanned Aerial Vehicle over the opportunity to interact with search (CIBnor) and the Center Currently, I am a 2nd year PhD our study site and take high research faculty and students for Scientific Research and student enrolled in the Environ- resolution aerial photographs to from environmental, geo and Higher Education of Ensenada, mental Science and Engineering help with site choice and de- computer science as well as BC (CICESE). While there, I had program at the University of scription. mathematics and education. The the opportunity to experience a Texas at El Paso (UTEP). At Building the tower site has been aim of our collaboration is to range of different disciplines UTEP I am working in the Sys- one of the most challenging tasks address the challenge of minimiz- including biology, , ocean- tem Ecology Laboratory (SEL) I have ever had, but I have been ing random and systematic ography, , remote under the direction of Dr. Craig fortunate to have had a lot of sources of error and improving sensing. These experiences Tweedie (www.sel.utep.edu). help from other students in the trust in data collected from broadened my vision and opened SEL is a fairly young lab and I SEL, access to experts in the novel technologies such as Eddy up a of possibilities. Ret- have just finished building our field, in particular Dr. Marcy covariance systems. Collabora- rospectively, I believe that was first flux tower site, which is Litvak at the University of New tion with CS has taught me how the reason I became interested located on the Jornada Experi- Mexico who has helped me tre- to build workflows, ontologies, a mendously. I was also lucky database and capacities to trace enough to attend two training provenance in my flux data and courses – the Open Path Eddy also the optimization of a geo- Covariance at CSI, Logan Utah, spatial site-choice tools. and the flux measurements and Our project focuses on the advanced modeling course con- study of the changes in vegeta- vened by University of Colorado tion structure and ecosystem Mountain research station at processes associated with Boulder, CO-. These colleagues change of ecosystem state inter- and training courses have preted as “desertification”, the boosted my confidence and have broad-scale conversion of peren- allowed me to bring new skills to nial grasslands to dominance by our young and growing research xerophytic woody plants and the lab. associated loss of and bio- The primary aim of our research logical resources including biodi- is to establish a flux tower site versity (Peters, D. et. al 2006). Figure 1: Aline Jaimes Page 9

Highlight Young Scientist

about, CO2, water and Energy balance, across spatial and tem- poral scales to improve the abil- ity to understand current and historic patterns and dynamics. 2) To study processes interac- tions across a range of scales and under different conditions to drive desertification dynamics and regulate conservation of biological resources. 3) Describe interactions driving landscape dynamics such that we can pre- dict spatial and temporal varia- tion processes to strategically promote conservation of biologi- cal resources.

contact: Aline Jaimes [email protected]

Systems Ecology Laboratory http://www.sel.utep.edu/

If you want to know more about our research please visit our website or contact me. Our site is still growing and we would be delighted to have other students who have similar research inter- est to come and conduct re- search here at JER.

Further Reading Havstad, K. M., Huenneke, Schlesinger, W., Eds. (2006). Structure and Function of a Chihuahuan Desert Ecosystem. The Jornada Basin Long-Term Ecological Research Site, Oxford University Press. Pp 447.

Figure 2: Flux tower at the Jornada Basin Long Term Ecological Research, NMSU Peters, D., H. S. William, et al. (2006). Future direction in Jornada research: The hypothesis is that spatial and and environmental drivers (i.e. cading events with effects on Applying an interactive landscape model temporal variation in ecosystem temperature, CO2) to influence ecosystem good and services. to solve problems. Structure and Func- dynamics is the result of patch cross-scale resource redistribu- The overall goals of my project tion of a Chihuahuan Desert Ecosystem. K. Havstad, L. Huenneke and W. structure interacting with trans- tion. These interactions feedback are: 1) Provide an analysis to Schlesinger, Oxford University Press: port vectors (i.e. , water) to patch structure to cause cas- integrate diverse observations 447. Page 10

Semiarid ECohydrological Array – SECA

Russell L. Scott, G. Darrel Jenerette, Travis E. Huxman

In this article we would like to highlight a little of the history of “The Southwestern ECohydrology Array (SECA)) is a multi-user network that serves and to assess / atmospheric exchange processes, as well as surface flux monitoring in our small part in semiarid ecosystems. SECA is administered through the USDA-ARS Southwestern of the world (southern Arizona, Watershed Research Center and the University of Arizona’s B2 Earthscience. The USA) and highlight some of the components of the array were constructed with funds from the USDA-ARS, Univer- research results and challenges. sity of Arizona, and the NSF-Science & Technology Center SAHRA.” In comparison to more mesic regions, there is a general lack of data on net ecosystem exchange were driven by basic water bal- ingly, our results have highlighted which are used to scale up along of carbon dioxide (NEE) in arid ance questions like, “how much the large evapotranspiration (ET) river reaches in this and other and semiarid regions. In these water do the plants use?” Ripar- amounts with annual ET often basins (Nagler et al., 2005; Scott areas, water is the dominant ian ecosystems are hotspots for exceeding precipitation by 2 -3 et al., 2008). control of NEE, and precipitation ecosystem flora and fauna diver- times (Scott et al., 2008; Scott et With the advent of low power is much more variable in time sity. Since many riparian ecosys- al., 2004; Scott et al., 2000) and and combined open-path water and space. Someone remarked at tems share the same groundwa- this data has been instrumental vapor and CO2 IRGAs, our in- an Ameriflux conference a few ter resource as the human popu- in reducing the uncertainties in terest in the interaction between years ago that nothing goes on lation in these basins, quantifying the water budget of the basin the water and carbon cycle was down here in terms of globally- their role in a basin’s water bal- (Scott et al., 2006). These data piqued. Riparian sites in arid ance is vital to water have also been used to develop lands experience high radiation relevant CO2 exchange proc- esses. Perhaps when looking at resource management. Accord- satellite-data-driven models loads, high vapor pressure defi- long-term and large-area means this might be true, but we have found that semiarid ecosystems can be both significant sinks and sources of CO2, with much greater interannual variability than a “typical” forested site. Additionally, we argue that wa- ter limitation affects ecosystem carbon exchange for at least some part of the growing season in all but the wettest ecosystems around the world. By looking at the drier end of this water- limitation spectrum, we have ample opportunities to better understand these effects. Our research using eddy covari- ance started in 2001 by estab- lishing three sites over dominant riparian ecosystems of the San Pedro River in southeastern Arizona (Fig. 1). At the time, we Figure 1: Figure 1 (low resolution): Location of the flux towers associated with SECA. Also, shown is the vegetation classification of Brown et al. [1979]. Page 11

Semiarid ECohydrological Array – SECA

ecosystems, which we started monitoring around 2004 (Fig. 3). Because of the lack of groundwa- ter access we are discovering that ecosystems with similar composition (e.g., a riparian mesquite shrubland and upland mesquite savanna) operate much differently, resulting in altered magnitudes and seasonality of

the CO2 flux response (Potts et al, 2006) We are also seeing that drought in these rainfall- dependent ecosystems results in

net annual CO2 loss and that this response varies depending on Time whether the drought occurs from lack of winter or summer Space rains (Scott et al., 2009). Finally, we have been able to combine Figure 2. Using space for time substitution to study mesquite encroachment effects on riparian grasslands. our site ET data with surface hydrological measurements of cits, and low rainfall amounts, accumulate more carbon in the gether to begin making mature small watershed water balances but deep-rooted vegetation can driest parts of the growing sea- conclusions. Early results for to show that the eddy covari- access groundwater that can son (Scott et al., 2004), a result riparian systems suggest that as ance technique appears to pro- result in a decoupling of above- that has been mirrored in the floodplain terrace grasslands are vide a highly accurate estimate of ground hydrometeorology and wettest parts of the world replaced by woody, mesquite- ET with the two independent below-ground hydrology. Ac- (Saleska et al., 2003). We are covered ecosystems the shal- measures agreeing on an average cordingly, we have observed using these data to develop lower-rooted grasses are less within 3% of each other annually large fluxes of CO2 in these whole ecosystem carbon models able to fully exploit stable and differed riparian systems that highlight to project likely changes associ- groundwater sources, whereas from -10 to +17% in any given the role of water limitation on ated with climate and land-cover the ecohydrological exchanges of year and site (Scott et al., 2009). ecosystem carbon fluxes. First, change (Jenerette et al., 2009). encroached ecosystems become We have contributed some of we have found that there are We have also begun to under- more decoupled from precipita- our data to the global Fluxnet large amounts of net carbon stand the consequences, in tion as the ecosystems become community (Santa Rita Mesquite uptake-- resulting from the con- terms of mass and material ex- more woody (Scott et al., 2006; and Kendall Grassland) with aims sequences of the general lack of change, of woody plant en- Jenerette et al., 2009). This to eventually offer all of it for water limitation for the domi- croachment, a phenomenon that results in a tradeoff between global use. As a prototype re- nant phreatophytic plants (deep- is occurring here and in many more carbon sequestration at gional network our sites have rooted grasses and trees) that dryland regions around the the expense of greater water use initially been used to describe can access groundwater and world (Goodale et al., 2002). in an region of over-exploited variation in whole ecosystem strong water limitation for the Along the San Pedro and in the groundwater resources. respiration pulses following rain microbial community that have upland (non-riparian) regions of With the exception of our sole- events (Jenerette et al. 2008) and only fleeting opportunities fol- southern Arizona (Fig. 1), we remaining mesquite woodland this work is leading into a global lowing rain events to break have established sites that repre- tower that has been in operation Fluxnet synthesis analysis. We down carbon (Jenerette et al., sent various levels of encroach- since 2001, we are now moving also continue to expand our 2008). The result of this inter- ment (Fig. 2). We are just start- beyond the riparian areas and domain and scope with a nearby action is that these ecosystems ing to pull all of our results to- into the surrounding “desert” mixed conifer site in the moun- Page 12

Semiarid ECohydrological Array – SECA

Scott, R.L., Cable, W.L., Huxman, T.E., Nagler, P.L., Hernandez, M., Goodrich, D.C., 2008. Multiyear riparian evapotranspiration and groundwater use for a semiarid watershed. J. Arid Environ. 72, 1232-1246,

Scott, R.L., Edwards, E.A., Shuttleworth, W.J., Huxman, T.E., Watts, C., Good- rich, D.C., 2004. Interannual and sea- sonal variation in fluxes of water and carbon dioxide from a riparian wood- land ecosystem. Agric. For. Meteorol. 122, 65-84,

Scott, R.L., Huxman, T.E., Williams, D.G., Goodrich, D.C., 2006a. Ecohy- drological impacts of woody-plant encroachment: Seasonal patterns of water and carbon dioxide exchange within a semiarid riparian environment. Global Change Biol. 12, 311-324,

Scott, R.L., James Shuttleworth, W., Goodrich, D.C., Maddock Iii, T., 2000. The water use of two dominant vegeta- tion communities in a semiarid riparian ecosystem. Agric. For. Meteorol. 105, 241-256.

Scott, R.L., Jenerette, G.D., Potts, D.L., Huxman, T.E., 2009. Effects of seasonal drought on net carbon dioxide ex- change from a woody-plant-encroached semiarid grassland. J. Geophys. Res. Figure 3. Santa Rita mesquite savanna from the air. The site is representative of a fully encroached desert grassland. [Biogeo.] 114, G04004,

Scott, R.L., Williams, D.G., Goodrich, tains surrounding our deserts to D.C., Cable, W.L., Levick, L.R., look at an elevation/precipitation McGuire, R., Gazal, R.M., Yepez, E.A.,

Ellsworth, P., Huxman, T.E., 2006b. transect and with amigos south References Chapter D: Determining the riparian Nagler, P.L., Cleverly, J., Glenn, E., Brown, D.E., Lowe, C.H., Pase, C.P., groundwater use within the San Pedro of the U.S.-Mexico border in the Lampkin, D., Huete, A., Wan, Z., 2005. 1979. A digitized classification system Riparian National Conservation Area state of Sonora (Instituto Tec- Predicting riparian evapotranspiration for the biotic communities of North and the Sierra Vista Subwatershed, from MODIS vegetation indices and nologico de Sonora, Universidad America, with community (series) and Arizona. association examples for the Southwest. meteorological data. Remote Sens. de Sonora) to look across gradi- Journal of the Arizona-Nevada Academy Environ. 94, 17-30, ents in the strength and impor- of Science 14 1-16. Republished 1994 in Biotic Communities: Southwestern Potts, D.L., Huxman, T.E., Scott, R.L., tance of the summer rainfall United States and Northwestern Mex- Williams, D.G., Goodrich, D.C., 2006. The sensitivity of ecosystem carbon from the North American Mon- ico, edited by David E. Brown, pp. 302- 315. University of Utah Press, Salt Lake exchange to seasonal precipitation and soon. Of course, we always City. woody plant encroachment. Oecologia 150, 453-463, welcome new collaborations. Goodale, C.L., Davidson, E.A., 2002. Saleska, S.R., Miller, S.D., Matross, D.M., Uncertain sinks in the shrubs. Nature 418, 593-594, doi:10.1038/418593a. Goulden, M.L., Wofsy, S.C., Da Rocha, Jenerette, G.D., Scott, R.L., Barron- H.R., De Camargo, P.B., Crill, P., Daube, B.C., De Freitas, H.C., Hutyra, L., Kel- Gafford, G.A., Huxman, T.E., 2009. Gross primary production variability ler, M., Kirchhoff, V., Menton, M., contact: associated with meteorology, physiol- Munger, J.W., Pyle, E.H., Rice, A.H., Rusell L. Scott ogy, leaf area, water supply in contrast- Silva, H., 2003. Carbon in Amazon ing woodland and grassland semiarid : Unexpected seasonal fluxes and riparian ecosystems. J. Geophys. Res. disturbance-induced losses. Science 302, Southwest Watershed Research [Biogeo.]G04010, 1554-1557, Center, United States Department of Agriculture, Agricultural Research Jenerette, G.D., Scott, R.L., Huxman, Scott, R.L., 2009. Using watershed water balance to evaluate the accuracy Service, Tucson, AZ T.E., 2008. Whole ecosystem metabolic pulses following precipitation events. of eddy covariance evaporation meas- Funct. Ecol. 22, 924-930, urements for three semiarid ecosys- tems. Agric. For. Meteorol. in press, [email protected] Page 13

Lateral versus vertical carbon fluxes in Baja California, Mexico Martín Escoto-Rodríguez, Stephen V. Smith and Stephen H. Bullock

Standard models and inventories The project, as its name indi- The region is topographically The underlying hypothesis is that of carbon balance place primary cates (“TERMAR” stands for complex. Shrubland communities a significant fraction of CO2 fixed emphasis on vertical exchanges “Tierra y Mar”, i.e. land and sea), modified by human influence by autotrophic-dominated com- between the atmosphere and was also designed to compare (introduced species) dominate munities is transported as or- both the land and the ocean. terrestrial and marine fluxes in the environment, with many of ganic matter and oxidized out- “Flujos TERMAR” is a project immediately adjacent regions. the low-elevation areas being side the immediate uptake sys- funded by CONACYT (the sites of agricultural development. tem. Moving organic matter from Mexican equivalent to the U. S. We study the area around En- The marine environment is char- one site to another is likely to National Science Foundation, senada, Baja California, Mexico. acterized by seasonally strong alter the oxidation rate. On land, NSF) and is designed to improve On land, this area is character- upwelling, characteristic of much the organic transport is by water understanding of the role of ized as a semi-arid Mediterra- of the Pacific coast of the Ameri- or wind erosion, transport, and lateral fluxes, along with vertical nean-climate regime (cool, wet cas. re-deposition. In the ocean the fluxes, in the carbon balance. winters, warm-dry summers). transport is by wind and tide

Figure 1. Flux tower at “El Mogor”. The cultivated areas are outside the tower’s footprint. Page 14

Lateral versus vertical carbon fluxes

Figure 2: Flux tower on Todos Santos Norte Island. The tower’s height has been increased twofold after this picture was taken. induced horizontal currents tion) with erosional rates, we slopes and 20% with alluvial carbon at ecosystem scales, if (including currents associated used the Revised Universal Soil deposits. The areas with steep there is less oxidation in deposi- with coastal upwelling). The Loss Equation (RUSLE) to model slopes lose carbon from erosion tional areas than in erosional importance of the hypothesis is long-term erosion as a function at a rate of at least 10 tons km-2 areas. -1 that local vertical fluxes of CO2 of precipitation, soil erosivity, yr . By comparison net ecosys- may over-represent the strength land cover/land use, and slope tem production (that is, vertical We have also examined the of CO2 sink (or source) commu- (Smith et al., 2007). This model- flux) is less than about 40 tons carbon isotopic signature of nities, because lateral transport ing has been undertaken with km-2 yr-1. Therefore, the dis- sediments in Todos Santos Bay, is an important linkage between GIS. From data on soil organic placement of material by erosion in order to determine what communities in nature. carbon (SOC), we could also can be of similar magnitude to portion of the organic carbon estimate the erosion rate of net ecosystem production in (OC) in those sediments is ma- In order to compare metabolic SOC. The studied watersheds areas (such as our study area) rine, and what fraction is terres- rates (particularly the difference eastward of Ensenada have 80% with complex topography. This trial in origin (Smith et al., 2008). between production and respira- of the land with steep (erosive) can elevate the sequestration of This becomes a measure of lat- Page 15

Lateral versus vertical carbon fluxes

eral transport of OC between try: one in Baja California Sur, proper description of the spatial- References land and the coastal ocean. We two in Sonora, one in San Luis scale variability of CO exchange Smith, S.V., Bullock, S.H., Hinojosa- 2 Corona, A., Franco-Vizcaíno, E., Escoto- have learned that the sediments Potosi and one in Jalisco. is still lacking. In coastal regions, Rodríguez, M., Kretzschmar, T.G., with maximum amount of ter- The terrestrial tower is located in particular, various processes Farfán, L.M., Salazar-Ceseña, J.M., 2007. Soil erosion and significance for carbon restrial material are most re- at Rancho “El Mogor” in Guada- seem either to enhance or re- fluxes in a mountainous mediterranean- moved from the coast, at the lupe Valley (Fig. 1). We began to duce gas exchange drastically. climate watershed. Ecological Applica- tions 17, 1379-1387. head of a submarine canyon. The collect data in July 2007. The For example upwelling events composition of organic carbon in study site has both evergreen (northwesterly , roughly Smith, S.V., Ibarra-Obando, S.E., Díaz- Castañeda, V., Aranda-Manteca, F.J., the bay is controlled by lateral and summer-deciduous shrubs. parallel to shore) and “Santa Carriquiry, J.D., Popp, B.N., Gonzalez- Yajimovich, O., 2008. Sediment organic transport and deposition as well Preliminary analyses showed net Ana” events (onshore winds) are carbon in Todos Santos Bay, Baja Cali- as marine production and the ecosystem exchange to be of both common in the study area fornia, Mexico. Estuaries and Coasts 31, 719-727. oxidation of part of the terres- about the expected magnitude. and will be of special interest. trial material. March and April, just after the Although pending more analyses Bullock, S.H., Escoto-Rodríguez, M., Smith, S.V., Hinojosa-Corona, A., Sub- In addition to those terrestrial rain season (~332 mm of average of data from the two towers, mitted. Carbon flux of an urban system and marine fluxes, we have ana- in Mexico. lyzed fluxes (both lateral and vertical) of the urban area of “The underlying hypothesis is that a significant fraction Ensenada (Bullock et al., submit- of CO2 fixed by autotrophic-dominated communities is ted). We considered issues such transported as organic matter and oxidized outside as the use of gasoline and other the immediate uptake system. fuels, human metabolism and waste generation, and industrial processes such as cement pro- duction. In this case, this urban annual rainfall), presented the our overall results suggest that area is entirely supported by the higher diurnal amplitude of CO2 lateral transfer and organic car- import of materials and energy. absorption with maximum peaks bon oxidation along the lateral -2 -1 The city of Ensenada emits about of about 10 μmol CO2 m s . In transfer pathway must be con- 6,400 tons C km-2 yr-1. These contrast, during September and sidered in an accounting of or- emissions would require an area October, when the soil was dry, ganic carbon mass balance both of 160 km2 of shrublands to take diurnal carbon uptake had peaks on land and in the ocean. -2 -1 up the carbon emitted from each of only about 1 μmol CO2 m s . km2 of the city. The marine tower was installed contact: In order to understand the dy- on Todos Santos Norte Island, M. Escoto-Rodríguez namics of vertical carbon fluxes about 20 km west of Ensenada Centro de Investigacion Cientifica y de in both the terrestrial and ma- (Fig. 2). We began collecting data Educacion Superior de Ensenada rine environments we are using in August 2008. Most coastal [CICESE] the eddy flux technique. We marine studies have been limited installed two eddy flux towers in to transect studies of insufficient [email protected] the study area. One tower is on duration to capture temporal shrubland, the most common variation and event-scale forcing research team: natural vegetation of this region, of CO2 flux. Intensive research M. Escoto-Rodríguez while the other was installed on at single sites over multiple years S.V. Smith the fringe of a nearby island to is necessary to determine how S.H. Bullock measure marine fluxes. To our the coastal ocean might adjust to knowledge, apart from these changes in climate and water- two towers there are just other shed land use, in order to ex- five towers in the whole coun- trapolate over large areas. A Page 16

CO2 fluxes in semi-arid sites on carbonate substrates located in southeast Spain Penélope Serrano-Ortiz, Enrique Pérez Sánchez-Cañete, Francisco Domingo, Ana Were, Luis Villa- garcía and Andrew S. Kowalski

Arid and semi-arid lands com- interpreted as a biological flux order to understand the func- annual temperature of 12ºC and prise nearly a third of the total (photosynthesis and respiration) tional behavior of such ecosys- mean annual precipitation of ca. land surface (Okin, 2001). These neglecting other processes. tems relating to CO2 exchanges 475 mm. The dominant ground water limited ecosystems are However, some studies have with the atmosphere to predict cover is bare soil, gravel and composed of patches of vegeta- revealed a contribution of geo- their response to climate change. rock (49.1%). The vegetation is tion and bare soil that interact chemical processes to the net diverse but sparse, with pre- In this context, our team com- with each other (Domingo et al., ecosystem carbon balance dominance (% ground cover) of posed of researchers from the 1999). Although such ecosys- (NECB) (Emmerich, 2003; Miel- three perennial species, Festuca Desertification and Geoecology tems are very sensitive to per- nick et al., 2005). In addition, scariosa (18.8%), Hormathophilla group (EEZA, CSIC, Almería) turbations such as climate other recent publications spinosa (6.8%) and Genista pumila and GFAT ( change or drought, little is (Kowalski et al., 2008; Serrano- (5.5%). The other two sites Group, University of Granada) known about their functional Ortiz et al., 2009) demonstrate (“Balsablanca” and established three flux stations behavior, including processes of that abiotic processes can tem- “Amoladeras”), located near sea located in southeast Spain CO exchange. Net CO fluxes porarily dominate terrestrial level and a few km from the 2 2 (Figure 1). The “Llano de los and their determinant processes carbon exchange with the at- coast in the “Cabo de Gata” Juanes” flux site, located at 1600 are keys to characterizing the mosphere in areas with carbon- Natural Park (Almería; 36º56’ m altitude and 25 km from the global carbon cycle and to as- ate substrates that occupy 12– 26.0’’; 2º1’58.8’’W), were estab- coast in the Sierra de Gádor sessing human impacts on eco- 17% of the Earth’s land surface lished in June 2006 and July 2007 (Almería; 36º55’41.7’’N; systems. In such research, CO (Ford and Williams, 1989). Thus, respectively. They have a mean 2 2º45’1.7’’W), was installed in exchange has generally been further research is needed in annual temperature of 18ºC and May 2004. It presents a mean

Figure 1. Flux stations located in southeast Spain in semi-arid ecosystems over carbonate soils: (a) Llano de los Juanes, (b) Balsablanca and (c) Amoladeras. Page 17

CO2 fluxes in semi-arid sites on carbonate substrates

dry period suggest that this be- havior is not directly related to biological processes. Leaf gas exchange measurements to- gether with soil chambers reveal that during dry periods most plants are senescent and soil respiration reaches minimum values. In addition, the WITCH geochemical model (Goddéris et al., 2006) estimates that geo- chemical precipitation processes are far from sufficient to explain the large magnitude of the day-

time CO2 emissions. Initial analy- ses suggest the importance of ventilation processes. This re-

leased CO2 detected by the eddy covariance system is related to 222 variations of CO2 and Rn in the soil and borehole. These preliminary results highlight the need to continue with these investigations in order to deter-

Figure2: Some examples of other techniques used in our study ecosystems: (a) taking soil air samples for stable isotopic analysis, (b) LI-6400 mine the importance of such Portable Photosynthesis System for measuring leaf gas exchange and (c) LI-8100 Soil Chamber for measuring soil respiration and (d) drilling processes in the NECB of semi- a borehole, arid ecosystems over carbonate annual precipitation of 200 mm. gether, the eddy covariance and geochemical processes, to substrates. At both sites, vegetation is domi- technique and meteorological separate net CO fluxes into 2 This research is supported nated by Stipa tenacissima with measurements cannot be applied geochemical and biological com- mainly by the regional govern- presence of biological crust alone to characterize the NECB ponents. ment of Andalusia (project GEO- (20%), but “Balsablanca” has 63% over such ecosystems. In this Flux measurements reveal two CARBO RNM-3721). Serrano- of Stipa tenacissima and 10% of context, several techniques are contrasting CO2 exchange be- Ortiz is funded by post-doctoral bare soil, gravel and rock, combined (Figure 2): (a) stable haviors during two predominant fellowship from the Ministry of whereas the ground cover at carbon isotopic analyses to dis- periods: the growing and dry Science and Innovation. In addi- “Amoladeras” is dominated by cern among different processes seasons. During growth periods, tion, this study is made possible bare soil, gravel and rock (43%), involved in the NECB; (b) port- these sites act as net daily car- by national [Sergio Sánchez-Moral with a 23% of Stipa tenacissima. able photosynthesis and (c) soil bon sinks. Measured CO2 fluxes and Soledad Cuezva, MNCN, All of these sites are character- respiration systems to measure are mostly correlated with light CSIC; Luis Villagarcía, University ized by summer droughts and leaf gas exchange and soil emis- during daytime and can reach of Pablo de Olavide; Cecilio asynchronous annual patterns of sions and estimate photosynthe- maximum CO2 uptake of ca. 6 μ Oyonarte, University of Almería] sunlight and precipitation. sis and respiration rates; (d) mol m-2 s-1 (Figure 3a). However, and international collaboration temporal variations of CO and The goals of making flux meas- 2 during dry periods, they act as with: Belgium [Ivan Janssens and 222Rn (quantitative index of the urements at these sites are the net daily carbon sources with Marilyn Roland, University of effects of natural ventilation) in quantification of the NECB and CO emissions correlating with Antwerp], France [Sylvain Delzon, soil and boreholes to determine 2 its interaction with the water atmospheric turbulence during Regis Burlett and Annabel Porté, the magnitude of CO ventilated balance, and the contribution of 2 daytime and reaching ca. 8 μmol University of Bordeaux; Yves from the lithosphere to the its determinant processes (biotic m-2 s-1 (Figure 3b). Preliminary Godderis, LMTG], The Nether- atmosphere; and (e) biogeo- and abiotic). Taking into account analyses regarding processes lands [Han Dolman, VU Univer- chemical modeling via coupling that these processes act to- involved in such emissions during sity Amsterdam] and Israel [Dan of existing models for biological Page 18

CO2 fluxes in semi-arid sites on carbonate substrates

-2 -1 Figure 3: Carbon dioxide flux behavior (FC, mmol m s ) for two different ecosystems in May 2009. (a) Growing season for the “Llano de los -2 -1 Juanes” site with daytime FC well correlated with incident photon flux density (PPFD, mmol m s ); (b) dry season for “Amoladeras” site with -1 daytime FC well correlated with turbulence (u*, m s ).

measurements of CO2 flux and Yakir and Kadmiel Maseyk, Weiz- evapotranspiration in a Chihuahuan mann Institute's]. Finally our desert grassland. J. Arid Environ. 60, 423-436, doi:10.1016/ research team is open to further j.jaridenv.2004.06.001. collaboration with other scien- Okin, G.S., 2001. Wind-Driven Deserti- tists interested in this line of fication: Process Modeling, Remote research. Monitoring, and Forecasting (Charter References 1). California Institute of Technology Pasadena, California, Pasadena, Califor- Domingo, F., Villagarcía, L., Brenner, A.J. nia, 12 pp. contact: and Puigdefábregas, J., 1999. Evapotran- spiration model for semi-arid shrub- Serrano-Ortiz, P., Domingo, F., Cazorla, Penélope Serrano-Ortiz lands tested against data from SE Spain. A., Were, A., Cuezva, S., Villagarcía, L., Agric. Forest Meteorol. 95, 67-84. Alados-Arboledas, L. and Kowalski, A.S., 2009. Interannual CO2 exchange of a Universidad de Granada, Spain Emmerich, E.W., 2003. Carbon dioxide sparse Mediterranean shrubland on a fluxes in a semiarid environment with carbonaceous substrate. J. Geophys. high carbonate soils. Agric. Forest Res. 114, G04015, [email protected] Meteorol.116, 91-102. doi:10.1029/2009JG000983.

Ford, D.C. and Williams, P.W., 1989. Karst Geomorphology and Hydrology. Unwin Hyman, London, 601 pp.

Goddéris, Y., François, L.M., Probst, A., Schott, J., Moncoulon, D., Labat, D. and Viville, D., 2006. Modelling weathering processes at the catchment scale: The WITCH numerical model. Geochim. Cosmochim. Acta 70, 1128-1147, doi:10.1016/j.gca.2005.11.018.

Kowalski, A.S., Serrano-Ortiz, P., Janssens, I.A., Sánchez-Moral, S., Cuezva, S., Domingo, F. and Alados- Arboledas, L., 2008. Can flux tower research neglect geochemical CO2 exchange? Agric. Forest Meteorol. 148 (6-7), 1045-1054.

Mielnick, P., Dugas, W.A., Mitchell, K. and Havstad, K., 2005. Long-term Page 19

New Mexico elevation gradient Marcy E. Litvak and Andrew Fox

In the last few years, our group pine woodland (Pinus ponderosa, piñon-juniper systems were work are to: has combined existing tower Quercus gambelii) and a subalpine funded through NSF NM- infrastructure with several new mixed conifer forest (Picea engel- EPSCoR and U.S. Forest Service 1) Quantify carbon, water funding opportunities to create a mannii, Abies lasiocarpa) in the and have been operational since and energy balance in six targeted network of tower sites Valles Caldera National Pre- May 2007 and November 2007, biomes that are broadly in six of the major biomes that serve. These towers were in- respectively. These six towers representative of the south- span much of the range in re- stalled in 2006 through an award are in biomes that span 1500 m western U.S. and specifically gional climate and plant func- from the National Science Foun- in elevation in the Southern examine how carbon, water tional types in Central and dation, Science and Technology Rocky Mountain-Mogollon Flo- and energy partitioning var- northern NM (Figure 1). Center for the of ristic Zone and together account ies as a function of vegeta- The two lowest elevation sites semi-Arid Hydrology and Ripar- for ~40% of the total land area in tion type and climate across are in a C4 desert grassland ian Areas (SAHRA) to the Uni- NM. Comparisons of long-term the elevation gradient. (Bouteloua eriopoda ) and a creo- versity of Arizona (http:// climate records, biomass and LAI sote shrubland (Larrea tridentata) www.sahra.arizona.edu/). The estimates between the tower 2) Provide quantitative de- at the Sevilleta National Wildlife two mid-elevation sites are sites and 10 additional randomly scriptions of the sensitivity Refuge and LTER site, 80 km newly established sites in a juni- chosen sites for each biome of carbon, water and energy south of Albuquerque. These per savanna (Juniperus mono- indicate that the tower sites are dynamics in these biomes to sites were originally installed sperma, Bouteloua eriopoda ) (16 representative of these biomes the principal environmental through the NASA-funded Big- km south of Willard, NM on a across the state (Figure 2). drivers, temperature and Foot program as EOS Land Vali- private ranch) and a piñon- The eddy covariance instrumen- precipitation. This is impor- dation Core Sites in 2001 (http:// juniper woodland (Pinus edulis, tation, micrometeorological tant given that climate models www.fsl.orst.edu/larse/bigfoot/ Juniperus monosperma) on private , and processing of all suggest that rising levels of CO2 index/html). The two high eleva- land 8 km south of Mountainair, fluxes is identical for all sites. and other greenhouse gases will tion sites are in a ponderosa NM. The juniper savanna and Our objectives with this net- increase temperature by up to

Figure 1: Biomes and locations at the New Mexico Elevation Gradient Network Page 20

New Mexico elevation gradient

namics of many ecosystems (Loik a piñon -juniper woodland in a et al. 2004, IPCC 2007). collaboration with Thom Rahn Changes in the frequency and and Nate McDowell at Los Ala- amplitude of precipitation or mos National Laboratory, Mike temperature fluctuations can Ryan and Rosemary Pendleton eventually reach threshold or from the USFS and funding from critical points that lead to a DOE EPSCoR. In January 2009, catastrophic shift in ecosystem we installed a second tower in a state (Scheffer et al. 2009). In piñon-juniper woodland <2 km the SW U.S., such shifts are from the existing piñon-juniper already common, often mediated tower, and girdled all of the by disturbances such as wildfire piñon trees >7 cm dbh in early or insect/pathogen outbreaks September (Figure 3) to simulate whose probability increases as the widespread piñon mortality the ecosystem become increas- observed in piñon -juniper ingly stressed. woodlands throughout the SW We are uniquely positioned with due to a combination of drought, our network to take advantage bark beetles and pathogenic fungi of several natural disturbances in 2002-2005 (Allen and Bres- that have triggered widespread hears 1998, Breshears et al. changes in ecosystem structure 2005, 2009; McDowell et al. Figure 2: Auxiliary sites are used to evaluate the represenativeness of NMEG sites in terms of (a) mean annual temperature (MAT), (b) mean annual precipitation (MAP), (c) leaf area across these biomes. In early 2008). With these paired tow- index (LAI) from MODIS, and (d) aboveground biomass. Black dots are auxiliary site data. NMEG sites are indicated by solid squares. 2009, a spruce budworm out- ers, we will be able to quantify break caused widespread defolia- the ecosystem consequences of 4oC by the end of this century, 2000, Cook et al. 2004, Seager tion throughout Central and widespread piñon mortality to and alter precipitation patterns et al. 2007, Wentz et al. 2007, northern NM, including at our carbon, water and energy bal- in the southwestern U.S. (IPCC Zhang et al. 2007, Leung et al. tower site in the subalpine ance in piñon -juniper wood- 2007). Predicted deviations in 2004). spruce-fir ecosystem in the lands. the precipitation regime for this Valles Caldera. In August 2009, Although occurring over a region include increased fre- 3) Quantify biome-specific a wildfire burned through the longer timescale, woody plant quency and/or duration of ex- patterns in how carbon stor- desert grassland eddy covariance invasion in the southwestern US treme events (prolonged age and water use in semi- tower site at the Sevilleta Na- over the last 150 years, has trig- drought or above-average pre- arid ecosystems respond to tional Wildlife Refuge, and we gered an equally dramatic change cipitation), changes in the fre- large scale changes in eco- installed an additional eddy co- in the composition and structure quency of rainfall events of dif- system structure. The expec- variance system 1 km away in of vegetation of the Sonoran and ferent sizes, and shifts in the tation is that predicted climate Nov 2009 in unburned grassland Chihuahuan deserts (Buffington seasonal distribution of precipita- change scenarios will fundamen- to use as a comparison. We also and Herbel, 1965; Archer et al., tion and snow cover (Allen et al. tally alter the structure and dy- initiated our own disturbance in 1988; Archer, 1989; Van Auken,

Figure 3: Panoramic view from flux tower showing piñon mortality subsequent to girdling Page 21

New Mexico elevation gradient

2000). Through a collaboration References ecosystems: climatology and ecohydrol- ogy of the western USA. Oecologia, 141: FluxLetter with Paolo D’Odorico, Stephan Allen, M.R., P.A. Stott, J.F.B. Mitchell, 269–281. deWekker (both from University R.Schnur, and T.L. Delworth. The Newsletter of 2000. Quantifying the uncertainty in McDowell N., Pockman W.T., Allen of Virginia), Jose Fuentes ( Penn forecasts of anthropogenic climate C.D., Breshears D.D., Cobb N., Kolb T., FLUXNET change. Nature, 407: 617-620. Plaut J., Sperry J., West A., Williams State University), Will Pockman Allen, C.D., Breshears, D.D., 1998. D.G. and Yepez E.A. (2008a). Mecha- and Scott Collins (both from Drought-induced shift of a forest- nisms of plant survival and mortality Vol.2 No.4 December, 2009 University of New Mexico), we woodland ecotone: rapid landscape during drought: why do some plants response to climate variation. Proceed- survive while others succumb to are using the desert grassland, ings of the National Academy of Sciences drought? New Phytologist, 178: 719-739. FluxLetter is produced creosote shrubland, and an addi- of the United States of America, 95: 14839-14842. quarterly at the FLUXNET tional tower in the grass- Scheffer M, Bascompte J, Brock WA, Office with support from the creosote ecotone at the Sevilleta Archer, S., C. Sci- Brovkin V, Carpenter SR, Dakos V, fres, C.R. Bassham, and R. Maggio (19 Held H, van Nes EH, Rietkerk M, Sugi- National Science Foundation. to investigate how this increase 88). Autogenic succes- hara G. (2009). Early warning signals for sion in a subtropical savanna: conver- critial transitions. Nature 461: 53-59. in creosote impacts carbon, sion of grassland to thorn woodland, E water and energy dynamics of col. Monogr., 58(2), 111-127. Seager R., Ting M.F., Held I., Kushnir Y., desert ecosystems and if vegeta- Lu J., Vecchi G., Huang H.P., Harnik N., tion-microclimate feedbacks Archer, S. (1989). Have southern Texas Leetmaa A., Lau N.C., Li C.H., Velez J. savannas been converted to woodlands and Naik N. (2007). Model projections promote shrub encroachment in in recent of an imminent transition to a more arid the Southwestern U.S. history? Am. Nat., 134, 545‐561. climate in southwestern North Amer- ica. Science 316: 1181-1184. With this existing network, we Breashears D., Myers O., Meyer C.W., are able to quantify carbon, Barnes F., Zou C., Allen C.D., McDow- Van Au- ell N.G. and Pockman W.T. (2009). ken, O.W. (2000). Shrub inva- water and energy dynamics along Tree die-off in response to global sions of North American semi- an elevation gradient that repre- change-type drought: mortality insights arid grasslands. An- from a decade of plant water potential nual Review of Ecology and Systematics, 31 sents the major biomes of the measurements. Frontiers in Ecology and : 197‐215. semiarid southwestern US. We the Environment, 7: 185-189. Wentz, F.J., L. Ricciardulli, K. Hilburn, encourage people who are inter- Breshears D.D., Cobb N.S., Rich P.M., and C. Mears. (2007). How much more ested in collaborating to contact Price K.P., Allen C.D., Balice R.G., rain will global warming bring? Science, Romme W.H., Kastens J.H., Floyd M.L., 317: 233-235. us. Belnap J., Anderson J.J., Myers O.B. and Meyer C.W. (2005). Regional vegetation Zhang, X., Zwiers, F.W., Hegerl, G.C., die-off in response to global-change- Lambert, F.H., Gillett, N.P., Solomon, S., contact: type drought. PNAS, 102: 15144-15148. Stott P.A., and Nozawa, T. Marcy E. Litvak (2007). Detection of human influence Buffington, L.C. and C.H. Herbel (1965). on twentieth century precipitation Vegetation changes on a semidesert trends. Nature, 448: 461-466. University of New Mexico grassland range from 1858 to 1963.

Ecological Monographs 35:139-164. This issue of FluxLetter was edited, designed and produced by: [email protected] Cook, E.R., C.A. Woodhouse, C.M. Eakin, D.M. Meko, and D.W. Stahle. 2004. Long term aridity changes in the Rodrigo Vargas western United States. Science, 306: Dennis Baldocchi 1015-1018. FLUXNET Office, 137 Mulford Intergovernmental Panel on Climate Hall, University of California, Change (IPCC). (2007) IPCC Fourth Berkeley, CA 94720 Assessment Report – Climate Change ph: 1-(510)-642-2421 2007: The Physical Science Basis. Cam- Fax: 1-(510)-643-5098 bridge University Press, Cambridge.

Leung L.R., Qian Y., Bian X., Washing- We plan to make the FLUXNET ton W.M., Han J. and Roads J.O. (2004). newsletter a powerful information, Mid-Century Ensemble Regional Cli- mate Change Scenarios for the West- networking, and communication ern United States. Climatic Change, 62: resource for the community. If you 75-113. want to contribute to any section or propose a new one please contact the Loik, M.E., Breshears, D.D., Lauenroth, FLUXNET Office. THANKS!! W.K. and Belnap, J. (2004) A multiscale perspective of water pulses in dryland