Collaborative Research: Abrupt changes in the structure and function of forest and woodland ecosystems in the Western United States: non-linear responses to changes in

climate, CO2 levels and fire regimesPROJECT SUMMARY

Intellectual Merit: Our interdisciplinary research will test the hypothesis that forest and woodland ecosystems in the Southwestern US are vulnerable to rapid non-linear changes in ecosystem composition, structure and function in response to projected changes in climate and climatic variability, including warmer temperatures and changes in the precipitation regime. The structure and species composition of these systems are determined by interactions among causal agents including climate, fire disturbance history, and pathogens, making it impossible to predict from direct observation the long-term, large-scale consequences of correlated changes in these factors. The key to testing the central hypothesis is consequently to embody each sub-hypothesis in a mechanistic, process-based terrestrial biosphere model that is capable of representing the interactions among the full set of possible explanatory factors, and then to test the model against comprehensive, multi-scale, multi-dimensional observations spanning timescales of hours (eddy flux data), decades (ecological measurements), and centuries (tree rings). The cross-cutting constraints provided by comprehensive retrospective observations in this model framework remove the degrees of freedom that allow the notorious “tuning” of models, allowing us to construct strong quantitative constraints on the interactions postulated in the hypotheses.

We will test 5 inter-related sub-hypotheses to explain rapid changes in ecosystem composition that occurred during the 1950s, and again in 2000-2003, testing the effects of changes in precipitation (H1), temperature (H2), rising atmospheric CO2 (H3), fire management (H4), and beetle outbreaks (H5). The resulting biosphere model will be capable of simulating ecosystem physiology and will link changes in ecosystem structure and function to individual and community response to external forcing.

The model will provide improved understanding of the causes of rapid shifts changes in ecosystem composition and function on ponderosa and pinyon-juniper ecosystems, giving us the capability to more accurately forecast the consequences effects of future environmental changes. We will then apply the constrained regional biosphere model to predict the long-term fate of Southwestern ecosystems over the next hundred years under a range of future climate, CO2 and fire-suppression scenarios. We will also couple the biosphere model to a state-of-the-art mesoscale meteorological model examine the potential role of regional-scale biosphere-climate feedbacks in reinforcing or mitigating changes in ecosystem composition that occur in response to climate variability. This work will test an additional sub-hypothesis (H6), that reductions in evapotranspiration provide positive feedback for the transition from Ponderosa Pinyon-Juniper Juniper-grassland, increasing aridity and inhibiting reversibility.

Broader Impacts:This research will provide much-needed knowledge about the underlying causes of observed rapid

changes in the composition, structure and functioning of Southwestern ecosystems. A key feature of this analysis is to simultaneously consider the impacts of land-use management, fire suppression, climatic effects, succession, and pests and their interactions. Our goal is to develop the capability to predict non-linear changes in vegetation that may arise from increasing climate variation and climate trends. In addition to educating graduate and undergraduate students in a highly interdisciplinary research project, this project will provide educational materials for K-12 students about the dynamic linkages between climate and atmospheric composition, ecosystem composition and disturbance regimes.

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RESULTS FROM MOST RELEVANT PRIOR NSF SUPPORTATM- 0221850 BE/CBC: Continental, Landscape and Ecosystem Scale Fluxes of Atmospheric

Carbon Dioxide (CO2) and Carbon Monoxide (CO) Gases 01/01/03-6/31/07 S. Wofsy, D. Hollinger & P.R. Moorcroft $1,600,000 This ongoing project has improved our understanding of terrestrial carbon sinks by linking process-level biological information obtained for individual plants or ecosystems over short time scales with observations and models that characterize the large spatial domain and long time scales of regional and global concern. We developed RAMS-ED2 a new, regional-scale coupled atmosphere-ecosystem model (see below, Methodology: RAMS-ED2) that was used to integrate data collected across a range of spatial and temporal scales, including tower and aircraft CO2 and water flux measurements and forest biomass inventories, into a constrained biosphere-atmosphere model that accurately captures both slow and fast ecosystem carbon dynamics in New England and Quebec. The model was tested against both atmospheric and ecosystem observations, demonstrating that it can quantitatively link properties of the terrestrial biosphere-atmosphere system with underlying fundamental biological and physical processes. It is now being used to determine the principal sources of long-term trends and interannual variability in carbon fluxes. Publications resulting from this research include:

Moorcroft, P.R. (2006) (Invited Feature). How close are we to a predictive science of the biosphere?   Trends in Ecology and Evolution (in press).   doi:10.1016/j.tree.2006.04.009

Matross, D.M., A. Andrews, M. Pathmathevan, C. Gerbig, J.C. Lin, S.C. Wofsy, B.C. Daube, E.W. Gottlieb, J.T. Lee, C. Zhao, P.S. Bakwin, J.W. Munger, and D.Y. Hollinger. Estimating regional carbon exchange in New England and Quebec by combining atmospheric, ground-based, and satellite data. Tellus 57B, in press.

Ise, T and Moorcroft, PR (2006).   Global-scale temperature and moisture dependencies of soil organic carbon decomposition: analysis using a mechanistic decomposition model   Biogeochemistry (in press).

Albani, M., P.R. Moorcroft, G. C. Hurtt The contributions of land-use change, CO2 fertilization and climate variability to the carbon sink in the Eastern United States. Global Change Biology (accepted).  

Pathmathevan M., S.C.Wofsy, D.M. Matross, X. Xiao, A.L. Dunn, J.C. Lin, C. Gerbig, J.W. Munger, V.Y. Chow, E. Gottlieb (2006). A Satellite-Based Biosphere Parameterization for Net Ecosystem CO2

Exchange: Vegetation Photosynthesis and Respiration Model (VPRM), Global Biogeochemical Cycles (in review)

Medvigy, D., P.R. Moorcroft, M. Albani, R. Avissar, R. L. Walko. (2006) RAMS-ED2: a Coupled Atmosphere-Ecosystem Model: Formulation and Results (in prep.)

Urbanski, S., C. Barford, S. Wofsy, C. Kucharik, E. Pyle, J. Budney, K. McKain, D. Fitzjarrald, M. Czikowsky, J. W. Munger (2006). Factors Controlling CO2 Exchange on time scales from hourly to decadal at Harvard Forest (submitted to J. Geophys. Res. )

Medvigy, D., P. R. Moorcroft, R. Avissar, and Robert L. Walko. (2005). Mass Conservation and Atmospheric Dynamics in the Regional Atmospheric Modeling System (RAMS). Environmental Fluid Mechanics 5: 109-134.

Moorcroft, P.R. (2003). Recent advances in ecosystem-atmosphere interactions: an ecological perspective. Proceedings of the Royal Society Series B: 270:1215-1227.

INTRODUCTIONRecent studies suggest that forests in the Southwestern US may be particularly vulnerable to

rapid, non-linear changes in ecosystem composition in response to climate change. It was observed (Allen and Breshears, 1998) that the ecotone boundary between ponderosa forests and pinyon-juniper woodlands shifted by 2 km in less than 5 years in a broad region of New Mexico during 1950s, and the ponderosa trees never recovered. A regional drought that caused widespread mortality of ponderosa appears to have been the proximal trigger, however, other factors were in play; in particular, the long-term persistence of the vegetation change appears attributable to decadal/centennial shifts in climate, abetted by prior fire-suppression that allowed pinyon-juniper to establish in the understory (Allen and Breshears 1998).

Regional drought recurred in 2000-2003, resulting in widespread mortality, this time of pinyon pine, possibly due to accompanying extremely high temperatures (Breshears et al., 2005). The ecosystem

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now appears to be shifting toward a juniper-grassland —a dramatic degradation from the ponderosa forests just 50 years earlier. These recent rapid changes in ecosystem structure and composition are super-imposed on a backdrop of large-scale shifts in the regional distributions of ponderosa and pinyon-juniper throughout the Holocene in response to the long-term changes in climate and atmospheric CO2 levels.

In this study, we propose to test the hypothesis that the forest and woodland ecosystems of the Southwestern US are vulnerable to rapid non-linear change in ecosystem composition, structure and function in response to projected changes in climate and climatic variability, in order to develop prediction capability for future vegetation of the Southwestern US. Our principal tool will be the Ecosystem Demography Model Version 2 (ED2). We will use ED2 to integrate data for past and present climate and vegetation with information on the ecological and eco-physiological characteristics of these ecosystems. The proposed work will enable us to determine the causes of past changes in vegetation distribution, structure and function and thus better predict how future changes in temperature, precipitation and atmospheric CO2, and fire suppression will affect Southwestern ecosystems.

BACKGROUNDEcology, Biogeography, and Physiology of Ponderosa and Pinyon-Juniper Ecosystems:

Ponderosa pine (Pinus ponderosa) occurs from southern Canada to Mexico, extending from the Pacific coast eastward as far as Nebraska (Figure 1). Moisture commonly limits ponderosa growth throughout its range (Burns and Honkala 1990) and its seedlings are readily killed by fire, but larger individuals are fire-resistant. More than 100 insect species attack ponderosa pine, with the western pine beetle (Dendroctonus bevicomis) the most common cause of mortality of mature trees (Burns and Honkala 1990). Pinyon pine (Pinus edulis) is co-dominant with juniper (Juniperus spp.) in pinyon-juniper woodlands that span the semi-desert zone, covering approximately 42.7 million ha from Texas to California (Burns and Honkala 1990). Areas that shift from ponderosa to pinyon-juniper often show increased soil erosion (Allen and Breshears 1998, Davenport et al. 1998). In both pinyon and ponderosa, recruitment pulses tend to occur during the first sustained wet period following a drought (e.g., Betancourt et al. 1996).

The Southwestern U.S. is characterized by highly seasonal precipitation and climate, with an arid fall, a variable winter/early spring, an arid late spring and fore-summer, and a relatively rainy summer (Swetnam and Betancourt 1998). As a result, drought is a key limiting factor for Southwestern forests (Meko et al. 1995). Climate scenarios for the region predict higher temperatures and increased precipitation variability (see the Climate Projections section below), suggesting increased frequency and intensity of droughts such as observed in the 1950s and 2000-03. Predicted increases in air temperature are likely to raise leaf temperatures and thus vapor pressure deficits, increasing water stress even in the absence of drought. The evapotranspiration (ET) rates of trees in the Southwest are poorly quantified, but ET seems to be dominated by the evaporation term, and to be sensitive to individual rain events (Kurc and Small 2004). During the summer monsoon season observed ET ranges from 0.5 – 4.0 mm day-1, with a seasonal average of 2 mm day-1 (Kurc and Small 2004, see also Lane and Barnes 1987).

Future changes in temperature or precipitation could alter species distributions across major portions of the region (Breshears et al. 2005). Relevant physiological attributes of ponderosa and pinyon-juniper are reasonably well known. Pinyon-juniper woodland species have higher radial growth and water use efficiency (WUE) during drought than ponderosa (Adams and Kolb, 2004), but net photosynthesis of pinyon drops off very rapidly with small (~2oC) increases in temperature (Barnes & Cunningham 1987), while ponderosa increases their root:shoot ratios (Maherali & DeLucia. 2000) in warmer conditions. In response to rising CO2,Ponderosa exhibits an acclimating growth response (Johnson et al 1997) without significant change in stomatal conductance (Maherali & DeLucia. 2000), while pinyon and juniper appear to decrease their stomatal conductance (Edgar and Koch 2000). Historical reconstructions of plant communities from materials found in packrat middens in the Southwest indicate that the rising aridity and increasing CO2 concentrations during the last de-glaciation resulted in desert shrubs replacing woodlands across much of the Southwest (Van de Water 1994; Betancourt 1990), consistent with this behavior.

The goal of our proposed work is to determine the environmental causes of rapid, non-linear ecological changes in composition, structure and function of woodland and forests ecosystems

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of the Southwestern US. If the predicted changes in climate and climatic variability occur, the observed replacement of ponderosa by pinyon-juniper, and subsequent conversion to juniper-grasslands, may continue to progress, implying radical changes in Southwestern ecosystems.

Rapid Shifts in Ecosystem Structure and Function Induced by Climate Variability: Data from the two droughts described in the introduction imply that semi-arid ecosystems in the

Southwest are prone to rapid and extensive shifts in vegetation in response to temperature and moisture anomalies. Large-scale mortality and permanent replacement of existing vegetation appears to have occurred when climate stress exceeded a threshold: during the severe regional drought of the 1950s (Figure 2), the ecotone boundary between ponderosa pine forests and pinyon-juniper woodland shifted by up to 2 km in just 5 years (Figure 3). The transition was documented by aerial photographs taken between 1935 and 1975, supplemented by measurements of living and dead ponderosa and of stem diameter increments at plots along the elevation gradient (Allen and Breshears, 1998). Additional measurements of stem diameter increment at plots along the elevation gradient (Allen and Breshears, 1998) highlighted how this shift was fundamentally caused by moisture stress, but was exacerbated by a stress-induced outbreak of bark beetles that amplified the drought-caused mortality.

The die-off of ponderosa pine released pinyon and juniper that had become established in the sub-canopy as a result of prior fire suppression (see Figure 4); the capability of pinyon and juniper to utilize near-surface water then exacerbated water stress on ponderosa and helped drive the vegetation transition. The vegetation change has persisted over the following ~50 years since the drought.

A second drought throughout the region in 2002-2003 induced pinyon mortality (Breshears et al, 2005). Total precipitation during 2000-2003 was not as low as during the 1950s regional drought, but temperatures were notably higher (Figure 2). Widespread mortality occurred on more than 12,000 km2 (1.2 million ha) in Utah, Colorado, Arizona and New Mexico, causing detectable changes in NDVI that were confirmed by regional aerial surveys and field inventories (Figure 5). Extensive mortality occurred even at high elevations, near the upper limit of pinyon distribution, in contrast to the 1950's drought that caused ponderosa mortality only at lower elevations. The impacts of these historical droughts imply that precipitation amounts and timing, temperatures, CO2 levels and past fire suppression interact non-linearly to control moisture availability, and thus the dynamics of growth, death and recruitment of different plant species in Southwestern ecosystems, and may presage the consequences of future climate change.

Climate Projections and Their Implications for Ponderosa and Pinyon-Juniper EcosystemsProjections of regional climate change from simulations of Atmosphere-Ocean General Circulation Models (AOGCMs) are generally viewed as highly uncertain, due to the relatively low resolution of the models, and the lack of convincing treatment of vegetation-atmosphere interactions (Houghton and Yihui, 2001). However, increased aridity in semi-arid regions of the Southwest, particularly during in summer (Figure 6), is a robust feature arising from basic thermodynamics and atmospheric circulation. Warmer climate exponentially increases potential evaporation, and atmospheric divergence over the Southwest US ensures export of water from the region, leading to reduced availability for plants.

In this proposal we investigate the effects of these climatic changes on regional vegetation. Current AOGCMs use very simple parameterizations of vegetation-climate interactions, and many do not simulate current vegetation. More sophisticated treatments are not justified in the current state of ignorance about vegetation-climate interactions. We plan to address this deficiency by developing a constrained terrestrial biosphere model to make credible predictions of climate change impacts on Southwestern vegetation.

OBJECTIVES AND HYPOTHESESThe objective of this research is to test the hypothesis that ponderosa and pinyon-

juniper ecosystems in the western United States are vulnerable to rapid non-linear changes in vegetation structure, composition and function in response to changing climate and atmospheric composition, and prior disturbance history. Our approach is to use a structured terrestrial biosphere model capable of assimilating a diverse, comprehensive array of long- and short-term observations available for these ecosystems. The ED2 model

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will be used to test 5 inter-related sub-hypotheses: that recent changes vegetation were caused by changes in: precipitation (H1), temperature (H2), rising atmospheric CO2 concentrations (H3), the history of fire management (H4), and bark beetle outbreaks (H5). A sixth sub-hypotheses will be tested, (H6) that there is a positive feedback between shifts from Ponderosa to grassland, lower ET, and increased aridity. The hypotheses will be embodied in different model formulations that will be tested against recent and historical observations of vegetation dynamics and ecosystem physiology in the region. METHODOLOGY

The structure and composition of Southwestern forest and woodland ecosystems are determined by a complex interactions involving the differential performance of different plant species in relation to their environment (light availability, moisture availability, temperature, and atmospheric CO2 concentrations), the modifying effects of plants on these environmental quantities, and the interactions between plant communities and fire disturbance regimes and pathogen outbreaks. The existence of multiple causal agents, the complex, multi-way interactions between species, and the long time scales and large spatial scales of the process, make it impossible to determine the causes of change in ecosystem structure and composition directly from either observations or experimental manipulations. The key to testing the central hypothesis is consequently to embody each sub-hypothesis in a mechanistic, process-based terrestrial biosphere model that is capable of representing the interactions among the full set of possible explanatory factors, and then to test the model against comprehensive, multi-scale, multi-dimensional observations. The cross-cutting constraints provided by comprehensive retrospective observations in this model framework remove the degrees of freedom that allow the notorious “tuning” of models, allowing us to construct strong quantitative constraints on the interactions postulated in the hypotheses.

The Ecosystem Demography Model Version 2 (ED2) is the framework that will be used to evaluate the different hypotheses for the causes of rapid change in the ecosystems of the Southwestern US. As described below, ED2 is unique amongst biosphere models its ability to link short-term, physiological responses to environmental conditions with realistic, long-term changes in ecosystem structure and composition, and to capture accurately the effects of sub-grid scale disturbances such as fires and pathogen outbreaks (Moorcroft 2006). To simulate sub-grid scale ecotone shifts over decadal time scales, we will reconstruct past climate at high resolution using downscaling methods (PRISM) in conjunction with historical station data. We will then test the sub-hypotheses embodied in ED2 against a diverse set of observations of ponderosa and pinyon-juniper structure, composition and function. The resulting biosphere model will have demonstrated capability to simulate ecosystem physiology and will link changes in ecosystem structure and function to individual and community response to external forcing. It will improve our understanding of the causes of rapid shifts changes in ecosystem composition and function, and allow credible forecasts of the ecosystem consequences of future environmental changes.The Ecosystem Demography Model Version 2

ED2 is an integrated terrestrial biosphere model incorporating hydrology, land-surface biophysics, vegetation dynamics and soil carbon and nitrogen biogeochemistry (Moorcroft 2003, Medvigy et al. 2006). The fast timescale fluxes of carbon, water, and energy between the land surface and the atmosphere are captured using leaf photosynthesis and soil decomposition modules coupled to a multi-leaf layer and multi-soil layer biophysical scheme (Figures 7 & 8). As in the original ED model (Moorcroft 2001, Hurtt et al 2002), ED2 is a structured ecosystem model that tracks long-term changes in the biophysical, ecological, and biogeochemical structure of the land surface using a system of partial differential equations that capture the dynamic changes in the sub-grid scale structure and composition of the ecosystem within each grid cell that result from the fast-time scale ecosystem dynamics playing out over yearly, decadal, and centennial timescales (Moorcroft et al. 2001, Moorcroft 2003). With this system of equations, ED2 is also able to accurately capture the dynamics of competition within plant communities, and incorporate the impacts of sub-grid scale disturbances on the structure and function of the land-surface within each grid-cell, including natural disturbances such as wind-throw and natural fires, and anthropogenic disturbances such as land-conversion and anthropogenic fire activity (e.g. see

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Hurtt et al. 2002). ED2 can interface with the TOPMODEL land-hydrology scheme (Walko et al. 2000) to predict surface and sub-surface patterns of lateral water transport.ED2 Model Optimization

A recent analysis, conducted as part of our NSF BE project (see Prior Results) analyzing terrestrial carbon dynamics in the Northeastern US, demonstrated the use of ED2 to assimilate eddy-flux and forest-inventory measurements to test hypotheses for the underlying causes of short-term and long-term ecosystem dynamics (Figure 9). ED2 was initialized with the observed canopy composition and ecosystem structure in the footprint of the Harvard Forest flux tower, and then fitted to the 1995 and 1996 hourly, monthly and yearly CO2 and ET flux data, and to observed basal area growth and mortality in these years (blue box in Figure 9a)1. Prior to optimization, the model significantly underestimated the seasonal cycle of Net Ecosystem Productivity (CO2 fixation measured by eddy flux) and significantly over-estimated rates of tree growth and mortality (measured biometrically), i.e. what appeared in the wood was not consistent with was removed from the atmosphere. After fitting, the model accurately captured the observed fluxes of CO2 and H2O, canopy growth, and mortality over timescales spanning hours to decades (Fig. 9a).

We then evaluated the performance of the optimized ED2 at a different site, Howland forest (Fig-ure 9b). The model was initialized with the observed canopy composition in the tower footprint, but model parameters were not re-optimized. Despite the markedly different forest composition between the Howland and Harvard Forest sites (conifer-dominated as opposed to mixed-hardwood), there was a sub-stantial improvement in model predictions of the 5-year CO2 flux record, and measured tree growth and mortality dynamics at Howland (Figures 9c and d). The original and optimized parameter values are shown in Table 1. The optimized values all fell within the specified acceptable ranges for each parameter. As the table shows, changes in parameters responsible for the improved goodness-of-fit include: an in-creased maximum photosynthetic rate of hardwoods, a marked increase in the rate of fine root turnover, and a decrease in the carbon allocation to fine roots in conifer species.

The ability to constrain the carbon allocation formulation through this use of multiple data con-straints is particularly significant since this aspect of ecosystem models plays a critical role in determining rates of plant growth and thus rates of above-ground biomass accumulation, but are nearly impossible to measure directly. The transferability between very different ecosystems provides confidence that the opti-mization of the model actually tests the hypotheses embodied in its formulation, rather than being a trivial exercise in model “tuning”.

RAMS-ED2As well as running as a stand-alone terrestrial biosphere model, ED2 can be run coupled to the

Regional Atmospheric Modeling System (RAMS) to simulate the long-term, regional-scale 2-way interaction between the atmosphere and biosphere. RAMS is based on the full set of dynamical equations

1 The parameters of the decomposition model were constrained in a separate below-ground optimization.

Parameter Initial FinalVm*(hw) 1.0 1.59Vm*(c) 1.0 1.21 0.020 0.0202M 8.0 7.15kw 16.8 26.8q (hw) 1.0 1.04q (c) 1.0 0.23rgrowth

(hw) 0.33 0.53rgrowth

(c) 0.33 -rfine-root

(hw) 0.2 0.11rfine-root

(c) 0.2 0.046fine-root 0.33 3.91stored

(hw) - 0.65

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Table 1. Initial and optimized values of the parameters optimized against the Harvard Forest flux-tower and forest inventory measure-ments shown in Figure 9. The list includes 3 leaf-level parameters: the maximum photosynthetic capacity of hardwoods and conifers relative to the initial value for each of the six plant functional types Vm

*(hw) and Vm

*(c), the slope of relationship between stomatal conductance & CO2 flux per unit leaf area m, and the rate of leaf respiration 1 hydrologic parameter: water availability per kg of fine root carbon kw; 2 allocation parameters: the fraction of carbon allocated to fine roots relative to leaves in hardwoods and conifers q (hw), q (c); 4 respiration parameters: fine-root respiration in hardwoods and conifers rfine-root

(hw) , rfine-root(c) and

the fraction of carbon allocated to growth that is lost to growth respira-tion rgrowth

(hw) , rgrowth(c) ; 2 turnover rates: fine root turnover fine-root and,

in hardwoods, a stored carbon turnover stored(hw) that replaces the

growth respiration tem rgrowth(hw).

that govern atmospheric motions, supplemented with parameterizations for turbulent diffusion, solar and terrestrial radiation, moist processes including the formation and interaction of clouds and precipitating liquid and ice hydrometeors, sensible and latent heat exchange between the surface (multiple soil layers, vegetation canopy, surface water) and the atmosphere, and the kinematic effects of terrain and of cumulus convection (Pielke et al., 1992). RAMS can simulate atmospheric dynamics at spatial scales ranging from grid sizes of a few of meters to hundreds of km. Two-way interactive grid nesting in RAMS allows simultaneous resolution (using local fine mesh grids) of hill-slope environmental gradients, atmospheric systems such as thunderstorms, and regional and synoptic scales. The fully-coupled nature of the RAMS-ED2 means that it can be used to examine potential feedbacks between regional-scale atmospheric forcing (temperature, sunshine, precipitation) and vegetation cover (affecting latent and sensible heat fluxes, albedo, roughness (c.f. Sternberg, 2001). These interactions can modify ecosystem responses to changes in climate, and modify regional climate itself, making the coupling between vegetation and climate a key component of predictions of regional vegetation change.

PRISM Climatological DownscalingEstimates of the regional amounts and spatial distribution of monthly and annual precipitation,

obtained from long-term meteorological records, are a critical input for this study. Study of changes in ecosystem structure and composition requires downscaling these data from regional to landscape scale. The PRISM (Parameter-elevation Regressions on Independent Slopes Model) is an expert system that uses point data and a digital elevation model (DEM) to generate fine-scale gridded estimates of climate parameters (Daly et al., 1994), as will be required for this study. PRISM is designed specifically to capture the small-scale topographic variability in climate in that occurs in the western US, using the DEM and a windowing technique to group stations onto individual topographic facets. PRISM develops a weighted precipitation/elevation (P/E) regression function to predict precipitation at the elevation of each cell using data from nearby stations, with greater weight given to stations with location, elevation, and topographic positioning (e.g. aspect) similar to that of the grid cell. In a model comparison, PRISM exhibited superior performance to various methods of kriging in Oregon, and has been successfully applied to the entire United States with excellent results.

Similar methods have been successfully used to downscale GCM model output in predictions of future climate (e.g. Wilby et al., 1997). Using both observed and GCM-derived predictor variables and diagnostic statistics, it is possible to downscale past climate from station data and future climate from GCMs to produce consistent past and future climate statistics at the ecotone scale (e.g. Landman et al., 2001; cf. Wilby and Wigley, 1997, 2000).Datasets for Model TestingThe proposed work will be built on the extensive available measurements of the effects of climate variability on the short-term physiology and long-term vegetation dynamics of Ponderosa pine forests and pinyon/juniper woodlands. Data sources include: eddy-flux measurements on instantaneous rates of carbon assimilation and evapotranspiration; a 4-year dataset of precipitation, temperature, soil moisture levels, tree mortality rates and NDVI measurements at Mesita del Buey NM; ground-based inventory observations documenting changes in ecosystem composition, structure and biomass spanning years to decades; and record Monthly climate data are available for all of the US from 1890 to present with spatial resolution of 2.5-arc min (~4 km) for temperatures (min, max, mean), dewpoint, and precipitation from the Spatial Climate Analysis Service (SCAS – see Table 4), plus tree-ring width data that span decades to centuries (see Tables 2 and 3).

PROPOSED WORKTask 1: Testing Hypothesized Effects of Climate, Disturbance History and CO2 Forcing in causing Historical Changes in Ecosystem Structure, Composition and Function The formatting is messed up here, and it results in losing a lot of space. Will have to be fixed but I could not do it with Word 2000. Microsoft products are really loathsome!

Table 2 Site-Level Measurements for validation of the ED2 Short term physiological responses to climateMeasurement locations Time period References

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(frequency)A. Metolius Oregon eddy flux-tower site

Net fluxes of CO2, H2Omomentum and heat

Ponderosa forests in eastern slopes of Cascades. 3 towers in Young (25 y), moderate (90 y) and old (250 y) stands

1996 - present (hourly)

Law et al 2003Insolation, temperature, humidity, soil moisture

Sap flow 2001-2002 Irvine et al., 2004B. Blodgett California eddy flux-tower siteNet fluxes of CO2, H2O,

momentum and heat Ponderosa plantation on western slope of the Sierra Nevada California

1999 - present (hourly)

Goldstein, et al.,2000 (updated) Insolation, temperature, humidity,

soil moistureSap flow 2000-2001 Kurpius et al, 2003C. Black Hills, South Dakota eddy flux-tower site

Net fluxes of CO2, H2O, momentum and heat Ponderosa forest 2004-present

(hourly)

Meyers (un-publ.). Data

avail. From Ameri-FluxInsolation, temperature, humidityD. Utah Juniper woodland eddy flux-tower siteNet Flues of CO2, H2O,

momentum and Heat Juniper woodland1999-present(hourly)

Leffler et al, 2002

Insolation, temperature, humidityE. Mesita del Buey Northern NM

Temperature, precipitation soil moisture Pinyon - Juniper woodland

(150 m x 100 m plot)

1989-2003 (bi-weekly)

Breshears et al (2005) Martens et al (1997)

NDVI 1989-2003 (weekly)Tree mortality Pre and post 2000 die-off

i) Effects of the 1950s drought on the ponderosa pinyon-juniper ecotone at Frijolito Mesa: A key test of model’s ability to simulate the likely effects of future timescales will be its ability to correctly capture the effects of the 1950s drought on ecosystem structure and composition. The ED2 model will be initialized with the ecosystem composition and structure indicated from the pre-drought aerial photographs. ED2’s predictions for the effects of the 1950s drought obtained will be directly compared against (i) the observed ecotone shift that occurred in New Mexico (Figure 3A), and (ii) the extent of ponderosa mortality as a function of elevation and topographic index (Figure 3B). ii) Patterns of mortality and changes in leaf area and soil moisture during 2000-2003 at Mesita del Buey: A second key metric will be the ability the different model formulations to capture the observed changes in soil moisture, leaf area and tree mortality at Mesita del Bey following the 2000-2003 drought.iii) Ecosystem dynamics measured at flux-tower and forest inventory sites: The hourly, monthly and yearly dynamics of CO2 uptake, evapotranspiration and annual rates of tree growth predicted by the different model simulations will be evaluated against site-level measurements of these quantities at the sites listed in Table 2, and a subset of the forest inventory plots across the region listed in Table 3 and plotted in Figure 5.

The approach to assessing the different model formulations will be similar the one used to develop the ED2 model formulation for the dynamics of Northeastern forest ecosystems (see Methodology section and Figure 9): a non-linear maximum likelihood fitting procedure will be used to estimate the unknown parameters of the ecosystem model, and AIC used to assess the statistical significance of changes in the goodness-of-fit of model when the different forcing terms are included in the model simulations. The physical characteristics for each site (soils and elevation, slope and aspect) will be specified from ground-based observations if available, or else from the datasets listed in Table 4. The climatological drivers for the simulations will be specified from the high-resolution SCAS dataset (Table 4), downscaled using PRISM to capture fine-scale, topographic-related variability in climate. The downscaled monthly climatological data will then be used to construct hourly temperature, moisture and humidity drivers for ED2 using the WGEN approach of Wilby and Wigley (1997), in which precipitation is represented as a first-order, two-state Markov process of daily rainfall occurrence, with precipitation amounts simulated using gamma distributions derived from station data. Hourly temperature and humidity statistics will be generated similarly using the 100-year variation of monthly means plus hourly-daily-monthly deviations derived by fitting the past 100 years to first-order Markovian time series, including temperature,

Table 3: Datasets for calibration and validation of the long-term vegetation dynamics of the ED2 land surface model

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VARIABLE Dataset TEMPORAL SPATIAL ReferenceExtent Resolution Extent Resolution

Changes in canopy composition / structure

Ecotone shift site

Aerial photo analysis Multi-year Northern NM

elevational gradient 1:5000 Allen and Breshears 1998; Allen 1989

NDVI dataset 1989-2003 weekly SW pinyon-juniper ecosystems 1km Breshears et al. 2005

Above-ground biomass by species

United States Forest Inventory

1985-2005 5-15 years AZ, CO, NM, NV, UT 7.3 m radius plots http://www.fia.fs.fed.us/

Metolius, Pringle Butte, Blacks Mountain

Single survey Single Survey

27 plots at 3 sites in central OR & northern CA

1ha tree inventory plots Youngblood et al.,2004

Woolsey plots and modern resurvey

Historical (1909-1913)Contemporary(1997-1999)

84-90 years

Arizona/ New Mexico

2-6 ha historical plots, 1.01 ha contemporary re-sampling

Moore et al, 2004

Stand dynamics(growth, mortality, recruitment, age structure)

Mesita del Buey Mortality measurements

Pre- and post 2000 die-off survey

Multi-year Northern NM plot 100m x 150m Breshears et al. 2005, Martens et al. 1997

United States Forest Inventory

1985-2005 5-15 years AZ, CO, NM, NV, UT 7.3 m radius plots http://www.fia.fs.fed.us/

Woolsey plots and modern resurvey

Historical (1909-1913)Contemporary(1997-1999)

84-90 years Arizona/ New Mexico

2-6 ha historical plots, 1.01 ha contemporary resampling

Moore et al, 2004

Timber inventories 1920-1990 5-10 years Single stand N AZ 800m x 400m Biondi, 1999

Vegetation Plots Survey Single

Survey1409 plots in AZ, NM, and S. CO 375 m2 Muldavin et al., 1990

Dendrochronology (disturbance history and growth response)

Ponderosa Pine 1950-2000 Annual 2 ecotone forests in

N AZ15 plots of 10 trees Adams et al., 2004

Walhalla Plateau plots 1757-1995 Annual North Rim Grand

Canyon, AZ 5 20x50m plots Mast and Wolf, 2004

Ponderosa Pine 300 year Annual Rocky Mountain

Nat'l. Park CO 9 plots Ehle and Baker, 2003

Ponderosa Pine and Juniper

545 year Annual Central OR -- Pohl et al., 2002

δ13C and tree ring 1985-1995 Seasonal 500km transect AZ-

NM 8 sites Leavitt et al., 2002

Tree-ring chronology

Several centuries Annual Single stand N AZ 800m x 400m Biondi, 1999

temperature precipitation, and humidity. Literature values will be used to specify the initial physiological and ecological attributes of a series of different plant functional types representing the range of species found across the region, including explicit representations of ponderosa, pinyon and juniper.

Table 4. Input datasets for the offline ED2 model simulationsQuantity Spatial resolution Time period ReferenceECMWF ERA-40 45-year climate 2.5° x 2.5° 1957-2002 Kallberg et al. 1999

Spatial Climate Analysis Service (SCAS) 2.5 arc minute 1890-present http://www.ocs.orst.edu/prism/

Soils 1:100000 N/A Miller and White, 1998 Topography 2 arc sec. Vert. Res: 10m N/A http://edc.usgs.gov//products/elevation/

dem.html

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Table 4. Input datasets for the offline ED2 model simulationsFire History 1° x 1° 1900-2000 Mouillot and Field (2005)Land Cover and Land-use Change Variable 1 km to 0.5o 1700-present Hurtt et al 2005

Friedl et al 2002

Task 2 Testing the hypothesis for the effects of fire disturbance historyThe second task will be to test the hypotheses that the history of fire suppression across the

region was a significant factors in facilitating the rapid changes in vegetation that occurred during the 1950s and 2000-present (H4)

The fire regime in the Southwestern US has changed considerably over the past hundred years (Figure 4). At the inter-decadal timescale, patterns of fire intensity are linked to change in the SOI index (Swetnam and Betancourt 1990); however, underlying this climate-driven inter-decadal variability is a long-term decrease in fire frequency over most of last century due to human fire suppression activities (Swetnam and Betancourt 1990).

The effects of fire disturbance history manifest themselves through changes in ecosystem structure and composition. In the context of the ED2 model simulations performed under Task 1, these alter the initial condition that defines the state of the ecosystem prior to the two drought events, which in Task 1 had simply been prescribed. The ED2 biosphere model has an existing simple fire sub-model that predicts the fraction of each grid-cell that burns each year due to natural fires, with the extent of fire activity varying as a function of the sub-grid scale distribution of moisture conditions and fuel availability within each grid cell. Testing the hypothesis that fire suppression was a significant factor in affecting the consequences of the 1950s and 2000-present droughts (H3) will occur in two steps:

(1) We will test whether fire suppression significantly altered regional fire regimes, and forest and woodland ecosystem composition prior to the rapid shifts in ecosystem composition, structure and function that occurred in the 1950s at Frijolito and 2000-2003 at Mesita del Buey. This will be evaluated by modifying the ED2 fire model to incorporate a time-dependent fire suppression term. The significance of fire suppression for ecosystem composition will then be evaluated by testing whether the inclusion of fire suppression terms into the ED2 fire sub-module significantly improve the ability of the ED model formulation developed under Task 1 to simultaneously predict: (i) the ecosystem structure and composition prior to the 1950 at Frijolito and the 2000-present vegetation shift recorded at Mesita del Buey (see Tables 2 and 3); (ii) the regional historical pattern of burned area Mouillot and Field (2005) 1o1o global fire history dataset (Table 4) interpolated onto the ED2 grid with the seasonal pattern of fires specified from the observed seasonality in fire frequency and burn area in Southwestern ecosystems (Barrows 1978); (iii) the century-scale and inter-decadal patterns of fire frequency variability (Swetman and Betancourt 1990). As in Task 1, the different model formulations will be evaluated by using a non-linear maximum likelihood fitting procedure to estimate the unknown parameters of the fire model and then using AIC to assess the statistical significance of changes in the model’s goodness-fit of fit with and without fire suppression forcing.

The regional-scale simulations will be performed by implementing the calibrated ED2 model formulation developed under Task 1 on an unstructured polygon-based grid that reflects the spatial heterogeneity in climate and soil types found across the Southwestern region (Figure 1)2. The attribute of each polygon will be specified from the datasets listed in Table 4. The model will then be spun-up for 300 years, with climate driver data for the first 200 years generated from the Spatial Climate Analysis Service (SCAS) historical regional dataset (Table 1) in conjunction with WGEN as described under Task 1. The final 100 years of climate driver dataset will be specified directly from the SCAS data set. The regional land-use history forcing will be specified from the Hurtt et al (2005) land-use history reconstruction (

(2) We will then test whether the changes in ecosystem composition arising from fire suppression significantly contributed to the rapid shifts in vegetation that occurred during the 1950s at Frijolito and 2000-present Mesita del Buey by comparing the ability of ED2 model simulations with and without the fire suppression term to capture the ecotone shift observed the observed changes in soil moisture, leaf

2 A description of simulations using the ED model irregular grid can be found in Albani et al 2006. In the proposed study ~1000 polygons would be used to cover the region shown in Figure 1. This is comparable to a 1 o x1 o grid with 20 sub-grid scale patches representing fine-scale topographic (aspect elevation and slope) heterogeneity.

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area and tree mortality at Mesita del Bey following the 2000-2003 drought. The magnitude of the fire suppression effect will be determined by comparing the differences in ecosystem composition and structure that dynamics occur in the simulations that include and exclude the history of fire suppression.

Task 3: Regional Scale Vegetation patterns and dynamics The third task will be to evaluate the model’s ability to accurately capture the observed regional patterns of vegetation composition, structure and dynamics.

As employed in the Northeast (see Figure 9), the predictive ability of the constrained model will then be tested against flux tower and forest inventory data not used for the model calibration and hypothesis testing. The model’s predictions of patterns of vegetation composition and structure across the region at the end of the simulated will be evaluated against to the observed spatial distribution of ponderosa and pinyon-juniper ecosystems across the Southwestern region (Figure 1) and the inventory-based measurements of forest structure and forest growth and mortality rates listed in Table 3. In addition, ED2’s predictions of decadal-to-century scale variability in rates of tree diameter growth will be compared against the long-term data from tree ring increments across the Southwest (Table 3)Task 4: Role of bark beetles in causing ecosystem change

The third task will focus on testing whether bark beetle infestation was a significant factor in driving the rapid ecosystem changes observed during the 1950s and 2000-present (H5)

Tree mortality that occurred during the recent droughts was associated with bark beetle infestations. While beetle-caused mortality appeared to be proximal cause of tree death, the underlying cause of appears to be periods of severe water stress during which trees cannot generate sufficient sap to defend themselves against bark beetle attack (Waring and Cobb 1992, Allen and Breshears 1998, Shaw et al. 2005, Breshears et al. 2005, Mueller et al. 2005). Evaluating the significance of bark beetles as an agent of tree mortality, that acts either independently or additively with the effects of climatic factors, is a challenge due to the absence of detailed data on the incidence of bark beetle infestation in relation to tree mortality, and the difficulties of developing realistic dynamical models of beetle abundance.

We will evaluate the significance of bark beetles as a driver of ecosystem change in two ways. First, we will compare the spatial pattern of tree mortality predicted by constrained ED2 model formulation developed under Tasks 1-3, to the observed patterns of tree mortality measured in by the Forest service aerial surveys (See figure 5B) to determine to what extent climate, CO2 and disturbance history factors alone can account for the observed patterns of tree mortality. The spatial patterns of mortality that arise from these influences will be distinct from the spatial patterns associated with beetle population expansion. Second, since the aerial surveys identify only dead trees and not the actual cause of death, we will perform an additional analysis using data on the extent of mortality actually caused by bark beetles from the USFS Forest Inventory and Analysis (FIA) plot measurements. We will use these data in conjunction with the aerial surveys and model predictions to determine what fraction of the regional scale mortality documented in the regional surveys is attributable to bark-beetle activity, to what extent this mortality is increased relative to background levels, and how closely bark-beetle mortality is linked to increased drought stress. Task 5 Forward model simulations and tests of climate-vegetation feedback (H6)

The final part of the study will be a prospective analysis in which we use the constrained model to predict the future state of forest and woodland vegetation in the Southwestern US over the next 100 years. The goal of these simulations will be to explore whether the predicted changes in temperature, moisture and CO2 are likely to result in rapid non-linear shifts in vegetation across the region, the extent to which these responses may be altered by changes in fire suppression. In addition, we will perform a series of coupled RAMS-ED2 simulations to assess whether regional-scale biosphere-atmosphere feedbacks tend to reinforce the effects of past or future changes in ecosystem composition and structure (H6).

Two available projections of future climate will be used in the prospective analysis: (1) the GFDL CM2 runs at (Knutson et al., 2005, available on the web) and (2) the IPSL (Pasteur Institute) runs (Hourdin et al., 2005) which we have already obtained from P. Ciais et al. To investigate long-term dynamics, the GCM climate projections will be downscaled to represent changes in regional climate using

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PRISM and the WGEN approach described under Task 1. Downscaled future precipitation will be linked to current climate by perturbing WGEN parameters in proportion to the changes in the GCM from present and future. Temperature statistics will be generated in a similar manner. For each set of climate projections, we will perform runs with and without CO2 forcing, and with and without fire suppression.

Output from the historical simulations conducted under Task 3 and the prospective simulations conducted under Task 4 will be used to initialize a series of coupled RAMS-ED2 simulations that will examine potential regional-scale feedbacks between changes in ecosystem structure and composition, and changes in future climate. For example, replacement of ponderosa by pinyon-juniper may affect latent heat fluxes and thus regional cloudiness, buoyancy generation, and Convective Available Potential Energy (CAPE). To assess the quantitative importance of these feedbacks on regional scales, we will conduct three 10-year simulations in which RAMS-ED2 is initialized with pre-1950s drought, post-1950s drought, or post 2000-2003 drought ecosystem structure and composition, and then forced with the GCM output for the period 2003-2012. We will then perform a 10-year simulation in which RAMS-ED2 is initialized with the predicted ecosystem composition for 2050 obtained from the offline model simulations, and run for the period 2050-2059; and similarly, a 10-year simulation initialized with the predicted ecosystem composition for 2090 and run for the period 2090-2099.

TASK SUMMARY TABLETask/ hypotheses to be tested

Spatial Scale Simulations Datasets for Evaluation Key predictions for distinguishing hypotheses / model evaluation

Task 1:Environmental Forcing(H1-H3 precipitation, temperature, CO2)

Site–level: sites include:- Frijolito (ponderosa die-off site)- Mesita del Buey (pinyon die-off site)- ponderosa and pinyon flux tower sites- subset of forest inventory plots

Factorial series of simulations that include/exclude: precipitation variability, temperature variability, temporal pattern of CO2

- changes in ecosystem composition at Frijolito during 1950s at Frijolito. Extent to which ponderosa mortality occurred as function of elevation and topography- 2000s-present die-off of pinyon and soil moisture levels at Mesita del Buey- hourly, monthly, and annual dynamics of CO2 uptake, evapotranspiration at flux tower sites - annual rates of growth at forest inventory sites

Can precipitation alone account for the both the 1950s die off at Frijoloito and the 2000-present die-offs at Mesita del Buey?

Is temperature variability a necessary driver for capturing the 2000-present die-off at Mesita del Buey?

Is increasing CO2 a necessary driver for capturing the 1950s die off at Frijoloito and the 2000-present die-off at Mesita del Buey?

Task 2:Fire History (H4)

Regional simulations on unstructured polygon grid - site-level simulations at Frijolito (ponderosa die-off site) & Mesita del Buey (pinyon die-off site)

Simulations with and without time-dependent fire suppression terms

- ecosystem structure and composition prior to the 1950s at Frijolito ecotone shift site - ecosystem structure and composition prior to the 2000-present pinyon die-off at Mesita del Buey.-long-term regional trends in bunred area- long-term & inter-decadal patterns of fire frequency variability

H4a The history of fire suppression across the region significantly affected the regional fire disturbance regime and ecosystem structure & composition at Frijolito prior to the 1950s die-off, and at Mesita del Buey prior to 2000-present die-off

H4b The history of fire suppression across the region was a significant factor in facilitating the 1950s ecotone shift and the 2000s die-off.

Task 3: Regional Simulations

Regional simulations on unstructured polygon grid

Regional simulation of constrained model developed under Tasks 1 & 2

- regional-scale patterns ofecosystem composition, growth and mortality

Does the model capture the regional patterns of ecosystem composition and patterns of growth and mortality?

Task 4: Beetle Dynamics (H5)

Regional simulations on unstructured polygon grid

Analyze patterns spatial of mortality that occurs in simulations performed under Task 3

- spatial patterns of mortality measured by forest service

- regional patterns of NDVI change.

If regional predictions predict pattern of die-off then Bark beetles are merely the proximal cause of the death following extended water stress and associated carbon costs

Are there anamolus areas of mortality not associated with moisture stress?

Regional Use constrained ED2 model Forward model simulations - Regional scale maps and

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Task 5: Forecasts to predict woodland and forest states over next 100 years; perform coupled ED2-RAMS simulations to asses if regional-scale atmosphere-biosphere feedbacks ; downscale GCM predictions with PRISM; runs with and without CO2 and with and without fire suppression

forecasting over next 100 yearsF1. GFDL RunsF2. ISPL Runs

changes relative to current and past;

TIMELINEYear 1:

1. Assembly and downscaling of SCAS climatological driver datasets.2. Compilation and quality control assessments of validation datasets.3. Parameterization of plant functional types.4. Testing of sub-hypotheses 1-3 regarding the role of changes precipitation, temperature and atmospheric CO2 concentrations in causing rapid ecosystem change by performing a factorial experiment using ED2 model and site-level measurements of: CO2 fluxes at the pinyon and juniper flux-tower sites; soil moisture and mortality dynamics at during 2000-present at Mesita del Buey; a sub-set of regional forest inventory-based measurements of rates of tree growth and mortality; and the changes in forest composition observed during the 1950s at the ecotone site.

Year 2:1. Verification of regional, inter-decadal scale dynamics of ED2 against regional-scale measurements of above-ground ecosystem structure and ecosystem dynamics.2. Test the effects of fire disturbance history (sub-hypothesis 4) by incorporating a fire suppression terms into the ED2 fire sub-model and evaluating its ability to predict the composition at the ecotone site and Mesita del Buey and against regional-scale patterns of decadal – century fire frequency data.

Year 3:1. Test sub-hypothesis 5 regarding the importance of bark beetle infestation a significant factor in driving the rapid ecosystem changes observed during the 1950s and 2000-present.2. Downscaling of GCM surface climatology fields to ecosystem model grid.3. Long-term, regional scale simulations of calibrated ED2 ecosystem model to predict the consequences of future temperature and precipitation changes and increasing atmospheric CO2 for ecosystem composition, structure and function. 4. Use model long-term regional-scale simulations to construct ecosystem die-off response surfaces and spatial distributions for future climate change and atmospheric CO2 levels.

5. Coupled ED2-RAMS simulations to assess potential importance of regional-scale biosphere-climate feedbacks.

MANAGEMENT PLANThe main project tasks will be performed at Harvard University with assistance from David

Breshears’ lab at the University of Arizona. The Harvard group will be responsible for evaluating the performance of the ED2 biosphere model in simulating short-term and long-term changes in ecosystem composition, structure, and performing coupled ED2-RAMS simulations to assess potential importance of regional-scale, biosphere-climate feedbacks. The Breshears lab will provide assistance with evaluation of ED2 model performance at capturing the consequences of the 1950s and 2000-present drought, and determining the effects of soil-moisture on ponderosa and juniper mortality. Breshears is also a member of the NSF-funded Drought Impacts on Regional Ecosystems network (DIREnet), and will ensure coordination between this research and other research projects on Southwestern ecosystems.

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BROADER IMPACTSScientific community: The proposed work will deliver a structured terrestrial biosphere model that

quantitatively describes the changes in vegetation cover, ecosystem structure, and plant function in the Southwest in response to multiple environmental changes, including: (1) temperature, (2) precipitation, (3) temperature (4) CO2, and (5) fire management.

The model will ingest and assimilate a very broad and comprehensive suite of data sets, including ecological measurements, remote sensing data, eddy flux data, and downscaled climate data. It will be rigorously validated using observed shifts in ecotone locations and in vegetation structure in response to past climate changes. The model will be applied to assess and to understand past changes in vegetation cover in the Southwest. It will be applied to the prediction problem for vegetation in a changing climate, by running the model with two AOGCM scenarios (downscaled to the ecotone level) for climate in the 21st century. The coupled interaction of climate change with vegetation change will also be assessed. This work will also deliver tabulated datasets for downscaled climate, model inputs and outputs, and model source codes and optimized model parameters that will be made available to the scientific community and the public, both directly and as a contribution to the NSF-funded Drought Impacts on Regional Ecosystems network (DIREnet).

K12 Education One month of salary per year has been included for an existing outreach specialist at Harvard to oversee the development of a targeted website for high school students that will enable K12 students to learn about the relationships between climate, vegetation and disturbance regimes. An additional theme will be highlighting the strengths of interdisciplinary approaches to addressing complex environmental problems. In addition, Moorcroft has a record of giving lectures in local high schools in the Boston area about his research and its relevance to society.

Training of undergraduates, graduates and post-docs: (i) All the PI’s have records of involving undergraduates in their research and mentoring undergraduate theses. Many of these students have since gone on to graduate school. In addition to the institutional funds available at both Harvard and Arizona universities for undergraduate research, we have budgeted funds to support a undergraduate student during the academic year at Harvard throughout the duration of the project. (ii) The proposal includes three years of support for a graduate student at Harvard. The nature of the research addressed by this proposal provides an ideal forum for graduate training in ecosystem ecology and climate science. To foster an integrated research experience, Breshears will serve as co-advisors on the committee of the graduate student at Harvard, and the graduate student will participate in the joint project meetings. (iii) The PI’s have effectively integrated research activities into formal teaching programs and Moorcroft has also begun a new Global Change Biology course at Harvard (OEB157).

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