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Now available in PDF format: Abstract Book [7.4 Mb] (posted 10 November 2005)

Abstracts for Posters

Ecosystems (P-EC)

Sub-Theme 4: Projections

P-EC4.1

A Modeling Study of Climate-Ecosystem Interaction Over North America

Ming Chen, Climate Change Research Center, University of New Hampshire, Durham, NH 03824, mchen@gust.sr.unh.edu

Huiting Mao, Climate Change Research Center, University of New Hampshire, Durham, NH 03824

Robert Talbot, Climate Change Research Center, University of New Hampshire, Durham, NH 03824

We used a regional climate version of the MM5 mesoscale atmospheric modeling system that was asynchronically and simultaneously coupled with the biogeographical model BIOME to explore vegetation-climate interactions over North America. The impact of climate change due to increased greenhouse gases on potential ecosystem evolution was assessed, and a future scenario of vegetation distribution was explored. Doubled CO₂ conditions induced strong high-latitude warming, while the southern U.S. became cooler in winter. Across almost all of the model domain precipitation tended to increase in all seasons with the highest intensification found over the Northeast, Southeast, and the Great Plains. In response to this future climate scenario, vegetation migrated northward systematically in the eastern United States. In particular, strong warming under the doubled CO₂ condition was simulated at high latitudes, and subsequently the sparsely vegetated area around Hudson Bay was predicted to be covered by cool conifer forests in the future warming climate. Over the Great Plains and part of the Midwest, water supply is the crucial factor that affects natural vegetation evolution, and more precipitation under doubled CO₂ led to temperate deciduous forests extending toward north and northwest. Grasslands in the northern half of the Great Plains will be replaced by cool conifer and mixed forests due to more precipitation in the future. However, no systematic changes in vegetation were predicted over the Rocky Mountains and Cascades in the West, partly due to the complex terrain and unsystematic changes in temperature and precipitation in the region. Averaged over the whole model domain, 39% of vegetation types has changed under doubled CO₂. Above results are based on model simulations using 108 km resolution, and they will be compared with runs using 50 km resolution to study the potential impact of model resolution on regional ecosystem response to climate change.

[Poster PDF]

P-EC4.2

Transient Dynamics of Vegetation Response to Past and Future Major Climatic Changes
in the Southwestern United States

Kenneth Cole, USGS Southwest Biological Science Center, Flagstaff, AZ, Kenneth.Cole@NAU.EDU

Kirsten Larsen, Merriam-Powell Center for Environmental Research, Northern Arizona University, Flagstaff, AZ

Phillip Duffy, Lawrence Livermore National Laboratory and University of California, Merced

Samantha Arundel, Department of Geography, Planning and Recreation, Northern Arizona University, Flagstaff, AZ

Predicting the effects of major climatic change on plant species requires both knowledge of the plant's climate tolerances as well as an understanding of the transient dynamics of massive change on ecological communities. The climatic tolerances of species can be modeled through geostatistical analyses of their Twentieth Century ranges and climates. These models can then be applied to GCM predictions of future climates in order to plot future regions of potential acceptable climates for each species. Unfortunately, in the topographically diverse southwestern U.S., these models of future potential climate space are of limited use unless they can be extrapolated to a meaningful landscape scale. In our research, we have modeled plant distributions, Twentieth Century climates, future GCM modeled climates, and future potential climate space for several species to a ~1 km grid scale. Future seasonal climate values were developed from monthly ~75 km output from the CCM3 model results downscaled using the delta-change technique. These modeled future distributions only represent areas where a species could potentially persist, not areas where a species is likely to occur. In order to distinguish a species' future potential climate range from its future likely range, we have designed spatial models incorporating the dynamics of change, especially migration. These models are parameterized using fossil data from species response to past examples of rapidly warming climate. Recent data from the desert southwest suggest that at the end of the Younger Dryas Period, 11,600 years ago, winter minimum temperatures rose at least 4.1 degrees C over a time span of less than 200 years. This abrupt temperature warming is the most recent analog in both pace and magnitude and for the changes expected in this region over the next 100 to 150 years. Abundant plant fossil records allow reconstruction of the ecological dynamics and plant migrations in response to this sudden warming event. Our results thus far demonstrate dramatic differences in future projected distributions for plant species, both in terms of the extent of their potential climate space and in their ability to respond to changing climates. For example, two large desert succulents characteristic of the
southwestern deserts respond in opposite ways the projected changes in climate. The potential range of Joshua Tree (Yucca brevifolia) is not only reduced and shifted northward by climate change, but the plant's lack of dispersal mechanisms should reduce its actual extent by at least 90%. In
contrast, the potential range of giant saguaro, (Carnegia gigantea) expands in all directions from its current range, and the plant's dispersal, aided by numerous animal vectors, should ensure its capability to take advantage of much of this expanded range.

[Poster PDF]

P-EC4.3

Potential Widespread Forest Dieback in North America: What is the Price of Uncertainty

Ronald P. Neilson, USDA Forest Service, Corvallis, Oregon

James M. Lenihan, USDA Forest Service, Corvallis, Oregon

Dominique Bachelet, Oregon State University, Corvallis, Oregon

Raymond J. Drapek, USDA Forest Service, Corvallis, Oregon

F.I. Woodward, University of Sheffield, Sheffield, England

M. Lomas, University of Sheffield, Sheffield, England

The VINCERA investigators

The dynamics of North American "natural" ecosystems were assessed under 6 future climate scenarios and included changing carbon balance,
vegetation distribution and fire disturbance. The VINCERA project ( Vulnerability and Impacts of North American forests to Climate: Ecosystem Responses and Adaptation) is an intercomparison among three dynamic general vegetation models (DGVMs). The scenarios are from the Canadian Climate Centre (CGCM2), the Hadley Centre (HADCM3) and Australia (CSIRO-MK2), each using two SRES trace gas emissions scenarios, A2 and B2. The three DGVMs are MC1, IBIS and SDGVM. We will present results from MC1 and SDGVM at a minimum, and possibly IBIS as well. SDGVM shows continual growth in all biomes through the 21st century; while MC1 shows an "early greenup—later browndown in most biomes." The difference is due to the direct CO₂ effect wherein SDGVM demonstrates a productivity and water use efficiency increase from current to 700 ppm CO₂ of about 58% compared to a range of 13 to 19% for MC1. The MC1 simulations produce a period of growth followed by significant dieback especially in eastern U.S. forests under all scenarios. The point of turnaround from greenup to browndown occurs about now for the temperate forests and about a decade from now in the boreal forests. The boreal forests shift into the taiga-tundra open woodland, but then experience another dieback in mid-21st century. There are also excursions of the central grasslands into the boreal forest zone. Dieback is triggered under two mechanisms. Reduced regional precipitation, variable among the scenarios, is one mechanism for dieback. However, a more insidious and pervasive effect is due to the influence of rising temperatures on evapotranspiration (ET) and the lengthening of the growing season. Even with the benefits of enhanced water use efficiency from elevated CO₂ and slight increases in precipitation, increases in temperature can produce widespread, very rapid forest dieback, followed by infestations and fires. Large areas of the eastern U.S. appear to be particularly vulnerable to this sequence of processes, as does the central boreal forest, due to the relatively flat regional climates. Dieback is driven by both increasing temperatures and decreasing precipitation in some regions under some scenarios, notably the Southeastern U.S. and the Northwestern U.S. Fire suppression can mitigate much of this loss, but will be costly. These results underscore the critical importance of addressing the uncertainties with respect to ecosystem water balance and the direct effects of elevated CO₂ concentrations.

[Poster PDF]

P-EC4.4

Vulnerability of Northern Prairie Wetlands to Climate Change: Implications for Waterfowl

Glenn Guntenspergen, USGS, glenn_guntenspergen@usgs.gov

Carter Johnson, South Dakota State University,

David Naugle, University of Montana

The Prairie Pothole Region (PPR) lies in the heart of North America and contains millions of glacially-formed, depressional wetlands embedded in a landscape matrix of natural grassland and agriculture. These wetlands provide valuable ecosystem services and produce 50-80% of the continent's ducks. We explored the broad spatial and temporal patterns across the PPR between climate and wetland water levels and vegetation by "moving" a wetland model (WETSIM) among 18 stations with 95-year weather records. Simulations suggest that the most productive habitat historically for breeding waterfowl would shift under a drier climate from the center of the PPR (Dakotas and southeastern Saskatchewan) to the wetter eastern and northern fringes, areas currently less productive or where most wetlands have been drained. Unless these wetlands are protected and restored, there is little insurance for waterfowl against future climate warming. WETSIM can assist wetland managers in allocating restoration dollars in an uncertain climate future.

P-EC4.5

Eastern Deciduous Forest Responses to Climatic Change Drivers: An Upland-Oak Forest Case Study

Paul J. Hanson, Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge Tennessee 37831-6422, hansonpj@ornl.gov

Stan D. Wullschleger, Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge Tennessee 37831-6422

Jeffery S. Amthor, U.S. Department of Energy, Office of Science, Germantown, Maryland

Mechanistic ecosystem models represent the scientific communities' primary method for evaluating complex multi-scale responses to climatic change, and the logical tool for testing hypotheses about ecosystem responses to specific scenarios of change. In this poster we provide examples of the abilities and limitations of ecosystem models to handle current environmental variations for upland-oak forests of the eastern United States and discuss their use for predicting forest responses to future climatic conditions. Current ecosystem models for deciduous forests are equipped to reproduce short-term physiological responses for historical environmental conditions, but have more difficulty capturing responses to past extremes (e.g., severe drought). An ensemble mean of multiple model outputs was shown to produce robust near-term predictions for a case-study upland-oak forest, and such an approach is likely to benefit model simulations conducted in support of other decision making processes.

Model simulations are only as good as experimentally derived knowledge of plant and ecosystem responses to environmental change. The ability of plants to acclimate to environmental change over time, the development of internal feedbacks from biogeochemical cycles, and changes in the seasonality of ecosystem processes all represent indirect, experimentally observed response drivers that must be incorporated into ecosystem models. Data for an upland-oak forest indicate that existing model codes need to incorporate "lessons learned" from large-scale experimental manipulations of temperature, elevated CO₂, ozone and precipitation to avoid serious over or under predictions of long-term ecosystem responses. Furthermore, although many models have been developed to simulate carbon, water, and energy exchange between forests and the atmosphere, comparatively few mechanistic models are equipped to simulate long-term productivity changes and mortality patterns that are of primary interest to decision makers. Conversely, models designed to predict plant succession typically have insufficient mechanistic rigor to incorporate the key physiological adjustments by plants and ecosystems revealed from experimental work.

A key goal of the U.S. Climate Change Science Program is to understand the potential consequences of global change for ecological systems. Few ecosystems, however, have been adequately studied in sufficient detail to derive policy-relevant conclusions directly from experimental data. Our results from experiments and modeling of upland-oak forests indicate that ecosystem forecasts relevant to decision making must be mechanistically sophisticated and based on rational scenarios of future climatic change if they are to logically address effects of future environmental changes.

Funding for this work was provided by the U.S. Department of Energy (DOE), Office of Science.

[Poster PDF]

P-EC4.6

Rising Atmospheric Carbon Dioxide as a Factor in the Success of Invasive Weeds

L.H. Ziska, Weed Ecologist, Crop Systems and Global Change Laboratory, USDA-ARS, 10300 Baltimore Avenue, Beltsville, Maryland 20705, lziska@asrr.arsusda.gov

Because international trade has increased the biotic mixing of flora across the globe, unwanted plant species are becoming widely established. The severity of damage induced by these species and their panoptic scale have produced a new class of unwanted plants, termed "invasive" or "noxious" weeds. Such invasive species are present in both managed (e.g. Canada thistle in agriculture) and unmanaged systems (e.g. cheat-grass in chaparral). To determine whether rising levels of atmospheric carbon dioxide (CO₂, the principle global warming gas) has been a factor in the success of such species, we have compared the potential response to recent and projected increases in CO₂ relative to other plant groups. Overall, data from our laboratory and other researchers indicates that invasive, noxious weeds, on the whole, have a larger than expected growth response to increasing CO₂ levels above the pre-industrial baseline. There is also increasing evidence that rising CO₂ can, in fact, preferentially select for these invasive, noxious species within plant communities. In addition, there is initial data suggesting that chemical control of such weeds may be more difficult in the future. However the small data set available to researchers and policy makers make such conclusions problematic, and emphasize the urgent need for additional investigations to address the biological and economic uncertainties associated with the role of rising CO₂ in the success and spread of invasive weeds.

[Poster PDF]