Effects of multiple changes in climate and atmospheric composition on terrestrial ecosystem structure and functioning in the southeastern United States: a regional synthesis

Hanqin Tian, Auburn University

Co-Investigators: Arthur Chappelka, Hua Chen, Ge Sun, and Shufen Pan, Auburn University

Collaborator: Steven McNulty, USDA Forest Service

Figure 1. Snapshots of the extent of cropland in the southern US in 1860, 1900, 1950, and 2000 (source: Chen et al. 2006).

Abstract

Terrestrial ecosystems in the southeastern United States (SE US) have experienced a complex set of climatic changes, increased atmospheric composition, and land-use and land-cover change. Little is known about how these alterations have affected the structure and functioning of terrestrial ecosystems in the SE US. The overall goal of this proposal is to quantify effects of climate variability and change, increased atmospheric CO₂ and tropospheric O₃, with changing patterns of land use and land cover on structure and functioning of terrestrial SE US ecosystems. Here we propose to synthesize and advance mechanistic understanding of ecological structure (LAI and biomass) and functioning (carbon and water cycling) at a regional scale with an emphasis on the factors that control gross primary production (GPP), net primary production (NPP), evapotranspiration and water yield. Our study will be organized by two linked questions: 1) How have ecosystem structure and functioning changed in the SE US in the past 100 years? and 2) What are the relative roles of multiple stressors of climate and atmospheric composition in affecting the changes in carbon pools and fluxes, and water fluxes at the regional scale?

The two research questions will be addressed through synthesis activities by using a combination of process-based ecosystem modeling, satellite-based observations, field studies and Forest Inventory Analysis (FIA) data. Specifically, we will (1) extrapolate the daily and monthly temperature and precipitation data from about 1200 weather stations in this region to 1 km spatial resolution from 1901 to present; (2) collect and analyze the historical climate extremes including El Niño/Southern Oscillation (ENSO) data, especially with emphases on the Gulf states; (3) reconstruct the tropospheric O₃ data of this region with 1 km spatial resolution from 1901 to present; (4) improve the land-cover change data sets by including spatial distribution of plantations with age information; (5) calibrate the Dynamic Land Ecosystem Model (DLEM) and the Terrestrial Ecosystem Model (TEM) using the FACE and AmeriFlux sites in this region including the Duke FACE (Free Air CO₂ Enrichment) site and the recently established eddy flux site on the eastern coastal plain of North Carolina; (6) conduct multi-simulations with single and combined stressors in climate and atmospheric composition to examine their impacts on ecological structure (LAI, forest age structure, biomass) and functioning (carbon and water cycling), and (7) uncertainty analysis associated with input data, spatial resolution, parameter sensitivity and model assumptions.

This proposed research emphasizes the Focus Area 4 to carry out synthesis research with a spatial scale of entire Southeast region. The products of this research will be made available to the larger scientific community via the web.

Figure 2. Average annual net carbon exchange (NCE) in the southern US (g C.m-2.yr-1). A. 1860-1900; B. 1901-1950; C. 1951-2000; D. 1981-2000. (source: Chen et al. 2006).

Figure 3. Changes in annual mean temperature (A) and annual precipitation (B) during 2002-2050 projected by GISS GCM2 and downscaled by using regional climate model (MM5) (source: Tian et al. 2008).

Figure 4. Equilibrium responses of net primary productivity (NPP) and total ecosystem carbon storage (TOTEC) to contemporary (2002) and projected (2050) climates (source: Tian et al. 2008).

Publications

Tian, HQ. X. Xu, C. Zhang, W. Ren, G. Chen, M. Liu, D. Lu and S. Pan. 2008. Forecasting and Assessing the Large-scale and Long-term Impacts of Global Environmental Change on Terrestrial Ecosystems in the United States and China. In: S. Miao, S. Carstenn, and M. Nungesser (Eds), Real World Ecology: large-scale and long-term case studies and methods. Springer-Verlag, New York.

Sun, Ge, Steven G. McNulty, Jennifer A. Moore Myers, and Erika C. Cohen. (In Press). Impacts of Multiple Stresses on Water Demand and Supply across the Southeastern United States. Journal of American Water Resources Association (JAWRA).

Chen, H., H. Tian, M. Liu, J. Melillo, S. Pan, and C. Zhang. 2006. Effect of land-cover change on terrestrial carbon dynamics in the southern USA. Journal of Environmental Quality 35:1533-1547.

Zhang, C., HQ. Tian, S. Pan, M. Liu, G. Lockaby, E. Schilling and J. Stanturf 2007. Effects of Forest Regrowth and Urbanization on Ecosystem Carbon Storage in a Rural-Urban Gradient in the Southeastern United States. Ecosystems: DOI 10.1007/s10021-006-0126-x

Zhang, C, H.Q. Tian, A. Chappelka, W. Ren, M. Liu and G. Chen (2007). Impacts of climatic and atmospheric changes on carbon dynamics in the Great Smoky Mountain National Park. Environmental Pollution 149 (2007) 336-347.

Tian, H.Q., X. Xu and X. Song. 2007. Drought impacts on terrestrial primary productivity. Journal of Plant Ecology 31(2): 231-241. (in Chinese with English abstract).

Xu, X., H.Q. Tian and S. Wan. 2007. Climate warming impacts on terrestrial ecosystem production. Journal of Plant Ecology 31(2): 175-188. (in Chinese with English abstract).

Ren W. and H.Q. Tian. 2007. Air pollution and terrestrial ecosystem production. Journal of Plant Ecology 31(2): 219-230. (in Chinese with English abstract).

Lu C., H.Q. Tian and Y. Huang. 2007. Ecological consequences of nitrogen deposition. Journal of Plant Ecology 31(2): 205-218. (in Chinese with English abstract).

Lu, A. and H.Q. Tian. 2007. Fire disturbance, global Change and terrestrial primary production, Journal of Plant Ecology 242-251. (in Chinese with English abstract).

Chen, GS and H. Tian. 2007. Effect of land use/land cover change on the terrestrial carbon cycle. Journal of Plant Ecology 31(2): 189-204. (in Chinese with English abstract).