Progress 10/01/05 to 09/30/10
Outputs
OUTPUTS: During the executive year (10/01/2005-09/30/2010), the project has produced the major outputs as follows (Organized as tasks): Task 1 Development and improvement of data sets. (1)Climate data: We have reconstructed historical climate data sets (including daily average, maximum, and minimum temperatures, dew point, and precipitation) for the Southeastern United States (SEUS) from 1895 to 2007; (2)Tropospheric ozone pollution data during 1940-2007; (3) Annual land use data sets for the period 1700-2007; (4)Cropland N fertilization data during 1945-2007; (5)Forest plantation area data during 1930-2040; (6)Collection of site and regional level observational data for model calibration and validation; (7)Remote sensing data for model input and validation: we collected MODIS LAI/NPP/GPP/ET for validating corresponding model results. In addition, based on the 30-meter resolution Landsat TM/ETM data set, we generated forest mortality data for Mississippi and Alabama states during 1984-2007. Task 2 Model development and improvement. An urban carbon cycle sub model was developed for the Dynamic Land Ecosystem Model (DLEM) during the project period to better simulate the urbanization impacts on carbon (C), water and nitrogen (N) cycling. A sub model for forest management and disturbance was also developed to address the impacts of forest disturbance (e.g., fire, insects, and hurricane) and management (e.g., forest harvest, fertilization, and site preparation). To improve the simulation accuracy of C cycle, we further improved the water cycle processes in DLEM through including the processes of multiple soil layers (10 layers), water and C transport between land and water bodies, and multiple driving forces for soil water movement. Task 3 Model evaluations at the site, watershed, and regional levels. The model results (such as soil C and N content, forest biomass, crop yield, plant NPP, and ET) were validated against field observational data and regional inventory data. The validation activities were carried out at 3 scales: site, watershed to regional scales. Task 4 Assessing the impacts of multiple environmental factors to ecosystem structure and function at multiple scales. (1)Impacts and contributions of multiple environmental factors on ecosystem C storage in the SEUS; (2)Estimates of NPP, ET, and water use efficiency in the SEUS; (3)Drought impacts on NPP and C storage in the SEUS; (4)Impacts of long-term land use change on C storage; (5)Impacts of cropland N fertilization on global warming potential; (6)Impacts of continuous forest disturbance on Cstorage: case study for Alabama and Mississippi; (7)Potential impacts of increased forest plantation area and intensive forest management practices on C storage during 1925-2040; (8)Impacts of climatic and atmospheric changes on C dynamics in the Great Smoky Mountains National Park; (9)Response of fuel load to future changes in climate and atmospheric composition; (10)Impacts of urbanization on C balance of terrestrial ecosystem in the SEUS from 1945 to 2007; (11) Effects of forest regrowth and urbanization on ecosystem C storage in a rural-urban gradient: case study for 3 counties in West Georgia. PARTICIPANTS: 1) Dr. Hanqin Tian is the Project Director, working on orgnaizing and managing the project and the obtained results; 2) Guangsheng Chen is a PhD graduate student working on forest management and disturbance modeling and analyzing data and research results; 3) Xiaofeng Xu is a PhD graduate student working on wetland ecosystem model; and 4) Chi Zhang is a PhD graduate student working on dynamic vegetation modeling and urban ecosystem modeling and involving in data generation and model results analysis. TARGET AUDIENCES: Climate change researchers, carbon cycle science community, urban planner, policy makers, and land managers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
(1)Net C sink during 1895-2007 was about 0.71 Pg C in the SEUS, which was primarily due to the effects of CO2 fertilization and followed by forest regrowth on previous cropland, and elevated N deposition. Our analysis indicated that climate fluctuation controlled interannual variations in C fluxes, while land use change dominated the decadal pattern.(2)NPP decreased significantly for large areas in the east under drought impacts during 1895-2007, while increasing in the west. NPP was noted to decrease up to 40 percent in some areas during extreme droughts. Changes in precipitation patterns caused C emissions of 0.16 Pg in the SEUS. The western SEUS (dry region) acted as a C sink, while the east (water-rich region) acted as a C source, which implied that the eastern SUS could face more serious droughts in the future though this region has a higher rainfall than that in the west. To reduce drought impacts and maintain ecosystem stability, we therefore suggested that irrigated cropland area and industrial water use should decrease in the east for the future.(3)C storage has decreased about 0.21 Pg due to urbanization effects during 1945-2007. We predicted a larger C emission in the future due to faster urbanization rate in the SEUS.(4)N fertilization has greatly increased C storage by 296 Tg in the SEUS cropland during 1945-2007, while N2O emissions were also enhanced by 2.97 Tg N. Combining the global warming potential (GWP) of both gases, N fertilization was a net source that enhanced the GWP by 304.6 Tg CO2. The GWP increased after mid 1970s and its effects for increasing C storage were saturated, suggesting that further increases in N fertilizer would not significantly stimulate C sequestration. To decrease GWP and maintain high crop yield in the future, our suggestions to the policy makers and land managers are to increase crop N use efficiency rather than N fertilizer amounts.(5)Disturbance in Mississippi and Alabama has caused a 1.3 percent annual mortality for forests during 1984-2007, resulting in a net C source of 0.23 Pg. Although small disturbance events may not significantly change forest structure, the legacy effects of disturbance on C storage could last over 100 years. Such estimations and predictions are valuable for forest managers to take appropriate measures to maintain forest ecosystem sustainability.(6)Increased forest plantation area and improved genetics increased C storage in the SEUS during 1925-2040. Longer forest rotation length could increase C storage and reduce N2O emission. An extension of 20 years above current forest rotation length could result in an additional C sequestration of 1200 g C/m2. N fertilization in forest resulted in higher NPP and C storage; however, the concomitant increases in N2O partially offset its functions for mitigating GWP. Slash burning could slightly increase NPP and forest biomass in a short term; however, the decreases in litter and soil C make slash burning a C source. Although large uncertainties exist, this study could help the local policy makers and land managers to understand the consequences of different management practices in a large-scale view and offer valuable guidance.
Publications
- Schwalm, C.R., C.A. Williams, K. Schaefer, R. Anderson, M.A. Arain, I. Baker, T.A. Black, G. Chen, P. Ciais, K.J. Davis, and other NACP participants. 2010. A model-data intercomparison of CO2 exchange across North America: Results from the North American Carbon Program Site Synthesis. Journal of Geophysical Research, 115, G00H05, doi:10.1029/2009JG001229.doi:10.1029/2009JG001229.
- Tian, H., X. Xu, M. Liu, W. Ren, C. Zhang, G. Chen, and C. Lu. 2010. Spatial and temporal patterns of CH4 and N2O fluxes in terrestrial ecosystems of North America during 1979-2008: application of a global biogeochemistry model. Biogeosciences 7: 2673-2694.
- Xu, X., H. Tian, C. Zhang, M. Liu, W. Ren, G.S. Chen, C. Lu, and L. Bruhwiler. 2010. Attribution of spatial and temporal variations in terrestrial methane flux over North America. Biogeosciences 7: 3637-3655.
- Zhang, C., H. Tian, X. Xu, W. Ren, A. Chappelka, D. Hui, M. Liu, C. Lu, S. Pan, and G. Lockaby. 2010. Impacts of urbanization on carbon balance of terrestrial ecosystem in the Southern United States from 1945 to 2007. (In revision)
- Zhang, C., H. Tian, Y.H. Wang, T. Zeng, and Y.Q. Liu. 2010. Predicting response of fuel load to future changes in climate and atmospheric composition in the Southern United States. Forest Ecology and Management 260: 556-564.
- Chen, G. 2010. Effects of disturbance and land management on water, carbon, and nitrogen dynamics in the terrestrial ecosystems of the Southern United States. PhD dissertation. Auburn University, Auburn, AL.
- Xu, X. 2010. Modeling methane and nitrous oxide exchanges between the atmosphere and terrestrial ecosystems over North America in the context of multifactor global change. PhD dissertation. Auburn University, Auburn, AL.
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: The primary activities, events, and products during this fiscal year (2009/1-2009/12) include: 1) All the data required for model simulation and result validation have been collected. 2) We have completed the model running for simulating carbon fluxes and storage in the southeastern United States. The modeling results have been analyzed and several papers have been submitted/accepted based on the analysis. 3) We finished the validation of model results. 4) We finished generating long-term (1950-2007) spatial data for forest harvest area, intensity and distribution, and forest age structure using remotely sensed data (TM/ETM+ data) and forest inventory data. 5) We presented the results from this project in the Second International Forests and Water Conference. Raleigh, NC, USA. 6) A PhD student (Chi Zhang) was graduated. He was supported by this project and his dissertation was based on the results of this project. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The results from this project will enable the public to be aware of the effects and interaction of multiple environmental stresses (including climate extreme such as drought, increasing atmospheric CO2, ozone pollution, N deposition, land-cover, and land-use change and disturbances) on carbon storage, forest and cropland productivity, and available water resources, which will also help the public to understand the major controls on the ecosystem carbon balance. The study for carbon and water interaction indicated that drought (or decreased water availability) could greatly decrease the net primary productivity of forest and cropland in the southeastern United States. However, vice versa, although it will increase carbon storage and thus reduce atmospheric CO2 concentration, large area of afforestation/reforestation could greatly reduce the water availability to human and the nature. Therefore, we conclude that a balance between carbon storage and water availability should be maintained in the future to keep the ecosystem health in the southeastern United States.
Publications
- Tian, H., G. Chen, M. Liu, C. Zhang, G. Sun, C. Lu, X. Xu, W. Ren, S. Pan, and A Chappelka. 2010. Model estimates of net primary productivity, evapotranspiration, and water use efficiency in the terrestrial ecosystems of the southern United States during 1895-2007. Forest Ecology and Management doi:10.1016/j.foreco.2009.10.009.
- Zhang, C., 2008. Terrestrial carbon dynamics of southern United States in response to changes in climate, atmosphere, and land-use/land cover from 1895 to 2005, Ph.D Dissertation, Auburn University.
- Tian, H., G. Chen, et al. 2009. Impacts of multiple environmental changes on water and carbon cycles in the terrestrial ecosystems of the Southeastern United States. The Second International Forests and Water Conference. Raleigh, NC, USA. September 14-19, 2009. Oral presentation.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: The primary progress we have made in the fiscal year (2008/1-2008/12) includes: 1) We ran the DLEM at many other sites provided by North America Carbon Program to recheck the model behaviors and reevaluate the model results. The model results were evaluated against 36 sites for the effects of land use and land cover change, natural disturbances, and human management on carbon sequestration and fluxes. 2) We have refined the historical land use/cover change data. Previously, we have developed the historical land use/cover change data (from 1895 to 2002) based on the NLCD 1992 TM images and the data resolution is 8 km * 8 km. Based on the newly classified NLCD 2001 Landsat TM/ETM images and historical inventory data of urban, forest and cropland, we regenerated the historical land use/cover change data sets (1 km * 1 km spatial resolution from 1895 to 2007). 3) The DLEM model was used to simulate the carbon cycle under conditions with land management and without natural disturbance for the entire southeastern United States. We are currently analyzing the model results and preparing a paper; 4) We are developing spatial data on forest area distribution, forest disturbance types and intensity and forest age structure by using remotely sensed data (TM/ETM+ data). These data have a resolution of 30 m * 30 m and processed in cooperation with a research group in the University of Maryland. Currently, these data sets cover all the 13 states in the southeastern United States and have a long time period from 1984 to 2007. PARTICIPANTS: 1) Dr. Hanqin Tian is the Project Director, 2) Guangsheng Chen is a PhD graduate student working on forest management and disturbance modeling, 3) Xiaofeng Xu is a PhD graduate student working on wetland ecosystem model, and 4) Chi Zhang was a PhD graduate student working on dynamic vegetation modeling and urban ecosystem modeling. TARGET AUDIENCES: Climate change researchers, carbon cycle science community, environmental policy makers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The DLEM model improved our capacity to study the effects and interaction of multiple environmental stresses including climate extreme such as drought, increasing atmospheric CO2, ozone pollution, N deposition, land-cover and land-use change and disturbances. It helps us to understand the carbon dynamics in terrestrial ecosystems at a daily time step and reveal the major controls on the ecosystem carbon balance. By reevaluating DLEM simulations against field data from additional sites across North America and improving model input data, we have improved the accuracy of assessing regional carbon budget for the southeastern United States. Our results obtained from the past fiscal year will let the public know that environmental change, land management and disturbance could greatly affect the carbon sequestration in the study region. This information is useful for policy makers and land managers to take appropriate measures to maintain or restore our natural ecosystems.
Publications
- Tian, et al. 2008. Understanding Large-Scale Patterns and Processes of Terrestrial Ecosystems in Changing Global Environment: the Integrated Regional Study Approach and its Applications to China and the United States. Miao S.L., S. Carstenn and M. Nungesser (Eds) Real World Ecology: Large-scale and Long-term Case Studies and Methods. Springer-Verlag, New York Nerlin Heidelberg.
- Zhang, C., Tian, H.Q.,et al. Impacts of urbanization on ecosystem carbon storage of the southern United States from 1865 to 2002. 93rd ESA Annual Meeting in Milwaukee, Wisconsin. August 3-8, 2008. Oral presentation.
- Xu, X.F., Tian, H.Q., et al. Effects of fire on phosphorus dynamics and cattail growth in a nutrient-enriched Everglades wetland as simulated by the wetland ecosystem model. 93rd ESA Annual Meeting in Milwaukee, Wisconsin. August 3-8, 2008. Poster.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: We have made good progress in the fiscal year (2007/1-2007/12), which includes the following: 1) We improved the dynamic land ecosystem model (DLEM) through developing a forest management and disturbance submodel, which simulates the impacts of natural disturbance and land management on carbon cycling and thus makes the DLEM simulation more realistic. We calibrated and validated the submodel with collected observational data from Southern Research Station, LTER sites (in Florida and North Carolina), and other individual studies. The regional simulations will be carried on in the 2008 fiscal year; 2) An urban carbon cycle submodel was also developed in the fiscal year to better simulate the urbanization impacts on carbon, water and nitrogen cycling. In addition, we improve the land-use change dataset by separating urban area into impervious surface, lawn and natural vegetation. We ran the model with the improved land-use change data in the southeastern United States. ; 3) We
also ran the DLEM which does not have the forest management and disturbance submodel to examine the potential impacts of future climate change on carbon sequestration from 2002 to 2050 in the southeastern United States. We found that the northern (Kentucky and Tennessee) and western (Texas and Arkansas) regions could be a significant carbon source, while the coastlines and the southern region could be a carbon sink in 2050; 4)We collected different resolution remote sensing images (ETM+/TM, AVHRR, MODIS) which cover four time periods (1980, 1990, 1995, 2006). These data will be used to extract forest age, land-use and land-cover change (primarily deforestation and afforestation) information which are used as model input data, and to estimate forest biomass, gross primary production and mortality which are used to validate the model results.
PARTICIPANTS: 1) Dr. Hanqin Tian is the Project Director, 2) Guangsheng Chen is a PhD graduate student working on forest management and disturbance modeling, 3) Xiaofeng Xu is a PhD graduate student working on wetland ecosystem model, and 4) Chi Zhang is a PhD graduate student working on dynamic vegetation modeling and urban ecosystem modeling.
TARGET AUDIENCES: Climate change researchers, carbon cycle science community, environmental policy makers
Impacts
The Dynamic Land Ecosystem Model (DLEM)improved our capacity to study the effects and interaction of multiple stresses including changes in climate, land use and atmospheric composition. It helps us to understand the carbon dynamics in terrestrial ecosystems at a daily time-step and reveal the major controls on the ecosystem carbon balance. The improvements of DLEM model through adding forest management and disturbance submodel and urban carbon cycle submodel can further greatly increase the accuracy for simulating carbon cycling in the southeastern United States. Our results indicate that urbanization, forest management and disturbance, and future climate change could greatly affect the carbon sequestration of terrestrial ecosystems in the southeastern US. Such estimations and predictions are valuable for policy makers and forest managers to take appropriate measures to protect our ecosystems and carbon storage.
Publications
- Lu C., H.Q. Tian, and Y. Huang. 2007. Ecological consequences of nitrogen deposition. Journal of Plant Ecology 31(2): 205-218.
- Chen, GS and H. Tian. 2007. Land use/land cover change and the global carbon budget. Journal of Plant Ecology 31(2): 189-204.
- Ren W. and H.Q. Tian. 2007. Air pollution and terrestrial ecosystem production. Journal of Plant Ecology 31(2): 219-230.
- Tian, H.Q., S. Wan, and K. Ma. 2007. Global Change Ecology: Global Change and Terrestrial Ecosystems. Journal of Plant Ecology 31(2): 173-174.
- Tian, H.Q., X. Xu and X. Song. 2007. Drought impacts on terrestrial primary productivity. Journal of Plant Ecology 31(2): 231-241.
- 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.
- Xu, X., H.Q. Tian and S. Wan. 2007. Climate warming impacts on terrestrial ecosystem production. Journal of Plant Ecology 31(2): 175-188.
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Progress 01/01/06 to 12/31/06
Outputs
The carbon dynamics of Southeastern US is controlled by multiple stresses, such as land-use change, climate change, and the changes of atmospheric chemical composition (e.g. CO2, tropospheric ozone, and nitrogen deposition). Based on our researches in last year, which evaluated the impacts of land-use change on an urban-rural gradient in the west Georgia, we further explored the effects of climate change and atmospheric change on the natural ecosystems. For this goal, we developed a new dynamic land ecosystem model (DLEM), a highly integrated ecosystem process model that couples major biogeochemical cycles and hydrological cycle to make daily and spatially-explicit estimates of carbon and nitrogen fluxes (CO2, CH4 and N2O) and pool sizes (C and N) in terrestrial ecosystems. Unlike TEM which has a monthly time-step, DLEM has a daily time-step, which gives it advantage to simulate the short-period processes such as plants' response to daily climate variations, and
emergent disturbances such as hurricane. DLEM is able to address responses of terrestrial ecosystems to multiple stresses including changes in climate, atmospheric composition, land use and natural disturbances. To determine the parameters, we calibrated the DLEM model against several intensively studied sites (e.g. the Duke Forest, NC; and the Walker Branch Watershed, Oak Ridge, Tennessee) in the Southeastern US. We then applied our new model to the Great Smokey Mountain National Park (GRSM) to estimate the impacts and interactions of climate and atmospheric stresses on the carbon dynamic of natural ecosystem of GRSM. Our results suggested that forests in GRSM have a C density as high as 15.9 kg m-2, about twice the regional average. Total carbon storage in GRSM in 2001 was 62.2 T g (T = 1012), 53% of which was in vegetation, the rest in the soil detritus pool. Higher precipitation and lower temperatures in the higher elevation forests result in larger total C pool sizes than in
forests at lower elevations. From 1971 to 2001, the CO2 fertilization effect dominated ozone and climatic stresses (temperature and precipitation), and the combination of these multiple factors resulted in net accumulation of 1 T g C in this ecosystem. For the study in the entire Southeastern US region, we developed a long-term (1895-2006) daily climate dataset of 8 km resolution for the Southeastern US. We currently are trying to refine our land-use change datasets by including the historical urban (or developed) area into our database. At the same time, we refined our database of the west Georgia ecosystems, by adding in more hydrological field datasets and field measured water pollution datasets in the study region.
Impacts
The Dynamic Land Ecosystem Model (DLEM) improved our capacity to study the effects and interaction of multiple environmental stresses. It helps us to analyze the carbon dynamics of ecosystems in a daily time-step and reveal the major controls of the ecosystem carbon balance. The application in the Great Smokey Mountain National Park showed that natural forest ecosystems have the potential to store large amounts of carbon. These carbon pools might be turned into a significant carbon source if disturbed by human activities. The human disturbances not only include deforestation and urbanization, but also include air pollution. The rising tropospheric ozone concentration in Great Smokey Mountain National Park, for example, was estimated to have reduced the ecosystem's carbon sequestration capacity by about 50%, during the last 30 years of 20th century. Such estimations and predictions are valuable for policy makers to make appropriate environmental regulations to protect
our ecosystem and its carbon storage. The long-term historical database that was/are developed by us will make it possible for us to conduct such analysis over the entire Southeastern US region.
Publications
- Zhang, C., Tian, H.Q., Chappelka, A.H., Ren, W., Chen, H., Pan, S.F., Liu, M., Styers, D., Chen, G., and Wang, Y. (2007) 2006. Impacts of climatic and atmospheric changes on carbon dynamics in the Great Smoky Mountains National Park. Environmental Pollution (accepted)
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Progress 10/01/05 to 03/01/06
Outputs
The overall goal of this project is to examine how land-use change, climate change, disturbance, and other stresses affect carbon storage and dynamics in the west Georgia and southeastern US. Our research work spans different spatial and temporary scales. For the spatial scale, we primarily focus on west Georgia including Muscogee, Harris and Meriwether counties and the southeastern US which includes 13 states. We have made great progress in this project. For the west Georgia, we used Landsat imagery data including MSS for 1974, TM for 1983 and 1991 and ETM for 2002 to find that from 1974 to 2002, urban land use for the area has increased more than 380 percent and most of new urban land uses were converted from forestland. For the same time period, cropland and pasture area has decreased by over 59 percent and most cropland acreage was converted to forest. As a result, the net change in forest area was small over the past 29 years. TEM simulated results suggest that C
uptake by forest regrowth ( 23.0 g C/m2/yr) was slightly larger than C released through the deforestation ( 18.4 g C/m2/yr) thus, making the three west Georgia counties a weak C sink. These results further indicated land-use change, especially forest regrowth on abandoned cropland and urbanization has significant impacts on carbon dynamics in this landscape. For the entire southeast, we reconstructed the annual land-cover data set from 1860 to 2003. The land-cover in this region has experienced three stages: cropland expansion converted from natural vegetation (e.g., forests and grassland), forest regrowth on abandoned croplands, and urbanization due to population increase. We have used TEM mode to simulate the effects of land-cover change on carbon storage and flux in this region. From 1860 to 2003, land-cover change resulted in loss of 10 Pg C of terrestrial ecosystems to atmosphere. This region is still a weak carbon source during 1980-2000, although increasing forest regrowth on
abandoned cropland is making a difference. In the next stage, we will further develop a dynamic ecosystem model to better incorporate disturbance (e.g., hurricanes) and forest management practices in the model, so we can model and monitor terrestrial ecosystem carbon dynamic better. We also plan to simulate how climate change will influence terrestrial carbon dynamics in this region.
Impacts
The west Georgia results are useful for county or city planning. The development of cities could choose different paths in order to reduce the negative impacts on environment. Right now, most new developed urban area is the result of deforestation, a process to release a large amount of carbon into atmosphere. The entire southeast results are valuable while policy makers review the effects of land-cover change such as urbanization on the carbon storage in this region.
Publications
- Chen, H., Tian, H.Q., Liu, M.L., Melillo, J., Pan, S.F., and Zhang, C. 2006. Effects of land-use change on terrestrial carbon dynamics in the southern USA. Journal of Environmental Quality, (in press).
- Zhang, C., Tian, H.Q., Pan, S.F., Lockaby, G., Schilling, E. B. and Stanturf J. 2006. Effects of forest regrowth and urbanization on ecosystem carbon storage in a rural-urban gradients in the southeast US, Ecosystems, (in press).
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