Assessing forest carbon sequestration and water supply interactions as influenced by climate and management practices

PARTNERS: USDA Forest Service Northern Research Station (NRS) Climate, Fire, and Carbon Cycle Sciences; North Carolina State University Department of Forestry and Environmental Resources

SUMMARY: Forest ecosystems provide essential products and services that include wood products, wildlife habitat, recreation, as well as steady and clean water supply and carbon sequestration. Not only do these services have tradeoffs with one another, but they also differ in their sensitivity to changing environmental conditions. Managing forests to provide an optimal balance of all benefits under variable climate is a challenge to all land-owners and stakeholders. To date, production forestry has maximized productivity, but recent studies show that certain management practices may compromise water yield, water quality, soil carbon or nutrient stocks vital for long-term sustainability. In the southeastern United States in particular, with fast-growing population centers and equally rapid expansion of plantation forestry, the latter must be developed in conjunction with societal needs. The current study looks at the mechanisms of coupling between carbon and water cycles, the responses to environmental variability and extremes, from short to long timescales. Researchers use a combination of methods including eddy covariance, sap flow, biometric surveys (Forest Inventory and Analysis, or FIA), soil and litter sampling, laboratory incubations and modeling to understand the key regulation points of ecosystem-level processes and forecast the changes under projected future climate conditions and alternative management scenarios. The study is a contributor to the Ameriflux and FLUXNET networks and various regional- to global-scale modeling activities.

EFETAC'S ROLE: Researchers have expanded investigations into carbon, water, and nutrient cycling interactions in the coastal plain, building on the record of these Forest Service-supported flux sites. Other aspects of the study are continuing with North Carolina State University collaborators Asko Noormets and J.-C. Domec. Extrapolation of this work continues to progress through the Water Supply Stress Index-Carbon and Biodiversity (WaSSI-CB) model, led by Eastern Threat Center research hydrologist Ge Sun. Funding for the new work comes from Department of Energy, and several grants have been submitted to the National Science Foundation. Researchers also collaborate with a number of people from Virginia Tech, University of Florida, Environmental Protection Agency, University of North Carolina-Chapel Hill and other Forest Service branches by providing long-term ground truthing at physiological, ecosystem, and hydrologic levels to various satellite validations, land surface models, and regional upscaling efforts.

STATUS: Completed

PROGRESS: Results from this project show that (1) soils are losing carbon despite the high productivity of pines, as harvest removals and heterotrophic respiration exceed litter inputs, (2) the high productivity is maintained due to easy access to ground water, and (3) that current productivity levels may not be sustainable due to declining soil carbon and nutrient stocks, and projected increase in the frequency of droughts. These findings highlight potential trade-offs in forest management and will need to be considered nationally as the competing needs for timber, clean water, carbon sequestration, greenhouse gas mitigation, wildlife habitat, recreation and other services are evaluated.

Recent publications discuss the results of this study:

Domec, J.C., J.S. King, E. Ward, A.C.Oishi, S. Palmroth, A. Radecki, D.M. Bell, G. Miao, M. Gavazzi, D.M. Johnson, S.G. McNulty, G. Sun, and A. Noormets. 2015. Conversion of natural forests to managed forest plantations decreases tree resistance to prolonged droughts. Forest Ecology and Management. In press.

Kang, M., Z. Zhang, A. Noormets, X. Fang, T. Zha, J. Zhou, G. Sun, S. McNulty, J. Chen. Responses of energy partitioning and surface resistance to drought in a poplar plantation in northern China. Biogeosciences Discussion 12: 345-388. (PDF)

McNulty, S., E. Cohen, G. Sun, and P. Caldwell. 2015. Chapter 1.7: Hydrologic Modelling for Water Resource Assessment in a Developing Country: The Rwanda Case Study. In Watershed Modeling (Michel Lafforgue ed.). In Press.

Sun, G., P.V. Caldwell, and S.G. McNulty. 2015. Modeling the potential role of forest thinning in maintaining water supplies under a changing climate across the conterminous United States. Hydrological Processes. In press.

Xie, J., G. Sun, H.-S. Chu, J. Liu, S.G. McNulty, A. Noormets, R. John, Z. Ouyang, T. Zha, H. Li, W. Guan, and J. Chen. 2014. Long-term variability in the water budget and its controls in an oak-dominated temperate forest. Hydrological Processes 28:6054-6066. (PDF)

Miao, G., A. Noormets, J-C Domec, C.C. Trettin, S.G. McNulty, G. Sun, and J.S. King. 2013. The effect of water table fluctuation on soil respiration in a lower coastal plain forested wetland in the southeastern U.S. Journal of Geophysical Research – Biogeosciences 118:1748-1762. (PDF)

Sun, G., P. Caldwell, S. McNulty, E. Ward, J.-C. Domec, and A. Noormets. 2013. Regional Carbon Sequestration and Climate Change: It’s All about Water. In 2nd Annual PINEMAP Report. Page 24-25.

Zhou, J., Z. Zhang, G. Sun, X. Fang, T. Zha, S. McNulty, J. Chen, Y. Jin, and A. Noormets. 2013. Response of ecosystem carbon fluxes to drought events in a poplar plantation in Northern China. Forest Ecology and Management 300:33-42. (PDF)

Domec, J.C., J. Ogee, A. Noormets, J. Jouangy, M. Gavazzi, E. Treasure, G. Sun, S.G. McNulty, and J.S. King. 2012. Interactive effects of nocturnal transpiration and climate change on the root hydraulic redistribution and carbon and water budgets of southern United States pine plantations. Tree Physiology 32 (6):707-723. (PDF)

Domec, J.C., G. Sun, A. Noormets, M.J. Gavazzi, E.A. Treasure, E. Cohen, J.J. Swenson, S.G. McNulty, and J.S. King. 2012. A comparison of three methods to estimate evapotranspiration in two contrasting loblolly pine plantations: age-related changes in water use and drought sensitivity of evapotranspiration components. Forest Science 58(5):497-512. (PDF)

Noormets, A., S.G. McNulty, J.C. Domec, M.J. Gavazzi, G. Sun, and J.S. King. 2012. The role of harvest residue in rotation cycle carbon balance in loblolly pine plantations. Respiration partitioning approach. Global Change Biology 18(10): 3186-3201. (PDF)

Sun, G., Caldwell, P.V., Georgakakos, A.P., Arumugam, S., Cruise, J., McNider, R.T., Terando, A., Conrads., P.A., Feldt, J., Misra, V., Romolo, L., Rasmussen, T.C., McNulty, S.G., and Marion, D.A. 2012. Impacts of Climate Change and Variability on Water Resources in the Southeastern US. Chapter 10 in Ingram, K.T., K. Dow, and L. Carter (eds.). Southeastern Regional Technical Report to the National Climate Change Assessment, Water Resources, Island Press. p. 210-236.

Domec, J.C., J.S. King, A. Noormets, E.A. Treasure, M.J. Gavazzi, G. Sun, and S.G. McNulty. 2010. Hydraulic redistribution of soil water affects whole stand evapotranspiration and net ecosystem carbon exchange. New Phytologist New Phytologist 187:171-183. (PDF)

Noormets, A., M.J. Gavazzi, S.G. McNulty, J.C. Domec, G. Sun, J. King, and J. Chen. 2010. Response of carbon fluxes to drought in a coastal plain loblolly pine forest. Global Change Biology 16:272-287. (PDF)

Sun, G., A. Noormets, M. Gavazzi, S.G. McNulty, J. Chen, J.C. Domec, J.S. King, D.M. Amatya, and R.W. Skaggs. 2010. Energy and water balance of two contrasting loblolly pine plantations on the Lower Coastal Plain of North Carolina, USA. Forest Ecology and Management 259:1299-1310. (PDF)

Domec, J.C., A. Noormets, J.S. King, G. Sun, S.G. McNulty, M.J. Gavazzi, J.L. Boggs, and E.A. Treasure. 2009. Decoupling the influence of leaf and root hydraulic conductances on stomatal conductance and its sensitivity to vapor pressure deficit as soil dries in a drained loblolly pine plantation. Plant, Cell & Environment 32:980-991. (PDF)

A slideshow and additional papers and presentations describing this study are also available.

LINKS:

Ameriflux, specific site pages:

FLUXNET

Fluxdata.org

Importance of hydraulic lift in maintaining carbon assimilation during drought

Ameriflux

Water Supply Stress Index