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Principal Investigator: Julie Whitbeck
Co-PI: Jay Gulledge
Institution: University of New Orleans and Tulane University
This project is funded by:
The National Institute for Global Environmental Change
http://www.nigec.tulane.edu/whitbeck.htm
We hypothesize that increased levels or duration of soil saturation in bottomland forests will reduce microbial activity, root respiration and thus soil respiration and will lead to the accumulation of a greater proportion of fixed carbon than in the soils of unsaturated bottomland forests, therefore the effect of sea level rise on net ecosystem CO2 exchange will be a function of the relative changes in this net carbon accumulation and gross productivity.
The proposed research on key carbon (C) fluxes of bottomland forest soils will provide the global change research community and policy makers with estimates of changes in 1) C inputs to soils, 2) C storage in these soils, and 3) the net flux of the greenhouse gas carbon dioxide (CO2) from the soils of this predominant deltaic woodland ecosystem as sea level rises. Study of C cycling and net C02 exchange between lowland forest ecosystems and the atmosphere is lacking worldwide, and understanding the impacts of rapid rise in relative sea level upon net ecosystem exchange is critical to predicting the consequences of these linked climate changes for the ecological processes of these extensive lowland deltaic, riverine and coastal forests and for regional and global estimates of net C flux between the earth and the atmosphere.
The rapid rise of relative sea level in many deltaic regions is leading to increased hydroperiod and increased saturation of the soils of forested wetlands adjacent to rivers and coasts. This research will provide estimates of the impacts of increased levels of soil saturation on forest productivity, carbon storage and carbon dioxide emission from extensive lowland areas. In addition to providing valuable timber, these forests function as a storm buffer and provide habitat to dozens of organisms of key ecological and cultural value. Understanding their contribution to regional carbon budgets as sea level rises will be critical to formulating regional strategies to cope with these two linked facets of climate change and to predicting the fate of these forests.
Bottomland hardwood forest is a major biome in Louisiana and throughout the Southeast U.S. and the Gulf Coast. Its distribution along rivers and coasts makes it particularly susceptible to increases in hydroperiod and soil saturation expected as sea level rises. The Barataria Preserve south of New Orleans offers an opportunity to study a bottomland hardwood forest of known land use history which is experiencing rapid relative sea level rise (2-3 cm/yr). We propose to examine the contributions of plant roots and soil microorganisms to Soil CO2 emission along a hydrologic gradient from elevated to submerged. In concert with CO2 flux measurements, root production and turnover will be examined as well as soil microbial properties (biomass, bacterial/fungal ratio, respiratory potential). Paired trenched and reference plots will be used to distinguish root + rhizosphere respiration from microbial respiration along the gradient. Fine root production and turnover will be measured with parallel carbon budget, compartment flow and minirhizotron approaches. These data will characterize the belowground C cycling dynamics in a typical bottomland hardwood forest, identify the primary source of and controls on soil CO2 efflux, and assess the consequences of seasonal flooding and sea level rise for belowground productivity, net C exchange and C cycling in this ecosystem.
