HR: 10:20h
AN: B22B-01 INVITED    [Abstracts]
TI: Ecohydrology Controls on Feedbacks Between Northern Wetlands and Climate Systems
AU: * Turetsky, M
EM: mrt@msu.edu
AF: Department of Plant Biology, Michigan State University, East Lansing, MI 49924, United States
AU: Harden, J
EM: jharden@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., MS 962, Menlo Park, CA 94025, United States
AU: McGuire, A
EM: ffadm@uaf.edu
AF: Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, United States
AU: Waddington, J
EM: wadding@mcmaster.ca
AF: School of Geography and Earth Sciences, McMaster University, Hamilton, ON L8S 4L8,
AB: Boreal regions contain large stocks of soil carbon, mostly in poorly drained areas where peat accumulating wetlands have served as a long-term sink for atmospheric carbon. It is unknown whether northern wetlands globally will continue to represent a net sink for atmospheric carbon dioxide, or whether changes in the Earth's climate will cause these ecosystems to release stored carbon back to the atmosphere. Such feedbacks between northern wetlands and regional or global climate systems will depend on interactions between wetland vegetation, peat properties, and hydrology. Within many wetlands, hydrology is the dominant control on plant community structure and decomposition rates. In turn, both plant and microbial activity determine the quantity and quality of litter, which govern the nature of peat accumulation and soil properties critical to hydrology. Here, we will present research from our field and modeling studies investigating the effects of drought, permafrost degradation, and wildfire on vegetation, carbon cycling, and hydrological processes in northern wetlands at multiple spatial scales. At local scales, our findings show that interactions among vegetation, soil, and hydrology can lead to unexpected and often complex changes in soil environments, with potential ‘carbon surprises'. For example, in a nonpermafrost peatland, we found that sustained drought led to peat subsidence that limited the development of oxic surface peat layers and inhibited ecosystem respiration. The decrease in porosity and water content with drought reduced seasonal ice thaw, which also likely limited microbial activity. In contrast, peatlands underlain by permafrost are increasingly experiencing thermokarst and soil flooding with increasing active layer depth. Changes in moss productivity post-thaw led to increased rates of organic matter accumulation, with very different hydrologic and soil properties than peat accumulated in permafrost settings. In addition to local experimentation and gradient studies, we are conducting modeling studies to understand how responses of wetlands may effect the climate system. We argue that carbon, water, and energy fluxes in northern wetlands can respond quickly to changes in climate. However, a comprehensive understanding of whether the main feedback of wetland responses to climate change is through atmospheric carbon concentrations, or whether there also are direct feedbacks to local and regional climate through water and energy exchange pathways requires integration of observational and modeling studies at a variety of spatial scales.
DE: 0428 Carbon cycling (4806)
DE: 0429 Climate dynamics (1620)
DE: 0475 Permafrost, cryosphere, and high-latitude processes (0702, 0716)
DE: 1807 Climate impacts
DE: 1890 Wetlands (0497)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting