HR: 1340h
AN: B43D-1583    [Abstracts]
TI: An Evaluation of Soil Carbon Layer Dynamic in the Context of Global Warming
AU: * Fan, Z
EM: fanz@colorado.edu
AF: Department of Geological Sciences, University of Colorado, Campus Box 399, 2200 Colorado Ave., Boulder, CO 80309, United States
AU: Neff, J C
EM: neffjc@colorado.edu
AF: Department of Geological Sciences, University of Colorado, Campus Box 399, 2200 Colorado Ave., Boulder, CO 80309, United States
AB: Boreal soils contain approximately 40-45% of the world's terrestrial soil C and may play an important role in the feedback between the global carbon cycle and climate change. Although there are a number of predictions of future boreal soil C dynamics under various warming scenarios, there are still many uncertainties due to the complexity and uniqueness of boreal soils. In most modeling analyses of boreal C cycle responses to warming, the deep, organic C rich layers are given little attention or assumed to have little role in future C dynamics. The objective of the study was to improve our understanding of the sensitivity of boreal soils to climate warming. A soil C model with dynamic soil layers and multiple C pools structure (fine, coarse, humic) was used to simulate C cycling in the Northern Study Area Old Black Spruce site of the Boreal Ecosystem and Atmosphere Study. The C model with the parameters used in the study has been shown to provide the best simulation on both soil 14C profile and total C for the study site. The simulation was designed in a factorial combination of two factors: temperature increase (0°C, 2°C, 4°C, 6°C, 10°C) and warming period (2000-2200, 2000-2400, 2000-2600, 2000- 3000). The model predicted that warming would lead to significant losses of soil C in the future that these losses would scale linearly with the magnitude of warming. The simulation results also indicated a shift in the sources of CO2 from soil decomposition from equally balanced between surface and deep (e.g. 55 cm) C sources under current conditions to a dominance of deep C contributions to CO2 by 2200, even with low to moderate warming. This result is driven by centennial scale changes in soil thermal regimes that facilitate the decomposition of large deep C stocks, despite their relative recalcitrance. These simulations also indicate that organic rich, deep boreal soils have long equilibration times, exceeding 1000 years in some cases, in response to temperature perturbations. Collectively, these results suggest that the deep soil C stocks in boreal forests are likely to be critically important to the future carbon dynamics in these regions and future work is needed to examine the feedbacks between vegetation change, primary productivity and soil carbon cycling in these regions.
DE: 0400 BIOGEOSCIENCES
DE: 0428 Carbon cycling (4806)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting