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THE BIOLOGICAL RESPONSE OF A SMALL CATCHMENT TO CLEAR-CUTTING
Citation:
CHENG, Y. W., M. STIEGLITZ, R. B. MCKANE, AND B. KWIATKOWSKI. THE BIOLOGICAL RESPONSE OF A SMALL CATCHMENT TO CLEAR-CUTTING. Presented at American Geophysical Union Fall Meeting, San Francisco, CA, December 11 - 15, 2006.
Description:
We modified a Plant-Soil Model (Stieglitz et al, 2006, GBC) that simulates the effects of a disturbance on stocks and fluxes of carbon (C) and nitrogen (N) in terrestrial ecosystems. The model was used to examine past, present and future changes in C storage and C-N dynamics at the WS10 catchment of the HJ Andrews LTER, located in the Pacific NorthWest, USA. Model parameters were initialized to simulate the build-up of C and N stocks from the beginning of the current post-glacial period (approximately 10,000 years BP) to present day. The built-up simulated values of aboveground stocks of plant and soil C were near measured present-day values. Regardless of whether we initialized soil C at 10 g C m-2 or 100 g C m-2, the system as a whole still took approximately 20,000 years to equilibrate. To examine the effect of a clear-cut on this old growth coniferous forest, we used the simulated results for year 10,000 of the post-glacial build-up to establish initial conditions and trajectories for the present-day ecosystem. Within 500 years after the clear cut, plant C was at 75 percent of the final equilibrium value, and thereafter, slowly equilibrated over the course of 8000 years. Within 200 years after the clear cut, soil C fell by 7500 g C m-2 or 38 percent. Thereafter, it rebounded and equilibrated after approximately 8000 years. The model results indicate that soil C stocks characteristic of pre-settlement stands will decline rapidly given typical forest harvest intervals (<100 years) for this region.