Belowground carbon processes in managed oak-hickory forests of southeastern Ohio.

摘要

Soil CO2 efflux (soil respiration) is the largest flux of carbon from terrestrial forest ecosystems. Understanding this flux in relation to forest thinning and prescribed burning is necessary for determining the effects of forest management on forest carbon dynamics. Since rising levels of atmospheric carbon dioxide are of global concern, my dissertation focused on providing insight into various aspects of soil respiration as it relates to forest management. Specifically, my research focused on (1) the effects of topographic position, canopy cover, and small-scale treatment on soil respiration (Rs) and soil microclimate; (2) modeling Rs with soil microclimate data and climate data; (3) the effects of large-scale forest thinning and prescribed fire on Rs and soil microclimate; and (4) the relationship between forest management and forest carbon budgets.;In studies of topographic position, canopy cover, and small-scale treatments, I discovered that landscape position affected Rs, with greater Rs on upper slopes than lower slopes. Low-intensity prescribed fire affected Rs, whereas high-intensity prescribed fire did not. Modeling of Rs supported the use of soil temperature for predicting Rs, with linear regression of ln (Rs) providing the best fit, as opposed to widely used Arrhenius-type nonlinear models. Additionally, I predicted Rs using air temperature and relative humidity data from the local weather station (R2 = 0.94). Studies of large-scale thinning and burning resulted in reduced Rs up to 3 growing seasons after forest harvesting, followed by elevated R s in the fourth growing season, and Rs comparable to control the fifth growing season following harvest. Prescribed fire led to greater Rs three growing seasons post-fire, and Rs comparable to control by the fourth growing season. Rs was reduced in burn treatments the growing season following a second prescribed burn in 2005. Air temperature was used to estimate annual soil respiration (Fsoil) for each treatment. Combining Fsoil with annual litter biomass and woody biomass increment, I was able to develop a forest ecosystem carbon budget for each treatment. These component fluxes are only estimates, but they provide the first step towards understanding the partitioning of carbon between ecosystem components within oak-hickory forests in southeastern Ohio.