Interactions between microclimate, soil respiration, and disturbances in a forest ecosystem: Lessons from the Teakettle Experimental Forest in California's Sierra Nevada

Forest management practices play an important role in forest sustainability and CO2 sequestration. This study focused on forest microclimate and soil respiration to understanding the effects of prescribed burning and thinning on ecosystem processes. I conducted this study in the Teakettle Experimental Forest, an old-growth, mixed-conifer forest in California's Sierra Nevada Mountains. From June 1999 to August 2002, automatic microclimate stations were installed at 18 locations and collected data of air temperature, relative humidity, soil surface temperature, soil temperature at 15 cm depth, soil moisture within 0–15 cm, soil heat flux, and wind speed. A series of soil respiration and in situ soil temperature and moisture were measured for determining the relationship between soil respiration and soil microclimate and the effects of prescribed burning and thinning treatments on soil respiration and microclimate. The results suggested that spatial variability of temperature varied with temporal scales. Elevation, canopy cover, and litter depth accounted for 25–94% of the spatial variability. The soil respiration rate varied significantly among the three patch types, including open canopy, closed canopy, and ceanothus shrub dominated patch type, from 0.62 to 1.47 and 0.37 to 0.98 g CO₂ m−2 h−1 during the measurement periods between 1999 and 2000, respectively. Soil respiration was correlated positively to soil temperature when soil moisture was unlimited, while soil respiration was correlated negatively to soil temperature when soil moisture was limiting. I developed an exponential model using a time lag to describe these relationship. After prescribed burning and thinning treatments, soil temperature, moisture, and below-canopy reference evapotranspiration increased. Soil respiration decreased significantly after burning. Thinning did not influence soil respiration significantly, but combinations of both treatments significantly increased soil respiration. Overall, this study provides fundamental information on microclimate and soil respiration for studying the effects of prescribed burning and thinning disturbances on ecosystem functions. This study also enhances our ability to model ecological processes using basic microclimatic data. Empirical models are valuable to understand the interactions between microclimate and ecological processes and provide reliable predictions for estimating the role of forest management activities in forest sustainability in the changing global climate.