Soil Respiration at Dominant Patch Types within a Managed Northern Wisconsin Landscape

Soil respiration (SR), a substantial component of the forest carbon budget, has been studied extensively at the ecosystem, regional, continental, and global scales, but little progress has been made toward understanding SR over managed forest landscapes. Soil respiration is often influenced by soil temperature (T_s), soil moisture (M_s), and type of vegetation, and these factors vary widely among the patch types within a landscape. We measured SR, T_s, M_s, and litter depth (LD) during the 1999 and 2000 growing seasons within six dominant patch types (mature northern hardwoods, young northern hardwoods, clear-cuts, open-canopy Jack pine barrens, mature Jack pine, and mature red pine) on a managed forest landscape in northern Wisconsin, USA. We compared SR among and within the patch types and derived empirically based models that relate SR to T_s, M_s, and LD. Increased levels of soil moisture and higher temperatures in June–September 1999 may have accounted for the up to 37% overall higher SR than in this same period in 2000. In 2000, SR and T_s values were lower, and the sites may have been experiencing slight water limitations, but in general T_s was a much more accurate predictor of SR during this year. Empirical predictions of SR within each patch type derived from continuous T_s measurements were in close agreement with measured values of SR during 2000, but eight of 22 of the simulated values were significantly different ( = 0.05) from the rates measured in 1999. The young hardwoods consistently had the highest SR, whereas the pine barrens had the lowest. Results from our field studies and empirical models can help land managers assess landscape responses to potential disturbances and climatic changes.