Soil Moisture and vegetation cover patterns after logging and burning an old-growth Douglas-fir forest in the Andrews Experimental Forest, 1960-1983

This soil moisture study was initiated in 1960 to investigate the effects of patch clearcut logging and slash burning (1962-63) in an old-growth Douglas-fir forest in the Oregon Cascade Range. Since soil moisture and vegetation sampling continued regularly until 1980, this is a unique data set that represents nearly two decades of post-treatment information. Plant cover exerts a profound influence on soil moisture levels through its effects on interception, infiltration, evaporation, and transpiration. In the Douglas-fir forests of the Pacific Northwest, clearcut logging and slash burning are common practices that can dramatically alter plant cover and soil moisture. Logging can increase soil moisture by temporarily reducing cover and associated water use, and burning may further augment soil moisture levels by suppressing the survival and regrowth of vegetation. Indeed, part of the rationale for slash burning in the region is to control shrubs and other vegetation that would otherwise compete with conifer seedlings for available moisture, light, and nutrients. Within a few years after burning, however, invading vegetation may deplete soil moisture to levels comparable to forested areas. Such observations point to the value of long-term information to better understand dynamic soil moisture and plant cover responses to forest practices.