Description

As part of a larger study of the use of fire and thinning to restore ecosystem function in eastern forests, we quantified spatial, temporal, and treatment-related variations in soil pH, available P, and N mineralization over two years in two southern Ohio mixed-oak forests (Zaleski State Forest and Raccoon Ecological Management Area/REMA). In each site, two watershed-scale treatment units of ~25 ha were sampled on a 50m grid for analysis of spatial autocorrelation and for assessment of temporal variability and treatment effects. Sampling occurred in summer 2000 (prior to treatment) and summer 2001 (after one unit in each site had been thinned+burned). Nutrient status differed more between sites than between treatment units within sites. Semivariance analysis of pretreatment samples demonstrated that pH, available P, and N mineralization were strongly structured spatially in all four treatment units (spatial structure >67%). There were no significant temporal differences in pH or N mineralization (2000 vs 2001) in control areas of the two sites; however, available P did decrease between 2000 and 2001. Neither patch size nor spatial structure changed significantly over this time. Analysis of covariance of post-treatment soil status indicated that the thinning+burning treatment resulted in significant increases in available P and soil pH at REMA but not Zaleski. Semivariance analysis indicated that the thinning+burning treatment increased patchiness (decreased patch size) in pH, but decreased patchiness in available P. Ecosystem restoration treatments affected both overall nutrient status and spatial structure in ways that should influence how plants and communities respond to such treatments.