Seasonal dynamics of the physicochemical and biological properties of soils in naturally regenerating, unmanaged and clear-cut beech stands in northern Spain

The physicochemical and biological properties of soils within an unmanaged beech stand and two stands clear-cut in 2001 or 1996 were studied and compared across the year 2008. The clear-cut stands were left to naturally regenerate and exhibited very different levels of tree density. Soil from the stand clear-cut in 2001 had the lowest contents of organic matter and nitrogen, showed high resistance to penetration and the pH varied throughout the seasons. Basal respiration achieved minimum values in summer in both the unmanaged stand and the stand clear-cut in 1996. However, basal respiration slightly fluctuated from spring to autumn in the stand clear-cut in 2001. The seasonal dynamics of protease and phosphatase activities were similar within the three stands: the maximum protease activity was detected in spring and the highest phophatase activity in winter. β-Glucosidase activity in autumn and dehydrogenase in winter were greater in the unmanaged than in the clear-cut stands. Moreover, dehydrogenase activity was extremely low in the stand clear-cut in 1996. Microclimatic parameters within the stands were significantly correlated with several biological properties of soils, with microclimate being strongly determined by the density of trees. Results also suggested that ectomycorrhizal fungi would be key components of the soil microflora in the beech forests.