Enzymatic activity of post - agrogenic gray forest soils on the highland oakwood “Forest on the Vorskla”

The enzymatic soil activity is a sensitive indicator of post agrogenic changes due to its quick response to cessation of agricultural use. The rate of the basal soil respiration (Vbasal), microbial carbon content (Cmic) and enzymatic activity (hydrolases and oxidases) were performed in the chronosequence of post-agrogenic gray forest soils (highland oakwood “Forest on the Vorskla”), which includes: arable soil; abandoned soils of 10, 30 and 40 years old, and mature oak forest, whose age exceeds 100 years. Mixed soil samples were collected from separate soil layers: 0-5, 5-10, 10-20 and 20-30 cm. An progressive increase of the Vbasal (from 0.4 - 0.5 and to 0.6 - 2.0 mg C kg-1 soil h-1) and Cmic (from 337 to 1433 mg C kg-1 soil) from arable soil to forest site was revealed for the upper 0-5 cm layer. As a rule, the young abandoned soils were characterized by the low activity of hydrolytic enzymes of carbon cycle. For the older abandoned soils (>30 years old), the hydrolase activity was 2-2.5 times higher than in younger one and comparable to that in the forest soil. In contrast, the oxidase activity was the highest in the arable and forest soils and decreased in the abandoned soils. We have shown that Cmic content explains about 50 - 70% variability of hydrolytic enzymatic activity of post-agrogenic soils. The correlation between the oxidase activity and Cmic has not been observed.