Temperate peatlands use-management effects on seasonal patterns of soil microbial activity and nitrogen availability

Abstract

Temperate peatlands are regionally important for farming but long-term cultivation, as well as reforestation after intense agricultural use, can have a significant impact on their soil microbial activity and nitrogen cycles. We studied peatlands in the central part of European Russia, which initially was a swamp forest ecosystem with fairly homogeneous properties of woody peat. Different sites in the area were subsequently under different types of land use. We studied 4 sites in order of increasing management intensity: near-pristine swamp forest, a reforested site after 50 years of intensive cultivation and 2 agricultural sites with 50- and 100-year histories of agricultural use. We examined the dynamics of microbial biomass C and N, dissolved organic C and N and mineral nitrogen during the growing season (May-November). We conclude that land use type can affect the seasonal dynamics of available and microbial nitrogen by changing the vegetation cover. For peatlands covered with natural vegetation, an important feature of the seasonal dynamics of N is microbial immobilization and storage during winter. High activity of β-1,4-glucosidase and low activity of peroxidase indicate that microorganisms consume mainly nitrogen and carbon from fresh plant litter, rather than carbon and nitrogen conserved in peat. Long-term peatland agricultural use has led to significant changes in the dynamics of available and microbial nitrogen and carbon during the growing season, and land management has greatly modified the limitations of the activity of microorganisms from the availability of nitrogen (in the forest) to the availability of carbon (in arable peatland). The changes in peatlands occurred in the first years or decades of their exploitation because we did not find significant differences in any of the indicators between the arable lands used for 50 and >100 years. We found that natural reforestation for 50 years has not yet fully restored microbial activity; however, for some parameters, this site has characteristics close to those of near-pristine swamp forest.