Soil microbiological monitoring of a pine forest after partial thinning for stand regeneration with beech seedlings

Abstract

A 62 year old pine stand located in northeastern Germany (Brandenburg, Ost-Prignitz, Revier Beerenbusch) was studied with respect to a thinned vs. an unthinned variant. Samples of the litter layer and the top mineral horizon of an acid brown earth were collected from five plots at each variant in April and November during 3 years (2000–2002), respectively. Soil microbial biomass (Cmic and basal CO2 respiration were assayed using an infrared gas analysis system. Soil organic carbon (Core) and total nitrogen (Nt) contents were determined using a C/N elemental analyzer. In addition, cellulose decomposition in soil was assayed using a mini-container system. The contents of Corg, Nt, Cmic and basal respiration activity in the humus layer and in the mineral soil horizon did not differ significantly during 3 years shortly after thinning. Furthermore, no difference was detected comparing spring and autumn samplings of 3 years under study. On the other hand, cellulose decomposition in soil was slightly but not yet significantly increased in the thinned variant. Thus, 3 years after thinning no significant actual impacts on soil ecological properties were detected, but first evidence for increased soil biochemical activities in the thinned variant was found. Long-term monitoring and spatially more detailed analyzes are required to reveal lasting impacts of thinning. Special emphasis needs to be directed on the composition of soil microbial communities and on specific activities related to soil organic matter transformation.