Litter Inhibitory Effects on Soil Microbial Biomass, Activity, and Catabolic Diversity in Two Paired Stands of Robinia pseudoacacia L. and Pinus nigra Arn.

Abstract: ResearchHighlights: Plantcoverdrivestheactivityofthemicrobialdecomposercommunity andaffectscarbon(C)sequestrationinthesoil. Despitetherelationshipbetweenmicrobialactivityand C sequestration in the soil, potential inhibition of soil microbial activity by plant cover has received little attention to date. Background and Objectives: Differences in soil microbial activity between two pairedstandsonsoilataveryearlystageofformationandacommonstoryuntilafforestation,canbe traced back to the plant cover. We hypothesized that in a black locust (Robinia pseudoacacia L.) stand thehigh-qualityleaflitterofthetree,andthatoftheblackberry(RubusfruticosusL.)understoryhadan inhibitory effect on soil microbial community resulting in lower mineralization of soil organic matter compared to the paired black pine (Pinus nigra Arn.) stand. Materials and Methods: We estimated potential mineralization rates (MR), microbial (MB), and active fungal biomass (AFB) of newly-shed litter, forest floor, and mineral soil. We tested the effects of litters’ water extracts on soil MR, MB, AFB and its catabolic response profile (CRP). Results: Newly-shed litter of black locust had higher MR than that of blackberry and black pine; MR, MB, and AFB were higher in forest floor and in mineral soil under black pine than under black locust. Water extracts of black locust and blackberry litter had a negative effect on the amount, activity of microorganisms, and CRP. Conclusions: The results demonstrate the potential for black locust and blackberry litter to have a marked inhibitory effect on decomposer microorganisms that, in turn, reduce organic matter mineralization with possible consequences at the ecosystem level, by increasing C sequestration in mineral soil.