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

Anna De Marco,Armando Zarrelli,Fabrizio Esposito,Björn Berg,Amalia Virzo De Santo

doi:10.3390/f9120766

Anna De Marco, Armando Zarrelli + Show 3 more

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https://doi.org/10.3390/f9120766

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Abstract

Research Highlights: Plant cover drives the activity of the microbial decomposer community and affects carbon (C) sequestration in the soil. Despite the relationship between microbial activity and 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 paired stands on soil at a very early stage of formation and a common story until afforestation, can be traced back to the plant cover. We hypothesized that in a black locust (Robinia pseudoacacia L.) stand the high-quality leaf litter of the tree, and that of the blackberry (Rubus fruticosus L.) understory had an 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.

Highlights

Forest ecosystems store carbon (C) in aboveground biomass belowground biomass, forest floor, and coarse woody debris, as well as in the mineral soil that is a significant component in C sequestration
The newly-shed litters of black locust and black pine somewhat differed for nutrient concentration and fractions of soluble C and N (Table 1)
Blackberry Newly-shed litter (NL) had lower N and higher Mn concentrations compared to black locust (p = 0.02, p = 0.03 respectively) and black pine (p = 0.04, p = 0.004 respectively)

Summary

Introduction

Forest ecosystems store carbon (C) in aboveground biomass (trees and understorey plants) belowground biomass (e.g., roots), forest floor, and coarse woody debris, as well as in the mineral soil that is a significant component in C sequestration. Plant cover drives the activity of soil microbial decomposer community [1] and affects total carbon stock and allocation in the forest floor and mineral soil [2,3]. The chemical composition of the litter species C-to-nitrogen (N), and lignin-to-N ratios control litter degradability and the environmental conditions for soil microbes [4]. Substances that suppress microbial activity in humus have been found in crowberry (Empetrum nigrum L.), a species common in boreal forests [8] and in walnut (Juglans sp.)

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