Short-Term Response of the Soil Microbial Abundances and Enzyme Activities to Experimental Warming in a Boreal Peatland in Northeast China

Yanyu Song,Aixin Hou,Wenwen Tan,Xiuyan Ma,Xianwei Wang,Changchun Song,Jinli Gao,Jiusheng Ren

doi:10.3390/su11030590

Abstract

Global warming is likely to influence the soil microorganisms and enzyme activity and alter the carbon and nitrogen balance of peatland ecosystems. To investigate the difference in sensitivities of carbon and nitrogen cycling microorganisms and enzyme activity to warming, we conducted three-year warming experiments in a boreal peatland. Our findings demonstrated that both mcrA and nirS gene abundance in shallow soil and deep soil exhibited insensitivity to warming, while shallow soil archaea 16S rRNA gene and amoA gene abundance in both shallow soil and deep soil increased under warming. Soil pmoA gene abundance of both layers, bacterial 16S rRNA gene abundance in shallow soil, and nirK gene abundance in deep soil decreased due to warming. The decreases of these gene abundances would be a result of losing labile substrates because of the competitive interactions between aboveground plants and underground soil microorganisms. Experimental warming inhibited β-glucosidase activity in two soil layers and invertase activity in deep soil, while it stimulated acid phosphatase activity in shallow soil. Both temperature and labile substrates regulate the responses of soil microbial abundances and enzyme activities to warming and affect the coupling relationships of carbon and nitrogen. This study provides a potential microbial mechanism controlling carbon and nitrogen cycling in peatland under climate warming.

Highlights

Soil microorganisms, which mediate carbon and nitrogen cycling, are key drivers of biogeochemical processes in terrestrial ecosystems [1] and play a vital role in terrestrial carbon and nitrogen cycling [2,3]
Three years of experimental warming significantly decreased the soil microbial biomass carbon (MBC) concentration from 1421.6 μg g−1 to 1197.2 μg g−1 in shallow soil (p < 0.05) and from 1478.7 μg g−1 to 841.6 μg g−1 in deep soil (p < 0.01) (Figure 1A)
Ammonia nitrogen contents in soils decreased significantly from 66.6 μg g−1 to 22.5 μg g−1 in shallow soil and from 47.9 μg g−1 to 19.6 μg g−1 in deep soil under warming (p < 0.01, Figure 1C)

Summary

Introduction

Soil microorganisms, which mediate carbon and nitrogen cycling, are key drivers of biogeochemical processes in terrestrial ecosystems [1] and play a vital role in terrestrial carbon and nitrogen cycling [2,3]. Little changes of microbial abundances could significantly affect soil organic carbon (SOC) decomposition, due to the fact that microbial communities and their ability to degrade SOC have different temperature sensitivities [5]. Kotroczó et al [14] found that increasing temperature could enhance soil respiration dependent on soil microbial activity. Peltoniemi et al [11] found that methanogen abundance decreased, but methanogenic communities remained similar after three-year experimental warming in boreal fens. These different responses of soil microorganisms and the carbon process depend on ecosystem types and would be influenced by geographical position, soil types, and vegetation characteristics [15,16,17]

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