Effects of soil fauna on microbial community structure in foliar litter during winter decomposition in an alpine meadow

Abstract

Interactions between soil fauna and microbial community in litter might ultimately manipulate the process of litter decomposition in terrestrial ecosystems. Little is so far known about such interactions during winter litter decomposition in cold biomes. This study aimed to understand the effects of soil faunal community on winter microbial community structure in folia litter during winter decomposition in cold biomes. Litterbags with foliar litter of Ajania nubigena and Carex atrofusca were respectively placed on the soil surface in an alpine meadow of Zhegu Mountain, Miyaluo Nature Reserve located in the upper reaches of Yangtze River and the eastern Tibet-Qingzang Plateau. After being incubated in situ on Nov. 13th, 2013, the litterbags were taken back on Dec. 6th, 2013 (Snow forming period, SFP), Mar. 5th, 2014 (Snow stable period, SSP) and Apr. 5th, 2014 (Snow melting period, SMP), respectively. The soil faunal and microbial communities in litter were measured by funnel method and phospholipid fatty acid (PLFA), respectively. The results showed that soil fauna generally increased the contents of total PLFA, fungal PLFA, and bacterial PLFA of microbial community in A. nubigena foliar litter, and raised the ratio of fungal PLFA to bacterial PLFA, but those in C. atrofusca foliar litter showed the opposite trends, implying that the interactions between soil faunal community and microbial community in winter litter decomposition depend on plant species. In the SFP, soil fauna increased fungal 18:2ω6, 9c PLFA content in A. nubigena foliar litter, but decreased bacterial 16:0, 16:1ω9c and 18:1ω7c PLFA contents; soil fauna in C. atrofusca foliar litter increased bacterial 18:1ω7c PLFA content, but decreased fungal 18:2ω6,9c PLFA content. In the SMP, soil fauna in C. atrofusca foliar litter increased bacterial 16:1ω9c PLFA content, but decreased the contents of bacterial a15:0 PLFA, and micro-eukaryotic 18:3 and 20:4 PLFA. More significant effects of soil faunal community on microbial community structure in both foliar litters were observed in the SMP. During this period, soil fauna increased the indexes of Shannon-Wiener diversity, Pielou evenness, Margalef richness and Simpson dominance in microbial community of A. nubigena foliar litter. Meanwhile, soil fauna decreased the indexes of Shannon-Wiener diversity and Pielou evenness in microbial community of C. atrofusca foliar litter, but increased the indexes of Margalef richness and Simpson dominance in microbial community. The results indicated that soil faunal community in litter greatly affects the structure and biodiversity of microbial community in foliar litter even under harsh environmental conditions, which in turn run the process of winter litter decomposition in the alpine meadow.