Journal
AGRICULTURE ECOSYSTEMS & ENVIRONMENT
Volume 239, Issue -, Pages 199-206Publisher
ELSEVIER
DOI: 10.1016/j.agee.2017.01.033
Keywords
Bacteria; Climate change; Carbon sequestration; Fungi; Microbial metabolism; Community composition
Funding
- NSF [DEB-0608287]
- WCS
- RSG
- DST [FT/LS-346/2012]
- STC [0332]
- MoEFCC
- IISc-DBT
- Council of Scientific and Industrial Research (CSIR)
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Understanding factors that regulate carbon (C) pools is of high importance for offsetting greenhouse-gas emissions. Soils represent a vast C pool, whose size and stability are strongly influenced by land-use. Grazing, by native herbivores and livestock, is the predominant land-use across over 40% of the terrestrial surface and influences over 109 Mg of soil-C annually in the world's dry regions. The interactions between plants, grazers, and soil microbes, is of critical importance for this soil-C pool. However, soil microbial responses to grazing, and associated feedbacks, remain poorly understood. Grazing management policies are unable to adequately accommodate key interactions that are important for effective ecosystem stewardship. After 10-yr of experimental herbivore-exclusion in the semiarid Trans-Himalayan ecosystem, we meastired grazer effects on soil microbial abundance in n = 30 herbivore exclosures, each paired with an adjacent control plot using substrate-induced respiration, microbial-carbon, and microbial-nitrogen (SIR, MBC, MBN). We found that grazing reduced soil microbial biomass by 13-16%, over the course of the vegetation growing season. But, the strength and direction of grazer effects varied through time at different points in the growing season. Grazing also shifted fungal:bacterial ratio towards dominance by fungi which were more tolerant of periodic dry-down and seasonal fluctuations in soil moisture than bacteria. So, grazer influence on microbial abundance and community composition may collectively play crucial roles in net soil-C dynamics. But, this effect is constrained by environmental factors, such as moisture availability. The projected climatic trend in the Trans-Himalaya is towards progressively wetter conditions, and this may counter grazer effect on microbes, alter microbial communities, and ultimately impact potential soil-C storage. So, accounting for projected changes in precipitation, in addition to managing stocking density of herbivores, may also be crucial for these large soil-C pools. (C) 2017 Elsevier B.V. All rights reserved.
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