Volume 125, February 2016, Pages 16–20
Highlights
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- Grazing affected bacterial community differently in plant patches and inter-canopies.
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- DGGE showed high similarity of bacterial community in plant-covered patches.
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- Cyanobacteria and diatom chloroplast sequences predominated at low and moderate grazing.
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- Grazing could alter biocrust autothophic bacteria/diatom composition by trampling.
Abstract
Our
objective was to assess whether long-term continuous sheep grazing was
associated with the bacterial community of the Patagonian Monte soils.
We randomly extracted soil samples from 5 plant-covered patches (PCP)
and the nearest inter-canopy areas (IC) at sites with low (L), moderate
(M) and heavy (H) grazing intensity. Bacterial communities were
evaluated by denaturing gradient gel electrophoresis (DGGE) and dominant
bands were sequenced. Dendrograms showed a different association among
grazing sites in PCP compared to IC areas. In PCP, M and H sites were
clustered and DGGE revealed a high similarity in the bacterial community
regardless of grazing intensity. In IC areas, analyses clustered L and M
sites. Band sequencing revealed that members of these communities
belonged to Sphingobacteria, Solibacteres, Gammaproteobacteria, Betaproteobacteria and Bacilli. Some of the band sequences related to Nitrosococcus oceani and Nitrosococcus watsonii which are restricted to marine environments and salt lakes. Microcoleus vaginatus
and diatom chloroplast-related sequences were mainly detected in IC
areas from L and M. Heavy grazing could alter autotrophic
bacteria/diatom composition in IC areas possibly due to physical
disturbance of biological crusts by trampling, threatening the potential
of crust re-formation. Grazing intensity affected soil bacterial
communities differently in PCP and IC areas with soil crust,
highlighting the importance of improving our understanding of microbial
diversity responses to land use.
Keywords
- Arid ecosystems;
- Grazing;
- Bacteria;
- Patagonia
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