Livestock exclusion reduces the spillover effects of pastoral agriculture on soil bacterial communities in adjacent forest fragments

Forest-to-pasture conversion is known to cause global losses in plant and animal diversity, yet impacts of livestock management after such conversion on vital microbial communities in adjoining natural ecosystems remain poorly understood. We examined how pastoral land management practices impact soil microorganisms in adjacent native forest fragments, by comparing bacterial communities sampled along 21 transects bisecting pasture-forest boundaries. Our results revealed greater bacterial taxon richness in grazed pasture soils and the reduced dispersal of pasture-associated taxa into adjacent forest soils when land uses were separated by a boundary fence. Relative abundance distributions of forest-associated taxa (i.e., Proteobacteria and Nitrospirae) and a pasture-associated taxon (i.e., Firmicutes) also suggest a greater impact of pastoral land uses on forest fragment soil bacterial communities when no fence is present. Bacterial community richness and composition were most related to changes in soil physicochemical variables commonly associated with agricultural fertilization, including concentrations of Olsen P, total P, total Cd, delta N-15 and the ratio of C:P and N:P. Overall, our findings demonstrate clear, and potentially detrimental effects of agricultural disturbance on bacterial communities in forest soils adjacent to pastoral land. We provide evidence that simple land management decisions, such as livestock exclusion, can mitigate the effects of agriculture on adjacent soil microbial communities.

Automated summary

The conversion of forests to pastures has been found to lead to global losses in plant and animal diversity. However, the impacts of livestock management on microbial communities in adjacent natural ecosystems after this conversion are not well understood. Research has shown that pastoral land management practices can affect soil microorganisms in adjacent forest fragments, with the presence or absence of boundary fences influencing the richness and composition of bacterial communities in forest soils. Soil physicochemical variables associated with agricultural fertilization were found to be closely related to the richness and composition of bacterial communities in forest soils. The study suggests that simple land management decisions, such as livestock exclusion, can help mitigate the detrimental effects of agriculture on adjacent soil microbial communities.