Legacy effects on soil microbial communities in human-dominated ecosystems

Background/Question/Methods

Legacy effects due to prior land use result in changes in vegetation and soil physical and chemical properties. These changes in biotic and abiotic factors directly influence soil microbial community structure and function in contemporary ecosystems. Land use history can positively or negatively influence crop production, and the strength and outcome of these legacy effects may be variable. A mechanism that may explain the persistence of legacy effects on microbial communities may involve carry over of dormant microbial seed banks in soils. Previous work has shown that manipulation of agricultural management can have lasting effects on microbial community structure and function. We collected soil samples from a long-term agricultural research site in southwest Michigan where rotational diversity was manipulated (monoculture to a five species crop rotation). Using molecular techniques, we assessed active and total bacterial community composition to examine the influence of rotational diversity on bacterial community composition. We also evaluated the relationship between microbial community composition and plant inputs across the rotational diversity gradient.

Results/Conclusions

Land use legacies in agriculture can be altered through changes in management strategies. In this case, bacterial communities developed under a history of row crop agriculture changed more distinctly in response to low intensity perennial stands compared to more intensively managed annual systems. In addition, rotational diversity can influence soil microbial diversity through manipulation of plant input effects on the active or total microbial seed bank. Microorganisms are integral to many important ecosystem services, and our ability to enhance positive plant-soil-microbial interactions is important to supporting desired outcomes (i.e., enhanced crop production) in agroecosystems.