As stated by a White House press release on Dec. 5, 2016, “Soil is essential to human life” and the statement particularly identified the grassland functions: “… it plays a critical role in ensuring water quality and availability; supports a vast array of non-food products and benefits, including mitigation of climate change; and sustains the biodiversity needed for ecological resilience.” The challenge to scientists is to carefully and critically document the relationships among soil biotic diversity, ecosystem function, and human well-being, and use this information to identify scenarios to mitigate undesirable change. In this introduction and overview, I summarize findings and advances made in the last decade in our understanding of grassland soil diversity-ecosystem services relationships.
Most studies reviewed here found positive correlations among soil biological diversity, resilience of plant communities, and selected ecosystem services. Defining and quantifying soil biodiversity remains problematic. The advances in the power and breadth of molecular and biochemical assays has greatly increased our understanding of factors shaping the microbial communities and their relationships to ecosystem processes. Functional traits, including carbon and nutrient use efficiencies, are now being identified with specific groups, and the consequences of these traits on soil characteristics and processes are becoming more evident. Difficulties remain in relating soil biodiversity to ecosystem processes at meaningful temporal and spatial scales. The few studies of top-down effects of suspected keystone soil organisms and consequences of trophic cascades remain as isolated reports and have not been integrated into regional soil health assessments. A current reality is that major advances in our understanding of soil biodiversity and grassland dynamics are largely emerging from research networks outside of the USA. The concern is that these networks do not focus on the current dominant stressors affecting soils in North America, making management decisions more uncertain and our grassland communities in general more vulnerable to ecological surprises. A home-grown initiative understanding the role of soil biological diversity, resilience, and grassland transformations to less-desirable states seems overdue.