Legacy effects of soil homogenization on tallgrass prairie restoration: toward resolved understanding of the relationship between soil heterogeneity and plant species diversity

Abstract

Within plant communities, niche-based species sorting can occur among distinct soil patches (microsites), increasing coexistence and diversity. Microsite edges (microedges) may also offer additional niche space. Therefore, in recently abandoned croplands, which often have uniform soils caused by a legacy of tillage (soil homogenization), the plant species diversity of future restoration efforts may be reduced. We conducted an experiment during the early establishment phase (3 years) of a tallgrass prairie restoration on former cropland to determine if soil homogenization decreases species diversity and alters community composition, and if microedges offer additional niche space. Heterogeneous plots with sand-or woodchip-enriched patches were compared to plots made up of the same components, but distributed homogeneously, and pits and mounds were compared to flat topsoil. Homogenization decreased diversity in flat topsoil plots relative to pit plots and increased diversity in woodchip plots. In both cases, the treatments with the lowest canopy cover and greatest plant density had the greatest diversity. Sand and topographic homogenization decreased diversity, but when a drought occurred in year two, the effect was suppressed in the sand treatment and magnified in the pit plots. Microedges had properties unique from adjacent patches. Overall, variability in heterogeneity-diversity relationships was affected by interactions with plant growth patterns and environmental conditions. Our results indicate that while the addition of contrasting soil microsites has the potential to promote increased diversity in grassland restoration on former cropland, the patch components and design must be optimized to achieve this management goal.

Active versus passive restoration of tallgrass prairie in the U.S. Midwest: plant species diversity and assemblage, net primary production and soil carbon sequestration

“…We regard our study area as a highly disturbed and fragmented land for decades if not a century. Agricultural practices, particularly long‐term plowing (Hall 2015), has homogenized the soil horizons (Anderson & Coleman 1985; Stover & Henry 2020) and depleted native seeds in soil. Sources of native seeds and other propagules are also not in close proximity to the fragmented land of arboretum of which closest remnant tallgrass prairie is approximately 30 km away.…”

Combined effects of soil 3D spatial heterogeneity and biotic spatial heterogeneity (plant clumping) on ecosystem processes in grasslands

“…Stover and Henry ( 2018 ) and ( 2020b ) hypothesized that micro‐edges have higher productivity and N retention due to complementarity, so the highest productivity would be found when there are distinct niches inside a patch compared to along the edges. This could explain our highest productivity at the 24 cm soil cell size at the second harvest because at 12 cm more of the surface can be seen as an edge which reduced the distinct niches inside the patches.…”