Plant community changes on restored grasslands across a largescale environmental gradient

Abstract

Identifying the factors that structure communities across an environmental gradient is a commonly studied and often debated topic in plant community ecology. Despite substantial attention, a consensus has not been reached regarding which factors are the most important or how communities respond. This is especially true for grasslands, where habitat loss has limited opportunities for systematic study across key environmental gradients. Here we overcome these limitations by examining CRP restored plant community responses to a large-scale environmental gradient and to two, common management approaches. We acquired 55 CRP sites across the state of Kansas representing short, mixed, and tallgrass prairie that were restored and managed using either CP2 or CP25 management strategies. The longitudinal environmental gradient was composed of changes in mean annual precipitation, temperature, elevation, soils, and disturbance regimes. Plant community and soil data were collected in the spring and summer of 2017. Mean annual precipitation was the most important predicator of species richness which had a positive, linear response across the gradient. To a lesser degree, management practices also played a role in determining community structure. The linear increase in richness that we observed across the precipitation gradient reflects the increase in species pool size from short to tallgrass plant communities and explained most of the richness variation despite large changes in plant communities. This linear richness response contrasts with unimodal responses to gradients reported elsewhere, highlighting uncertainties at the high end of resource gradients. These findings provide insight into the diversity constraints and fundamental drivers of change across a large-scale gradient representing a wide variety of habitats and conditions in grassland systems.