Niche differentiation of tallgrass prairie plants species along soil hydrological gradients

Abstract

This study addressed whether the distribution of species in frequently burned lowland tallgrass prairies is driven by gradients in soil hydrology. On three study sites, the hydrological conditions in 1 m2 vegetation survey plots where quantified as the number of days the soil was anaerobic less than 15 cm below the surface, and the surface of the soil was drier than 0.4 m3·m−3. On each site, the centroid of each species hydrological niche was defined as the hydrological conditions in plots where it occurred, weighted by its abundance. Species found on all sites maintained a consistent ranking between sites along the soil drying gradient, but not the anaerobic gradient. The levels of niche overlap between species pairs along both hydrological gradients were significantly less than the overlap from randomly assigning species to the hydrological gradients. Indicator species analysis suggested that on each site the communities were best described as consisting of two subgroups. The hydrological niches of the species in these subgroups were significantly different from one another, suggesting that these subgroups are associated with wet or dry habitats. Overall, these analyses suggest that hydrology plays a major role in determining the structure of these frequently disturbed communities.