Changes in species biomass in the Coastal Prairie of Texas when light and nutrients are altered

A 2 × 2 factorial experiment using light and nutrients as factors was carried out over 2½ years in a remnant, native Coastal Prairie of Texas. Light level, nutrient level, and date of sampling all had significant influences on total biomass, but changes were subtle, suggesting additional limiting factors. More obvious were changes in biomass of individual species, especially the dominant C4 grass species. Schizachyrium scoparium (Michx.) Nash (little bluestem), Paspalum plicatulum Michx. (brownseed paspalum), and Sorghastrum nutans (L.) Nash (Indian grass), three C4 grasses, maintained their biomass at low nutrient levels throughout the study. Sorghastrum nutans responded to higher nutrient levels with increased biomass, whereas the biomass of S. scoparium and P. plicatulum decreased. Results suggest that remnant grassland communities dominated by P. plicatum and S. scoparium are relatively stable communities maintained by yearly mowing, which removes biomass and nutrients. With the accumulation of litter, surface light levels would decrease, soil nutrients would increase, and S. nutans biomass would increase at the expense of P. plicatulum and S. scoparium. Key words: C4 grasses, fertilization, grassland, productivity, shading.