Species-specific effects of grass litter mass and type on emergence of three tall grass prairie species1

Because the mat of dead grass stems and leaves, or litter, is a conspicuous feature of grasslands and has been shown to affect various plant processes, I performed a growth chamber experiment on the effect of both grass litter mass (density) and type (species mixes) on emergence of three common prairie grass species. I found that (1) switchgrass (Panicum virgatum) emergence decreased significantly at the highest litter density, but different types of litter had no effect; (2) little bluestem (Schizachyrium scoparium) emergence decreased significantly at the highest litter density and with those litter types that included switchgrass litter; and (3) indiangrass (Sorghastrum nutans) emergence increased significantly at medium density and decreased significantly under its own litter. The results show that the smallest-seeded species had reduced emergence through the litter mat and that amount of litter was more important than type of litter. In conclusion, the full range of litter effects occurred: (1) two species were inhibited by density while the other species was facilitated, and (2) one species was inhibited by litter from another species, one species was inhibited only by its own litter, and one species was unaffected by the species composition of the litter. Finally, the results indicate a potential for grass litter of different species to differentially influence regeneration of tall grass prairie species.