A Resource-Based Approach to Assessing Interseeding Success in Reconstructed Tallgrass Prairies

Abstract

Interseeding is a common method used to increase species richness within established reconstructed grasslands. This process depends upon the ability of the practitioner to produce resource conditions that facilitate seedling emergence in systems where such emergence is often limited. We tested effects of a mowing disturbance on interseeding success by seeding a mix of 10 common tallgrass prairie species into 1-m² plots within two warm-season grass dominated grasslands. We clipped the vegetation on a subset of the plots once or repeatedly and measured environmental variables including litter depth, soil surface light, soil moisture, and soil nitrate within the first growing season. While clipping consistently increased soil surface light, seeded species emergence varied in response to measured environmental resources between sites. In the lowland site, emergence over two growing seasons was primarily explained by microsite and early season light availability. In the more recently burned upland site, emergence was primarily limited by later season light conditions associated with clipping. Despite this variation, seed additions increased plot-scale species richness irrespective of clipping effects mainly as a result of high establishment of wild bergamot (Monarda fistulosa) in both sites. It appears that effects of season-long defoliation management on seedling emergence depend on microsite conditions at seeding and we conclude that soil surface and established vegetation management are necessary when interseeding to increase grassland species richness.