Competition limits first-year growth and flowering of wiregrass (Aristida beyrichiana) at a sandhills restoration site

Abstract

Uncertainty in ecosystem restoration can be mitigated by information on drivers of variability in restoration outcomes, especially through experimental study. In southeastern USA pine savannas, efforts to restore the perennial bunchgrass wiregrass (Aristida beyrichiana) often achieve variable outcomes in the first year. Although ecotypic differentiation and competition with other native vegetation are known to influence wiregrass seedling establishment and growth, to our knowledge, no studies have examined interactions between these drivers. We experimentally quantified individual and interactive effects of competition, seed source, and soil type on wiregrass density, size, and flowering culm production in the field. We sowed seeds from dry and wet sites reciprocally into dry and wet soils and weeded half of the plots. We found that competition removal resulted in significantly larger plants and a greater proportion of flowering plants with more culms on average, regardless of seed source or soil type. Seeds sourced from a wet site resulted in more plants per plot than seeds from a dry site, which might have been influenced by the greater number of filled seeds from the wet site. After seedlings become established, competition contributes to variation in growth and reproduction. Although competition removal could help start wiregrass populations, the necessity of mitigation depends on fire management needs.