Differential responses to defoliation frequency in little bluestem (Schizachyrium scoparium) in tallgrass prairie: implications for herbivory tolerance and avoidance

摘要: Plant responses to herbivory are complex. In grasses, relative growth rate (RGR), seed, and vegetative reproduction, resource allocation, architecture vary differentially often nonlinearly with grazing intensity. High tolerance may be achieved through compensatory photosynthesis leaf growth, or demographic mechanisms such as activation of a belowground dormant bud bank. This study assessed the relationship between frequency Schizachyrium scoparium (little bluestem) in tallgrass prairie, examined roles tiller (meristem) populations its persistence under grazing. Genets were subjected varying simulated frequencies for period 2 years. Strong differential observed among plant traits. RGR, biomass, flowering showed strong nonlinear reductions response increasing clipping frequency, no evidence threshold effects. However, meristem density was unaffected, plants maintained large bank across all treatments. Tiller natality decreased initially, but increased >4 clippings, suggesting that declines RGR partially offset by natality, variation genet size is driven more demography than individual growth. Increased also resulted buds at different positions (emerging within vs. outside subtending sheath), explaining shift prostrate form many caespitose grasses persistent Thus, although this grass species lacks capacity foliage re-growth, maintenance contribute avoidance, respectively, long-term grazed grasslands.