A Comparison of Regeneration Dynamics Following Gap Creation in a Degraded Grassland

摘要

Seven treatments were implemented in a degraded steppe in north China to evaluate the effects of gap creation on two native species regeneration. Shoot gaps and root gaps (10cm, 20cm and 40cm in diameters), no gaps (control). Shoot gaps were formed by removing vegetation without restricting the re-growth of neighbor roots back into the gap. Root gaps were accomplished by using PVC pipes sunk in the soil of shoot gaps. Seedling growth performance after 90 days of growing were recorded for both species. Seedling emergence and survivorship of both species were greater in gaps than in controls. However, the gap size showed a significantly negative effect on Agropyron cristatum's survivorship. Growth performance of Agropyron cristatum and Stipa krylovii differ in their response to gap disturbance. Gaptreatments had positive effects on seedling growth (including seedling height, dry weight, and numbers of tillers and leaves) of Stipa krylovii, but had negative effects on seedling growth of Agropyron cristatum. The two species have significantly different responses to gap disturbance. All results suggest that Stipa krylovii is a gap-enhanced species, and Agropyron cristatum is not. Gap creation promoted the seedling establishment. Different species differ in their regeneration dynamics when the gap is available.