The Effects of Gap Disturbance on the Seedling Emergence, Survival and Growth of Two Different Native Species in Inner Mongolia

摘要

A field study was conducted to investigate the effects of gap disturbance on the seedling establishment process of two native species. Seeds of Agropyron cristatum and Stipa krylovii were reseeded to artificially created gaps in a degraded steppe in North China. There were seven treatments: shoot gaps and root gaps (10cm, 20cm and 40cm in diameters), no gaps (control). Shoot gaps were formed by removing above ground vegetation and below ground biomass without restricting the re-growth of neighbor roots back into the gap. The root gaps were accomplished by using polyvinyl chloride pipes sunk in the soil of shoot gaps to exclude neighboring roots. Seedling emergence, survival and growth performance after 90 days of growing were recorded for both species. Gap disturbance significantly increased soil moisture, especially for root gaps. Gap size significantly promoted seedling emergence. Emergence increased for both species as gap size increased. 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. 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. Predation by insects may be one of the key reasons to explain the stand dominance in this grassland. The results implythat we should take different coping strategies with different species in the process of restoration by reseeding native species.