Facilitation Among Species Under Different Elevation And Grazing Disturbance

Facilitation among plants is one of the hotspots in ecology,which plays an important role in community construction and ecosystem function.Many studies predicts that the intensity of facilitation increased with stress gradient.However,there is large controversy on this hypothesis,in particular for the net outcome among plants along stress gradient.Also few studies have focused on SGH along different stress conditions.In this paper,we explored the facilitation among the shrub Dasiphora fruticosa and understory species at community,functional group and species levels,and the shift of facilitation along different elevation and grazing disturbance by using a removal experiment in the meadow on the Tibetan plateau.We found: 1)D.fruticosa significantly changed the composition of understory community and increased the productivity of community due to the presence of facilitation.2)Facilitation of shrub showed no significant difference between different elevation at the community level,and the facilitation did not increased with elevation.3)Facilitation at community level did not have difference between fence and grazing,which was due to the facilitation balanced each other at functional group and species level.4)The variation of facilitation at species level was related to the strength and types of gradient.5)The species competed with D.fruticosa at low elevation or fenced will be less competed or facilitated by D.fruticosa,which probably due to their trade-off between competitive and stress-tolerant ability.Our results analysis the variation of facilitation at the community,functional group and species levels,and differential responses of facilitation to different elevation and grazing disturbance,which stress the importance of facilitation among D.fruticosa and its understory species in constructing community and maintaining diversity in the alpine meadow.