Relationships Between Plant Diversity And Community Stability At Two Spatial Scales During Abandonment Succession In Subalpine Meadow

The relationship between plant diversity and stability has been a topical and controversial issue in community ecology research for a long time,and those studies have mainly focused on small（local）spatial scales.Studies at local scales have shown that community diversity and stability change with succession time,but it is unclear how succession time affects plant diversity and community stability at different spatial scales and the relationship between the two.In this study,we investigated the changes in plant diversity and temporal stability of community productivity（including functional and compositional stability）at two spatial scales（0.25 m²plot and 1.25 m²transect）during abandonment succession（abandoned for 1 year,3 years,5 years,15years,30 years and 100 years,respectively）in subalpine meadows on the eastern edge of the Tibetan Plateau through a continuous 7-year（2003-2010）observation experiment,and explored the stabilization mechanisms of plant diversity on community productivity at two different spatial scales during the abandonment succession.The main results were as follows:1.During secondary succession,plant diversity（αandγdiversity）at both plot scale and transect scale significantly increased,butβ_rich diversity（the difference in species composition between plots）decreased.This indicates that the species turnover rate decreases with increasing succession time.2.During secondary succession,species stability as well as functional and compositional stability of both plot scale（α）and transect scale（γ）communities increased significantly.In addition,species stability was significantly and positively correlated with communityαstability,andαstability was significantly and positively correlated withγstability.This suggests that communityαstability at small spatial scales can improve communityγstability at large spatial scales,i.e.,plant communities with higher species stability have higherαfunctional and compositional stability,which in turn increases the stability of ecosystems at regional scales.3.Species asynchrony and spatial asynchrony（asynchronous dynamics among communities）did not change significantly with increasing successional time,but both significantly increased communityαfunctional stability andγfunctional stability,respectively.This result supports the species insurance hypothesis and the spatial insurance hypothesis.That is,decreases in the abundance of some species（community productivity）are compensated by increases in the abundance of other species（community productivity）,thus buffering temporal fluctuations in the abundance of the whole community（regional community productivity）.4.Structural equation modeling suggests that plantαdiversity increases with succession time,thereby increasing communityαfunctional and compositional stability,and ultimately indirectly increasingγfunctional and compositional stability.β_simpdiversity is not affected by succession time,but enhancesγfunctional stability by increasing spatial asynchrony.Thus,bothαdiversity andβ_simp diversity promote functional stability at the transect scale（γ）.In addition,structural equation modeling also indicated that plantαdiversity had a greater effect on communityγstability thanβ-diversity.These results suggest that in future ecological restoration and conservation,it is important to pay attention to changes inβdiversity while maintaining higherαdiversity in communities,so as to avoid the negative effects of biotic homogenisation on ecosystem stability.5.Overall,this study reveals that plant diversity plays a key role in the maintenance of ecosystem stability at two spatial scales during secondary succession,demonstrating the temporal and spatial dependence of biodiversity on the temporal stability of ecosystems.Therefore,in the context of future global change and biodiversity loss,studying the influence and mechanisms of biodiversity on ecosystem stability at both temporal and spatial scales is more useful for understanding and appreciating the relationship between biodiversity and ecosystem function as well as stability at the landscape scale.