The Relationship Between Plant Diversity And Productivity Along A Successional Stage Of Restoration On The Alpine Meadow

Although a great deal of researches concern to relationships between biodiversity and ecosystem functioning, there is as yet no agreement as to how different components of diversity, including species diversity, functional group diversity and functional trait diversity, could influence ecosystem properties. In this study, by using a spatial sequence approach instead of a temporal one, the relationship between different components of plant diversity and aboveground primary productivity were investigated along a successional stages of restoration on the alpine meadow in Qinghai-Tibetan Plateau. The different components of diversity, including species diversity, functional group diversity and functional traits diversity, were used as diversity index. The gradients of recovery succession included1,3,5,10, and15years respectively. The main conclusions drawn from the study are as follows:1. Species diversity varied significantly with the recovery succession. Species number increased from9to37, while Shannon index increased from0.81to3.13as the succession of grassland change form1year to15years. There was a positive correlations between species number and succession and a unimodal relationship between Shannon index and succession.2. Plant functional group diversity and species number within functional groups increased with the successional gradients. Functional groups increased from2(annual forbs and grass) to5(annual forbs, grasses, legumes, sedges and perennial forbs). Functional group index varied from0.73to3.17as the grassland succession change from1year to15years. There were also positive correlations between succession and functional group number and functional group index. Besides, species number within functional group in grass, perennial forbs. sadges and legumes all increased significantly, while species number within annual forbs decreased significantly.3. Plant functional traits and functional trait diversity varied greatly along the successional gradient. Plant height, relative growth rate and specific leaf area declined significantly with the succession prolonged, leaf dry mass content, however, rose significantly. There are negative correlations between plant height, relative growth rate and specific leaf area and succession gradient, but positive correlations between leaf dry mass content and succession. Functional trait diversity increased from0.1591in the beginning of succession to0.5424in the fifteen years of succession. There also existed positive correlation between them.4. Aboveground net primary productivity decreased with succession, there was a negative correlation between them. The relationship between species number, Shannon index and productivities was negative correlated. Functional group diversity, including both functional group number and functional index, are negative correlated with productivity along the successional gradient. Among the four functional traits, plant height, relative growth rate and specific leaf area showed positive correlations with productivity. Contrast with this, leaf dry mass content showed a negative correlation with productivity. Functional trait diversity, however, showed significantly negative correlations with productivity.These results suggested that succession had an inmportant influence on different component of plant diversity——spciece diversity, functional group diversity and functional trait diversiy. As the succession progress, plant diversity increased greatly, the grassland developed more healthy. Grassland productivity, however, decreased as the succession extend because of the intensity of interspecific competition incrased and the limitation of avalable resource in soil. Therefor, in order for biodiversity protection and productivity recovering, the measures of enclosure and appropriate utilization should be adopted in the grassland management in the future.