Effects Of Available Soil Space On Functional Traits-productivity Relationship

In recent years, as the development of the studies on the relationship between biodiversity and ecosystem functioning, plant functional traits and functional diversity (FD) is getting more and more attention. This study has been became a new research focus. However, little is know about the general conclusions behind these effects of functional traits and functional diversity on ecosystem functioning.Using 8 annual plant species, an outdoor pot experiment was conducted to investigate effects of plant functional traits and FD in different biotop space, including six functional traits of nutritional indicators:plant height, root depth, relative growth rate, special leaf area, leaf dry mass content, root mass per unit leaf area and biomass production. To investigate the link between diversity and aboveground biomass (a surrogate index of community productivity) at the specie's level by the quantitative calculation of functional diversity, and the effect of different vailable siol space, we united six single-trait as complicated traits. The results shown that:(1) Eight plant species significantly differed in their functional traits measured in different biotop space. There are 5 traits, including plant height, root length, relative growth rate, special leaf area and biomass production, increased significantly with the increasing of biotope space. While leaf dry mass content and root mass per unit leaf area showed no significant increase trend. Plant function traits were affected significantly by the availability of soil resource. These results suggested that function traits of different species showed significant phenotypic plasticity.(2) General linear correlation analyzing indicated that aboveground biomass was significantly correlated with plant height, root deepth, relative growth rate, special leaf area, respectively, but not correlated with leaf dry mass, and negatively correlated with root mass per unit leaf area. This results suggest that relative growth rate, special leaf area,plant height and root depth are the key functional traits which have important influence on ecosystem functioning, and their effects increased with the increasing of soil available resources.(3) Calculation of the functional diversity index in plant communities showed that functional diversity was significantly correlated with species number, also significantly correlated with aboveground biomass. These results provide support for a linear increase of the magnitude of positive diversity effects on productivity with increasing available soil space, and this increase was mainly caused by complementarity effects between functional traits of species in the large biotope space. In conclusion, our results indicated that function trait and function diversity has different contribution on ecosystem functioning processes. Functional diversity, the range and distribution of functional trait values, had significant effect on productivity, and that these effects enhanced greatly with the increase of biotop space. It is necessary that consider the functional trait and functional diversity in the study of biological diversity-ecosystem functioning relationship. Functional trait lead to various conditions about suppression and promotion, to affect ecosystem structure and functioning. Therefore, in the study of relationship between function diversity and ecosystem functioning, the comprehensive effect of multi-trait must be considered. It is important to further reveal mechanisms controlling diversity - ecosystem function relationships in different environments.