[Response and plasticity of functional traits in to N and P addition].

Analyzing the effects of nutrient addition on the functional traits of desert plants is important for revealing the responses of desert plant species to environmental changes. In this study, we examined the responses of whole plant, root, stem, leaf and fruit traits of to the addition of N and P, with an experiment with three (low, medium and high) N and P addition levels and three N/P ratios (5:1, 15:1 and 45:1). The results showed that functional traits of had divergent responses to NP addition level and N/P ratio. With the increases of NP addition level, the biomass and specific leaf area were increased, while the root-shoot ratio, leaf dry matter content, root tissue density and specific root length were decreased. Belowground biomass, specific root length and net photosynthetic rate increased with the increases of N/P ratio. The coefficient of variation of 17 functional traits was 7.3%-69.1%. The biomass, root-shoot ratio and speci-fic root length were sensitive traits to NP [plastic index (PI)>0.5], with greater variability (49.4%-69.1%), whereas the leaf length-width ratio, leaf thickness, leaf tissue density, and leaf stem dry matter content were conservative traits (PI<0.20). The results of principal component analysis (PCA) showed that the position of in the multivariate feature space exhibited lateral migration with the changes of NP addition levels, with a tendency of higher aboveground and belowground biomass and a lower root-shoot ratio. Leaf tissue density was negatively related to leaf thickness and specific leaf area. Leaf dry matter content was negatively correlated with leaf thickness and specific leaf area but positively associated with leaf tissue density. Biomass had a positive correlation with specific leaf area and a negative relation to specific root length. The results of stepwise regression analysis showed that specific root length, specific leaf area and leaf net photosynthetic rate were major functional traits affecting the biomass of . adapted to the fluctuations of soil nutrient environment through changing resource utilization strategy, altering root carbon allocation, and also the trade-off and covariance among traits and inconsistent response.