Effects Of Mowing And Nitrogen Addition On The Functional Diversity And Ecosystem Multifunctions In A Typical Steppe

Grasslands play import role in maintaining multiple ecosystem functions and services.Mowing,a common management in temperate grasslands,potentially have profound impacts on its structure and functions by moving plants and declining nutrient return and reducing the competition from large plant species.A large number of studies have been made on plant functional traits,community composition and net primary productivity in grassland ecosystems under mowing,but most have been conducted independently.The consequence of mowing on the grasslands at different ecological levels(i.e.,species,community and ecosystem)have not been well understood.Moreover,few studies have been conducted to test interaction of mowing and nutrient availability.To answer these questions,we established a mowing and nitrogen addition experiment in a degraded typical steppe in Inner Mongolia,studied three dominant plants of typical grassland(i.e.,Leymus chinensis,Stipa krylovii and Cleistogenes spuarrosa)and 11 plant morphological traits and leaf chemical traits at species level and community level,and their relationships with ecosystem multiple functions.The results are as follows:(1)The responses of plant traits to clipping and N addition showed intra-species variations.The species in the upper canopy(i.e.,Leymus chinensis and Stipa krylovii)in mowed plots have lower plant height,leaf length and leaf area than unmowed plots.However,Cleistogenes spuarrosa,the lower plant,showed less responses to mowing.N addition promoted leaf N content and decreased C:N ratio of Leymus chinensis and Stipa krylovii.We did not detect the significant interaction between mowing and N availability.(2)The functional traits based on community weighted trait after clipping was nearly dependent on the dominant species,showing similar responses with Leymus chinensis and Stipa krylovii.There were obviously interannual differences for various traits,but there was no interactive effect with mowing or nutrient enrichment.(3)Mowing promoted to a greater biodiversity,particularly under high N levels,but did not change the species composition.The plant diversity decreased with N fertilization only occurred in plots without mowing.The functional diversity showed complex changes under the treatments by N increasing and mowing.(4)Moreover,we did not observe the significant consequence of ecosystem multifunctionality based on ANPP and soil nutrient cycling,while a weak improvement of multifunctionality of degraded grassland ecosystems with N addition in several plots without mowing.(5)Plant traits had deeper impacts on ecosystem multifunctionality without mowing disturbance.Unexpected,we did not find the close relationship between multifunctionality and species diversity,which suggesting that importance of key species in determining the ecosystem functions for arid grasslands.The experiment evidence indicates that the identity and of some key species their traits determine the community traits and ecosystem functioning,rather than species diversity in temperate grasslands.The lower diversity due to over utilization before the present experiment may constraint the contribution of other species to ecosystem multifunctionality.