Differences Of Soil Properties Effects By Community And Population Levels In Alpin Meadow On The Qinghai-tibetan Plateau

Degraded of the grassland is main due to overgrazing and nutrient deficiency in Qinghai-Tibet Plateau,the degradation are the decrease of grassland productivity and soil quality,so reasonable grassland management is an important means of decrease grassland degradation and maintenance grassland productivity.Three Grazing modes?cold season grazing,rotational grazing and enclosure?were used to study the patch community and pot experiment were to research single population in the northeastern margin of the Qinghai-Tibet Plateau,Combining field investigation with laboratory potting.1)Three grazing modes?Cold Season Grazing,Rotation Grazing and Closure?affect the main vegetation patches?Gramineae,Cyperaceae,Gramineae+Cyperaceae,Polygonaceae,Compositae and Leguminous patches?of plant community characteristics,MBC,MBN and C,N,P contents and in alpine meadow;2)Under cold season grazing grassland,rhizosphere and ¹³C partitioning characteristics of Gramineae and Cyperaceae communities in alpine meadow;3)Clipping?0 and C?and fertilization?0,N,NP?influence the vegetation populations of biomass allocation and soil C,N,MBC,MBN and enzyme activities in alpine meadow.At the plant community and population level,the differences of vegetation and soil processes in alpine meadow and their responses to management modes were quantitatively analyzed.To clarify the role of vegetation and soil ecosystem under grazing and fertilization management in alpine meadow,this research provides a theoretical basis for carbon sequestration management,grassland degradation and remediation in alpine grassland.The main results as follows:Enclosure promotes the change of Cyperaceae patches to Gramineae patches,thus reduces underground biomass in Alpine Meadows;Patch type had no effect on soil organic C and total N,and enclosure reduced soil organic C content in alpine meadow;The above-ground biomass,MBC,DOC,available P,inorganic N and SOC C mineralization rates of Gramineae patches were higher than other vegetation patches in three grazing modes.Similar amounts of C were assimilated by the two functional plant groups,the sedges transferred greater proportions of photosynthetic C to the roots and soil?through rhizodeposition?than the grasses,responding to their greater root biomass and root to shoot ratio.The replacement of sedges by grasses in the plant community thus decreased the sequestration of soil C in meadows on the Tibetan Plateau.Addition of N and NP promoted aboveground biomass of Elymus nutans and Poa pratensis,but had no effect on aboveground biomass of Kobresia linearis and Kobresia humilis;N and NP fertilization reduced the root biomass of Kobresia linearis,while N and NP fertilization and clipping promoted the root biomass of Kobresia linearis;MBC,MBN,DOC and inorganic N in species were significantly different between fertilization?N and NP?and clipping?C?,but fertilization and mowing had no effect on soil organic C with functional groups;N fertilization alone and mowing increased MBN of Elymus nutans,while N and NP fertilization,mowing and fertilization×mowing had no effect on MBC of Elymus nutans;The soil enzyme?acid phosphatase,alkaline phosphatase,urease and dehydrogenase?with plant species were different under mowing,fertilization and mowing×fertilization;N and NP application significantly decreased soil alkaline phosphatase activity,while N×cutting treatment significantly increased soil acidity and alkaline phosphatase activity of Kobresia linensis;NP and N×clipping reduced the activity of soil acid phosphatase in Elymus nutans,while application of NP and mowing promoted the activity of alkaline phosphatase in the Elymus nutans;Mixed application of N,NP and mowing promoted soil urease activity of Elymus nutans;Application of N,NP and clipping promoted soil urease activity of Elymus nutans,N×clipping reduced soil urease activity of Kobresia humilis.Enclosure promotes the change of Cyperaceae patches to Gramineae patches,thus reduces underground biomass in Alpine Meadows;The replacement of sedges by grasses in the plant community thus decreased the sequestration of soil C in meadows on the Tibetan Plateau;Addition of N and NP promoted aboveground biomass of Elymus nutans and Poa pratensis,but had no effect on aboveground biomass of Kobresia linearis and Kobresia humilis;N and NP fertilization reduced the root biomass of Kobresia linearis,while N and NP fertilization and clipping promoted the root biomass of Kobresia linearis;Fertilization and clipping had different effects on soil nutrients of different functional groups,but fertilization and clipping had no effect on soil organic C.