Effects Of Grazing On Litter Decomposition And Litter Arthropod In Ningxia Desert Steppe

Grazing is one of the main disturbance modes in Ningxia desert steppe,which is easy to lead land degradation and desertification,and then seriously damage the structure and function of grassland ecosystem.Litter decomposition is one of the key process links in the material cycle of grassland ecosystem.And litter arthropod in litter decomposition is an important biological driving force to accelerate material cycle.However,it is still unclear about the effect of grazing disturbance on litter decomposition process and the distribution of litter arthropod in Ningxia desert steppe.The present study was to explore the effect of grazing on the relationship between litter decomposition and litter arthropod in Ningxia desert steppe.This study have investigated the litter decomposition rate and nutrient release of Leymus secalinus,Lespedeza potaninii and their mixture within 30-and 250-mesh litterbags under grazing and enclosure management in Ningxia semiarid grasslands.We mainly carried out the following research:(1)Determined the decomposition variation characteristics of L.secalinus,L.potaninii and their mixture under the enclosure and grazing grassland,and clarified the regularity of litter decomposition rate and nutrient release under grazing;(2)Investigated the litter meso-and microfauna diversity of L.secalinus,L.potaninii and their mixture at different decomposition times,and counted the distribution of litter arthropod during the decomposition of the litter,and explored the response of litter arthropod diversity in different litter under the enclosure and grazing grassland;(3)Calculated the contribution rate of arthropod to litter decomposition,the influence of soil animals on litter decomposition under grazing conditions was analyzed.The research results are of great significance for understanding the relationship between aboveground and underground ecosystems under grazing disturbance,and provide ecological arguments for ecosystem management,grassland nutrient cycle and degraded ecosystem restoration in Ningxia desert grassland.The main conclusions are as follows:(1)There was significant difference in litter arthropod diversity both in grazing and enclosure grassland.And it has a significant increased with the litter arthropod richness and Shannon-wiener index,but there was no significant effect on litter arthropod density.In addition,the density of litter arthropod showed a significant increase in L.secalinus,L.potaninii with the prolongation of litter decomposition time.While the density of litter arthropod in mixture litter showed fluctuations.The peak time of litter arthropod density varies greatly in different species of litter.The results of RDA analysis showed that the soil p H,soil moisture and soil electrical conductivity had significant effect on the distribution of litter arthropods community structure in enclosure grassland(P<0.01),while the soil silt and sand content had significant effect on the distribution of litter arthropods community structure(P<0.05).(2)There were no significant differences in final litter mass remaining rate(R_m)of plant litter from size-mesh treatments in enclosure grasslands,from both in 30-mesh litterbags in grazing grasslands.However,R_m was significant higher in L.potaninii than L.secalinus and mixture from250-mesh litterbags in grazing grasslands.In 30-mesh and 250-mesh litterbags,the litter decay constant(k)in L.potaninii was significantly higher in grazing than enclosure grassland.The contribution rate of litter arthropods(P_fau)was significant higher in L.potaninii and mixture than L.secalinus in enclosure grassland.But in grazing grassland,the P_fau was significant higher in L.potaninii than mixture,whereas the L.secalinus values are intermediate.However,there was a significant higher in P_fau of mixture in enclosure than grazing grassland.Correlation analysis showed that the final mass remaining rate of litter was negatively correlated with the content of litter N and P,but positively correlated with litter lignin/N and C/P(P<0.05).(3)In enclosure grassland,there was no significant difference between the final residual rate of litter C in L.potaninii,L.secalinus and mixture.There was significantly higher the final residual rate of litter N and P in the 250 mesh and the N in the 30 mesh in L.potaninii than the L.secalinus and mixture.However,there was significantly higher the final residual rate of P in L.potanini and mixture than L.secalinus.In grazing grassland,there was significantly higher the final residual rate of litter C and P in the 250 mesh and the N and P in the 30 mesh L.potaninii than mixture,whereas the L.secalinus values are intermediate.The final residual rate of N element showed that L.potaninii was significantly higher than L.secalinus and mixture.There was not significant effect on the final residual rate of C-N-P.But the effect of mesh treatment in mixture was significantly lower than.the final residual rate of N in the mixture under 30-and 250-meshes showed that the grazing was significantly lower than the enclosure grassand.And the residual rate of P in L.secalinus showed that the grazing was significantly higher than the enclosure grassland.Mantel test and PCA analysise showed there was considerable effect the release of C-N-P in litter with the distribution of litter arthropod diversity and phy-chemical properties of soil.Comprehensive analysis showed that grazing disturbance resulted a significant decrease with the richness and diversity of litter arthropod indirectly by reduces the distribution of soil particle size.And grazing affects the distribution of litter arthropod to slow down the decomposition of L.potaninii,but the decomposition of L.secalinus and mixture had promoting through initial nutrient concentrations and synergistic mixing effect respectively.In addition,Grazing disturbance had little effect on the release rate of C in L.secalinus,L.potaninii and mixture.The grazing disturbance mainly slowed down the release of N by reduction of soil p H and structure in L.secalinus,while the chemical characteristics significantly restricted the release of N in L.potaninii.The release of P in single litter is complex that mainly affected by the combined effect of the quality of litter substrate mass and soil physicochemical properties.However,the release of litter N and P in mixture had accelerate by synergistic mixing effect in grazing disturbance.