Response Mechanism Of Desert Rodent Communities And Dominant Species To Different Disturbances

Harsh climate conditions and intensive human disturbance made desert ecosystemsextremely vulnerable. Rodents play a crucial role in such an ecosystem. Studies onresponses of desert rodent communities and dominant species to natural and humandisturbances are significant to understand driving mechanisms for desert mammal diversityand ecosystem stability. From2006to2011, a study was conducted at cultivated, grazingexclusion, rotational grazed and over gazed sites to investigate effect of grazing andcultivation on rodent communities in Alashan, Inner Mongolia, China. Two sites wereestablished in each habitat, and rodent communities were monitored using live trappingmethod. Vegetation and climatic information were also recorded for each study site. Theresponses of rodents to disturbances were analyzed in two ways. For dominant species,population dynamics and survival probabilities were measured. Relationships of populationabundance with climate, soil compaction and vegetation data were analyzed usingstructural equation modeling (SEM) to test effects of disturbances on rodent dominantspecies. For communities, stabilities and structures with different bionomic strategies weremeasured in different habitats. Response mechanisms of rodent communities todisturbances were also tested by SEM. The results demonstrated that1) intensive grazingreduced food quality and vegetation cover. Grazing and cultivation reduced totalabundance of rodents，and various dominant species occurred under different disturbances.2) Over grazing reduced the population abundance of Meriones meridianus and Dipussagitta，and delayed D. sagitta population peak. Cultivation reduced population abundancefor jerboas, and advanced population peak for M. meridianus.3) A difference in survivalprobability between male and female M. meridianus was detected in grazing exclusion site.Disturbance promoted survival probability of male M. meridianus, while it restrainedfemales. Survival probabilities of jerboas were not influenced by human disturbances andgender difference.4) In non-cultivated sites，including over grazed, grazing exclusion androtational grazed sites，the vegetation shield offered the maximum direct effect ondominant rodents, but indirect effect was largely from soil compaction. Dominant speciesin cultivated sites received more negative effects directly from grasses/forbs, but itreceived more negative effects indirectly from climatic conditions.5）Cultivation decreasedK-Stress-tolerant-Slow (KSS) strategists. Grazing suppressed both KSS and r-Ruderal-Fast(rRF) strategists, and had more negative influence on rRF strategists than any other treatments.6) A significant reduction of rodent community diversity found in cultivatedsites, while community diversity did not significantly differ among over grazed, grazingexclusion and rotationally grazed sites. Cultivation and grazing respectively restrainedcommunity resistance and resilience.7) In non-cultivated sites, including over grazed,grazing exclusion and rotationally grazed sites，both rodent community diversity and totalabundance were influenced by vegetation shield directly, but it was affected by soilcompaction indirectly. In cultivated sites, grasses/forbs had more negative effects on rodentcommunity diversity and total abundance directly than any other factors, while climaticconditions contributed more indirectly on rodent community diversity and total abundance.