| The alpine grassland ecosystem cover more than 60% of the Qinghai-Tibet Plateau,and provide important ecological service,such as biodiversity conservation,carbon storage,water supplement,and climate regulation on a global scale.Eospalax baileyi is a subterranean herbivorous rodent endemic to the Qinghai-Tibet Plateau,and is also the dominant pest of alpine meadows regarded by the governments.As an important component of the subterranean ecosystem of alpine meadows,plateau zokor has an impact on the structure of the above-ground plant community and the function of the subterranean ecosystem through foraging,burrowing,and building mounds.Currently,studies on the ecological effects of small rodent activities in alpine meadows are increasing,mainly focusing on the effects of their building mounds on plant community characteristics and soil nutrients.However,there is a lack of understanding of biodiversity and functioning relationships which integrating the multi-trophic levels(from plants to soil invertebrates),and impact pathways involved in complex ecological systems.It is important to clarify the effects of plateau zokor disturbance on the structure and function of biomes in alpine grasslands and its impact mechanisms to scientifically evaluate its negative effects and protect grassland biodiversity.This study selected five levels of disturbance according to the differences in spatial pattern indices of the area,edge,and splitting of the zokor mounds and investigated the characteristics of soil physical and chemical properties,plant communities,soil macroinvertebrate communities,and microbial communities.Focusing on two dimensions of species and functional diversity,the study evaluated the effects of zokor disturbance on the structure and function of grassland biological communities,analyzed the key environmental factors driving the structure and function change of biological communities in alpine grasslands under zokor disturbances,and finally determined the pathway of disturbances affecting the structure and function of biological communities.The results of this study are as follows:1.Soil moisture content significantly increased,while soil temperature and compactness significantly decreased under plateau zokor disturbance(p<0.05).The content of total soil potassium and p H showed little change.The organic carbon and total nitrogen only significantly reduced under extremely heavy disturbance,while the content of ammonium nitrogen,nitrate nitrogen and available phosphorus tended to increase and then decrease with disturbance intensity.Soil sucrase and urease activities decreased significantly under the all disturbance intensities,while alkaline phosphatase activity increased with the increase of disturbance intensities and then decreased.Soil temperature had a significant positive effect on sucrase and urease activities,and soil ammonium nitrogen had a significant positive effect on alkaline phosphatase activity.2.The species richness,Simpson dominance and Shannon-Wiener index of plant communities significantly increased under plateau zokor disturbance(p<0.05),plant above-and below-ground biomass had changed.The increase of forbs species richness was the driving factor that increased plant community species diversity.The loss biomass of grass functional group reduced the underground biomass of plant community,and the compensatory growth of forbs promoted the aboveground biomass of the plant community.The structural equation modeling results showed that plateau zokor disturbance has a positive effect on plant species diversity mainly by changing soil hydrothermal conditions.At the same time,the reduction in soil carbon and nitrogen caused by plateau zokor disturbance suppressed plant species diversity.3.The plateau zokor disturbance significantly changed the functional traits and diversity of plant community.Firstly,the weighted average of plant community traits has been changed,such as the relative chlorophyll content,carbon content and phosphorus content of leaves increased significantly under plateau zokor disturbance(p<0.05),while plant height,specific leaf area and leaf nitrogen content decreased significantly(p<0.05).Secondly,plateau zokor disturbance increased the functional richness of plant community,but decreased the functional divergence and Rao Q index of plant community.The structural equation modeling results showed that plateau zokor disturbance caused variation in functional diversity of plant communities by affecting soil water conditions;on the other hand,it contributed to variation in functional trait diversity mainly through changes in soil moisture,temperature and organic carbon content,and finally regulated the functional diversity of plant community.4.Under plateau zokor disturbance,the soil macroinvertebrate communities showed a significant increase in species richness,abundance,Simpson dominance index,and Shannon-Wiener index(p<0.05).The increase in the herbivorous functional group’s richness and abundance was the driving factor for the increased species diversity,while the loss of biomass in this group caused a reduction in the biomass of the soil macroinvertebrate communities.There was a positive correlation between species richness and abundance of soil macroinvertebrate communities and biomass under plateau zokor disturbance.The structural equation modeling results suggested that soil moisture,soil organic carbon,and plant species richness were the key factors affected by plateau zokor disturbance,leading to changes in the species diversity of the soil macroinvertebrate communities.5.The functional traits and diversity of soil macroinvertebrate communities were significantly altered by the plateau zokor disturbance.While the disturbance increased the functional dispersion and Rao Q indices significantly(p<0.05),there was no significant change in functional richness and divergence indices.According to the results of structural equation modeling,plateau zokor disturbance impacted the functional diversity of soil macroinvertebrate community by altering soil moisture content.It also regulated the functional diversity of body length traits,eventually leading to the effect on the functional diversity of the macroinvertebrate community.By reducing the average biomass of individuals and changing the invertebrate diversity components such as species richness,abundance,and body length of CWM,plateau zokor disturbance maintained the total biomass stability of soil macroinvertebrate community.6.The α diversity and functional characteristics of the soil bacterial community were significantly altered by plateau zokor disturbance.The disturbed grasslands had a different species composition of soil bacterial community compared to the Control,with significant changes in the relative abundance of dominant bacterial taxa at the phylum and family levels(p<0.05).Moreover,soil bacterial species richness(Abundance-based Coverage Estimator and Chao1 indices)and Shannon diversity index were significantly increased under plateau zokor disturbance(p<0.05).The disturbance caused by zokors increased positive microbial taxon interactions and decreased average network connectivity,as shown by ecological network analysis.The structural equation modeling results demonstrated that soil moisture condition and plant species richness were altered by plateau zokor disturbance,which mainly affected the soil microbial α diversity.7.The disturbance caused by plateau zokors had a significant impact on the soil microbial metabolic activity and functional diversity.The disturbance increased the microbial metabolism of sugars,amino acids,carboxylic acids,polymers,and amines,and also led to higher functional diversity indices,including AWCD,evenness,and Shannon-Wiener(p<0.05).However,the Simpson dominance index decreased.According to the structural equation modeling results,the zokor disturbance increased the functional diversity of soil microbes by changing soil moisture conditions,organic carbon content,and plant species richness.To summarize,the disturbance caused by plateau zokors has a considerable impact on the species and functional diversity of plant,soil macroinvertebrate,and microbial communities in alpine grasslands.Through tunneling and mound building,the zokors increase the heterogeneity of soil hydrothermal resources at the microhabitat level,thereby altering the soil physical and chemical environment and regulating plant diversity.Additionally,this disturbance affects the diversity of macrofauna and microbial communities through soil-plant interactions.These findings offer valuable insights into conserving biodiversity,scientific control of rodent pest in alpine grassland,and implementing adaptive ecosystem management practices for alpine grasslands on the Qinghai-Tibet Plateau. |
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