Response Of Plant Beta Diversity To Plateau Pika Disturbance In Alpine Meadows

Plateau pika（Ochotona curzoniae）is a small burrowing herbivore,and is endemic in the Qinghai-Tibet Plateau.The disturbance by this small herbivore can change plant community composition and inducing forward/reverse succession in alpine meadows.Plantβdiversity is usually used to measure the changes of plant composition in communities along environmental gradients,and reveal the ecological processes of grassland communities along environmental gradients.Therefore,understanding the response of plantβdiversity to plateau pika disturbance is helpful to explain the changes of plant community and ecological process of alpine meadows.Previous studies have used Whittaker index to verify that the disturbance by small burrowing herbivore can increase plantβdiversity of grassland community at a single area.However,how the response of the specific way of plantβdiversity to the disturbance by small rodent herbivore is not well documented.Previous studies have demonstrated that plantβdiversity changes mainly involve two pathways,consisting of turnover and nestedness,which can provide information for protection sites or some species.Therefore,this study selected three sites（Gonghe county,Haiyan county of Qinghai province and Luqu county of Gansu province）with different environments to find whether relationship between plantβdiversity and plateau pika disturabcne had a general pattern.In addition,each disturbance intensity of plateau pika was considered as a single site in stuty areas,by which this study can reveal specific pathway of plantβdiversity responding to plateau pika disturbance in alpine meadows.These results can present the specific protection strategies:protection sites,species,or both.The findings of this study can provide the scientific basis for maintaining alpine meadow through management of plateau pika.The main conclusions are as follows:1.Plateau pika disturbance increased plantβdiversity of alpine meadowsThe alpine meadow plantβdiversity with plateau pika absence areas was significantly lower than plateau pika present areas.There was a positive linear correlation between plateau pika disturbance intensity and alpine meadow plantβdiversity index（R~2=0.387,P<0.001）,indicating that plateau pika disturbance and its intensity had common characteristics on plantβdiversity of alpine meadows.2.There are both turnover pathway and nestedness pathway which caused plantβdiversity changed induced by plateau pika disturbance in alpine meadowsUsing multiple sites method analyzing three study sites unification,the main pathway of plantβdiversity changed with the disturbance of plateau pika in alpine meadows is turnover（turnover accounted for 80.6%）,which nestedness only accounted 19.4%.The individual site analysis result showed nestedness pattern is dominant in Luqu county（accounting for 77.4%）while turnover pattern is dominant in Haiyan county（accounting for 80.7%）.In Gonghe county,it is the result of turnover and nesting both pathways（accounting for 51.5%and 48.5%,respectively）.All three study areas were analyzed by matching sites method which showed that the the average proportion of turnover component was accounting for 67.8%.For each study area,the average proportion of nestedness components in Luqu county is 83.0%,the average proportion of turnover components in Haiyan county is 71.8%,the average proportion of turnover and nestedness in Gonghe county is 47.9%and 52.1%respectively.According to the species diversity protection mechanism behind the two ways for the entire study area,managers should protect multiple disturbance sites for maintaining species diversity.According to a single study site,managers should pay attention to the protection of species and sites at the same time in Gonghe county.In Haiyan county,paying attention to the protection of sites is more important while the Luqu county should pay more attention to the protect the species.According to the turnover(β_sim),nestedness(β_nes)and totalβdiversity(β_sor)values of paired sites,all loci could be divided into 3-4 groups with different disturbance intensity of plateau pika in alpine meadows.The number of plant species distributed in different groups was significantly different.3.The species and loci which should be protected in the whole analysis area were identified under plateau pika different disturbance intensity.At the same time,priority conservation strategies were identified with the three study areas were identified separatelyWhen considering the three sites as a whole,T₁,T₃,T₂₀,T₂₂ and T₂₃ contributed significantly to the plantβdiversity of alpine meadows with plateau pika disturbance gradient.Therefore,protecting loci with disturbance intensity of 0,153?hm^-2 in Gonghe county,1072?hm^-2,1363?hm^-2 in Haiyan county and loci with disturbance intensity of 0 in Luqu county is important.When three study areas is considered separately,Luqu county should give priority to the conservation of species with high contribution values,such as Artemisia hedinii,Carex moorcroftii,Lagotis brachystachya,Aconitum gymnandrum,Elsholtzia densa,Thermopsis lanceolata and Lamiophlomis rotate.In Haiyan county,priority should be given to the conservation of multiple loci,especially some with high contribution values to plantβdiversity,such as T₁（0 disturbance intensity）,T₂(83?hm^-2),T₁₁(1363?hm^-2).For the same reason,we should not only protect the loci with highβdiversity contribution in Gonghe county,such as T₁（0 disturbance intensity）,T₃(153?hm^-2),T₁₀(612?hm^-2),but also protect the species with high plantβdiversity contribution which mainly including Anemone rivularis,Kobresia capillifolia,Polygonum macrophyllum,Leontopodium nanum and Ranunculus tanguticus.