Effect Of Plateau Pika Disturbance On Leaf Trait And Stoichiometry Of Dominant Plants Of Alpine Meadow In The Qinghai-Tibet Plateau

The plateau pika is an endemic small mammal in the Qinghai-Tibetan Plateau, and also is key species of alpine meadow ecosystems. This small animal disturbs alpine meadow ecosystem by burrowing behavior and consuming some plants, and this kind of disturbance influences the plant growth and development with different effectiveness by via altering alpine meadow habitat and competition relationship among different plants. Consequently, the distance of plateau pika regulates succession direction of plant community. As an importantly plastic morphology characteristic of plant, the plant leaf trait is often used to indicate the survival and the adaptive strategy of plants. Therefore, understandings the influence of plateau pika distance on plants leaf traits is able to disclose the mechanism of plateau pika distance regulating succession direction of plant community from the level of individual. The plants leaf trait generally is influenced by the biology characteristic of plants and environment, and plant leaf stoichiometry often show the relationship between plants and soil in the process of plant adapting the change of environment. It is necessary to analyze the influence of plateau pika disturb on the plant leaf stoichiometry for determining the response of plant leaf traits to plateau pika disturbance. Our research is to determine the response of leaf traits and ecological stoichiometry of main dominant plants of alpine meadow to plateau pika disturbance in the east edge region of Qinghai-Xizang plateau by using active burrow entrance density of plateau pika to substitute the disturbance level of plateau pika which will not only provide important theoretical information for regulating the succession direction of alpine meadow drives by plateau pika, but also improve the method of research the relationship between small animal lives in grassland and plant. The some results were drawn as following:1 Clarified the response of plant community of alpine meadow to plateau pika disturbanceThis study showed that the dominant role of dominant plant Kobresia capillifolia decreased gradually while the dominant role of some associate plants decreased and that of some associate plants increased as the disturbance level of plateau pika increased. The plant community biomass, height and cover of alpine meadow were the biggest at disturbance level Ⅲ, indicating that the plant community succession was positive when the disturbance level of plateau pika increased from level I to level III, and it was negative when the disturbance level of plateau pika was over the level III.2 Presenting the respond of several plant leaf traits to plateau pika disturbanceThe indicators of plant leaf trait showed a different performance with the increase of plateau pika disturbance level. The plant leaf chlorophyll content at disturbance II and III levels was higher than those at disturbance I and IV levels, and the carotenoid content of plant leaf decreased gradually as the disturbance level of plateau pika increased. The special leaf area (SLA) of Kobresia capillifolia was significantly higher than those of Elymus nutans and Anemone rivularis (P<0.05), but their response to disturbance level of plateau pika was related to year, in which the SLA decreased gradually in 2013, but firstly decreased and then increased in 2014 with the increase of disturbance level. The LDMC (leaf dry matter content) significantly increased in 2013 (P<0.05), but firstly decreased and then increased in 2014 in the increasing process of disturbance level of plateau pika. In a word, leaf chlorophyll and carotenoid content was more stable than SLA and LDMC when they responded to disturbance level, and the rational disturbance of plateau pika contributed to enhancing the LDMC.3 Determining the influence of plateau pika disturbance on the ecological stoichiometry of the dominant plants and the soilThe leaf N and P content of dominant plant firstly increased and then decreased, and they and their ratio (N:P) was the biggest at disturbance level Ⅱ and Ⅲ. The soil N and P content was not obviously changeable when the disturbance level increased from Ⅰ to Ⅲ, and they significantly decreased when the disturbance level was over Ⅲ (P<0.05), whereas the soil N:P ratio significantly increased as the disturbance level of plateau pika increased (P<0.05). These results suggested that the appropriate disturbance of plateau pika did not contribute to soil degradation.4 Analyzing the relationship between plant leaf trait and the ecological stoichiometry of plant with soil.Leaf P content not only had significantly negative relationship with the carotenoid content (P<0.01), but also had remarkable negative relationship with the chlorophyll content (P<0.05); The LDMC descended gradually as the chlorophyll content increased (P<0.05). The negative relationship was found between chlorophyll content and SLA. The remarkable positive relationship was observed between SLA and LDMC (P<0.05). The increase of leaf N content of dominant plant leaf was along with the decrease of the leaf P content (P<0.01). The leaf P content of dominant plant was similar to the soil P content. The soil N content and P content showed a common increasing trend. The leaf N content of dominant plant was reverse to the soil N content.