Effects Of The Yak Feeding On Plant Seed Germination And Grazing Patterns On Beetle Diversity In Zoige Alpine Meadow

In the grazing ecosystem, herbivorous animals feed the branches and leaves of plants and also feed plant seeds, the digestive process may affect seed germination. At the same time, the plant biomass that herbivorous animals feed returns to nature in the form of dung instead of incomplete digestion. Zoige alpine meadow is one of the important bases of animal husbandry in our country, the yak and its waste(yak dung) has a huge number. The decomposition process of yak dung affects the ecological system of nutrient cycling.This study taking the grazing system of Zoige alpine meadow as the research object, to explore effects of the feeding and digestion of yak on plant seed germination characteristics by measuring the size, germination rate, germination lag time, germination index and average germination time of seeds collected from the yak dung, and studying the community structure of decomposers functional group(dung beetle) of the yak dung in four kinds of grazing mode(prohibited grazing pastures, winter pastures, summer pastures, and annual grazing pastures) by field simulation experiments. The main results were as follows:1. The species composition of seeds in yak dung showed obvious seasonal dynamic. There are two, six, six and five kinds of seeds from June to September respectively. The number of different plant seeds first increase and then decrease over time. The seeds of Scirpus pumilus, Carex muliensis, Kobresia setchwanensis, Polygonum viviparum lighter after processing, seeds of Poa pratensis, Ranunculus tanguticus, Polygonum macrophyllum heavier after processing.2. Digestion of yak inhibits the germination of weed seeds such as Polygonum viviparum, Ranunculus tanguticus, and Polygonum macrophyllum. But it improves the germination rate of gramineous plants such as Poa pratensis, and makes its germination lag time and mean germination time shorten, germination speed slower. The seeds of cyperaceae plants such as Carex muliensis and Scirpus pumilus are not affected because of its own deep dormancy.3. The quantity of beetles in summer pastures and annual grazing pastures is significantly higher the quantity of beetles in prohibited grazing pastures and winter pastures. The diversity index of beetle in prohibited grazing pastures and winter pastures is higher in summer pastures and annual grazing pastures, but the richness index of beetle is just the opposite. The populations and species of beetle gradually increase firstly and reduce over sampling time under the dynamic of the season of a single grazing mode. The quantity of beetles in summer pastures and annual grazing pastures is also higher the quantity of beetles in prohibited grazing pastures and winter pastures in single sampling.The above results show that the feeding and digestion of yak can affect seed germination process, and different grazing patterns can also affect the community and the structure of dung beetles. These results indicate the grazing yak can affect plant seed germination and plant community structure.