The Effect Of Extreme Precipitation On Plateau Pika(Ochotona Curzoniae)

The extreme precipitation happened on July20,2009, during which the amount of precipitation was92.8. mm during three hours. Under this background, the dynamics of plant communities and plateau pika (Ochotona curzoniae) population, and the relationship between them were investigated from2008to2011, before and after extreme precipitation. The main results are as follow:1. Affected by the extreme precipitation, plant height and coverage increased at first and then, reduced, while the species diversity showed an increasing trend at first and then decreased. Aboveground biomass also decreased significantly compared with other three years.2. Population density of plateau pika showed a unimodal pattern in general. While in grazing area, population density of plateau pika manifested a bimodal curve in the year of extreme precipitation, The lowest point appeared in August (P<0.01), it then had a certain degree of rebound in October.3. The extreme precipitation had a great effects on monthly body weight of plateau pika, the data in August2009differed significantly from other three years (P<0.05). The yearly fluctuation showed a unimodal pattern, and the highest value appeared in2010. Restricted by density-dependent factors and environmental change, the body weight dropped to lowest value in2011.4. Because of affected by the extreme precipitation, survival rate of the plateau pika populations reduced to the lowest point in July2009, and had a significant differences (P<0.05) compared with the same period of other three years. Survival rate rised again in2010, and then, tend to be stable. This patterns consistent with " density-dependent" theory.5. The sex ratio of plateau pika was influenced greatly by extreme precipitation in2010, which deviated significantly from1:1. The sex ratio of other years, however, gradually tend to be1:1.6. There existed a closely correlations between extreme precipitation and plant communities、population density of plateau pika. Extreme precipitation first play an important role on plant communities, changing the height of plant communities, coverage, diversity, and vegetation biomass. With the changes of each plant community index, consequently, the population density of plateau pika change too.These results suggested that the population density of plateau pika was restricted by density-dependent theory:the extreme precipitation resulted in great decreasing in population number of plateau pika, but it rised again after1and2years of precipitation. Therefore, to carry out effective control measures will get twice the result with half the effort.