食物总氮及繁殖密度对高原鼠兔种群动态的耦合效应

The mechanistic basis of why grassland degradation leads to small mammal outbreaks has been a central focus of ecological research since last decades. We will test the multifactorial hypothesis and the prediction of nitrogen limitation hypothesis that the nitrogen content of plants limits the population size and growth of plateau pikas on the Qinghai-Tibet Plateau at our enclosure research sites in field. We will experimentally manipulate plant nitrogen content and pika breeding density to test these hypothesises. Specifically, pikas will be kept in enclosures and we will use a full-factorial design of pika density (high vs. low) and nitrogen content (fertilization vs. control) for a total of four enclosed sites. Using behavioral observations and live-trapping techniques, we have the unique opportunity to quantify fecundity, recruitment,juvenile and adult survival, age structure, social structure, mating system, spacing behavior, and home range size. Moreover, we will also quantify grass nitrogen content in the four enclosures. Quantifying these parameters will allow us to clearly identify the mechanistic basis of why grassland degradation leads to pika outbreaks on the Qinghai-Tibet Plateau, which further degrades the grassland leaving it unsuitable for livestock grazing. The primary objectives of this study are to examine couple effects of extrinsic and intrinsic factors on population dynamics and try to explain the possible mechanisms of small mammal outbreaks with grassland degradation on the Qinghai-Tibet Plateau.

草地退化引起植食性小哺乳动物种群暴发及危害发生的机制一直是种群生态学和恢复生态学关注的焦点。本项目以高原鼠兔为对象，在野外大型实验围栏内，采用重复析因实验设计，应用种群统计学、行为生态学以及营养生态学的原理和方法，通过施肥增加植物总氮含量、构建不同繁殖密度种群等处理，测定外部与内部因子交互作用条件下，种群年龄结构、繁殖强度、补充量、幼体存活及生长发育速率、空间行为、社群结构及婚配制度等参数，分析种群波动与食物质量的关系，探讨外部环境与种群内部因子对种群生活史特征和数量动态的综合作用模式；检验食物"氮素限制学说"的预测，验证小型哺乳类种群调节的复合因子假设；目的在于理解高原鼠兔种群波动的生态学过程，揭示青藏高原小型哺乳动物种群危害发生的机制。

草地退化引起植食性小哺乳动物种群暴发及危害发生的机制一直是种群生态学和恢复生态学关注的焦点。本项目以高原鼠兔为对象，在野外大型实验围栏内，采用重复析因实验设计，应用种群统计学、行为生态学以及营养生态学的原理和方法，通过施肥增加植物总氮含量、构建不同繁殖密度种群等处理，去除第一胎幼体、添加食物等处理，测定外部与内部因子交互作用条件下，种群年龄结构、繁殖强度、补充量、幼体存活及生长发育速率、空间行为、社群结构及婚配制度等参数，分析出种群波动与食物数量、质量以及自身繁殖的关系，探讨了外部环境与种群内部因子对种群生活史特征和数量动态的综合作用模式，并对食物“氮素限制学说”的预测进行了必要的验证，为揭示青藏高原小型哺乳动物种群危害发生的机制奠定了基础。