LTREB: Experimental Manipulation and Monitoring of an Arid Ecosystem at Portal, Arizona

拟议的研究将继续对啮齿动物和蚂蚁进行长期操作，并对啮齿动物、蚂蚁和植物进行标准化普查，以提供关于个人、种群和社区对实验扰动和环境背景时空变化的反应的数据。 本研究将验证几个假设：1）啮齿动物的种群丰度受到极端气候事件的强烈影响。 虽然增加的降水通常会对干旱环境中的动物种群产生积极影响，但研究将研究冬季和夏季的高降雨事件如何导致啮齿动物的高死亡率; 2）种群动态与气候同步。 种群的变化往往是由食物丰富度的变化所驱动的，因此以不同食物为食的物种往往表现出不同的种群动态。 该研究将测试食种子和杂食性蚂蚁的种群动态是否与大尺度气候波动同步，如厄尔尼诺事件; 3）气候和牲畜放牧相互作用，以控制沙漠-草原过渡。 研究将比较禁牧围栏内外植被的变化，以评估荒漠化和草地恢复的假设机制; 4）生物抵抗力和生产力影响物种入侵。 该研究将测试拟议的群落多样性和生产力的对比效应，以解释该地点最近入侵的植物物种的丰富程度。 研究这个系统将提供一般的见解，有用的生态学家，保护生物学家和牧场主在干旱草原栖息地工作，生物和非生物因素如何影响丰富的动物和植物种群。

The proposed research will continue long-term manipulations of rodents and ants and standardized censuses of rodents, ants and plants to provide data on responses of individuals, populations and communities both to experimental perturbations and to background temporal and spatial variation in the environment. The research will test several hypotheses: 1) Population abundances of rodents are strongly influenced by extreme climatic events. While increased precipitation generally affects animal populations in arid environments positively, the research will examine how both winter and summer high rainfall events can result in high rodent mortality; 2) Population dynamics are synchronized by climate. Population changes are often driven by changes in food abundance and so species feeding on different foods often exhibit different population dynamics. The research will test whether the population dynamics of seed-eating and omnivorous ants are synchronized by large-scale climatic fluctuation, such as El Nino events; 3) Climate and livestock grazing interact to control the desert-grassland transition. The research will compare vegetation changes that have occurred both inside and outside the grazing exclusion fence to evaluate hypothesized mechanisms of desertification and grassland restoration; 4) Biotic resistance and productivity affect species invasion. The research will test the proposed contrasting effects of community diversity and productivity to explain the abundance of a recent invading plant species at the site. Studying this system will provide general insights, useful to ecologists, conservation biologists and ranchers working in arid grassland habitats, into how biotic and abiotic factors affect the abundance of animal and plant populations.