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，以提供关于个体、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。这项研究将检验几个假设：1)啮齿类动物的种群丰度受到极端气候事件的强烈影响。虽然降水增加通常会对干旱环境中的动物种群产生积极影响，但该研究将研究冬季和夏季高降雨事件如何导致高啮齿动物死亡率；2)种群动态与气候同步。人口变化通常是由食物丰富度的变化驱动的，因此以不同食物为食的物种往往表现出不同的人口动态。该研究将测试食种蚁和杂食性蚁的种群动态是否在厄尔尼诺事件等大规模气候波动中同步；3)气候与畜牧业相互作用，控制着荒漠-草地的转变。研究将比较放牧隔离围栏内外的植被变化，以评估荒漠化和草地恢复的假设机制；4)生物抗性和生产力影响物种入侵。这项研究将测试群落多样性和生产力的对比效应，以解释最近入侵的植物物种在该地点的丰富程度。研究这个系统将为生态学家、保护生物学家和在干旱草原栖息地工作的牧场主提供有用的一般见解，了解生物和非生物因素如何影响动植物种群的丰度。

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.