LTREB: Collaborative Research: Experimental Manipulation and Monitoring of the Chihuahuan Desert Ecosystem at Portal

PI请求LTEB支持继续在亚利桑那州奇瓦瓦附近的门户网站进行实验研究。20公顷的研究地点包含24个围栏地块，每个0.25公顷的面积。自1977年以来，他们一直保持着从10个地块中清除部分或全部啮齿动物和/或蚂蚁的工作，自1988年以来，又从另外4个地块中清除了这些动物。啮齿动物、蚂蚁和植物的标准化调查提供了有关个体、种群和群落对实验扰动和环境背景时空变化的反应的宝贵数据，迄今的结果表明：1）啮齿动物、蚂蚁和植物种群的复杂年际和季节动态：2）啮齿动物、鸟类和蚂蚁对冬季一年生植物种子的直接捕食作用; 3）袋鼠鼠的竞争对其它食种子啮齿动物种群密度和物种多样性的直接影响：4）袋鼠鼠对植被、其它啮齿动物、鸟类和蜥蜴的间接影响; 5）整个生态系统的重组，包括木本植被的大量增加和许多动物物种的迁移、殖民或丰度的变化，显然是由20世纪70年代末以来的气候变化引起的; 6）在狭窄的范围内对紧急性质的调节，如物种多样性、生物量和啮齿动物和植物的能源利用，尽管物种组成因环境变化而发生了很大的变化。未来五年的研究内容包括：1）继续进行啮齿动物、蚂蚁和植物的实验操作和标准化普查; 2）关注大尺度上的空间格局和过程; 3）调查实验操作和生物功能群对生态系统过程的影响; 4）研究蚂蚁群落的动态;（5）评估气候、放牧和火对荒漠灌丛向干旱草地过渡的交互影响。

The PIs request LTREB support to continue experimental studies in the Chihuahuan Desertnear Portal, Arizona. The 20-ha study site contains 24 fenced plots, each 0.25 ha inarea. They have maintained the removal of some or all species of rodents and/or ants from10 plots continuously since 1977 and from an additional 4 plots since 1988. Standardizedcensuses of rodents, ants, and plants provide invaluable data on responses of individuals,populations, and communities both to experimental perturbations and to background temporaland spatial variation in the environment.Results to date demonstrate: 1) complex interannual and seasonal dynamics of rodent, ant,and plant populations; 2) direct effects of seed predation by rodents, birds, and ants onwinter annual plants; 3) direct effects of competition by kangaroo rats on populationdensities and species diversity of other seed-eating rodent species; 4) indirect effectsof kangaroo rats on vegetation, other rodents, birds, and lizards; 5) reorganization ofthe entire ecosystem, including large increases in woody vegetation and extinctions,colonizations, or shifts in abundance of many animal species, apparently caused by achange in climate since the late 1970's; 6) regulation of emergent properties, such asspecies diversity, biomass, and energy use of rodents and plants, within narrow boundsdespite large shifts in species composition in response to environmental change. The proposed research for the next five years includes: 1) continuation of experimentalmanipulations and standardized censuses of rodents, ants, and plants; 2) focus on spatialpatterns and processes over a wide range of scales; 3) investigation of the experimentalmanipulations and functional groups of organisms on ecosystem processes; 4) examination ofthe dynamics of the ant community; and 5) assessment of the interacting influences ofclimate, livestock grazing, and fire on the transition between desert shrubland and aridgrassland.