LTER Cross-site: Regional Variation in Direct and Indirect Influences of Animals on a Chihuahuan Desert Grasslands

Peters， Debra p新墨西哥州立大学《动物对奇瓦瓦沙漠草原的直接和间接影响的区域变化》在奇瓦瓦沙漠草原上，草向灌木的流失和灌丛草地的开垦是几个直接和间接过程中出现的群落动态中的重要问题。这些项目将研究生物对奇瓦瓦沙漠草持续生长和恢复的直接和间接影响。他们建议评估不同动物类群对优势草种黑葛的影响。该研究将：1)确定不同动物活动对几种植物生长过程的相对重要性；2)验证地方和区域牧草生长模式的变化与动物活动和丰度的变化有关的假设。他们将在两个奇瓦瓦沙漠LTER站点（Sevilleta和Jornada以及Big Bend国家公园）内的草和灌木为主的栖息地对种子、幼苗和成年植物进行一系列的排除实验。通过比较动物类群在草生长成功的地方和草生长不成功的地方的影响，将对动物影响植被的具体假设进行检验。具体来说，他们将研究四种假设的机制：a)蚂蚁和啮齿动物捕食导致的种子损失；b)啮齿动物挖掘的贮藏坑中种子保护和发芽增加；c)小型哺乳动物和蚱蜢对幼苗和成虫的食草性导致的死亡率和种子产量减少；d)食腐蚂蚁在成虫下筑巢导致的营养丰富和/或水的可用性增加的积极影响。这些实验将帮助我们在更大的范围内了解动物的丰度和草的补充。这项工作将阐明动物在产生和维持荒漠草原格局和动态方面的作用。它还将有助于从多尺度的角度来看待直接和间接的植物-动物相互作用的重要性。对许多系统具有生态意义的研究领域。

Peters, Debra PNew Mexico State UniversityDEB 0087289"Regional variation in direct and indirect influences of animals o a Chihuahuan Desert grasslands"In Chihuahuan desert grasslands, the loss of grass to shrubs and the reclamation of grasslands from shrublands are important problems in community dynamics that emerge from several direct and indirect processes. The PIs will investigate direct and indirect biotic influences on the persistence and recovery of Chihuahuan desert grass. They propose an assessment of the effects of different animal taxa on the dominant grass species, black grama Bouteloua eriopoda. The will: 1) determine the relative importance of different animal activities for several plant processes and 2) test the hypothesis that variation in local and regional patterns of grass establishment are related to variation in animal activities and abundances. They will perform a series of exclusion experiments on seeds, seedlings, and adult plants inhabiting grass- and shrub-dominated habitats within two Chihuahuan desert LTER sites (the Sevilleta and Jornada and Big Bend National Park). By comparing the effects of animal taxa where grasses are successful versus where they are not, tests of specific hypotheses by which animals influence vegetation will be performed. Specifically, they will examine four hypothesized mechanisms: a) seed loss due to predation by ants and rodents, b) seed protection and increased germination in cache pits dug by rodents, c) mortality and diminished seed production due to herbivory by small mammals and grasshoppers on seedlings and adult plants, and d) the positive effects of nutrient enrichment and/or increased availability of water due to the nesting of scavenging ants under adult plants. These experiments will help us understand animal abundance and grass recruitment at broad scales. The work will clarify the role of animals in generating and maintaining patterns and dynamics in desert grasslands. It will also contribute to a multi-scale perspective on the importance of direct and indirect plant-animal interactions... a research area of ecological significance to many systems.