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

DEB 0087289“动物对奇瓦瓦沙漠草原直接和间接影响的区域差异”奇瓦瓦沙漠草原中，草的流失、灌木的流失和从灌木丛中开垦草原是群落动态中的重要问题，这些问题来自几个直接和间接的过程。PIS将调查直接和间接的生物影响对奇瓦瓦沙漠草的持久性和恢复。他们提出了一项关于不同动物分类群对优势草种黑格拉玛Bouteloua eriopoda的影响的评估。将：1)确定不同动物活动对几个植物过程的相对重要性，以及2)检验局部和区域建草模式的变化与动物活动和丰度变化有关的假设。他们将在奇瓦瓦沙漠的两个LTER地点(塞维莱塔、乔尔纳达和大本德国家公园)内，对以草和灌木为主的栖息地的种子、幼苗和成年植物进行一系列排除实验。通过比较草本植物成功的动物分类群和不成功的动物分类群的效果，将对动物影响植被的具体假设进行测试。具体地说，他们将研究四种假设的机制：a)蚂蚁和啮齿动物捕食造成的种子损失；b)啮齿动物挖出的掩埋坑中种子的保护和发芽增加；c)小型哺乳动物和蝗虫的草食导致的死亡和种子产量减少对幼苗和成年植物的影响；以及d)营养丰富和/或由于在成年植物下筑巢而增加水分的可获得性的积极影响。这些实验将帮助我们了解大范围内的动物数量和草的补充。这项工作将阐明动物在产生和维持沙漠草原的格局和动态中所起的作用。它还将有助于从多尺度的角度看待植物-动物直接和间接相互作用的重要性……对许多系统具有生态学意义的研究领域。

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.