Dissertation Research: Testing the effects of large mammalian herbivores on savanna dynamics and community structure with regional- and continent-scale natural experiments

论文研究：通过区域和大陆规模的自然实验测试大型哺乳动物食草动物对稀树草原动态和群落结构的影响

• 批准号: 1501306
• 负责人: Robert Pringle
• 金额: $ 1.51万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-06-01 至 2016-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1501306&HistoricalAwards=false
• 关键词: Dissertation; Research; Testing; effects; large

The goal of this project is to determine how population declines of large mammalian herbivores (e.g., elephants, wildebeest, buffalo, antelopes, and zebra) affect African savanna habitats. Small-scale experimental studies have shown that because these large herbivores consume huge quantities of plant material, losing these species is likely to profoundly affect vegetation. The researchers will test how population declines and consequent changes in the frequency of two types of large herbivore-plant interactions alter savanna vegetation. In order to determine whether tree species reliant on large-mammal seed dispersal have declined in abundance, the research team will conduct fieldwork in Gorongosa National Park, Mozambique, where poaching during the 1977-1992 civil war nearly eliminated all large mammals. Second, by analyzing historical and modern satellite imagery, the researchers will test whether recent, human-driven declines in elephant populations across African protected areas lead to increased tree cover and possibly consequent threats to species adapted to historically sparse tree cover in African savannas. Elephants are particularly important savanna herbivores because they topple trees, potentially maintaining open savanna habitats. Many U.S. ecosystems have also experienced recent, dramatic changes in mammalian herbivore pressure as deer populations have exploded, and this research will advance our understanding of ecosystem responses to changed herbivory regimes. Project results will be incorporated into an undergraduate course on ecology and conservation. Results will be disseminated through scientific articles, blogs on park and affiliated websites, and online videos produced by the E.O. Wilson Biodiversity Foundation.Vegetation structure and composition is shifting in savannas across Africa due to altered fire regimes and climate change, but the extent to which declining herbivore populations are responsible for changing vegetation is unclear. Fieldwork in Gorongosa will include comparisons of vegetation in woodland patches that recruited prior to and since large mammal declines to test whether new woodland communities are relatively devoid of mammal-dispersed plants. This pattern is known from tropical forests where seed-dispersing mammals have declined, but the extent to which savanna trees depend on large mammals for dispersal is unknown. To test support for the hypothesis that recent declines in elephant populations lead to increased savanna tree cover, the researchers will build statistical models predicting changes in remotely sensed tree cover for African parks from published estimates of elephant density along with remotely sensed fire and rainfall data.

该项目的目标是确定大型哺乳动物食草动物（例如大象、角马、水牛、羚羊和斑马）的数量下降如何影响非洲稀树草原栖息地。小规模的实验研究表明，由于这些大型食草动物消耗大量的植物材料，失去这些物种可能会对植被产生深远的影响。研究人员将测试种群数量下降以及随之而来的两种大型食草动物与植物相互作用的频率变化如何改变稀树草原植被。为了确定依赖大型哺乳动物种子传播的树种是否大量减少，研究小组将在莫桑比克戈龙戈萨国家公园进行实地考察，1977-1992年内战期间的偷猎几乎导致所有大型哺乳动物灭绝。其次，通过分析历史和现代卫星图像，研究人员将测试近期人类驱动的非洲保护区大象数量下降是否会导致树木覆盖率增加，并可能对适应非洲稀树草原历史上稀疏树木覆盖的物种造成威胁。大象是特别重要的稀树草原食草动物，因为它们会推倒树木，从而有可能维持开放的稀树草原栖息地。随着鹿数量的激增，美国许多生态系统最近也经历了哺乳动物食草动物压力的巨大变化，这项研究将增进我们对生态系统对食草动物制度变化的反应的理解。项目成果将纳入生态与保护本科课程。结果将通过科学文章、公园和附属网站上的博客以及 E.O. 制作的在线视频进行传播。威尔逊生物多样性基金会。由于火情变化和气候变化，非洲大草原的植被结构和组成正在发生变化，但食草动物数量减少在多大程度上导致植被变化尚不清楚。戈龙戈萨的实地工作将包括对大型哺乳动物减少之前和之后补充的林地植被进行比较，以测试新的林地群落是否相对缺乏哺乳动物分散的植物。这种模式是从热带森林中得知的，那里传播种子的哺乳动物已经减少，但稀树草原树木在多大程度上依赖大型哺乳动物进行传播尚不清楚。为了测试对最近大象数量下降导致稀树草原树木覆盖率增加的假设的支持，研究人员将建立统计模型，根据已发布的大象密度估计值以及遥感火灾和降雨数据来预测非洲公园遥感树木覆盖率的变化。