Collaborative Research: Ecological legacy effects of megacarcasses in African savanna ecosystems

大象和犀牛等大型动物，因其体型极大而被称为“巨型动物”，对它们生活的生态系统造成了巨大的影响。它们通过推倒树木和放牧草来创造巨大的草坪，帮助形成为其他动物提供便利的栖息地，从而改善环境。但是，很少有研究表明这些巨型动物的身体在它们死亡后对生态系统的影响。它们的身体代表着巨大的营养来源，对它们身体所在的生态系统区域具有长期的生态遗产。例如，非洲象是最大的陆地动物，但关于它们巨大的身体(高达6000公斤)的营养物质如何影响稀树草原生态系统，人们几乎一无所知。这个奖项提出了一个主要问题：大象巨型种群如何影响非洲稀树草原的生态？这项工作将解决这些巨藻如何影响微生物在土壤中的营养循环、植物初级生产力和物种多样性，以及脊椎动物草食动物(如斑马和长颈鹿)和无脊椎动物草食动物(如蝗虫)的食草性。这项研究将支持1名博士后学者、研究生和本科生在生态学以及科学交流和推广方面的指导。主要的更广泛的影响将是制作一部名为《巨型食草动物的遗产》的科学纪录片，这部纪录片将‘跟踪’非洲稀树草原上一头大象的生死，将这些大象的生命周期置于更广泛的生态背景中，了解它们如何影响生态系统，以及它们目前对面临消失的生态系统的影响。为了解决最主要的问题，该奖项将使用南非克鲁格国家公园(KNP)不同年龄(15岁以上)的大象身体。该奖项将结合50个兆卡地区的土壤(物理、化学和生物特性)、植物(生产力和多样性)、食草动物(脊椎动物和无脊椎动物)调查以及温室实验，评估大象身体的营养脉冲如何驱动生态系统过程的综合反应。重要的是，在KNP，大象巨型飓风分布在降雨量(375-700毫米)和土壤肥力(肥力较低的砂质、花岗质土壤与肥力较高的粘土、玄武质土壤)的不同梯度上。这些降雨和土壤养分的梯度为测试非生物环境如何影响陆地巨型飓风的生态系统级遗留效应提供了一个强有力的实验框架。最后，通过将来自实地的关于巨型飓风对生态系统过程的影响的数据与KNP的大象种群数据库相结合，研究人员将使用生态建模来展示随着大象随着时间的推移自然死亡，巨型飓风的分布如何在整个稀树草原的生态系统过程中产生变异性。这项研究将是对巨型飓风对陆地生态系统的生态遗产的第一次审查。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Large animals such as elephants and rhinoceros, called ‘megafauna’ for their extreme size, have outsized impacts on the ecosystems they live in. They engineer their environments by knocking down trees and grazing grasses to create large lawns, helping to form habitats that facilitate other animals. But, there is little research that addresses the impact that the carcasses of these megafauna, or ‘megacarcasses’, have on ecosystems after they die. Their carcasses represent huge sources of nutrients that have a long-lasting ecological legacy on the areas of ecosystems where their carcasses occur. For example, African elephants are the largest land animals, but almost nothing is known about how the nutrients from their massive carcasses (up to 6,000 kg) affect savanna ecosystems. This award asks the main question: How do elephant megacarcasses affect the ecology of African savannas? The work will address how these megacarcasses affect nutrient cycling in the soil by microbes, plant primary production and species diversity, and herbivory by vertebrate herbivores, such as zebra and giraffe, and invertebrate herbivores, such as grasshoppers. This research will support the mentoring of 1 postdoctoral scholar, graduate and undergraduate students in ecology as well as science communication and outreach. The main broader impact will be the production of a scientific documentary, The Legacy of Megaherbivores, which will ‘follow’ the life and death of an elephant in the African savanna, that will put the life cycle of these elephants into broader ecological context, understanding how they impact ecosystems and the current implications for ecosystems facing their disappearance. To address the overarching question, the award will use elephant carcasses of different ages (up to 15+ years old) in Kruger National Park (KNP), South Africa. Combining soil (physical, chemical and biological properties), plant (productivity and diversity), and herbivore (vertebrate and invertebrate) surveys at 50 megacarcass sites along with greenhouse experiments, the award will assess how nutrient pulses from elephant carcasses drive integrated responses of ecosystem processes. Importantly, the elephant megacarcasses are distributed across gradients of rainfall (375-700 mm) and soil fertility (less-fertile sandy, granitic soils vs. more-fertile clayey, basaltic soils) in KNP. These gradients of rainfall and soil nutrients provide a robust experimental framework for testing how the abiotic environment impacts the ecosystem-level legacy effects of terrestrial megacarcasses. Finally, by combining the data from the field on the effects of megacarcasses on ecosystem processes with a database of elephant population across KNP, the researchers will use ecological modeling to show how the distribution of megacarcasses generates variability in ecosystem processes across the savanna landscape as elephants naturally die over time. This study will represent the first examination of the ecological legacies of megacarcasses on terrestrial ecosystems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.