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

大象和犀牛等大型动物，因其体型巨大而被称为“巨型动物”，对它们所生活的生态系统产生了巨大的影响。它们通过砍伐树木和放牧草地来改造环境，形成有利于其他动物生存的栖息地。但是，很少有研究解决这些巨型动物的尸体或“巨型尸体”在它们死后对生态系统的影响。它们的尸体代表了巨大的营养来源，对它们尸体所在的生态系统地区有着持久的生态遗产。例如，非洲象是最大的陆地动物，但人们对它们巨大的尸体（重达6000公斤）中的营养物质如何影响热带草原生态系统几乎一无所知。这个奖项的主要问题是：大象的巨型尸体是如何影响非洲大草原的生态的？这项工作将研究这些巨型尸体如何通过微生物、植物初级生产和物种多样性影响土壤中的养分循环，以及脊椎动物食草动物（如斑马和长颈鹿）和无脊椎食草动物（如蚱蜢）的食草性。本研究将支持1名博士后、研究生和本科生在生态学方面的指导，以及科学传播和推广。主要的更广泛的影响将是制作一部科学纪录片，《大型食草动物的遗产》，它将“跟随”非洲大草原上一头大象的生与死，这将把这些大象的生命周期置于更广泛的生态背景下，了解它们如何影响生态系统，以及目前面临它们消失的生态系统的影响。为了解决这个首要问题，该奖项将使用南非克鲁格国家公园（KNP）不同年龄（最多15岁以上）的大象尸体。结合土壤（物理、化学和生物特性）、植物（生产力和多样性）和食草动物（脊椎动物和无脊椎动物）在50个巨型尸体地点的调查以及温室实验，该奖项将评估大象尸体的营养脉冲如何推动生态系统过程的综合反应。重要的是，大象的巨型尸体分布在KNP的降雨量（375-700毫米）和土壤肥力（较不肥沃的沙质、花岗岩土壤与较肥沃的粘土、玄武岩土壤）的梯度上。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尸体的生态系统水平遗留效应提供了一个强大的实验框架。最后，通过将来自大型尸体对生态系统过程影响的实地数据与整个KNP的大象种群数据库相结合，研究人员将使用生态模型来展示随着大象自然死亡，大型尸体的分布如何在整个稀树草原景观的生态系统过程中产生变化。这项研究将首次对陆地生态系统中巨型尸体的生态遗产进行研究。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.