RAPID: Impact of exceptional drought on transformation of a savanna grassland

克鲁格国家公园（KNP）是一个生物多样性的热点，正在经历有记录以来最严重的干旱之一。这场干旱导致许多放牧物种的饲料量大幅下降，其结果是种群数量大幅下降。剩下的动物只能食用低质量、大多难吃的饲料。这些变化将如何改变未来的植物群落尚不清楚。近十年来，科学家们一直在研究在过去被认为是正常气候条件下，火灾频率和大型食草动物对KNP稀树草原生态系统过程的影响。随着极端干旱的到来，他们现在有机会研究火灾和放牧的影响如何随着气候条件的变化而变化，以及这对植物生产力和大型食草动物种群的影响。气候模型预测全球极端气候会加剧，这一现象在今天的天气模式中已经很明显，因此非常有必要更好地了解这些罕见的气候事件如何重塑生态系统。除了加深对稀树草原的了解和检验基本的生态学理论外，这项研究还将提供极端气候对植物及其食草动物影响的重要信息，这将对管理国家公园的决策者具有重要价值。拟议的研究将在现有的长期放牧和火灾实验的背景下，记录历史上异常干旱对KNP稀树草原（以木本和草本植物混合为特征）的影响。记录罕见气候事件的潜在变化本质本身就是一个难得的机会，生态学家很少有机会，但有预处理数据和长期的、可重复的实验，可以操纵最可能与极端干旱相互作用的关键干扰，这是前所未有的。由于预测此次异常干旱将于2017年初结束，因此RAPID项目的重点是在此次异常气候事件结束时收集数据，以评估干旱、火灾和放牧引发植物群落变化的可能性，从而导致美味草的相对丰度增加。这项研究不仅对理解草原生物多样性的决定因素有意义，而且对增加我们对罕见的极端气候如何改变生态系统的认识也有意义。目前，KNP管理人员正在努力解决草地退化的长期趋势，这导致了野生动物美味饲料的损失。目前的异常干旱虽然在短期内加剧了这一问题，但可能会提高大部分KNPs草原的饲料质量。此外，该项目将在美国研究人员和南非科学家之间建立密切的合作关系。该项目的首席科学家将继续与KNP科学家密切合作，以确保所有结果以一种告知KNP管理决策的方式进行沟通。所有数据集和结果的传播将通过设在科罗拉多州立大学的专门网页实现。

Kruger National Park (KNP), a biodiversity hotspot, is experiencing one of its worst droughts on record. This drought has resulted in large declines in forage for many grazing species, which have experienced significant population declines as a result. The remaining animals have been left to consume low quality, mostly unpalatable, forage. How these changes may alter future plant communities is not known. For almost a decade, scientists have been studying the impact of fire frequency and large grazers on ecosystem processes in savanna grassland in KNP under what used to be considered normal climatic conditions. With the onset of extreme drought, they now have an opportunity to study how the effects of fire and grazing may change as climatic conditions change, and what this might mean for plant productivity and populations of large grazer species. Climate models predict an intensification of climate extremes globally, a phenomenon that is already evident in weather patterns today, so there is a great need to develop a better understanding of how these rare climatic events may be reshaping ecosystems. In addition to enhancing understanding of savanna grasslands and testing fundamental ecological theory, this research will provide crucial information on the impact of climate extremes on plants and their grazers, which will be of great value to decision makers that manage national parks. The proposed research will document the effects of a historically exceptional drought on a savanna grassland (characterized by a mixture of both woody and herbaceous plants) in KNP in the context of an existing long-term grazing and fire experiment. Documenting the potentially transformational nature of rare climatic events is in itself an opportunity seldom afforded ecologists, but to have pre-treatment data and a long-term, well-replicated experiment in place that manipulates the key disturbances most likely to interact with extreme drought is unprecedented. Because forecasts are for this exceptional drought to conclude in early 2017, this RAPID project focuses on gathering data at the end of this exceptional climate event to assess the potential for drought, fire and grazing to trigger a shift in the plant community that will result in an increase in the relative abundance of palatable grasses. This research has implications for not only understanding the determinants of grassland biodiversity, but also for increasing our knowledge of how rare climate extremes may transform ecosystems. Currently, KNP managers are grappling with a long-term trend of grassland degradation which has led to the loss of palatable forage for wildlife. The current exceptional drought, while exacerbating this problem in the short-term, may increase forage quality across much of KNPs grasslands. In addition, this project will establish close collaborative ties between US researchers and scientists in South Africa. The lead scientists on this project will continue to work closely with KNP scientists to ensure that all results are communicated in a way to inform management decisions in KNP. Dissemination of all datasets and results will be achieved via a dedicated webpage, housed at Colorado State University.