RAPID: Collaborative Research: Do negative plant-soil feedbacks outweigh positive ectomycorrhizal mutualisms in dipterocarp rainforest?

树种多样性高是南美洲、非洲和东南亚热带雨林的特点。然而，生态学家仍然很难解释，当如此多的物种都使用相同的一小部分资源(光、水、养分)时，它们如何能够足够不同地共存。从理论上讲，应该只有几个占主导地位的竞争对手能够坚持下去。解释这一难题的一个假说是，土壤真菌会导致树苗随着树木种群的增长而死亡，从而防止任何一个物种变得比任何其他物种更常见。目前对这一主题的研究是有希望的，但存在两个主要缺陷。首先，它在很大程度上仅限于中美洲和南美洲的热带雨林，尽管世界各地的土壤真菌存在根本差异。其次，它没有考虑到一些土壤真菌对苗木有益而不是有害。在这个项目中，研究人员将利用马来西亚婆罗洲一次罕见的大规模播种活动来建立实验，以测试关于世界上这个生态开发不足的地区植物与真菌正相互作用的假说。这项工作具有巨大的潜力，可以让人们对塑造热带雨林惊人多样性的生态过程有新的见解。除了提高我们对维持热带生物多样性的生态学理解之外，通过这项研究获得的见解将有助于保护东南亚极度濒危的热带雨林生态系统。尽管这些热带雨林占据了全球生物多样性的很大一部分，并在全球生物圈的功能中发挥着关键作用，但该地区正在经历令人震惊的森林砍伐速度。通过研究影响苗木补充的因素，这项研究将提供成功重新造林和恢复退化森林所需的重要知识。此外，这项研究将揭示这些热带雨林中生物多样性的鲜为人知和潜在危险的微生物维度。最后，这项工作将为美国大学的研究生提供宝贵的培训，让他们在非常复杂的生态系统中工作，并提高美国参与这些生态系统的能力。

High tree species diversity is a characteristic feature of rainforests in South America, Africa and Southeast Asia. However, it continues to be difficult for ecologists to explain how such a large number of species can be different enough to coexist when they all use the same small set of resources (light, water, nutrients). Theoretically, only a few dominant competitors should persist. One hypothesis explaining this conundrum is that soil fungi cause seedlings to die as tree populations grow, thus preventing any one species from becoming much more common than any other species. Current research on this topic is promising but has two primary shortcomings. First, it has largely been limited to Central and South American rainforests, despite fundamental differences in soil fungi around the world. Second, it has not considered that some soil fungi benefit, not harm, seedlings. In this project, investigators will take advantage of a rare mass seeding event in Malaysian Borneo to establish experiments that will test hypotheses about positive plant-fungal interactions in this ecologically under-explored part of the world. The work has great potential to lead to new insights into the ecological processes that shape the astounding diversity of tropical rain forests. In addition to improving our ecological understanding of the maintenance of tropical biodiversity, the insights gained through this research will help conserve the critically endangered rainforest ecosystems of Southeast Asia. Although these rainforests harbor a major share of global biodiversity and play a critical role in the function of the global biosphere, the region is experiencing alarming rates of deforestation. By studying the factors that impact seedling recruitment, this research will provide important knowledge required for successful reforestation and restoration of degraded forests. In addition, the study will shed light on the little known and potentially at risk microbial dimensions of biodiversity in these rainforests. Finally, this work will provide invaluable training for graduate students at US universities to work in a very complex ecosystem and increase US capacity to engage in these ecosystems.