DISSERTATION RESEARCH: Interactions among nitrogen and phosphorus through plant-microbial mutualisms in tropical rain forests

论文研究：热带雨林中植物-微生物互利作用下氮磷之间的相互作用

• 批准号: 1601408
• 负责人: Cory Cleveland
• 金额: $ 1.89万
• 依托单位: University of Montana
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1601408&HistoricalAwards=false
• 关键词: DISSERTATION; RESEARCH; Interactions; among; nitrogen

The tropics contain some of the largest, fastest growing and carbon-rich forests on Earth. As they grow, tropical trees store large amounts of atmospheric carbon dioxide in their biomass, slowing the increase in atmospheric carbon dioxide and hence the pace of climate change. Yet, all trees require large amounts of soil nutrients, especially nitrogen and phosphorus, to grow, and it remains unclear whether the supply of soil nutrients will be sufficient to meet the demands of predicted tree growth in the future. For example, soil phosphorus concentrations are relatively low in tropical forest soils, and some research suggests that low phosphorus supply may limit increases in tree growth and carbon storage. However, previous work suggests that some tropical trees may be better than others at obtaining scarce nutrients because of their relationships with soil microorganisms that enhance the ability to scavenge nutrients. This research will explore how different tropical trees access soil nutrients and whether these microbial partnerships offer some trees an advantage over their competitors. Overall, this research will improve the understanding of how tropical forests may respond to global environmental change.Trees capable of symbiotic nitrogen (N) fixation, a plant-microbial mutualism that converts atmospheric N into biological forms, are abundant in tropical forests. Previous work suggests that N fixing trees have an advantage over non-N fixing trees in acquiring soil phosphorus (P) via the production of N-rich phosphatase enzymes that mineralize organic P and by hosting arbuscular mycorrhizal fungi that scavenge for inorganic P. This advantage could lead to competition for soil P in which N fixing trees outperform non-N fixing trees. This project will explore the interactions between N fixing and non-N fixing trees via an experimental seedling study on the Osa Peninsula, Costa Rica in which multiple species from each plant group will be grown alone or in competition under five P treatments that vary by the P compound being delivered. In addition, previous work suggests that this N and P interaction may not be constrained to trees that fix N, but may be evident in trees that have high foliar N regardless of fixation. Thus, foliar N may be an indirect control of P acquisition on an individual plant basis, as well as on a landscape scale if plants with similar foliar N concentrations are aggregated. Therefore, this research will also explore the relationships between foliar N, P acquisition, and the biogeochemical consequences across a set of individual emergent canopy trees and forest plots characterized by high and low foliar N. The results from both projects have the potential to elucidate complex plant-microbially mediated N and P interactions that operate above- and belowground, and on multiple spatial scales.

热带地区拥有地球上最大、生长最快、富含碳的森林。随着热带树木的生长，它们在生物量中储存了大量的大气二氧化碳，减缓了大气二氧化碳的增加，从而减缓了气候变化的速度。然而，所有树木的生长都需要大量的土壤养分，尤其是氮和磷，目前尚不清楚土壤养分的供应是否足以满足未来预测树木生长的需求。例如，热带森林土壤的土壤磷浓度相对较低，一些研究表明，低磷供应可能会限制树木生长和碳储存的增加。然而，先前的研究表明，一些热带树木可能比其他树木更善于获取稀缺的养分，因为它们与土壤微生物的关系增强了它们清除养分的能力。这项研究将探索不同的热带树木如何获取土壤养分，以及这些微生物伙伴关系是否为某些树木提供了优于竞争对手的优势。总的来说，这项研究将提高对热带森林如何应对全球环境变化的理解。能够共生固氮(N)的树木在热带森林中是丰富的，这是一种植物-微生物的共生关系，可以将大气中的N转化为生物形式。先前的研究表明，固氮树比非固氮树在获取土壤磷(P)方面具有优势，其途径是产生富氮磷酸酶（矿化有机P），并寄存清除无机P的丛枝菌根真菌。这种优势可能导致固氮树在争夺土壤P方面优于非固氮树。该项目将通过在哥斯达黎加奥萨半岛进行的一项实验幼苗研究，探索固氮和非固氮树木之间的相互作用。在该研究中，来自每个植物群的多个物种将在五种不同的磷处理下单独或竞争生长，这些处理因所输送的磷化合物而异。此外，先前的研究表明，这种N和P的相互作用可能并不局限于固定N的树木，但在具有高叶氮的树木中可能很明显，无论固定与否。因此，在单个植物的基础上，叶面氮可能是磷获取的间接控制因素，如果叶面氮浓度相似的植物聚集在一起，在景观尺度上也是如此。因此，本研究还将探索叶面氮、磷获取与生物地球化学后果之间的关系，这些关系涉及一组突生树冠树木和以叶面氮高和叶面氮低为特征的森林样地。这两个项目的结果都有可能阐明复杂的植物-微生物介导的氮、磷相互作用，这种相互作用在地上和地下以及多个空间尺度上运作。