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DISSERTATION RESEARCH: Biotic control of resource retention in arid lands: testing the fungal loop hypothesis

论文研究：干旱地区资源保留的生物控制：检验真菌循环假设

基本信息

批准号：
1503898
负责人：
Robert Sinsabaugh
金额：
$ 1.96万
依托单位：
University of New Mexico
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2015
资助国家：
美国
起止时间：
2015-07-01 至 2017-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1503898&HistoricalAwards=false
关键词：
DISSERTATION RESEARCH Biotic control resource

项目摘要

Plants and microorganisms cycle carbon and nitrogen between the atmosphere and the biota to drive the activities that they need to survive and reproduce. The role of plants and microbes in these cycles are well-understood in mesic (moist) environments but are unresolved in drylands. In arid regions, plants and microbes usually grow for only brief periods following rainfall events. During dry times, resources like carbon or nitrogen can be lost from the ecosystem and returned to the atmosphere, and therefore unavailable for organisms when the next rain comes. One mechanism for conserving resources occurs when direct exchanges between plants and microbes make water and nutrient use more efficient. For example, fungi in roots provide water and nitrogen to plants and receive carbon from plant photosynthesis. The proposed research will test they hypothesis that in arid lands, thread-like soil fungi connect plant roots to microbe-encrusted soils to more efficiently transfer and retain nutrients. This study will improve our capacity to predict the effects of climate changes on plant-microbe interactions. Results from this study will be shared with land managers so that restoration activities protect or manipulate the soil fungi to improve production and reduce degradation to arid lands. Workshops will be designed for school children and the public to increase understanding of the unique features of organisms in arid lands.In arid lands, producers (plants and biological soil crusts) are spatially separated with patchy distributions and are temporally separated due to differential responses to soil moisture, and thus resources released by one may be lost before being accessed by the other. The fungal loop hypothesis proposes that plants and biocrusts are functionally coupled by fungi that transfer water and nutrients between them, reducing resource loss. Observations support the hypothesis, but experimental manipulations of fungi have not yet been conducted. This dissertation work directly tests the mechanisms and ecological effects of fungal connections between plants and biocrusts. First, to determine whether fungal connections between plants and biocrusts exist and if they enable more efficient resource transfer than physical processes, mesh will be used to inhibit root or fungal connections. Experiments using stable isotopes (N, C) will compare transport rates via fungi to rates via physical processes alone. Second, connection (mesh) and plant/biocrust removal treatments will be imposed to test whether fungal connections affect a) the individual performance of plants and biocrusts, b) net plant-biocrust interactions, and c) resource retention. These experiments will be replicated under two precipitation regimes to determine if the fungal loop shows context-dependency with respect to water, one of the resources driving production in arid lands. Understanding the conditions that enable efficient resource cycling will refine predictions on the drivers of productivity and resource dynamics in arid lands. Proposed improvements will determine which fungal taxa occur in biocrusts, rhizospheric soil, and within roots and how these fungi are affected when fungal connections with plants or biocrusts are intact or inhibited and under different watering regimes. Stable isotope probing will be used to identify which fungal taxa are active (versus dormant), and therefore most likely to drive resource transfers between plants and biocrusts. The primary goal of stable isotope probing is to identify fungal taxa involved in the fungal loop. Connecting fungal identity and diversity to resource transfers among producers is essential for understanding the mechanisms of resource cycling in arid ecosystems.

植物和微生物在大气和生物群之间循环碳和氮，以驱动它们生存和繁殖所需的活动。植物和微生物在这些循环中的作用在中温（潮湿）环境中已得到充分理解，但在旱地中尚未得到解决。在干旱地区，植物和微生物通常只在降雨事件后短暂生长。在干旱时期，碳或氮等资源可能会从生态系统中丢失并返回到大气中，因此在下一次降雨时生物体无法使用。当植物和微生物之间的直接交换使水和养分的利用更有效时，就会产生一种保护资源的机制。例如，根中的真菌为植物提供水和氮，并从植物光合作用中接收碳。这项拟议中的研究将验证他们的假设，即在干旱地区，线状土壤真菌将植物根系连接到微生物覆盖的土壤，以更有效地转移和保留养分。这项研究将提高我们预测气候变化对植物-微生物相互作用影响的能力。这项研究的结果将与土地管理人员分享，以便恢复活动保护或操纵土壤真菌，以提高产量并减少干旱土地的退化。将为学生和公众设计讲习班，以增加对干旱地区生物独特特征的了解，在干旱地区，生产者（植物和生物土壤结皮）在空间上分散分布，在时间上也分散分布，这是因为对土壤湿度的反应不同，因此一方释放的资源可能在另一方获得之前就已丧失。真菌环假说提出，植物和生物结壳在功能上通过真菌耦合，在它们之间转移水分和养分，减少资源损失。观察结果支持这一假设，但真菌的实验操作尚未进行。本论文的工作直接检验了植物与生物结皮之间真菌联系的机制和生态效应。首先，为了确定植物和生物结壳之间是否存在真菌连接，以及它们是否能够比物理过程更有效地进行资源转移，将使用网状物来抑制根或真菌连接。使用稳定同位素（N，C）的实验将比较通过真菌的传输速率与仅通过物理过程的速率。其次，将实施连接（网）和植物/生物壳去除处理，以测试真菌连接是否影响a）植物和生物壳的个体表现，B）植物-生物壳的净相互作用，以及c）资源保留。这些实验将在两种降水制度下重复进行，以确定真菌循环是否表现出对水的上下文依赖性，水是干旱土地上驱动生产的资源之一。了解能够实现有效资源循环的条件将改进对干旱地区生产力和资源动态驱动因素的预测。提出的改进将确定哪些真菌类群发生在生物结皮，根际土壤，根内，以及如何影响这些真菌时，真菌与植物或生物结皮的连接是完整的或抑制，并在不同的浇水制度。稳定同位素探测将用于确定哪些真菌类群是活跃的（与休眠），因此最有可能推动植物和生物结壳之间的资源转移。稳定同位素探测的主要目标是鉴定参与真菌环的真菌类群。将真菌的特性和多样性与生产者之间的资源转移联系起来，对于理解干旱生态系统中的资源循环机制至关重要。