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，以驱动他们需要生存和繁殖的活动。植物和微生物在这些周期中的作用在介质（潮湿）环境中得到了充分理解，但在旱地尚未解决。在干旱地区，降雨事件后通常仅在短时间内生长。在干旱时期，碳或氮之类的资源可能会从生态系统中丢失并回到大气中，因此在下一次降雨时无法使用生物。当植物和微生物之间的直接交换使水和营养用途更有效时，就会发生一种保存资源的机制。例如，根中的真菌为植物提供水和氮，并从植物光合作用中获得碳。拟议的研究将检验他们假设，在干旱的土地上，类似螺纹的土壤真菌将植物的根部连接到微生物的土壤中，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菌相互作用的影响的能力。这项研究的结果将与土地管理者共享，以便恢复活动保护或操纵土壤真菌，以改善生产并减少对干旱土地的降解。研讨会将为学童和公众设计，以增强对干旱土地中生物的独特特征的了解。在干旱的土地上，生产者（植物和生物土壤外壳）在空间上被斑点分布进行空间分离，并且由于对土壤的水分的不同响应而在暂时分离，因此可能会释放出一种资源，然后在其他人释放之前丢失。真菌环假设提出，植物和生物质体是由真菌在功能上耦合的，这些真菌将水和养分之间传递，从而减少了资源损失。观察结果支持该假设，但尚未进行真菌的实验操作。这项论文工作直接测试了植物与生物库物之间真菌联系的机制和生态影响。首先，为了确定植物与生物质量之间的真菌连接是否存在，以及它们是否可以比物理过程更有效的资源传输，将使用网格来抑制根或真菌的连接。使用稳定同位素（N，C）的实验将通过真菌将运输速率与仅通过物理过程进行比较。其次，将施加连接（网状）和植物/生物清除处理，以测试真菌连接是否影响a）植物和生物库物的个体性能，b）净植物 - 二氮相互作用，c）资源保留。这些实验将在两个降水状态下进行复制，以确定真菌环是否显示出对水的上下文依赖性，这是驱动干旱土地生产的资源之一。了解能够有效资源循环的条件将完善对干旱土地生产力和资源动态驱动因素的预测。拟议的改进将确定生物质量，根际土壤以及根内发生的真菌分类群，以及当真菌与植物或生物植物的连接完好无损或抑制以及在不同的浇水方面时，这些真菌如何受到影响。稳定的同位素探测将用于确定哪些真菌分类群是活跃的（相对于休眠），因此最有可能驱动植物和生物质量之间的资源转移。稳定同位素探测的主要目标是确定与真菌环中有关的真菌分类单元。将真菌的身份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资源循环的机制至关重要。