Collaborative Research: Understanding spatiotemporal dynamics of plant-soil feedbacks: Consequences for shrub-grass interactions in a dryland ecotone

由于人类造成的环境变化速度很快，了解允许物种迁移到新的适宜栖息地的因素变得越来越紧迫。该项目结合了实地和实验室实验，以评估植物-植物和植物-微生物的相互作用如何影响木馏油的迁移，木馏油是北美温暖沙漠（索诺兰、奇瓦瓦和莫哈韦）最常见和最重要的灌木之一，进入邻近的草原。木本植物以草原为代价的扩张，这种现象被称为灌木侵占，是全球性的，预计在未来气候变暖和大气中二氧化碳含量升高的情况下会加速。生活在植物根系内和根系附近的微生物（植物微生物组）可能在影响灌木入侵率中起关键作用，但它们对灌木建立和迁移成功的影响尚未得到研究。为了预测植物-微生物和植物-植物（在这种情况下是灌木/草）的相互作用如何在未来气候中驱动或减缓植物种群的扩张，需要评估这些相互作用发生的空间和时间尺度。利用野外和实验室实验以及数学模型，该项目将能够预测植物-植物和植物-微生物的相互作用如何在地理分布的限制下重塑灌木和草物种的丰度和分布。灌丛-草地动态影响生态系统储存的碳量，推动牧场管理决策，影响保护生物多样性的战略，仅在北美就延伸了3.3亿公顷。该项目在多个层面对学生进行培训，并与利益相关者和管理人员建立伙伴关系，以确保知识转移造福社会。科学与艺术的合作也嵌入到研究活动中，包括3d打印植物模型的设计和创造，以及植物形态的艺术诠释。这些模型和微生物植物相互作用的博物馆展览将被创建，以扩大公众宣传，并创造微生物和植物相互关系的美学表达。提出的研究将阐明植物根系和土壤相关微生物如何在环境变化下影响植物物种范围的运动。研究活动包括获取关于决定范围扩展的关键参数的新的定量数据：植物影响其微生物环境的空间范围和时间速度，以及与植物/植物竞争相互作用相比，微生物/植物反馈的相对强度。野外观测实验将通过解决以下问题来确定植物-微生物相互作用的潜在机制：(1)在范围限制发生冲突的过渡带中，基础物种之间的植物-土壤反馈的空间程度是多少？这个问题将通过空间明确的田间和温室配对实验来解决，以量化植物/微生物反馈的空间程度，因为它们影响草和灌木的性能。(2) CO2升高如何影响这些过渡带微生物反馈和基础物种之间的共存？这个问题将通过生长室实验来解决，以对比在环境和升高的CO2下草和灌木之间的微生物反馈和竞争。(3)随着时间的推移，植物物种通过什么机制培育出独特的微生物群落？这个问题将通过田间实验来解决，以评估植物对土壤和微生物的改造机制以及每种机制的时间尺度。最后，将利用这些实验和观测数据建立定量模型，以解决以下问题：(4)土壤微生物如何在物种范围极限下促进范围扩张、收缩或稳定，以及二氧化碳浓度升高将如何改变范围极限动力学？该项目在空间和时间背景下评估植物/土壤反馈方面开辟了新的领域，使用了一个有充分记录的、具有重要生态学意义的、实验上易于处理的范围转移：美国西南部C3木本灌木对C4草地的侵占。灌木侵占可以极大地改变生物多样性和生态系统过程，包括碳储存。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Understanding factors that allow species to migrate into new suitable habitats has become increasingly urgent because of the rapid pace of human-caused environmental change. This project combines field and lab experiments to evaluate how plant-plant and plant-microbe interactions influence the migration of creosote, one of the most common and important shrubs of the warm deserts of North America (Sonoran, Chihuahuan and Mojave), into adjacent grasslands. The expansion of woody plants at the expense of grassland, a phenomenon called shrub encroachment, is global in scale and expected to accelerate under future warmer climates and elevated atmospheric CO2. The microbes that live in and near plant roots (the plant microbiome) likely play key roles in affecting the rate of shrub encroachment but their influence on shrub establishment and migration success has not yet been examined. To predict how plant-microbe and plant-plant (in this case shrub/grass) interactions will drive or slow plant population expansion in future climates requires evaluating the spatial and temporal scales at which these interactions occur. Using both field and lab experiments and mathematical models, this project will enable forecasts of how plant-plant and plant-microbe interactions reshape the abundance and distributions of shrub and grass species at the limits of their geographic distributions. Shrubland-grassland dynamics affect the amount of carbon stored by an ecosystem, drive rangeland management decisions, influence strategies to conserve biodiversity, and extend over 330 million hectares of North America alone. This project trains students at many levels, and builds partnerships with stakeholders and managers to ensure knowledge transfer to the benefit of society. A science-art collaboration is also embedded in the research activities, including the design and creation of 3D-printed plant models and artistic interpretations of plant morphologies. A museum exhibit of these models and microbe plant interactions will be created to expand public outreach and create an aesthetic expression of the inter-relationships of microbes and plants.The proposed research will elucidate how plant root and soil associated microbes influence plant species range movements under environmental change. Research activities include the acquisition of novel quantitative data on key parameters that determine range spread: the spatial extent and temporal speed at which plants influence their microbial environment and the relative strength of the microbe/plant feedbacks compared to plant/plant competitive interactions. Experiments on field observations will determine the underlying mechanisms of plant-microbe interactions by addressing the following questions: (1) What is the spatial extent of plant-soil feedback between foundation species at ecotones where range limits collide? This question will be addressed using spatially-explicit paired field and greenhouse experiments to quantify the spatial extent of plant/microbe feedbacks as they influence both grass and shrub performance. (2) How does elevated CO2 affect microbial feedbacks and coexistence between foundation species at these ecotones? This question will be addressed using a growth chamber experiment to contrast microbial feedbacks and competition between grass and shrubs under ambient versus elevated CO2. (3) By what mechanisms do plant species cultivate unique microbial communities through time? This will be addressed with a field experiment to evaluate mechanisms underlying soil and microbial modification by plants and the temporal scale of each mechanism. Finally, quantitative models will be developed using the data from these experiments and observations to address the question, (4) How do soil microbes contribute to range expansion, contraction, or stabilization at species range limits, and how will elevated CO2 change range limit dynamics? The project breaks new ground ni evaluating plant/soil feedbacks in a spatial and temporal context using a well-documented, ecologically important, and experimentally tractable range shift: the encroachment of C3 woody shrubs into C4 grasslands in the American Southwest. Shrub encroachment can dramatically alter biodiversity and ecosystem processes, including carbon storageThis award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.