Collabortive Research: Water availability controls on above-belowground productivity: Herbivory versus plant response

合作研究：水资源可用性对地上生产力的控制：食草与植物反应

• 批准号: 1456597
• 负责人: Osvaldo Sala
• 金额: $ 55.85万
• 依托单位: Arizona State University
• 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: 2015-06-15 至 2020-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1456597&HistoricalAwards=false
• 关键词: Collabortive; Research; Water; availability; controls

Ecosystems fix carbon from the atmosphere through photosynthesis, which is then allocated to aboveground plant structures, such as leaves and branches, or to belowground structures, such as roots. Our current understanding of the factors that control belowground carbon allocation is significantly weaker than aboveground allocation. Yet, in grasslands the amount of carbon that goes belowground each year is much larger than the amount of carbon allocated aboveground. Our rudimentary understanding of the controls of belowground carbon allocation and the ratio of aboveground to belowground carbon is a significant knowledge gap, as roots are a major input of organic material and nutrients into soil. Predictions of future carbon storage in these ecosystems hinge on our understanding of the effects of environmental availability on allocation of carbon belowground. This study addresses the questions: How does precipitation affect the above/belowground partitioning of carbon? During drought periods, are above and belowground structures equally affected, or are roots affected less than leaves and branches? Finally, is the effect of precipitation on carbon allocation constant or does it vary from deserts to humid grasslands? This project will install experiments in New Mexico, Colorado and Kansas to understand the effect of precipitation on the partitioning of carbon above versus belowground and the underlying mechanisms.This proposal presents three novel hypotheses based on: (1) a plant-response mechanism, suggesting decreased belowground allocation with increasing water availability, and (2) a trophic-cascade mechanism, suggesting the opposite pattern derived from the differential sensitivity of root feeders and their predators to water availability. A final hypothesis (3) suggests that the magnitude of plant responses decreases from arid to humid grasslands while the magnitude of the trophic-cascade phenomenon increases. The trophic-cascade mechanism may be constrained by the abundance of belowground predators in arid grasslands, which is greater in humid ecosystems. The experimental design includes complementary field and microcosm experiments located in three different ecosystem types: Chihuahuan Desert Grassland, NM, Shortgrass Steppe, CO, and Tallgrass Prairie, KS. The field experiment includes additions and reductions of precipitation at each site. The microcosm experiment is based on monoliths subjected to 4 soil fauna treatments x 5 water manipulations. Soil fauna treatments consist of (1) soil devoid of fauna (just native bacteria and fungi), (2) defaunated soil inoculated with nematode root feeders, (3) defaunated soil inoculated with nematode root feeders and nematode predators, and (4) control. Microcosm tubes will be located in each of the water manipulation plots using individuals of the dominant grass species of each ecosystem type. This project will train a post-doctoral fellow and graduate and undergraduate students, including students from underrepresented groups. Collaboration with the Asombro Institute for Science Education, a non-profit organization that provides award-winning science education to more than 12,000 children and 4,500 adults annually in southern New Mexico and western Texas, will include establishing a demonstration project of a soil-observation window at the Chihuahuan Desert Nature Park. Partnerships with the "Ask A Biologist" program will result in an article on the interactions between plants and belowground organisms and how these interactions are modulated by water availability. The project will contribute special events associated with the effects of climate on belowground processes during a summer sustainability program that engages local teachers and students, and the "Managing the Planet" series aimed at the general public.

生态系统通过光合作用固定大气中的碳，然后将其分配给地上植物结构（例如叶子和树枝）或地下结构（例如根）。 我们目前对控制地下碳分配因素的理解明显弱于地上分配。然而，在草原中，每年进入地下的碳量远远大于地上分配的碳量。我们对地下碳分配的控制和地上与地下碳的比率的初步了解是一个重大的知识差距，因为根是有机物质和养分进入土壤的主要输入。对这些生态系统未来碳储存的预测取决于我们对环境可用性对地下碳分配影响的理解。这项研究解决了以下问题：降水如何影响碳的地上/地下分配？ 在干旱期间，地上和地下结构是否受到同样的影响，还是根部受到的影响小于树叶和树枝？ 最后，降水对碳分配的影响是恒定的还是从沙漠到潮湿的草原有所不同？ 该项目将在新墨西哥州、科罗拉多州和堪萨斯州进行实验，以了解降水对地上与地下碳分配的影响及其潜在机制。该提案提出了三个基于以下假设的新颖假设：（1）植物响应机制，表明随着可用水量的增加，地下分配减少；(2)营养级联机制，表明相反的模式源自根部饲养者及其捕食者对可用水量的不同敏感性。最后的假设（3）表明，从干旱草原到潮湿草原，植物反应的强度降低，而营养级联现象的强度增加。营养级联机制可能受到干旱草原丰富的地下捕食者的限制，而在潮湿的生态系统中地下捕食者的数量更多。实验设计包括位于三种不同生态系统类型的互补实地和微观实验：新墨西哥州奇瓦瓦沙漠草原、科罗拉多州短草草原和堪萨斯州高草草原。现场实验包括在每个地点增加和减少降水。微观世界实验基于经过 4 次土壤动物处理 x 5 次水处理的巨石。土壤动物处理包括（1）没有动物群的土壤（只有本地细菌和真菌），（2）接种线虫根部饲养者的动物区系丧失的土壤，（3）接种线虫根部饲养者和线虫捕食者的动物区系丧失的土壤，以及（4）控制。 将使用每种生态系统类型的优势草种的个体将微观世界管放置在每个水处理地块中。该项目将培训一名博士后研究员以及研究生和本科生，包括来自代表性不足群体的学生。与 Asombro 科学教育研究所的合作将包括建立一个土壤观测窗口示范项目，该研究所是一个非营利组织，每年为新墨西哥州南部和德克萨斯州西部的 12,000 多名儿童和 4,500 名成年人提供屡获殊荣的科学教育在奇瓦瓦沙漠自然公园。与“询问生物学家”计划的合作将产生一篇关于植物和地下生物之间的相互作用以及这些相互作用如何通过水的可用性调节的文章。该项目将在当地教师和学生参与的夏季可持续发展计划以及针对公众的“管理地球”系列期间举办与气候对地下过程影响相关的特别活动。