Collaborative Research: Responses of Productivity and Nutrient Dynamics to Elevated CO2 in an Intact Mojave Desert Ecosystem

内华达州沙漠FACE设施（NDFF）是一个长期的研究项目，研究完整的莫哈韦沙漠生态系统对二氧化碳浓度升高的反应。 在前四年的NDFF操作，我们发现，初级生产大幅增加，在CO2浓度升高，但只有在潮湿的年份，和异国情调的一年生草的反应比本地灌木和一年生植物更强烈。 因此，我们的初步研究结果表明，生态系统类型（旱地），代表30%的地球陆地表面积可能不会以一种简单的方式响应CO2浓度升高，如现有的全球变化模型所预测的，在这些结果和我们的沙漠FACE实验的长期性质的背景下，我们建议在这项研究中解决三个首要问题：1。CO2浓度升高是否会继续刺激外来一年生物种的不成比例增加，从而改变莫哈韦沙漠的群落组成和结构？2.我们所观察到的对二氧化碳逐步增加的反应，产量的增加和营养动态的变化会随着时间的推移而持续吗？3.我们能否采用已被证实的沙漠生态系统功能模型来预测未来莫哈韦沙漠生态系统将如何应对二氧化碳浓度升高？这一建议的智力价值在于我们的概念方法，我们专注于物种组成和生态系统功能之间的功能相互作用，捆绑在一起的一个明确的建模组件。 该模型将是一个既定的，经过验证的沙漠模型（帕尔斯，补丁干旱土地模拟器），将用于开发生物和非生物控制的碳，氮和水通量在这个干旱的生态系统中升高CO2的综合理解的适应。 这项拟议研究的更广泛的影响将是检查外来物种的潜在入侵，以应对CO2浓度升高，以及这一过程如何影响生态系统功能，因此生态系统服务，在沙漠环境中。 通过这个研究项目，我们也正在五个研究校园之间建立一个有凝聚力的网络。 迄今为止，我们的研究小组在NDFF培训本科生，研究生和博士后学者，包括代表性不足的群体的成员方面有着良好的记录。 这项研究将同样培养广泛的学生和博士后，无论是在NDFF和我们的支持实验室。

The Nevada Desert FACE Facility (NDFF) is a long-term research project examining the responses of an intact Mojave Desert ecosystem to elevated CO2. In the first four years of NDFF operation, we found that primary production increased substantially at elevated CO2, but only in wet years, and that an exotic annual grass responded more strongly than did native shrubs and annuals. Therefore, our initial results suggest that an ecosystem type (drylands) that represents 30% of the earth's terrestrial surface area may not respond to elevated CO2 in a simple manner, as predicted by existing models of global change.In the context of these results and the long-term nature of our desert FACE experiment, we propose to address three overarching questions in this study:1. Will elevated CO2 alter community composition and structure in the Mojave Desert by continuing to stimulate a disproportionate increase in an exotic annual species?2. Will the increases in production and changes in nutrient dynamics that we have observed in response to a step-change increase in CO2 be sustained over time?3. Can we adapt proven models of desert ecosystem function to predict how this Mojave Desert ecosystem will respond to elevated CO2 in the future?The intellectual merit of this proposal lies in our conceptual approach in which we are focusing on the functional interactions between species composition and ecosystem function, tied together by an explicit modeling component. The model will be an adaptation of an established, validated desert model (PALS, the Patch Arid Lands Simulator) that will be used to develop a synthetic understanding of biotic and abiotic controls on carbon, nitrogen, and water fluxes to elevated CO2 in this arid ecosystem. The broader impact of this proposed study will be an examination of the potential invasion of an exotic species in response to elevated CO2, and how this process may impact ecosystem function, and therefore ecosystem services, in a desert environment. Through this research program, we are also forging a cohesive network between five research campuses. To date, our research group has an excellent record of training undergraduate, graduate, and postdoctoral scholars at the NDFF, including members of underrepresented groups. This study will similarly train a wide spectrum of students and postdocs, both at the NDFF and in our support laboratories.