Dry Season Biogeochemistry of California Ecosystems

地球上至少有三分之一的土地经常遭受干旱，气候模型表明，未来干旱将更加频繁和严重。然而，在干旱时期生态系统中发生的生物过程通常只在研究降雨后发生的情况后才进行推断。然而，重要和令人惊讶的过程可能发生在旱季。例如，在干燥的沿海加州夏季，草原的土壤干燥，植物死亡，但土壤微生物的几个重要群体的数量和质量增加，即使它们的活动显然非常有限。这种不可预见的情况似乎是由于微生物独特的干旱生存生理学，以及干燥土壤中出现的非常薄的水膜的断开，这限制了它们所吃食物的扩散，也限制了它们捕食者的运动。该项目将评估在干旱的夏季，在对比沿海加州生态系统（草地，林地，和查帕拉尔）的关键土壤微生物的种群的变化，调节它们的物理和生物因素，其他相关的土壤生态过程的动态，以及它们对整个生态系统动态的集体影响。塞奇威克保护区的讲解员项目是外联项目的关键要素。该项目的科学家将定期为讲解员举办实地培训班，并提供有关土壤的最新材料和有关这一具体研究项目的结果。超过800名K-12学生和100名成年人已经参观了项目现场。此外，研究生和本科生都将在本研究期间接受培训。

At least one third of the Earth's land experiences regular drought, and climate models suggest droughts will be more frequent and intense in the future. However, the biological processes that occur in ecosystems during the dry periods have generally only been studied by inference after studying what happens after rains return. Yet, important and surprising processes can occur during the dry season. For example, during the dry coastal California summer, soils of the grasslands are dry and the plants are dead, but the population size and mass of several important groups of soil microbes increase, even though their activity is apparently very limited. This unforeseen circumstance appears to result from a combination of the unique drought survival physiology of microorganisms, as well as disconnections in the very thin films of water that occur in dry soils that limit the diffusion of food they eat but also limit the movement of their predators. This project will evaluate changes in populations of key soil microbes through the dry summer in contrasting coastal California ecosystems (grassland, woodland, and chaparral), the physical and biological factors that regulate them, the dynamics of other related soil ecological processes, and their collective impacts on whole-ecosystem dynamics. The docent program at the Sedgwick Reserve is the key element of the outreach program. The scientists of this project will run regular in-the-field training sessions for the docents and provide up-to-date materials on soils generally and on the results of this specific research project. Over 800 K-12 students and 100 adults have already visited the project site. In addition, both graduate and undergraduate students will be trained during this research.