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，在干旱期生态系统中发生的生物过程通常只是在研究了降雨恢复后发生的情况后通过推断来研究的。然而，重要和令人惊讶的过程可能发生在旱季。例如，在加利福尼亚沿海干燥的夏季，草原上的土壤干燥，植物死亡，但几组重要的土壤微生物的数量和质量却增加了，尽管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，以及干燥土壤中非常薄的水膜的断裂，这限制了它们所吃食物的扩散，也限制了它们的捕食者的活动。该项目将评估干旱夏季加州沿海生态系统（草地、林地和灌木林）中关键土壤微生物种群的变化，调节它们的物理和生物因素，其他相关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计划是外展计划的关键要素。该项目的科学家将定期为讲解员举办实地培训课程，并提供关于一般土壤和这一具体研究项目结果的最新材料。800多名K-12学生和100多名成年人已经参观了项目现场。此外，在本研究期间，研究生和本科生都将接受培训。

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.