Effects of Increased Season Length on Plant Phenology, Community Composition, Productivity, and Ecosystem Carbon Fluxes in Alaskan Tundra: Implications for Climate Warming

9321626欧伯鲍尔全球变暖将大大增加高纬度生态系统的活动季节长度，但这些地区的许多植物物种具有适应短生长季的物候模式。影响物候期的一些因素，但不是全部，都会随着全球变暖而改变。这些物种受到将随着全球变暖而不变的信号的限制，例如光周期，将无法对延长的季节长度做出反应。因此，这些生态系统的物种组成、生产力和碳通量将发生重大变化。本项目以阿拉斯加冻土带为模式系统，解决以下问题：1)优势物种物候模式的约束条件是什么？2)物种将对延长的资源可获得期做出哪些生理调整？3)在野外模拟的延长季节下，优势物种的生长、生态系统生产力和生态系统碳通量将如何变化？这些问题将通过控制环境研究和季节长度的田间操作相结合来解决。生长室研究将考察光周期、土壤和气温以及叶龄对选定的优势生长类型物种的物候模式和碳增益的影响。实地研究将考察延长活跃期对物候、生长、生产力和生态系统碳平衡的影响。这项研究的结果将被用来开发冻土带植物的物候模式模型，该模型可以用来评估物种对延长的生长季节的反应。***

9321626 Oberbauer Global warming will substantially increase the length of the active season for high latitude ecosystems, but many plant species in these areas have phenological patterns adapted to short growing seasons. Some, but not all, of the factors that affect phenological stages will change with global warming. Those species constrained by cues that will be unchanged with global warming, such as photoperiod, will be unable to respond to extended season length. As a result, species composition, productivity, and carbon fluxes from these ecosystems will change substantially. Using Alaskan tundra as a model system, this project addresses the questions: 1) What are the constraints on phenological patterns for the dominant species? 2) What physiological adjustments will species make in response to an extended period of resource availability? 3) How will growth of the dominant species, ecosystem productivity, and ecosystem carbon fluxes change under field-simulated extended seasons? These questions will be addressed using a combination of controlled-environment studies and field manipulations of season length. Growth chamber studies will examine the effects of photoperiod, soil and air temperature, and leaf age on phenological patterns and carbon gain of selected species of the dominant growth forms. Field studies will examine the effects of extended active period on phenology, growth, productivity, and ecosystem carbon balance. Results from this study will be used to develop a model of phenological patterns of tundra plants that can be used to evaluate species' responses to extended growing season. ***