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

全球变暖将大大延长高纬度生态系统的活跃季节，但这些地区的许多植物物种具有适应短生长季节的物候模式。一些（但不是全部）影响物候阶段的因素将随着全球变暖而改变。那些受全球变暖影响不变的因素（如光周期）限制的物种，将无法对季节长度的延长做出反应。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。本项目以阿拉斯加苔原为模型系统，解决了以下问题：1)优势种物候模式的制约因素是什么？2)当资源供应延长时，物种会做出哪些生理调整？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发生怎样的变化？这些问题将通过控制环境研究和季节长度的现场操作相结合来解决。生长室研究将检查光周期、土壤和空气温度以及叶龄对优势生长形式中选定物种的物候模式和碳增益的影响。野外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。该研究结果将用于建立冻土带植物物候模式模型，该模型可用于评估物种对延长生长季节的反应。* * *

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. ***