Collaborative Proposal: Mechanisms of Low Temperature Tolerance in Chaparral Shrubs

加利福尼亚州南部9528369的查帕拉尔植被毗邻美国最大的大都市区之一，占据了宝贵的分水岭土地。Chaparral阻止土壤侵蚀，保持坡面稳定，为野生动物提供浏览和覆盖，并提供美学和娱乐价值。虽然以前的研究主要集中在轮虫对火和水胁迫的反应上，但越来越多的证据表明，耐低温是导致轮虫分布和丰度的一个重要因素。根据频率，零度以下的气温事件对牧区社区的重要性可能与火灾和干旱一样重要。在冰冻事件后，观察到了本地植物的生产力损失、伤害，有时甚至死亡。幼苗可能特别脆弱，因为火灾后植物覆盖率的减少可能会使它们在夜间暴露在潜在致命的辐射冻结中。这项研究将检验以下假设：苗木比成虫更容易受到低温伤害，树干木质部(木材)的冷冻诱导的栓塞(空气堵塞)可以导致枝条死亡，以及冷冻诱导的栓塞量与木材的结构和解冻速度有关。内陆海岸最低温度的陡峭梯度和加利福尼亚州南部最近被烧毁的地点相结合，提供了一个极好的模型系统。研究结果将对土地利用管理产生影响，例如缓解南加州的火烧区；重建植被项目；以及使用对温度敏感的茶树物种作为气候指标。

9528369 Chaparral vegetation in southern California neighbors one of the largest metropolitan areas in the United States and occupies invaluable watershed land. Chaparral deters soil erosion, maintains slope stability, furnishes browse and cover for wildlife, and provides aesthetic and recreational value. While research has previously focused on the response of chaparral to fire and water stress, there is growing evidence that low temperature tolerance is an important factor underlying chaparral distribution and abundance. Based on frequency, subzero temperature episodes may be as important to chaparral communities as fires and drought. Loss in productivity, injury, and in some cases death of native plants has been observed after freezing events. Seedlings may be particularly vulnerable as the reduction of plant cover after fire can expose them to potentially lethal radiation freezes at night. This research will examine the hypotheses that seedlings are more vulnerable to low temperature damage than adults, freezing induced embolism (air blockage) of the stem xylem (wood) can cause shoot death, and the amount of freezing-induced embolism is related to both wood structure and rate of thaw. The combination of a steep gradient in minimum temperatures from the coast inland and recently burned sites in southern California provide an excellent model system. The results will have implications for land use management, such as mitigation of fire-burned areas in southern California; for revegetation projects; and for the use of temperature sensitive species of chaparral as climate indicators.