Collaborative Proposal: Mechanisms of Low Temperature Tolerance in Chaparral Shrubs

9528369加州南部的查帕拉尔植被与美国最大的都市区之一相邻，占据了宝贵的分水岭土地。 查帕拉尔阻止土壤侵蚀，保持斜坡稳定，为野生动物提供食物和覆盖物，并提供美学和娱乐价值。 虽然之前的研究主要集中在 查帕拉尔对火和水胁迫反应，越来越多的证据表明，低温耐受性是查帕拉尔分布的一个重要因素 和丰富。 根据频率，零度以下的温度事件可能是重要的查帕拉尔社区的火灾和干旱。 在冰冻事件之后，已经观察到本地植物的生产力损失、伤害和在某些情况下死亡。 幼苗可能特别脆弱，因为火灾后植被覆盖减少， 致命的辐射会在晚上冻结 本研究将检验以下假设：幼苗比成年人更容易受到低温伤害，冷冻诱导的木质部栓塞（空气阻塞）可以导致新梢死亡，冷冻诱导栓塞的数量与木材结构和解冻速度有关。 从沿海到内陆的最低温度的陡峭梯度和最近在南加州燃烧的地点的组合提供了一个很好的模型系统。 研究结果将对土地利用管理产生影响，例如减轻加州南部火灾地区的影响;对重新植被项目产生影响;以及将对温度敏感的查帕拉尔物种用作气候指标。

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.