Collaborative Research: Linking Xylem Functional Traits to Life-History Type in California Chaparral

加利福尼亚州南部的气候属于地中海气候，其特点是冬季温和，夏季干旱时间长，野火时有发生。主要的植被是查帕拉尔，它特别适应夏季的脱水和火灾。在周期性的火灾中，有三种策略可以使Chaparal存活并持续存在：火灾后不发芽，火灾后临时发芽，以及火灾后专职发芽。我们假设这三种策略与脱水耐受性有关。我们将通过确定导致植物水分运输系统失效的脱水阈值来评估脱水耐受性。这一失败是由于严重水分胁迫下木质部栓子的形成，即当植物的管道系统(木质部导管)被气泡堵塞，切断流向叶片的水分，导致枝条死亡。本研究的主要目的是阐明不同种类查帕尔灌木的木质部功能特征与生活史类型之间的联系。我们假设在木质部抗栓塞性、木质部传导性效率和木质部机械强度之间存在权衡，这取决于柴胡物种对野火的三种生活史策略。与反复发生的野火、水源涵养、侵蚀控制、城市扩张和娱乐有关的问题在查帕尔地区比加州任何其他类型的荒地都更加明显。研究结果将广泛传播给负责管理和保护圣莫尼卡山脉自然资源的当地机构，以及包括国家公园管理局和国家公园管理局讲解员在内的教育团体。这些发现将允许对加州更广泛的查帕尔社区和世界上其他四个地中海类型的气候区域进行推广。这项拟议工作的结果将完善对下个世纪牧师分布和社区结构预期变化的预测，以应对预期的气候变化，即加州将变得更温暖、更干燥，圣安娜风和野火增加。

The climate of southern California is a Mediterranean-type, characterized by mild winters, protracted summer drought, and periodic wildfire. The dominant vegetation is chaparral, which is uniquely adapted to summer dehydration and fires. There are three strategies by which chaparral survive and persist through periodic fire: non-sprouters after fire, facultative sprouters after fire, and obligate sprouters after fire. We hypothesize that these three strategies are coupled to dehydration tolerance. We will estimate dehydration tolerance by determining the threshold in dehydration that causes the water transport system of plants to fail. This failure is caused by xylem embolism formation under severe water stress, that is, when the plumbing system (xylem conduits) of plants become blocked by air bubbles, cutting off water flow to leaves, leading to shoot death.The primary objective of our research is to elucidate the mechanisms linking xylem functional traits to life history type among diverse species of chaparral shrubs. We hypothesize that there are trade-offs among xylem embolism-resistance, xylem conductivity efficiency and xylem mechanical strength and these depend on the three life history strategies that chaparral species have in response to wildfire.Issues related to recurrent wildfire, water conservation, erosion control, urban expansion and recreation are more pronounced in regions of chaparral than in any other type of wild land in California. Results from the research will be disseminated widely to local agencies responsible for management and conservation of natural resources in the Santa Monica Mountains, and to educational groups including docents for the State Park Service and the National Park Service. The findings will allow generalizations to the broader chaparral community of California and to the other four Mediterranean-type climate regions of the world. Results from the proposed work will refine predictions of expected shifts in chaparral distribution and community structure over the next century in response to an anticipate climate change to a warmer, drier California with increased episodic Santa Ana winds and wildfire.