RAPID: The Endless Summer: Implications of a 100-year drought for the functional biology of native Californian plants and ecosystems

加州正在经历160年来最严重的干旱。虽然目前干旱的原因还不完全清楚，但它类似于在未来气候变化情景下预测加州将出现的气温升高和降雨模式更加不稳定。 极端事件，如目前的干旱，预计也将作为“触发器”的生态系统组成和功能的变化，因为景观适应温暖和干燥的条件。 面对气候变化，管理加州的生物多样性及其自然环境所提供的服务具有挑战性，因为物种和生态系统对干旱（和其他极端气候事件）的反应仍然知之甚少。 在复杂的土壤、地形和地质条件下生长的植物种类繁多，这意味着同样的干旱条件可能导致植物所经历的水分胁迫产生截然不同的结果。 该项目利用加州世纪一遇的干旱，研究水分胁迫对生长在不同生境的不同植物物种的影响，以评估不同的植物适应如何导致一系列干旱胁迫和对生态系统变化的敏感性。 这项研究将有助于在多个教育阶段（博士后学者，研究生和本科生）培养年轻科学家。研究结果将与保护和资源管理人员广泛分享，为加强保护优先事项的规划和应对干旱的可能干预措施提供依据，尽管极端干旱事件在世界范围内越来越普遍，但对这些事件期间植物表现的详细监测仍然很少。量化植物对极端干旱事件的反应的多样性提供了一个机会，以推进我们的理解的基本（机械）的原因，如何以及为什么特定的植物策略可能是更好或更不适合应对极端的生理压力。干旱引起的变化，预计将推动植被群落的瞬态动态，可能引发物种的过渡和推动生态系统规模的生态水文到新的状态。该项目将主要利用生理测量作为干旱胁迫的指标，特别是叶水势、气孔导度、天然栓塞和冠层面积。 这些测量将每月在旧金山弗朗西斯科湾区的两个密集研究地点进行。 干旱对光合作用和植物碳储存的影响将使用碳同位素作为指标进行测量。 工厂使用的水源将通过水的氧和氢同位素来确定。 以前安装的土壤湿度和气象设备将用于跟踪特定地点的小气候和水文条件。 研究结果将有助于了解本地植物物种的生理极限极端干旱和套房的植物性状介导干旱胁迫，使植物生存或死亡。

California is experiencing the most severe drought to occur in 160 years of state meteorological records. While the causes of the current drought are not yet fully known, it is similar to the warmer temperatures and more erratic rainfall patterns that are predicted to occur in California under future climate change scenarios. Extreme events such as the current drought are also anticipated to act as 'triggers' of change in ecosystem composition and function as the landscape adapts to warmer and drier conditions. Managing California's biodiversity and the services performed by its natural environment in the face of a changing climate is challenging because the response of species and ecosystems to drought (and other extreme climate events) is still poorly understood. The wide variety of plant species growing in complex soils, topography and geology mean that the same imposed drought conditions may lead to dramatically different outcomes in terms of the water stresses experienced by plants. This project takes advantage of the once-in-a century Californian drought to study the effects of water stress in different plant species growing in different habitats in order to evaluate how different plant adaptations lead to a spectrum of drought stress and susceptibility to ecosystem change. The research will contribute to the training of young scientists at multiple stages of their education, (postdoctoral scholars, graduate students and undergraduate students). The results will be widely shared with conservation and resource managers, providing a basis for enhanced planning of conservation priorities and possible interventions in response to drought.Although extreme drought events are becoming more common worldwide, detailed monitoring of plant performance during these events remains scarce. Quantifying the diversity of plant responses to extreme drought events provides an opportunity to advance our understanding of the underlying (mechanistic) reasons for how and why particular plant strategies may be either better or more poorly suited for coping with extreme physiological stress. Drought-induced changes are expected to drive the transient dynamics of vegetation communities, possibly triggering species transitions and pushing ecosystem-scale ecohydrology into novel states. The project will primarily draw on physiological measurements as indicators of drought stress, specifically leaf water potentials, stomatal conductance, native embolism and canopy area. These measurements will be made on a monthly basis at two intensive research sites in the San Francisco Bay Area. The effects of the drought on photosynthesis and plant carbon stores will be measured using carbon isotopes as an indicator. The sources of water used by the plants will be determined using oxygen and hydrogen isotopes of water. Previously installed soil moisture and meteorological equipment will be used to track site-specific microclimatic and hydrological conditions. Results will contribute to understanding of the physiological limits of native plant species to extreme drought and the suites of plant traits that mediate drought stress so that plants either survive or die.