Climate feedbacks and benefits of semi-arid forests (CLiFF)

陆地生物圈通过复杂的相互作用并最终通过其对大气CO2浓度和地表能量平衡的影响来影响地球气候。在这方面，关于干旱环境中的森林的资料很少，因此，我们在以色列半干旱森林中进行的广泛研究是独一无二的：由于对全球大部分土地的变暖和干燥的持续预测，其意义超出了当地范围。最近，我们证明了森林在干旱条件下的生存和高生产力与发展一个独特的“对流效应”，导致大量的显热通量从地表到大气，显着影响森林小气候，当地环境和大气动力学。半干旱森林生态系统与其他生态生理调整相结合，不仅有可能在预测的气候变化下生存，而且有可能改变当地和潜在的区域气候。我们的目标是量化干旱环境中独特的森林功能的过程，以及它对当地环境和气候的影响。这将通过将我们的生态系统尺度研究从冠层尺度转变为整个叶片到行星边界层尺度（从底部20米到整个10公里的表面-大气界面）来实现。这将基于魏茨曼团队在以色列的独特平台和地点的整合，以及KIT团队在大气边界层动力学，受控环境研究设施和建模方面的专业知识和技术能力。我们项目的意义在于提供关于在目前很少开发但广阔的半干旱地区植树造林潜力的定量信息（约占陆地面积的18%），如果变暖和干旱趋势继续下去，对森林功能和碳固存的影响，以及对当地环流、湿度、这将为当前和未来条件下干旱环境适应和缓解相关的管理和政策制定提供新的手段。

The land biosphere influences the Earth climate through complex interactions and ultimately through its effect on atmospheric CO2 concentrations and on the surface energy balance. In this context, little information is available on forests in dry environments and our extensive study in semi-arid forests in Israel is therefore unique: its significance goes beyond the local scale owing to the persistent predictions of warming and drying for large proportions of the global land area. Recently, we demonstrated that the survival and high productivity of forests under dry conditions is associated with the development of a distinctive "convector effect" that results in massive fluxes of sensible heat from the surface to the atmosphere, significantly affecting both the forest microclimate, and the local environment and atmospheric dynamics. Combined with other ecophysiological adjustments, the semi-arid forest ecosystem has the potential not only to survive under predicted climate change, but also to alter local and, potentially, regional climates. Our objective is to quantify both the processes underlying the distinctive forest functioning in the dry environment, and the impact it has on the local environment and climate. This will be achieved by transforming our ecosystem scale study from the canopy scale, to that of the entire leaf to planetary boundary layer scales (from the bottom 20 m, up to entire 10 km of the surface-atmosphere interface). This will be based on the integration of the unique platforms and locations of the Weizmann team in Israel, with the expertise and technological capabilities of the KIT team for atmospheric boundary layer dynamics, controlled environmental research facility, and modeling. The significance of our project is to provide quantitiative information on the potential of afforestation in currently little explored but vast semi-arid regions (~ 18% of the land surface), on forest functioning and carbon sequestration if warming and drying trends continue, and on the effects of changes in local circulation, moisture, and surface temperatures on the regional climate.This will provide new means for management and policy development associated with adaptation and mitigation in dry environments under present-day and future conditions.