Forests of the future: what, when and how will trees get their water?

地球的大气层正在发生变化，二氧化碳浓度的增加通过对植被的影响改变了地球的外观。在某些地方，地球变得越来越绿，地球上的树木似乎正在改变它们使用水的方式（参考文献）。这些变化将影响全球的森林和水资源，但到目前为止，我们还没有一种方法来测试树木在未来如何应对更高的二氧化碳。该项目将通过使用一个全球独一无二的实验设施来填补这一重要空白，该实验设施人工提高了英国中部古老橡树林（BIFoR FACE）的CO2浓度。就树木用水量的变化而言，这可能会减少，因为气孔打开的频率会降低，或者冠层叶面积可能会增加（“CO2施肥效应”），从而产生更高的总体蒸腾速率。这些关于“多少”的问题很重要，但还有一个关键的、迄今为止被忽视的问题，即树木吸收和使用了“哪些”水。该项目将利用稳定同位素作为一种方法来追踪在BIFoR CO2富集实验（FACE）中树木在生长季节所使用的水，以获得未来森林将使用哪些水的第一个机械见解。这项工作将具有重要的意义，将直接告知我们如何看待未来的森林和集水区。森林再生工作正在全球范围内扩大，并被广泛认为提供了许多有益的生态系统服务，但未来这些森林将如何适应不断变化的水和气候动态，这是非常不确定的。这个项目将提供关键的见解，了解他们如何应对水压力，我们如何考虑他们的种植和管理。最后，这项工作还将通过研究结果如何在更大范围内应用，特别是树木使用的水如何反过来改变土壤和河流的可用水，从而改变下游水资源的供应，为集水区水管理提供信息。这些森林和水资源的影响将直接与环境局的项目合作伙伴和合作者以及林业部门的其他合作伙伴一起工作，使学生能够将研究转化为政策实践。

The earth's atmosphere is changing, with increasing CO2 concentrations changing the way the planet looks through its impact on vegetation. The earth is getting greener in some places, and trees all over the earth appear to be changing the way they use water (refs). These changes will impact forests and water resources globally, but until now we have not had a way to test how trees will actually respond to higher CO2 in the future. This project will help fill this important gap by using a globally unique experimental facility that is artificially enhancing the CO2 concentrations of an old growth oak forest in central UK (BIFoR FACE).In terms of changes to tree water use, this may decrease because stomata will open less frequently, or alternatively the canopy leaf area may increase ('CO2 fertilization effect'), creating higher overall transpiration rates. These questions over "how much" are important, but there is also the critical, and as yet overlooked, question of "which" water is being taken up and used by trees. This project will utilise stable isotopes as a method to trace the water being used by trees over the growing season at the BIFoR CO2 enrichment experiment (FACE) to gain the first mechanistic insights into which water the forest of the future will use.This work will have important implications that will directly inform how we think about forests and catchments of the future. Forest regeneration efforts are expanding globally and are widely recognised as providing many beneficial ecosystem services, but how resilient these forests of the future will be with changing water and climate dynamics is highly uncertain. This project will provide critical insights into how they might respond to water stress, how we might think about their planting and management. Finally, this work will also inform catchment water management by examining whether how the results might apply at larger scales, specifically how the water being used by trees in turn changes the water available for soils and rivers and hence the supply of water resources downstream. These forest and water resource implications will be worked on directly with project partners and collaborators in the Environment Agency, as well as other partners in the forestry sector, allowing the student to also translate research into policy practice.