The effect of severe drought on CO2 uptake by plants and carbon dynamics in the plant-soil system

干旱事件被认为是由于气候变化而增加的频率和持续时间。特别是，德国夏季的严重干旱很可能会加剧，那里的植物通常会积极生长并吸收二氧化碳，这可能会受到干旱的强烈影响。由于后一种效应强烈地依赖于植物的生理和抗旱性，人们认为更耐旱的植物可以进一步吸收二氧化碳，而其他植物则会死亡。这对植物驱动的碳在土壤中的固持有很大的影响，因此，由于干旱可能也会促进土壤中的碳流失，所以植物-土壤系统中的碳通量也会受到影响。此外，植物是否能够适应干旱以进一步抵御严重干旱仍然是值得怀疑的。在当前的提案中，我们将证明植物对二氧化碳的吸收，碳从植物到土壤的转移，以及两种不同植物群落(草和石楠)的土壤碳通量，这两种植物群落以前暴露在年度干旱或控制条件下，受干旱加剧的影响。这将在一个三重13CO2脉冲实验中被追踪，该实验是在2011年夏天安装在拜罗伊特事件I实验上的雨棚下进行的。在安装雨棚后的第1、5、9周进行的每一次13CO2标记之后，每周收集植物和土壤样本，从而能够在单个植物隔间和土壤中进行13C示踪，并与没有收到同位素标记的重复进行比较。这项研究将服务于以下中心目标：1.确定干旱对植物吸收C的影响和C向土壤的转移。2.确定两个植物群落中耐旱性较低或较高的植物种类。3.评估严重干旱对土壤碳储量的影响。这些信息对于了解未来气候条件下植物-土壤系统中植物群落的反应和碳收支是非常必要的。

Drought events are regarded to increase in frequency and duration due to climate change. Especially, severe droughts most likely increase in Germany during summer season, where commonly plants actively grow and assimilate CO2, which can be strongly affected by drought. As the latter effect strongly depends on physiology of plants and drought resistance, more drought tolerant plants are thought to further assimilate CO2, while others die. This has a strong influence on the plant driven sequestration of C in soil and thus the C fluxes in the plant-soil system as drought might also promotes C loss in soil. Furthermore, it remains questionable, if plants are able to adapt to drought to further resist to severe droughts.In the current proposal, we will proof CO2 uptake by plants, translocation of C from plants to soil and soil C fluxes of two different plant communities (grass and heath), which were previously exposed to annual drought or control conditions, as affected by increasing drought. This will be traced in a triple 13CO2 pulse experiment, which was carried out under rainout shelters installed on the Bayreuth EVENT I experiment in summer 2011. After each 13CO2 labeling, carried out in weeks 1, 5, 9 after the installation of the rainout shelters, plant and soil samples were collected weekly, thus enabling 13C tracing in the individual plant compartments and soil, which is compared to replicates that did not receive the isotopic label.This research will serve the following central goals: 1. Determine effect of increasing drought on C uptake by plants and C translocation towards soil. 2. Identify plant species of lower or higher drought tolerance in both plant communities. 3. Assess the effect of severe drought on soil C storage. Such information is strongly required to understand plant community responses and carbon budgets in the plant-soil system as under future climatic conditions.