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

人们认为，由于气候变化，干旱事件的频率和持续时间增加。特别是，德国的严重干旱最有可能在夏季增加，在夏季，植物通常积极生长并吸收二氧化碳，这可能受到干旱的强烈影响。由于后者的影响很大程度上取决于植物的生理和抗旱性，更多的耐旱植物被认为进一步吸收二氧化碳，而其他植物则死亡。这对植物驱动的土壤中碳的固存有强烈的影响，因此植物-土壤系统中的碳通量作为干旱也可能促进土壤中碳的损失。此外，植物是否能够适应干旱，从而进一步抵抗严重的干旱，这仍然是个问题。在目前的提案中，我们将证明植物对二氧化碳的吸收，植物向土壤的C转运以及两个不同植物群落（草和荒地）的土壤C通量，这些植物群落以前暴露于年度干旱或控制条件下，受到干旱加剧的影响。这将在三重13CO2脉冲实验中进行追踪，该实验于2011年夏天在拜罗伊特EVENT I实验上安装的避雨棚下进行。在安装雨棚后的第1,5,9周进行13CO2标记后，每周收集植物和土壤样品，从而在单个植物隔间和土壤中进行13C追踪，并与未接受同位素标记的重复进行比较。本研究将服务于以下中心目标：1。确定干旱加剧对植物吸收碳和碳向土壤转运的影响。2. 在两个植物群落中鉴定耐旱性较低或较高的植物物种。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群落的反应和植物-土壤系统中的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.