Processes of litter and soil organic matter transformation during extreme drying/wetting as assessed by compound-specific isotope approaches

最近，根据气候模式的建议，在欧洲已经可以观察到密集的干旱和暴雨。降水量、强度和频率的变化可以改变温带森林生态系统的土壤结构和土壤有机质质量，从而改变土壤周转。从田间和实验室研究的干燥和湿润实验或从自然干燥和湿润期的观察中报告了相互矛盾的结果。为了验证不同的解释，稳定同位素和放射性同位素以及生物标志物分析的组合似乎是一个有前途的工具。这可以通过在干、湿场建立示踪实验来实现（13 C和15 NJ）和受控实验室研究（14 C、13 C和15 N）中的13 C、14 C和15 N特征，并且通过分析不仅在大量SOM中而且在表征化学限定的SOM池的生物标志物（例如微生物和植物来源的糖）中的13 C、14 C和15 N特征，磷脂脂肪酸（PLFA）和苯多羧酸（BPCA）。生物标志物和同位素（δ 13 C，14 C和δ 15 N）分析的组合不仅可以推断干燥/润湿后的SOM周转，而且还可以确定在实验操作下SOM分解和周转过程中所涉及的微生物群落和化学定义的化合物的命运。

Recently, intensive droughts followed by heavy rainfall can already be observed in Europe as proposed by climate models. Shifts in amount, intensity and frequency of precipitation could change soil structure and soil organic matter quality and thus turnover in temperate forest ecosystems. Contradicting results have been reported from drying and wetting experiments in field and laboratory studies or from observations of natural drying and wetting periods. To verify different interpretations, a combination of stable and radio-isotopes and biomarker .analyses seems a promising tool. This can be achieved by establishing tracer experiments in the drying and wetting fields (13C and 15NJ and in controlled laboratory studies (14C, 13C, and 15N) and by analysing the 13C, 14C and 15N signatures not only in the bulk SOM but also in biomarkers characterizing chemically defined SOM pools, e.g. microbially and plant-derived sugars, phospholipid fatty acids (PLFA) and benzenepolycarboxylic acids (BPCA). The combination of biomarker and isotope (δ13C, 14C and δ 15N) analysis allows not only deducing SOM turnover after drying / wetting but also to identify the involved microbial community and the fate of chemically defined compounds during SOM decomposition and turnover under the experimental manipulations.