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

最近，根据气候模型的提议，欧洲已经可以观察到紧随其后的密集干旱和暴雨。降雨量、强度和频率的变化会改变土壤结构和土壤有机质质量，从而改变温带森林生态系统的周转。从野外和实验室研究中的干燥和潮湿实验，或从自然干燥和湿润期的观察中，已经报告了相互矛盾的结果。为了验证不同的解释，稳定和放射性同位素以及生物标记物的组合分析似乎是一个很有前途的工具。这可以通过在干燥和湿润领域(13C和15NJ)以及在对照实验室研究(14C、13C和15N)中建立示踪剂实验，并通过分析13C、14C和15N的特征，不仅在散装的SOM中，而且在表征化学定义的SOM池的生物标志物中，例如微生物和植物来源的糖、磷脂脂肪酸(PLFA)和苯多羧酸(BPCA)。结合生物标志物和同位素(δ13C、14C和δ15N)分析，不仅可以推断干湿后有机质的周转，还可以在实验操作下确定所涉及的微生物群落和有机质分解和周转过程中化学定义的化合物的去向。

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.