State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University
The National Natural Science Foundation of China (Grant No. 51979071) and the Fundamental Research Funds for the Central Universities (Grant No. B220202034)
采集2021年生长季和非生长季新安江源区常绿针叶林土壤-植物-大气多源水样进行氢氧稳定同位素测试，分析不同来源水分同位素组成（δ18O和δ2H）的差异及变化特征，评估不同季节多水源采样方案（植物不同部位、土壤不同深度）对蒸散发组分区分的影响程度，进而优化我国南方湿润区森林生态系统蒸散组分区分的氢氧稳定同位素采样方案。结果显示：多源水δ18O和δ2H在土壤-植物的水分传输过程中逐渐富集，非生长季较生长季更为富集。植物各部位水分的动力学分馏强度随着同位素不断富集而逐渐增大。河道水与山泉水同位素组成分布较为接近，大气水汽相较于其他水源明显最为贫化。土壤水同位素组成垂向分布主要呈现三种不同的规律：随深度增加而减小、先增大后减小或先减小后增大。浅层土壤水同位素组成变化范围大于深层土壤水，拐点位于50—90 cm。由植物各部位与土壤的水同位素组成分布特征及其差异可知符合同位素稳态假设的杉木最佳取样部位为韧皮部。比较基于不同深度土壤蒸发水汽同位素组成δE计算得出的T/ET（蒸腾与蒸散发比率），发现生长季T/ET整体变化量为13.46 %，低于非生长季21.42 %。即土壤取样深度的变化在相对干冷条件下对T/ET的影响较大，推断出适宜杉木林的土壤取样深度约为20—30 cm。研究成果可为湿润区半湿润区蒸散发组分区分同位素采样方案设计、蒸散发估算模型构建提供科学依据，并为生态系统蒸散发组分分割、植物蒸腾水分溯源研究奠定有效基础。
In this study, multi-source water samples from the soil-plant-atmosphere continuum (SPAC) were collected for hydrogen and oxygen stable isotopes measurement in an evergreen coniferous forest across the source area of Xin’an River during both the growing and non-growing seasons of 2021. By analyzing the differences and their variation characteristics of water isotopic compositions (δ18O and δ2H), we evaluated the influence of different sampling schemes (plant part and soil depth) on evapotranspiration partitioning in different seasons. Finally, the sample collection scheme based on isotope technique was optimized to partition evapotranspiration in forest ecosystems in humid areas of southern China. The results showed that the δ18O and δ2H of water from different sources were gradually enriched in the soil-plant water transport process, and more enriched in the non-growing season. The intensity of dynamic fractionation of water in different parts of plants increased gradually with the enrichment of isotopes. The distribution of isotopic compositions of stream water and spring water was similar, and the atmospheric water vapor was the most depleted compared with the water from other sources. The vertical distribution of isotopic compositions of soil water is different, which mainly presents three different forms: decreased with increased depth, increased first and then decreased, or decreased first and then increased. The variation of soil water isotopic compositions in shallow layer was larger than that in deep layer. The inflection points of δ18O and δ2H were ranged from 50 to 90 cm vertically. According to the distribution characteristics and differences of water isotopic compositions of soil and different parts of plant, phloem was the best sampling part that met the isotope steady-state assumption in Cunninghamia lanceolata forest. By comparing the T/ET (transpiration to evapotranspiration ratio) based on the isotopic compositions of water vapor in soil evaporation (δE) of different soil depths, it was found that the range of T/ET in the growing season was 13.46%, lower than that in the non-growing season (21.42 %). It means that the variation of soil sampling depth has a greater influence on T/ET under relatively dry and cold condition, further it can be inferred that the suitable soil sampling depth of Cunninghamia lanceolata is about 20—30 cm. The research results can provide a scientific basis in sampling scheme design and model establishing of evapotranspiration estimation, and lay an effective foundation for the separation of evapotranspiration components in ecosystems and the traceability of plant transpiration water across other humid and semi-humid regions.
蔡越,邢万秋,王卫光,吴宇桐,陈顼.基于同位素技术的蒸散组分区分采样方案优化研究.生态学报,,(). http://dx. doi. org/[doi]复制