基于碳稳定同位素的滨岸草地生态系统土壤有机碳贡献研究

通过测定4种长三角地区常见的滨岸草本植物（百慕大、白花三叶草、高羊茅与白茅）所在样地中不同形态的土壤碳库含量及土壤有机碳稳定同位素丰度来探索该区域土壤碳库及碳稳定同位素分布特征，并利用稳定同位素混合模型，研究滨岸草地生态系统对土壤碳库的贡献。结果表明：（1）土壤中总碳、有机碳、溶解性有机碳含量随着深度的增加而逐渐降低。总碳、有机碳、溶解性有机碳在4种植物样带的表层土壤中，平均含量分别为2211、1144、5395 mg·kg-1;而深层土壤中则仅为1557、707、1947 mg·kg-1，远低于表层土壤中的含量。且土壤总碳、有机碳及溶解性有机碳两两之间存在极显著的正线性相关；（2）土壤有机碳稳定同位素在垂直方向上表现出C3植物δ13C值随深度增大而增大、C4植物δ13C值随深度增大而减小两种特征。两类植物的平均土壤有机稳定碳同位素δ13C值分别由表层土壤中的-2524‰、-2233‰变化为深层土壤中的-2435‰、-2327‰；（3）借助稳定同位素混合模型计算后发现：不同植物对土壤有机碳的贡献率及有机碳累积速率完全不同。其中百慕大贡献率为1219%、累积速率为6279 g·m-2·a-1；白花三叶草贡献率1434%、累积速率为7534 g·m-2·a-1;高羊茅贡献率为3595%、累积速率为18184 g·m-2·a-1；白茅贡献率为1851%、累积速率为9770 g·m-2·a-1。

Using Stable Carbon Isotope to Study Contribution Rate of Soil Organic Carbon in A Riparian Grassland Ecosystem

Soil carbon pool and abundlance of organic carbon stable isotopes were investigated at the Yangtze River Delta region across which the coastal herbaceous plants (Cynodon dactylon, Trifolium repens, Festuca arundinacea and Imperata cylindrica) occupy commonly, and this pool was quantified with Stable Isotope Mixing Model as the contribution of coastal grassland ecosystem. The results of this study show: (1) the average contents of total carbon, organic carbon and dissolved organic carbon correlate significantly with each other and decrease with increasing soil depth from 2211 g·kg-1, 1144 g·kg-1, and 5395 mg·kg-1 to 1557 g·kg-1, 707 g·kg-1, and 1947 mg·kg-1, respectively. (2) On the contrary, while the δ13C values of C3 plants increased with the depth increasing in the vertical direction, the δ13C values of C4 plants decreased with the depth. From upper layer to deeper layer, the average δ13C value of two types of plants change from -2524‰,-2233‰ to -2435‰,-2327‰; (3) The stable isotope mixture model found the contribution rate of different plants to soil organic carbon and the organic carbon accumulation rate was completely different among those four plants. The contribution rate of Cynodon dactylon, Trifolium repens, Festuca arundinacea, and Imperata cylindrical is 1219%, 1434%, 3595% and 1851% with the cumulative rate of 6279 g·m-2·a-1, 7534 g·m-2·a-1, 18184 g·m-2·a-1, and 9770 g·m-2·a-1, respectively