典型滨岸草地生态系统碳稳定同位素组成及分布特征

通过测定上海市青浦区东风港百慕大、白花三叶草、高羊茅和白茅等4种典型滨岸草本植物各组织以及不同垂直深度土壤有机质δ¹³C值,对滨岸草地生态系统的植物-土壤碳稳定同位素特征进行了分析.结果表明: 白花三叶草、高羊茅属于C3植物,百慕大、白茅属于C4植物,其茎叶、凋落物和根系各组织间δ¹³C值无显著差异.C3和C4植物样带表层土壤有机质δ¹³C值随着土壤深度递增而呈现截然不同的变化特征,这与样带本底δ¹³C值以及碳稳定同位素分馏效应有关,同时还受植物根系分布深度的影响.植物输入是土壤有机碳(SOC)的最主要来源,植物有机体δ¹³C组成对土壤有机质δ¹³C值有直接影响,植物各组分δ¹³C值与土壤有机质δ¹³C值均存在极显著相关.4种草本植物样带SOC含量与δ¹³C值均呈极显著相关,其中,C3植物样带SOC含量与δ¹³C值呈线性负相关,C4植物样带SOC含量与δ¹³C值呈线性正相关.

Composition and distribution characteristics of stable carbon isotope in typical riparian grassland ecosystem

Plant-soil carbon stable isotope characteristics of riparian herbaceous ecosystem were ana-lyzed by measuring the δ¹³C value of plant tissues from four typical riparian herbaceous plants, which were Cynodon dactylon, Trifolium repens, Festuca arundinacea and Imperata cylindrical, and that of soil organic carbon (SOC) from different vertical depths along Dongfeng Port River in Qingpu District, Shanghai. The result showed that T. repens and F. arundinacea were C3 plants while C. dactylon and I. cylindrical were C4 plants. There was no significant difference between the δ¹³C va-lue of stem and leaf, litter and root of the four herbaceous plants. The surface SOC δ¹³C value of C3 and C4 plants strips showed different trends with soil depth, which could be related to the background SOC δ¹³C value, soil carbon stable isotope fractionation effect and plant root distribution depth as well. Plant input was the main source of SOC and the δ¹³C composition of plant organisms had direct effect on the SOC δ¹³C value. The δ¹³C value of plant components were significantly correlated with the δ¹³C value of SOC. The SOC content and δ¹³C value were significantly correlated in the four herbaceous plants strips. The SOC content and δ¹³C value showed linear negative correlation in C3 plant strips and linear positive correlation in C4 plant strips.