首页 > 分享 > 互花米草入侵对滨海湿地土壤碳库的贡献——基于稳定同位素的研究

互花米草入侵对滨海湿地土壤碳库的贡献——基于稳定同位素的研究

花匠小妙招
2024-12-21 04:32

摘要：

互花米草(Spartina alterniflora)因良好的促淤能力被引种至我国东海岸, 目前已成为我国滨海湿地分布最为广泛的入侵种。当前的研究大多关注其生产力增加对生态系统固碳能力的直接影响, 却忽视了对其间接作用的定量研究, 如促淤对土壤碳库的贡献。该研究以上海崇明东滩湿地为研究地, 选择具有不同入侵时长(4年、6年、10年)的互花米草斑块, 同时选择芦苇(Phragmites australis)斑块和光滩作为对照, 采集土壤、植物和水体样品。通过测定土壤总碳、总氮、有机碳以及植物和土壤有机质的碳、氮稳定同位素比值(δ13C和δ15N), 分析土壤碳库的变化; 同时, 针对群落结构不同的互花米草斑块分别采用同位素二源混合模型和三源混合模型定量分析土壤有机碳的来源。结果表明: (1)互花米草斑块土壤有机碳含量和δ13C值逐年增加。互花米草入侵能显著增加土壤有机碳库, 并随入侵时间的延长表现出累积效应。土壤碳氮比值随入侵时间的增加而降低, 并趋近于雷德菲尔比率, 表明植物入侵增加土壤碳、氮输入的同时, 海源的潮汐输入也是土壤碳库的重要来源。(2)互花米草对土壤碳库的贡献随入侵时长的增加而增加, 而潮汐输入对土壤碳库的贡献率则不断降低。在入侵时长为4年的斑块中, 潮汐输入的贡献率在90.0%以上; 在入侵10年的斑块中, 潮汐输入的贡献率仅为18.4%, 而互花米草植株的贡献率高达73.5%。这说明互花米草对土壤碳库的贡献在入侵早期以促淤为主, 入侵后期主要依靠自身碳输入。

关键词: 贡献率, 混合模型, 互花米草, 土壤碳库, 稳定同位素

Abstract: Aims

Spartina alterniflora was introduced into China because of its strong sedimentation promotion ability, currently, it became one of the most invasive species along coastal areas. Most researches focused on its high productivity which directly increased soil carbon (C) input. However, little is known about its indirect contribution to soil carbon via increased sedimentation.

Methods

Spartina alterniflora patches with different invasion history (4, 6, and 10 years) was selected in Chongming Dongtan wetland, and Phragmites australis and mudflat were chosen as control respectively. The plant, soil and water samples were collected for C and nitrogen (N) analysis. Based on the stable isotope ratio of C and N in plant and soil organic carbon, the contribution of soil organic carbon pool from S. alterniflora patches were estimated by using 2 and 3 sources mixing model, respectively.

Important findings

(1) The soil organic C content and stable carbon isotope ratio of S. alterniflora patches increased with time. Spartina alterniflora invasion cumulatively enhanced soil organic carbon pool. The soil C:N ratio decreased with invasion history and became close to the redfield ratio, indicating the important role of sedimentation input. (2) The contribution of invasive S. alterniflora to soil organic carbon pool increased with time, but the sedimentation contribution dropped gradually. In patch with 4 years invasion history, the contribution ratio of sedimentation was more than 90.0%. While in patch invaded 10 years ago, the sedimentation contribution reduced by 18.4%, and in comparison, S. alterniflora contributed up to 73.5% to soil organic carbon pool. These findings suggested that S. alterniflora contributed to soil organic carbon pool mainly by promoting sedimentation in early invasion period, while gradually relied on its own productivity with invasion time.

Key words: contribution ratio, mixing model, Spartina alterniflora, soil carbon pool, stable isotope