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

doi:10.17521/cjpe.2015.0091

摘要/Abstract

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

王丹, 张荣, 熊俊, 郭海强, 赵斌. 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. 植物生态学报, 2015, 39(10): 941-949. DOI: 10.17521/cjpe.2015.0091

WANG Dan,ZHANG Rong,XIONG Jun,GUO Hai-Qiang,ZHAO Bin. Contribution of invasive species Spartina alterniflora to soil organic carbon pool in coastal wetland: Stable isotope approach. Chinese Journal of Plant Ecology, 2015, 39(10): 941-949. DOI: 10.17521/cjpe.2015.0091

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2015.0091

https://www.plant-ecology.com/CN/Y2015/V39/I10/941

图/表 8

图1 研究区域和样点分布图。图中MF、PA、SA分别代表光滩、芦苇斑块和互花米草斑块采样点。

Fig. 1 Location of the study area and sampling sites. The MF, PA, SA represent mudflat, Phragmites australis and Spartina alterniflora sampling points, respectively.

表1 互花米草和芦苇植株碳、氮稳定同位素比值(δ13C、δ15N)

Table 1 The δ13C and δ15N values of Spartina alterniflora and Phragmites australis plants

植株 Plant	区域 Area	δ¹³C (‰)	δ¹⁵N (‰)
互花米草 Spartina alterniflora (C₄)	SA-4	-14.66	5.29
互花米草 Spartina alterniflora (C₄)	SA-6	-14.42	3.06
	SA-10	-13.59	2.18
芦苇 Phragmites australis (C₃)	PA-6	-26.04	4.65
芦苇 Phragmites australis (C₃)	PA-10	-26.24	4.74

图2 互花米草斑块土壤总碳(16 ± 0.6)和有机碳(12 ± 1.3)(mg·g-1 dry soil)的变化(平均值±标准误差)。图中A、B、C、D分别为对照光滩、入侵时长为4年、6年和10年的互花米草斑块。

Fig. 2 Changes in soil total carbon (16 ± 0.6) and organic carbon (12 ± 1.3) (mg·g-1 dry soil) in Spartina alterniflora patches (mean ± SE). The A, B, C and D represent the mudflat, Spartina alterniflora patches of about 4 years, 6 years and 10 years of invasion time, respectively.

图3 互花米草斑块土壤碳氮比。

Fig. 3 The soil C:N ratio in Spartina alterniflora patches.

图4 互花米草斑块和光滩土壤碳、氮稳定同位素比值(δ13C、δ15N)垂直变化(平均值±标准误差)。MF、SA-4、SA-6和SA-10分别表示光滩、互花米草入侵4年、6年和10年的土壤。

Fig. 4 Vertical changes in the values of δ13C and δ15N of different Spartina alterniflora patches and mudflat soil (mean ± SE). The MF, SA-4, SA-6 and SA-10 represent the mudflat, S. alterniflora patches of about 4 years, 6 years and 10 years of invasion time, respectively. δ13C, stable carbon isotope ratio; δ15N, stable nitrogen isotope ratio.

图5 互花米草斑块中土壤碳库各贡献源比例。其中SA、POC、PA分别代互花米草植株、悬浮颗粒有机碳和芦苇植株对土壤碳库的贡献比例。

Fig. 5 Proportions of soil carbon pools in Spartina alterniflora patches. The SA, POC and PA represent the proportion of S. alterniflora plant, particulate organic carbon and Phragmites australis plant, respectively.

图6 土壤碳库的两个来源及具有一个元素的混合模型示意图。图中三角形为SA-4的样点土壤, POC和SA分别代表潮汐悬浮沉积物和互花米草两个来源。

Fig. 6 Mixing diagram for a mixing model utilizing one isotope value and two sources for the soil organic carbon pool, the triangles represent the soils of SA-4 sampling points, the POC and SA represent sediment and Spartina alterniflora plant sources, respectively.

图7 土壤有机碳库的3个来源及具有两个元素的混合模型示意图。图中圆形和小三角形分别代表SA-6和SA-10采样点土壤, PA、SA和POC分别代表芦苇、互花米草和潮汐沉积物来源。

Fig. 7 Mixing diagram for a mixing model utilizing two isotope values and tree sources for the soil organic carbon pool, the circles and small squares represent the soil of SA-6, SA-10 sampling points. The PA, SA and POC represent Phragmites australis plant, Spartina alterniflora plant, and sediment, respectively.

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