闽江河口区互花米草入侵不同年限下湿地土壤有机碳变化

为阐明互花米草的固碳潜力,论文在闽江河口区鳝鱼滩湿地选择不同入侵年限的样地,对其0~60 cm土壤理化性质和碳库变化进行测定与分析。结果表明：1） Y₄（<4 a）、Y₈（4~8 a）和Y₁₂（8~12 a）3个采样点土壤有机碳含量均值分别为 15.5、17.77和19.71 g·kg^-1,土壤有机碳密度均值分别为10.68、12.29和15.01 kg·m^-3,总有机碳储量均值分别为65.24、73.99和90.30 t·hm^-2,其中表层0~20 cm土壤有机碳增加最为显著;2）互花米草入侵引起湿地土壤粘粒和粉粒组成增加,容重和砂粒组成降低,表层土壤C/N增加明显;3）土壤有机碳含量与pH值、盐度、土壤含水量、C/N、平均粒径、粘粒组成呈显著正相关,与容重、砂粒组成呈显著负相关。通过研究发现,短期入侵的互花米草湿地土壤有机碳持续增加,具有较强的有机碳富集能力,在单位面积上可以有效增强河口湿地生态系统的碳蓄积。

Change of Soil Organic Carbon with Different Years of Spartina alterniflora Invasion in Wetlands of Minjiang River Estuary

The Minjiang River estuarine wetlands is an important tidal wetland ecosystem in Southeast China, as it locates at the boundary between mid and southern subtropical climate zones. The exotic C₄ grass Spartina alterniflora was found in Minjiang River estuary in 2002, and since then it had rapidly replaced native plants and become one of the dominant vegetation types in the Shanyutan wetland. Plant invasions could change the quantity and quality of the soil organic carbon (SOC) pool, and thus have potential impacts on ecosystem function and global carbon cycling. In order to understand the carbon sequestration potential of Spartina alterniflora, we investigated SOC, soil organic carbon density (SOCD), soil organic carbon stock (SOCS) and soil physico-chemical properties at 0-60 cm depth of Spartina alterniflora wetlands with Y₄ (﹤4 a), Y₈ (4-8 a) and Y₁₂ (8-12 a) chronosequence using space instead of time method. SOC of Y₄, Y₈ and Y₁₂ in the Spartina alterniflora wetlands in the Shanyutan ranged between 14.34-16.95, 16.92-20.18 and 17.34-23.5 g·kg^-1, respectively with mean values of 15.5, 17.77 and 19.71 g·kg^-1. SOCD of Y₄, Y₈ and Y₁₂ of ranged between 9.59-12.08, 11.31-13.11 and 13.94-16.08 kg·m^-3, respectively with mean values of 10.68, 12.29 and 15.01 kg·m^-3. The SOCS in 0-60 cm were 65.24, 73.99 and 90.30 t·hm^-2, respectively. What’s more, the SOC in the surface soil of 0-20 cm increased significantly as invasion years extended. Soil C/N, clay and silt composition all increased with invasion years, while soil bulk density and sand composition decreased. SOC was influenced by many factors. The high positive correlation between SOC and C/N suggests that they mainly derive from terrigenous organic matters. Furthermore, SOC and soil moisture, salinity, pH, mean grain size, clay fraction were significantly positively correlated, while negatively correlated with bulk density and sand fraction. They played an important role in determining SOC through affecting microbial activity. Our results suggested that the increase of SOC in the Spartina alterniflorawetland in the short-term possibly due to the large amount of input litter biomass and lower decompo-sition. Spartina alterniflora has strong ability of accumulating organic carbon and effectively enhanced the carbon storage in the estuary wetland.