| 摘要: |
| 土壤有机碳分解的温度敏感性（Q10）是预测生态系统碳循环对全球气候变化的关键参数。全球湿地水文节律正在迅速变化，然而淹水差异对湿地土壤Q10的影响还较少受到关注。在淹水差异梯度上，土壤有机碳质量对Q10的调控机制也未明确。以鄱阳湖的东湖洲滩湿地为研究对象，在淹水时长差异诱导形成的3个植被群落样带（泥滩带、苔草带和芦苇带）各采集0-10 cm、10-20 cm和20-30 cm土壤，在实验室内测定不同温度（10、15、20、25、30℃）下各植被带3个深度土壤有机碳的分解速率，运用指数方程拟合Q10，探讨淹水时长梯度上土壤有机碳分解速率和Q10的变化规律。运用傅里叶变换红外光谱（Fourier Transform Infrared Spectroscopy，FTIR）技术测定土壤有机物的官能团结构，结合土壤有机碳含量（Soil Organic Carbon，SOC）、可溶性有机碳含量（Dissolved Organic Carbon，DOC）和微生物碳含量（Microbial Biomass Carbon，MBC）等有机碳组分，明确土壤有机碳质量对Q10的影响机制。结果表明，在10、15、20、25、30℃的温度下，土壤有机碳分解速率的平均值分别为19.19、31.00、51.67、77.28和109.32 μgCO2 d-1·g-1·dry soil。各个植被带的土壤有机碳分解速率均随着土壤深度的增加而显著降低。然而，在3条植被带之间，只有0-10 cm的土壤有机碳分解速率存在显著差异（P = 0.030），表现为芦苇带＞苔草带＞泥滩带。土壤Q10的平均值为2.48，没有受到植被带和土壤深度的显著影响。FTIR数据显示，随着土壤深度和淹水时长的增加，洲滩湿地易分解的脂肪类有机物比例逐渐下降，但难分解的芳香类有机物比例逐渐升高。相关分析和结构方程模型表明土壤有机碳分解速率的主要影响因素为含水量、微生物碳含量、pH和营养盐含量等。土壤有机物官能团结构、pH和总氮等因素对土壤Q10有显著影响。表层土壤Q10与脂肪类有机物正相关，与芳香类有机物含量负相关。 |
| 关键词: 土壤有机碳 洲滩湿地 Q10 FTIR 鄱阳湖 |
| DOI： |
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| 基金项目:国家自然科学基金项目（面上项目，重点项目，重大项目） |
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| Decomposition rate and temperature sensitivity of soil organic carbon in a typical shoal wetland of Poyang Lake |
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liujie,zhengbofu,Gong Leiqiang,YuDingKun,Zhan Huiying,Shen Ruichang
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1.School of Resources and Environment, Nanchang University;2.Jiangxi Institute of Ecological Civilization;3.Administration Bureau of Poyang Lake National Nature Reserve in Jiangxi Province;4.Jiangxi Province Key Laboratory of Watershed Ecosystem Change and Biodiversity
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| Abstract: |
| Temperature sensitivity of soil organic carbon decomposition (Q10) is a key parameter to predict the contribution of ecosystem carbon cycle to global climate change. The hydrological rhythm of global wetlands is changing rapidly. However, little attention has been paid to the effects of waterlogging differences on wetland soil Q10. The regulation mechanism of soil organic carbon mass on Q10 in the differential waterlogging gradient is also unclear. In this study, soil samples of 0-10 cm, 10-20 cm and 20-30 cm were collected from three vegetation community transect zones (mudflat zone, Carex zone and phragmites australis zone) induced by different flooding duration in the East Lake marshland wetland of Poyang Lake. The decomposition rate of soil organic carbon (SOC) at three depths in each vegetation zone under different temperatures (10, 15, 20, 25, and 30℃) was measured in the laboratory. The Q10 was fitted with exponential equation to explore the changes of SOC decomposition rate and Q10 across the waterflooding duration gradient. Fourier Transform Infrared Spectroscopy (FTIR) was used to determine the functional group structure of Soil Organic matter. We also examined the effects of soil Organic Carbon on Q10 and its components, including SOC, Dissolved Organic Carbon (DOC) and Microbial Biomass Carbon (MBC). The results showed that the average decomposition rates of soil organic carbon were 19.19, 31.00, 51.67, 77.28 and 109.32 μgCO2 d-1·g-1·dry soil at 10, 15, 20, 25 and 30℃, respectively. The decomposition rate of soil organic carbon significantly decreased with the increases of soil depth in all vegetation zones. However, there was a significant difference in the decomposition rate of SOC only at the depth of 0-10 cm among the three vegetation zones (P = 0.030), with an order of P. austrum > Carex > mudflat. The mean value of soil Q10 was 2.48, which was not significantly affected by vegetation zone and soil depth. FTIR data showed that the proportion of easily decomsolvable fatty organic matter gradually decreased, while the proportion of refractory aromatic organic matter gradually increased with the increases of soil depth and flooding time. Results of correlation analysis and structural equation model showed that the main factors affecting soil organic carbon decomposition rate were water content, microbial carbon content, pH, and nutrient content. The functional group structure of soil organic matter, pH and total nitrogen significantly affected soil Q10. Q10 in the surface soil was positively correlated with fatty organic matter and negatively correlated with aromatic organic matter. |
| Key words: soil organic carbon lakeshore wetland Q10 FTIR Poyang lake |
