Wang Kun, Bi Boyuan, Zhu Kanghui, Wen Miao, Han Fengpeng
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, College of Natural Resources and Environment, Northwest A & F University, Yangling, Shaanxi, 712100, China.
Shannxi Key Laboratory of Qinling Ecological Intelligent Monitoring and Protection，School of Ecology and Environment, Northwestern Polytechnical University, Xi'an, 710129, Shaanxi, China.
J Environ Manage. 2024 Mar;354:120318. doi: 10.1016/j.jenvman.2024.120318. Epub 2024 Feb 21.
In desert wetlands, the decline in ground water table results in desertification, triggering soil carbon and nutrient loss. However, the impacts of desertification on soil dissolved organic carbon (DOC) properties which determine the turnover of soil carbon and nutrients are unclear. Here, the desertification gradient was represented by the distance from the wetland center (0∼240 m) traversing reed marshes, desert shrubs and bare sandy land in the Hongjian Nur Basin, north China. Soil DOC properties were determined by ultraviolet and fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC). Results showed that soil DOC content decreased significantly from 107.23 mg kg to 8.44 mg kg by desertification (p < 0.05). However, the proportion of DOC to soil organic carbon (SOC) was gradually significantly increased. According to spectral parameters, microbial-derived DOC decreased from 0 to 120 m (reed marshes to desert shrubs) but increased from 120 to 240 m (desert shrubs to bare sandy lands), with a reverse hump-shaped distribution pattern. The molecular weight and aromaticity of DOC increased from 0 to 120 m but decreased from 120 to 240 m, with a hump-shaped distribution pattern. For the DOC composition, although the relative abundances of humic-acid components remained stable (p > 0.05), they were ultimately decreased by serious desertification and the amino acids became the dominant component. A similar change pattern was also found for humification index. Additionally, MBC and C:N were the two most important variables in determining the content and spectral properties, respectively. Together, these findings relationships between the soil DOC properties and desertification degree, especially the increase in DOC proportion and the decrease in humification degree, which may reduce soil C stabilization in the Hongjian Nur Basin.
在沙漠湿地中，地下水位下降导致沙漠化，引发土壤碳和养分流失。然而，沙漠化对决定土壤碳和养分周转的土壤溶解有机碳（DOC）特性的影响尚不清楚。在此，以中国北方红碱淖流域从湿地中心（0至240米）穿越芦苇沼泽、沙漠灌木和裸露沙地的距离来表示沙漠化梯度。通过紫外和荧光光谱结合平行因子分析（PARAFAC）来确定土壤DOC特性。结果表明，沙漠化使土壤DOC含量从107.23毫克/千克显著降至8.44毫克/千克（p<0.05）。然而，DOC占土壤有机碳（SOC）的比例却逐渐显著增加。根据光谱参数，微生物源DOC在从0至120米（从芦苇沼泽到沙漠灌木）范围内减少，但在从120至240米（从沙漠灌木到裸露沙地）范围内增加，呈现反驼峰状分布模式。DOC的分子量和芳香性在从0至120米范围内增加，但在从120至240米范围内降低，呈现驼峰状分布模式。对于DOC组成，尽管腐殖酸组分的相对丰度保持稳定（p>0.05），但在严重沙漠化时最终降低，氨基酸成为主要成分。在腐殖化指数方面也发现了类似的变化模式。此外，MBC和C:N分别是决定含量和光谱特性的两个最重要变量。总之，这些发现揭示了土壤DOC特性与沙漠化程度之间的关系，特别是DOC比例的增加和腐殖化程度的降低，这可能会降低红碱淖流域的土壤碳稳定性。
