沙柳沙障腐烂过程对土壤碳氮磷化学计量特征的影响.

One type of semi-buried mechanical barricade, the Salix psammophila sand barrier has been widely used in a wind-sand protection system in northwest China. However, the sand barriers are inevitably deteriorated under biodegradation, weathering, desorption-alternation, as well as the biological and abiotic factors, due to the exposure to the field environment for a long time. Decay and decomposition of sand barriers can alter the resource availability of dune soil, which is vital for understanding the biogeochemical process and nutrient cycling in desert ecosystems. Previous research has focused on the above-ground part of the sand barriers to intercept the wind and sand. But, it is still lacking in the ecological contributions and biogeochemical element cycling of the underground part of the desert soil during the long-term setting process. Therefore, this study aims to explore the effects of Salix psammophila sand barriers decay on the content and stoichiometric characteristics of the soil carbon (C), nitrogen (N), and P (phosphorus). The main environmental factors were determined to analyze the decay characteristics, soil physicochemical properties, and soil enzyme activities. The field test was conducted in the Hobq Desert (within the town of Duguitara, Inner Mongolia, China). The naturally degraded sample plots were selected in the windbreak and sand fixation areas adjacent to the roads with similar geographic characteristics and vegetation types for years 1, 3, 5, 7, and 9. The general situation of the sand barrier was determined at the experimental site. The test samples were collected and measured using the "space instead of time and in situ sampling". The results showed that the chemical composition of the barrier body decreased significantly (P<0.05), whereas, the soil moisture content and available nitrogen were improved during the process of Salix psammophila sand barriers decay. The extracellular enzyme activities of β-1, 4-glucosidase (BG) and β-1, 4-N-acetylglucosidase (NAG) increased first and then decreased, reaching the peak in the 5th year with the increase of time. In the first 7 years of decay, there was no change in the soil C/N ratio, but increased significantly at 9 years (P<0.05) with an increase of 41.20 %, compared with 1 year. The ratio of soil C/P and N/P increased significantly in the first 5 years, and they were 1.83 and 1.76 times higher at 5 years than at 1 year, respectively. The ratios of C/P and N/P were positively correlated with the dissolved organic carbon (DOC), available nitrogen (AN), organic carbon (SOC), total nitrogen (TN), and β-1,4-glucosidase (BG). By contrast, the ratio of C/N was negatively correlated with the β-1,4-N-acetylglucosidase, cellulose (Cel), and lignin (Lig), and only positively correlated with the mass loss rate (ML). Dissolved organic carbon and available nitrogen were positively correlated with the total carbon, total nitrogen, total phosphorus, and mass loss rate, respectively, but negatively correlated with the cellulose. The results of redundancy analysis further confirmed that cellulose and mass losses were the main factors affecting soil C, N, and P content and their stoichiometry. Therefore, the decay process of the Salix psammophila sand barrier can be expected to increase the soil C, N, and P content, indicating a long-term and effective control measure. These findings can provide a strong reference for the relationships between the decay process of Salix psammophila sand barriers and soil elements stoichiometry. Great contribution can be offered to the decision making on the Salix psammophila sand barriers in wind erosion protection and vegetation restoration in desert areas. [ABSTRACT FROM AUTHOR]