排水对小兴安岭森林沼泽湿地溶解性有机碳和有效氮磷的影响

选取不同排水年限的兴安落叶松人工林湿地(1974年排水、1985年排水、1992年排水、2003年排水)和天然森林沼泽湿地(兴安落叶松沼泽湿地)为研究对象,探讨排水对小兴安岭森林沼泽湿地土壤溶解性有机碳(DOC)和有效氮磷的影响。结果表明,天然沼泽排水后,在土壤垂直剖面上,不同排水年限的森林湿地与天然沼泽湿地的土壤溶解性有机碳含量均呈递减变化。与天然森林沼泽湿地相比,排水湿地各土层DOC含量均显著低于天然沼泽湿地(P0.05)。天然森林沼泽,表层(0—10 cm)的土壤SOC含量、DOC/SOC、土壤有效氮含量均大于排水森林沼泽,但是有效磷含量却低于排水森林沼泽(P0.05)。在土壤表层(0—10 cm),排水年限与DOC、SOC、DOC/SOC、土壤有效氮呈显著性负相关,与有效磷呈显著性正相关(P0.05)。天然沼泽排水后,表层(0—10 cm)土壤的DOC含量与有效氮(铵态氮、硝态氮)含量成正比,与有效磷含量成反比(P0.05)。

Effect of drainage on dissolved organic carbon and available nitrogen and phosphorus in the wetland forests of Xiaoxing'an Mountain

The effect of drainage on soil dissolved organic carbon (DOC) in the Xiaoxing''an Mountain forests was investigated by selecting Larix gmelinii plantation wetlands of different ages (drain in 1974, drain in 1985, drain in 1992, and drain in 2003), as well as a natural forest swamp wetland (L. gmelinii marsh). The results showed that soil DOC content decreased vertically with soil depth for all sites. Compared with the natural forest wetland, the DOC content in all soil layers was lower (P<0.05). The soil organic carbon (SOC) content, DOC/SOC, and soil available nitrogen (N) in the surface layer (0-10 cm) of the natural forest swamp were all higher than those in the drained forests. In contrast, the available phosphorus (P) content was lower in the natural wetland than in the drained forests (P<0.05). In the soil surface (0-10 cm), the time since drainage was significantly negatively correlated with DOC, DOC/SOC, SOC, and soil N, and was significantly positively correlated with the available P (P<0.05). After drainage of the soil surface (0-10 cm), DOC and available N (ammonium nitrogen, nitrate nitrogen) were inversely proportional to the effective P (P<0.05). In the forest wetlands where drainage ditches were dug, the soil moisture status was changed to promote the forest growth. Overall, the area of the Xiaoxing''an Mountain forest wetlands covers 106.96 ten thousand ha, with great carbon sequestration potential. Its average carbon density was higher than natural forest carbon densities, as well as the carbon density of the forest vegetation in Heilongjiang Province. It therefore plays an important role in the regional carbon cycling. Since the 1970s, the wetlands in the Xiaoxing''an Mountain forests have been greatly influenced by human activities, and mainly by wetland drainage. Movement of soil DOC with wetland drainage occurred in the directions of the water movement. A portion of the soil DOC moved along the horizontal and vertical direction of the drainage ditches, or was lost directly to the water. At present, research on the impacts of human activities on DOC is mainly focused on how wetland reclamation for farmland changes DOC, as well as the effects of different land use patterns on soil DOC.In this study, we researched the forest swamps of the Xiaoxing''an Mountain forests. We conducted a quantitative study on the changes of soil DOC and SOC after drainage and transformation, in order to understand the role of DOC in the regional ecosystem''s carbon cycle and the mechanisms of carbon transformation, in order to provide a theoretical basis for the management and sustainable development of the regional wetland ecosystems.