论文部分内容阅读
流域内植被类型是土壤氮素淋溶迁移的重要影响因子,降雨丰水季节不同植被类型土壤氮素淋溶是量化评价流域土壤氮素流失和水质变化的关键。本研究采用离子交换树脂袋法分析降雨丰水期槭树-蒙古栎林、落叶松人工林和山杨林3种植被类型土壤NH_4~+-N和NO_3~--N淋溶季节动态特征。结果发现,降雨丰水期(7—9月)不同植被类型土壤无机氮含量(NH_4~+-N和NO_3~--N)动态变化差异显著(P<0.05),NH_4~+-N在无机N中占73.4%~93.3%,槭树-蒙古栎林、山杨林NO_3~--N含量7月份最大,而落叶松人工林NO_3~--N含量8月份最大;土壤氮素淋溶的主要成分是NO_3~--N,落叶松人工林土壤氮潜在性淋溶高于槭树-蒙古栎林和山杨林;土壤微生物生物量碳(MBC)和氮(MBN)随着土层加深逐渐减小,阔叶林MBC和MBN显著大于落叶松人工林;土壤N淋溶量与MBN呈显著负相关,证明土壤微生物N固持作用能减少N淋溶流失。据此结果,建议在该流域开展水源涵养林建设中应加强河岸带天然林保护和促进人工水源涵养林转变为天然次生林。
The type of vegetation in the basin is an important factor affecting leaching and migration of soil nitrogen. The leaching of soil nitrogen from different vegetation types in rainfall-abundant seasons is the key to quantitatively evaluate soil nitrogen loss and water quality in the basin. In this study, the ion exchange resin bag method was used to analyze the dynamic characteristics of NH_4 ~ + -N and NO_3 ~ -N leaching in the three vegetation types of Chinese maple-Mongolian oak forest, Larix gmelinii plantations and Populus davidiana plantations during rainfall-wet period. The results showed that the dynamic changes of inorganic nitrogen (NH_4 ~ + -N and NO_3 ~ - N) were significantly different in different vegetation types in rainy seasons (July to September) (P <0.05) N accounted for 73.4% -93.3%, and the content of NO_3 ~ --N in Maple-Mongolian oak forest and Populus davidiana forest was the largest in July, while the content of NO_3 ~ --N in Larix gmelinii plantation was the largest in August; the content of nitrogen leaching The main component was NO_3 ~ - N, and the potential nitrogen leaching was higher in the Larix gmelini plantation than that in the maple-Quercus mongolica forest and Populus davidiana forest. With the deepening of the soil layer, MBC and MBN increased, The MBC and MBN of broad-leaved forest were significantly larger than that of Larix gmelinii plantation; the N-leaching of soil was negatively correlated with MBN, which proved that the immobilization of soil microorganism N could reduce the N leaching loss. According to the results, it is suggested that the protection of natural forest in riparian zone should be strengthened and the artificial water conservation forest be transformed into natural secondary forest in the construction of water conservation forest in this basin.