小流域不同土地利用类型氮素平衡特征

Nitrogen Budgets Characteristics of Different Land Use Patterns in a Small Catchment

以土地利用类型为研究单元,在实际调查的基础上,对蛇鱼川小流域氮素收支进行估算,分析各土地利用单元中氮素的来源与去向,并对比不同土地利用单元中氮素的输入、输出及盈余强度。结果表明,养殖区氮素输入、输出强度最高,生态林最低,经济林氮素输入强度约是耕地的3倍。经济林和耕地的主要氮素输入源均为肥料输入,其中,经济林农家肥氮素输入占比达83.32%,耕地则以化肥输入为主(占56.44%),主要的输出源也为肥料施用损失;生态林主要输入源为固氮输入,占比高达70.05%,输出源主要为天然输出;居民区和养殖区主要氮素输入源分别为食品和饲料输入。流域内各土地利用类型均呈氮素盈余状态,而不同土地利用类型氮素盈余强度差异明显,其中,养殖区和经济林盈余强度较高,分别为4795.15和493.72kg·hm^-2,耕地次之(139.13kg·hm^-2),生态林和居民区较低,分别为77.17和68.52kg·hm^-2。人类活动是影响小流域氮素平衡的重要因素,减少施肥量,控制肥料损失,加强畜禽养殖系统内氮素管理是该流域氮素管理的重点。

Taking land use as the research unit, nitrogen budget of different land use in Sheyuchuan small catchment was studied on the basis of actual survey. Input, output and surplus of nitrogen in different land use were estimated to discuss the sources and route of nitrogen cycle in this small catchment. Results show that, the breeding area had the highest intensity of nitrogen input and output, and the ecological forest had the lowest;the input intensity of economic forest was three times that of cultivated land. Fertilizer was the main nitrogen input in economic forest and cultivated land, which organic fertilizer in economic forest accounting for 83.32%, while chemical fertilizer was the main input in cultivated land accounting for 56.44%, which resulted in fertilizer application loss as the main output source. The main input source of ecological forest was nitrogen fixation accounting for 70.05%, and the output was mainly natural. Nitrogen in residential and breeding areas were mainly based on food and feed inputs. Nitrogen in all land use types in the catchment was surplus, while the difference in surplus intensity of different land use types was obvious. Among them, the breeding area (4 795.15 kg·hm^-2) and economic forest (493.72 kg·hm^-2) have the highest surplus intensity, followed by cultivated land (139.13 kg·hm^-2). Ecological forest (77.17 kg·hm^-2) and residential area (68.52 kg·hm^-2) have the lowest surplus intensity. The results imply that reducing fertilization, controlling fertilizer loss and strengthening nitrogen management in livestock and poultry systems are the focuses of nitrogen management in this catchment.