Abstract:

Nitrogen retention is a key ecological regulation service, and land-use change is the main driving force affecting its spatiotemporal dynamics. Revealing the response mechanism of nitrogen retention functions to land use pattern evolution is of great significance for promoting sustainable agricultural development in watersheds and effectively controlling non-point source pollution. By coupling the FLUS and InVEST models, this study simulated land use changes in the Shiyang River Basin under different development scenarios for 2035 and assessed the response of its nitrogen retention function. The study found that 1) the current year’s nitrogen retention amount was 1.61×10⁴ t, the cultivated land protection scenario was 1.82×10⁴ t, the natural development scenario was 2.10×10⁴ t, and the ecological protection scenario was 2.13×10⁴ t. The nitrogen retention amounts in different scenarios were significantly higher than that in the current year, with the ecological protection scenario showing the largest increase and the cultivated land protection scenario showing a relatively smaller increase. 2) Using the natural breakpoint method, the nitrogen retention intensity across counties under different scenarios was classified into five levels, identifying Yongchang County and Liangzhou District as important areas for water quality purification functions. 3) Compared to the current year, under the cultivated land protection and natural development scenarios, the land-use type with the largest increase in nitrogen retention is farmland, whereas under the ecological protection scenario, grassland sees the most increase in nitrogen retention. 4) Population density was the dominant driving factor influencing the spatial differentiation of nitrogen retention in the watershed (q=0.126). The most influential interaction factor was soil type ∩ population density, with a q-value of 0.221. Nitrogen retention exhibited significant spatial clustering effects, displaying “high-high” and “low-low” clustering characteristics. These results provide a scientific basis for enhancing nitrogen retention capacity and controlling non-point source pollution in watersheds.

Key words: nitrogen retention function, multi-scenario simulation, FLUS model, InVEST model, Shiyang River Basin

摘要：

氮保持是关键的生态系统调节服务，土地利用变化是影响其时空动态的主要驱动力；揭示氮保持功能对土地利用格局演变的响应机制，对促进流域农业可持续发展和有效控制面源污染具有重要意义。该文通过耦合FLUS与InVEST模型，模拟石羊河流域2035年不同发展情景下的土地利用变化，进而评估其氮保持功能的响应。研究得出，1）现状年氮保持量为1.61×10⁴ t、耕地保护情景为1.82×10⁴ t、自然发展情景为2.10×10⁴ t、生态保护情景为2.13×10⁴ t，不同情景的氮保持量均较现状年显著提升，但生态保护情景增幅最大，耕地保护情景相对较小。2）以自然断点法将不同情景下的县域氮保持强度分5级，确定永昌县和凉州区为水质净化功能重要区。3）对比现状年，耕地保护情景与自然发展情景下氮保持量增量最多的土地利用类型为农田，而生态保护情景下，氮保持量增加最多的为草地。4）人口密度是影响流域氮保持量空间分异的主导驱动因子（q值为0.126）；影响力最强的交互因子为土壤类型∩人口密度，q值达0.221。氮保持量在空间上呈现显著的聚集效应，表现为“高-高”和“低-低”聚集特征。研究结果可为流域提升氮保持能力以及面源污染防控提供科学依据。

关键词: 氮保持功能, 多情景模拟, FLUS模型, InVEST模型, 石羊河流域