Objective This study investigates the variation in chlorophyll content and its environmental drivers among riparian forests of different topographic types in the Irtysh River Basin, Xinjiang of northwestern China, providing scientific insights for regional ecological adaptation and vegetation management.

Method This study focused on riparian forests in the Irtysh River Basin, integrating climatic, soil, and topographic factors. The Mann-Whitney U test was employed to analyze the differences in chlorophyll indices between riparian forests of two topographic types, thereby identifying variations in chlorophyll content and environmental conditions. Furthermore, Spearman correlation analysis, redundancy analysis (RDA), variation partitioning, and partial Mantel tests were conducted to systematically explore the response characteristics of chlorophyll content to climatic, soil, and topographic factors, as well as their synergistic regulatory patterns.

Result (1) The chlorophyll a, chlorophyll b, and total chlorophyll contents in valley riparian forest were significantly higher than those in plain riparian forests, while the chlorophyll a/b ratio showed no significant difference. The plain riparian forests were characterized by lower elevation, weaker radiation, lower aridity, and higher temperature, with coarser soil texture, higher bulk density, and more alkaline conditions. In contrast, the valley riparian forests were located at higher elevations with stronger radiation, higher aridity, and lower temperature, and their soils contained higher nutrient and organic matter contents, indicating overall better soil fertility. (2) The chlorophyll content in plain riparian forests was primarily regulated by the combined effects of climatic and soil physicochemical factors, with soil playing a dominant role, whereas that in valley riparian forests was mainly influenced by the coupling between topographic and soil texture factors, with topography exerting the greatest effect. The independent contribution of climatic factors was insignificant in both topographic types.

Conclusion The chlorophyll contents of riparian forests across different topographic types in the Irtysh River Basin exhibite significant variation. Its formation is jointly regulated by climatic, topographic, and soil factors, with distinct dominant drivers among topographic types, reflecting the coordinated response and ecological adaptation of vegetation to multidimensional environmental gradients in arid regions. These findings provide a scientific basis for understanding the photosynthetic regulation patterns and ecological adaptation strategies of riparian forests in arid zones and offer valuable guidance for regional ecological restoration and vegetation management.