Abstract: Natural stable isotope methods can track the natural isotopic signals of elements such as carbon, nitrogen, hydrogen, and oxygen, thus providing a high-precision low-cost alternative for performing large-scale studies in forest ecology. This paper systematically reviews the three major methodologies of natural stable isotope methods (source partitioning, fractionation tracing, and ecological indicators) and their specific applications in studies on forest hydrological processes, nutrient cycling, food web structure, carbon allocation strategies, and responses to global change. Source partitioning quantifies material sources and migration pathways using isotopic mixing models. Fractionation tracing reveals the intensity and mechanisms of ecological processes based on isotopic fractionation effects. Ecological indicators translate isotopic signals into quantitative parameters such as water-use efficiency, climatic factors, and nitrogen saturation status. Although this approach demonstrates unique advantages in revealing the spatial patterns and temporal dynamics of ecological processes, it still faces challenges such as an incomplete quantitative theory of fractionation, analytical tool complexity, and a lack of standardised guidelines. Future efforts should strengthen research on fractionation mechanisms, develop user-friendly tools, and formulate standardised application guidelines to promote the application of this method in forest ecology.

Key words: Natural stable isotope methods, Forest ecology, Source partitioning, Fractionation tracing, Ecological indicators