Abstract: Plant water source depends on the distribution of available water in the environment, and the capability of plants in capturingwater. In dry season, the soil water in thin soil region cannot satisfy the demand of normal plant growth, and whether the plants can use the water stored in weathered bedrock is the key for them to maintain their normal water consumption. This paper reviewed the research methods for determining the plant water source in thin soil region, including investigating and analyzing the characteristics of root growth and distribution, monitoring the changes of water content at various depths below ground surface, monitoring and analyzing the seasonal variation of plant water status, and identifying the plant water source by stable isotope techniques. The advantages and disadvantages of these methods and their potential applications in tracing plant water source in karst region of Southwest China were discussed.

Key words: thin soil region, plant, water source, research method, stable isotope, grape, bud, dormancy induction, inducing factor, respiratory metabolism.