Abstract: Jungle rubber, a rubber agroforestry based on tropical rainforest structure, is more in line with the thought of sustainable development for rubber garden than rubber monoculture. Thus, exploring the interspecific composition and structure of jungle rubber by investigating plant water use strategies will help optimize the efficiency of current rubber monoculture. The aim of this study was to compare the water use strategies of plants between jungle rubber and rubber monoculture. The stable isotope (δD, δ¹⁸O, and δ¹³C) methods were used to investigate the plants’ water source and use efficiency. The results showed that: (1) Soil water content in jungle rubber was higher than that in rubber monoculture in both rainy and dry seasons, indicating that soil water condition of jungle rubber was better. (2) The absorbed water of rubber trees in rubber monoculture from the diverse soil layers varied considerably between the two seasons. During the rainy season, greater water uptake of the monoculture rubber trees was from the 0-5 cm soil layer, occupying 81.6% of total water source, while during the dry season, the higher uptake was from the 5-15 cm soil layer, with a proportion of 49.6%. However, the water source of rubber trees in jungle rubber was relatively steady, and their water uptake from the deeper soil layer was greater than from the shallow soil layer, conducing to a deeper expansion of roots. (3) The water use efficiency of rubber trees in jungle rubber was generally more stable than that in rubber monoculture. Thus, the difference of leaf δ¹³C values of rubber trees in jungle rubber was smaller than that in rubber monoculture during the dry season, showing that the rubber trees in jungle rubber had a weaker drought stress. Meanwhile, rubber trees adjusted their water use strategies by enhancing leaf δ¹³C to improve their tolerance of seasonal drought. In conclusion, jungle rubber was a promising sustainable management with better soil water condition and more flexible plant water use strategies compared to the traditional rubber monoculture.

Key words: Streptomycin resistance strain, Wheat rhizosphere, Colonizing dynamics