The rubber (Hevea brasiliensis) agriculture industry is an economically important industry and the rapid expansion of rubber monoculture plantations has caused numerous problems. Rubber-based agroforestry can provide ways of more environmentally friendly rubber cultivation. However, there has been a certain bias in the selection of intercrops, driven primarily by economic interests. Therefore, there is an urgent need for accurate and reasonable evaluation of intercrops in terms of water use and optimization of cropping patterns.
In a study published in Agriculture, Ecosystems & Environment, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences tried to investigate water uptake dynamics and interspecific water interactions for three types of rubber-based agroforestry systems using intercropped tea (Camellia sinensis) and orange (Citrus reticulata).
Using stable isotope techniques, the researchers identified plant seasonal water use patterns in different agroforestry systems. They used water stable isotopes (δD, δ18O) to assess soil water partitioning and leaf δ13C to analyze the water use efficiency.
They found that the plants in agroforestry systems faced less water shortage than those in rubber monoculture, and tea is a better intercrop in which rubber-tea system increased 13% and 17% of soil water content than rubber-orange system and rubber monoculture, respectively. The soil water content increased with the increase of species composition. Compared with rubber monoculture, the agroforestry systems increased the soil water by 18%.
They also discovered that rubber trees are sensitive to changes in soil water and can flexibly adjust the proportion of water they obtain from different soil horizons. Intercrop plants cause rubber trees in agroforestry systems to use more water from deeper soil layers than rubber monoculture.
"We speculate that constructing species-rich rubber agroforestry is an alternative strategy to alleviate the water limitation caused by rubber monocultures," said Prof. LIU Wenjie of XTBG.
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