Water is essential to plant life; thus, plant water use patterns are directly influenced by spatiotemporal patterns in water availability. How do plants uptake water, and how do coexisting plants share a water source when water availability is limited? It is crucial for improving water management in rubber agriculture because the water use of rubber trees has been neglected for a long time, and seasonal drought in Xishuangbanna is becoming increasingly serious.
Prof. LIU Wenjie and his team of Xishuangbanna Tropical Botanical Garden (XTBG) used stable isotope methods to investigate the water use patterns of rubber trees and tea trees coexisting in the same dry environment. They selected a rubber-tea agroforestry system for observation and divided the experimental field into seven sites (i.e., seven locations along the slope) to measure the soil water content (SWC) at each site for three soil layers (i.e., 0–5, 5–30, and 30–80 cm depths).Concurrently, they measured the water isotopic compositions (δD and δ18O) in the soil and in the plant xylem to quantitatively distinguish the plant water sources and study below-ground water transport.
They found that the soil water contents (SWCs) of the tea rows were greater than the SWCs in the rubber rows. The SWCs of the uphill and downhill tea rows were significantly greater than the contents in the rubber rows. The values of δD and δ18O from the xylem water of the rubber trees were significantly lower than the values from the tea trees.
Furthermore, the MixSIAR model (a Bayesian mixing model) indicated that rubber trees relied heavily on water from deep (30–80 cm) soil layers and tea trees primarily uptake water from the intermediate (5–30 cm) soil layer. Rubber trees absorbed soil water evenly from each row along the slope in the dry season.
The study demonstrated that hydrological niche segregation is driven by resource competition for water when availability is most limited. Tea trees and rubber trees can coexist in a rubber-tea agroforestry system by having different but complementary vertical water use patterns during the dry season, allowing weak interspecific competition for water and efficient water use during soil drought stress.
The water use patterns ensured a collaborative hydraulic redistribution in this agroforestry system. Therefore, soil water would be well redistributed below ground in the rubber-tea agroforestry system, and sufficiently abundant soil water could move from the tea rows to the terrace, where drought stress easily occurs, to maintain plant root health under the soil of the terrace. Such water movement in a plant community may also increase plant nutrient availability and thus benefit plant growth.
The study entitled “How do plants share water sources in a rubber-tea agroforestry system during the pronounced dry season?” has been published in Agriculture, Ecosystems & Environment.
Contact
LIU Wenjie Ph.D Principal Investigator
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
E-mail: lwj@xtbg.org.cn
