Can intercropping with the world's three major beverage plants help improve the water use of rubber trees?

Abstract

1. The dramatic expansion of rubber plantations in mainland South-East Asia and southwest China has caused many eco-environmental problems, especially negative hydrological consequences. These problems have gradually worsened and pose formidable threats to rubber agriculture, especially in the light of increasingly frequent extreme weather events. Although rubber-based agroforestry systems are regarded as the best solution for improving the sustainability of rubber agriculture and environmental conservation, plant water use and related interactions have rarely been examined in such systems. 2. We primarily used stable isotope (dD, d 18 O and d 13 C) methods to test whether intercropping could improve the water use and extreme weather tolerance (extreme cold and drought in our study) of rubber trees in three types of promising agroforestry systems (i.e. rubber with tea, coffee and cocoa) in Xishuangbanna, China. 3. We found that the rubber tree is a drought-avoidance plant with strong plasticity with respect to water uptake. This characteristic is reflected by its ability to cope with serious seasonal drought, allowing it to avoid interspecific competition for water. The rubber trees showed wasteful water behaviour unless they were intercropped with tea or coffee. However, these intercropped species exhibited drought-tolerance strategies and maintained lower water use efficiencies to strengthen their competitive capacity for surface soil water. The stable d 13 C values of the intercrop leaves indicated that all the agroforestry systems have stable internal microclimatic environments or higher resistance. 4. Synthesis and applications. This study suggests that interspecific competition for water can enhance the water use efficiency of drought-avoidance plants (i.e. rubber trees) and lead to complementarity between the root distributions of plants in rubber agroforestry systems (i.e. rubber with tea, coffee and cocoa). All agroforestry systems have higher resistance, but tea was the most suitable intercrop in terms of water use because the interspecific competition for water was moderate and the agroforestry system retained much more soil water and improved the water use efficiency of the rubber tree. Considering the root characteristics of the tea trees, we suggest that the crops selected for intercropping with rubber trees should have a relatively fixed water use pattern, short lateral roots and a moderate amount of fine roots that overlap with the roots of the rubber trees in the shallow soil layer.

Land Degradation Controlled and Mitigated by Rubber‐based Agroforestry Systems through Optimizing Soil Physical Conditions and Water Supply Mechanisms: A Case Study in Xishuangbanna, China

“…First, a large proportion of the water active zone in the three systems was confined to the upper 20·0 cm of the soil profile. This water distribution pattern could explain how water is supplied to the shallow soil layers (<30 cm); the rubber trees heavily relied on this water supply, especially in the RM (Wu et al ., ). Second, a large proportion of the water buffer zone was confined to the deeper soil layers.…”

“…The hot dry season is a transitional period, with less rainfall and higher air temperature (exceeding 38 °C). The foggy cool and hot dry seasons are collectively referred to as the dry season owing to the lack of rainfall (Wu et al ., ). The soil depth under the vegetation is approximately 2 m. The soil in the study area is well drained, and it has a clay loam texture (42% coarse sand, 34% silt and 24% clay).…”

“…Therefore, water availability, which is associated with the growth and survival of plant communities, is heavily affected (Qiu, 2010), although rubber trees have strong plasticity with respect to water uptake and capability to avoid interspecific competition for water (Liu et al, 2014). Soil water absorption varies across different root distribution patterns in different agroforestry systems (Liu et al, 2014;Wu et al, 2016). Rubber trees show well-developed root systems, and their lateral roots extend to more than 9 m (Priyadarshan, 2011).…”

Seasonal and spatial variations of water use among riparian vegetation in tropical monsoon region of SW China

“…To quantify the contribution of potential water sources of plants, a variety of mixing models were developed, such as IsoSource, SIAR, and MixSIR (Moore & Semmens, 2008;Parnell et al, 2013;Phillips & Gregg, 2003;Phillips, Newsome, & Gregg, 2005;Wu, Liu, & Chen, 2016a;Wu, Liu, & Chen, 2016b). In the recent years, a new Bayesian mixing model of MixSIAR was applied to calculate the relative waterabsorbing proportions of potential sources (Ma & Song, 2016;Wu, Liu, & Chen, 2017).…”

Rubber Trees Demonstrate a Clear Retranslocation Under Seasonal Drought and Cold Stresses

“…Formerly an evergreen species growing under moderate annual drought, rubber has adapted to withstand months of drought and cold stresses by becoming deciduous; annually shedding leaves in mid-dry season (late January and February). Previous studies on rubber plantations focused on impacts of land-use conversion on tropical biodiversity, soil and water conservation, and local climate change (Feng, 2007; Li et al, 2007; Powers et al, 2011; De Blécourt et al, 2013; Li, 2013; Xu et al, 2014; Li et al, 2015; Liu et al, 2016; Wu et al, 2016; Zhou et al, 2016). However, little research has been conducted on nutrient strategies of rubber trees and soil roles in these processes under drought and cold stresses; nor impacts on soil nutrients and microbiota.…”