Preferential flow is the process by which water moves unevenly through soils via preferred path rather than uniform flow. It has always been hotspot of research regarding soil water flow, biological activity, and carbon and nitrogen dynamics. However, the mechanism of water flow exchange between two adjacent zones (with and without root system) and the pattern of soil water supply for rubber are still unclear. 

In a study published in Forest Ecology and Management, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) showed that complementary relationship for water interaction between preferential flow domain (PFD, matching the root zone) and non-preferential flow domain (NPFD, matching the remote root zone) could be beneficial for rubber plants growth and development. 

Considering the differences in root distribution, soil properties, and water flow paths between the root zone and its surroundings, the researchers evaluated water flow behavior in preferential flow domain (PFD) and non-preferential flow domain (NPFD). 

The researchers quantified the spatio-temporal characteristics of PFD-NPFD system and conducted a high resolution soil sampling and water content monitoring w in the field. 

The results showed that soil properties in the PFD led to a quick water response to rainfall. PFD was characterized by small storage capacity and large flow capacity, and NPFD was of large storage capacity and low flow capacity.  

In a system PFD-NPFD, PFD delivered over-saturated water to NPFD during rainfall while NPFD provided available water (deference between field capacity and wilting coefficient) to PFD for rubber tree. 

"Our findings have important implications on the understanding of ecohydrological processes and water supply mechanisms in rubber plantations and natural forests", said Prof. LIU Wenjie, principal investigator of the study.

 Conceptual model for soil water dynamic behavior in preferential flow and non-preferential flow domains. (Image by Jiang Xiaojin)