Plant roots can significantly influence soil organic carbon (SOC) decomposition via the rhizosphere priming effect (RPE). While woody plant roots are often composed of complex hierarchal systems, and can be classified into absorptive roots and transport roots based on root functions, order and traits, our understanding of the contribution of absorptive roots vs. transport roots to the RPE is limited. “Because of the significant effects on rhizodeposition, root functional traits may be important regulators explaining the variation in the RPE caused by tree species, which has not been empirically confirmed yet,” said Prof. WANG Peng from the Institute of Applied Ecology of the Chinese Academy of Sciences. 

Recently, his team conducted a series of experiments by employing a ¹³C natural abundance approach with tree seedlings and soils, with aims to investigate how C allocation to and functional traits of absorptive roots influence the RPE. 

They found that there was a significant positive relationship between the RPE and C allocation to absorptive roots across soils and among tree species. This finding suggests that compared to transport roots, absorptive roots may be predominant for causing the RPE of tree species. Furthermore, specific surface area of absorptive roots accounted for most of the variation in the RPE corrected by absorptive root biomass (i.e. specific RPE). One reason could be that specific surface area together with other morphological traits may to a greater degree affect the rhizodeposition and thus the spatial extension of enzyme activities. “Our findings suggest that absorptive root morphological traits may play an important role in regulating the RPE,” said Prof. WANG. 

Despite the enormous challenges of scaling up the RPE to ecosystem C cycling, a sustained effort to develop an appropriate scaling factor for the RPE will greatly improve our understanding of its role in mediating ecosystem responses to global change and/or human disturbance. To our best knowledge, this study provides an important first avenue for linking the RPE to properties of absorptive roots of tree species,” said Prof. WANG. 

Fig 1.Conceptual model of linkage between absorptive roots and rhizosphere priming of tree species (Image by WANG Peng) 

These findings were being published entitled “Linking absorptive roots and their functional traits with rhizosphere priming of tree species” in Soil Biology & Biochemistry”.  

This study was supported by the National Key R&D Program of China, and the National Natural Science Foundation of China.