Print PageRoot-related processes such as root turnover, root respiration, and root decomposition are poorly quantified at both ecosystem and global scales. This is in part because we do not know how to define ephemeral roots, what factors and mechanisms control decomposition of ephemeral roots and preservation of root decomposition products, and how root morphological and chemical traits of different species from different biomes influence ecosystem C and nutrient cycling.
Results/Conclusions
The progress in root functional classification, root trait quantification, and theories of decomposition may be helpful for resolving these challenges. In consequence, the reevaluation of many root-related ecosystem processes may be needed. I outline three areas in which such reevaluation is possible. First, replacement of fine root concept by ephemeral root module concept suggests that the current estimates of fine root turnover at both local and global scales may be highly inaccurate in part because ephemeral roots may constitute only a small fraction of fine roots. Second, new data on physiology and chemistry of ephemeral roots and new theories of decomposition suggest that the role of live roots and root-derived soil organic matter (SOM) in the decomposition and accumulation of SOM may have been underestimated. Live roots promote SOM decomposition by priming decomposition and thus assisting the mining of nutrients from older or physically-protected SOM. At the same time, the recalcitrant nature of ephemeral roots may slow down root decomposition and the close contact of roots with soil may allow for greater physical protection of root detritus by soil minerals, leading to long-term stability of SOM. Third, wide variation in root morphological and chemical traits across biomes, which have not been well understood previously, suggests that root resource acquisition strategies may be diverse and variation in root traits may translate into substantial differences in critical ecosystem processes. We found that roots of different species (biomes) vary widely in root diameter, root architecture and root chemistry, and these variations may lead to systematic differences in nutrient cycling, root respiration and organic matter decomposition from scales of plant individuals to ecosystems. In conclusion, I suggest that globally-coordinated experimental testing and data acquisition on root functional traits should lead to significant advancement in the quantification of root-related ecosystem processes and the development of new theories in root ecology.
