Fine roots of trees - A new perspective

Abstract

King et al. have demonstrated that the lifespan of the fine roots of loblolly pine is shorter for smaller roots compared to larger roots, and that EM fungi greatly increase the life expectancy of very small roots. Nitrogen additions also increased the rate of fine root growth and mortality. These results combined with other evidence suggest the position of an individual root on the branching fine root system is directly related to its lifespan and physiological function. The traditional approach of studying fine roots across divergent plant taxa according to arbitrary size classes has serious limitations. Diversity in fine root form and physiological activity between species and environments, and in relationship to symbiotic fungi, may be directly related to the acquisition of essential, growth-limiting soil resources. We will continue to improve our understanding of how the fine roots of trees function if we now turn to the systematic study of the form and physiology of individual roots on the branching root system. We may eventually learn that variability in fine root branch structure and function is just as anatomically, physiologically, and ecologically important as is variability in shoot system structure and function. After all, plants must acquire growth limiting water and nutrients in a highly heterogeneous volume of soil where they host a variety of symbiotic fungi and compete directly with other plants and a biologically complex soil food web. Surely, millions of years of organic evolution must have resulted in multiple 'fine root' solutions to this complex ecological challenge.