Nutrient heterogeneity in fine roots of six subtropical natural tree species

Abstract

Fine roots, commonly defined as roots < 2 mm in diameter, are often treated as a homogeneous mass compartment. However, this approach ignores the distinct branching structure of fine root systems, roots of different branch orders play different roles in belowground carbon and nutrient cycling. To date, it is remarkable how little we know about the chemical properties in fine root and the correlation between fine root and leaf in chemical properties, especially in subtropical evergreen broadleaved forest. So, in this study, intact fine root segments and leaves of six dominant tree species (Cinnamomum micranthum; Tsoongiodendron odorum Chun; Cinnamomum chekiangense; Castanopsis fabri; Altingia gracilipes; and Castanopsis carlesii) were sampled in an evergreen broadleaved forest located at the Wanmulin Nature Reserve, Jian忆 ou, Fujian province. We focused on: (1) the relationship between branch order and root nutrient concentrations; (2) the correlation between the chemical and morphological traits of fine root and between the chemical traits of root and leaf; (3) the effect of root order and tree species on root chemical traits. For Cinnamomum micranthum, C content increased as root order increased, while there was no distinct trend for the other five species. There was a negative relationship between root branch order and N and P concentration, and a positive relationship between root branch