Fine roots (≤2 mm in diameter) are the primary organ used by plants to acquire soil water and nutrients for growth (Jackson et al., 1997; de Kroon, 2007). They contribute a great deal to ecosystem production and the nutrient cycle in forests (Silver
et al., 2005; Børja et al., 2008). It has been reported that below ground biodiversity in most forest ecosystems is higher than the aboveground biodiversity (Pärtel et al., 2012). A large proportion of the plant biomass is stored belowground and primary production occurs in the roots(Enquist and Niklas, 2002; Poorter et al., 2012). Furthermore, fine root turnover contributes considerably to net primary productivity (NPP) in forest ecosystems (Gill and Jackson, 2000). Hence, belowground interactions among different plant species play important roles in forest community structure, dynamics, and ecosystem functions (Turnbull et al., 2007; Jones et al., 2011). However, belowground interactions among species and the contributions of a species to ecosystem function are poorly understood compared with the aboveground component
(Pechácˇková et al., 1999; Mommer et al., 2008). The foremost challenge to understand belowground functions in forests is the ability to identify the fine root tree species. The color, size, epidermal characteristics, and morphological traits of roots from different species are too similar to distinguish visually (Mommeret al., 2010; Ugawa et al., 2010). In particular, in subtropical areas, natural forests have more diverse tree species whose roots inter-mingle and intertwine so that the fine roots are more difficult toidentify.