Root neighbourhood level and species-level relative root
distribution
Examination of relative root distributions revealed the concentration of
fine roots in the 0-10 cm soil zone in our experimental subtropical
forest. Both root richness and abundance were largely reduced below 40
cm (Fig. 2). Similarly, individual species’ root abundance declined
sharply and became variable in the deeper zones, presumably due to
higher edaphic heterogeneity (Fig. S5). Consequently, although we
examined root distributions only within the 0-30 cm soil zone, this
allowed the examination of c. 70% of fine roots’ placement
patterns and interspecific interactions across the 0-100 cm soil profile
(Fig. 2b).
Our study partially supported the differentiation of relative root
distributions among species. Although a majority of species had the
highest root abundance in the 0-10 cm soil zone, some canopy trees
predominantly placed their roots in the 10-20 cm soil zone or were
homogeneously distributed throughout the 0-30 cm soil zone (Fig. 3b).
These findings expand prior studies indicating similar root depths of
coexisting temperate trees (Valverde-Barrantes et al. 2015),
raising the possibility of interspecific vertical root segregation
through differentiation in relative root distributions (Schmid & Kazda
2001; Herben et al. 2018).