Figure 3. Fine root biomass of each species at different soil depths along four soil rock fragment content (0%, 25%, 50%, and 75%) and three years of growth. Bars represent means ± SE; n = 3. Different lowercase letters indicate significant differences between rock fragment content levels, *, **, and *** designate differences at P< 0.1, P < 0.05, and P < 0.01, respectively.