Figure 1. Models of vertical fine root distribution in each species across different soil rock fragment content (0%, 25%, 50%, and 75%) and years of growth. The curve of each rock fragment content was derived from the β parameter (P < 0.05 for all cases and did not show). β was estimated by 3 repetitions as the following function: Y = 1-β d, where the cumulative root fraction of fine root (Y ) from the surface to any depth (d). Larger values of β indicate deeper rooting profiles.