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.