Figure 3. Non-metric multi-dimensional (NMS) ordination of bryophyte
community composition on nurse logs (n = 98) of varying decay stages and
the forest floor using a Bray-Curtis distance matrix on percent cover.
Two-dimensional stress = 0.16 with 1000 permutations. The ellipses show
the covariance matrix centered on the mean of each nurse log decay stage
and the forest floor (solid black line). Nurse logs were classified into
three decay stages (modified from Christy & Mack 1984): NL1 = bark
still intact and can hold weight when stepped on (light grey dotted line
solid black line), NL2 = some to various debris falls upon contact (grey
dashed dot line), NL3 = foot completely in log, several pieces
fragmented off of the log (dark grey dashed line). Species codes are
from Table S1. Environmental variables that significantly correlated
with NMS axes are shown in black, heavy arrows and those that did not
significantly correlate with axes are shown in grey. Bryophyte depth
(BD) correlated significantly with the axes (r2 =
0.47, p < 0.001) but not canopy cover (CC,
r2 = 0.06, p = 0.08) or tree seedling density
(seedling, r2 = 0.02, p = 0.4). Species codes
are in red and are the first three letters of the genus and the first
three letters of the species (found in Table S2).
Table 1. Spearman rank correlation coefficients between explanatory
variables for the generalized linear model for seedling density.