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.