Rp. Griffiths et al., SPATIAL-DISTRIBUTION OF ECTOMYCORRHIZAL MATS IN CONIFEROUS FORESTS OFTHE PACIFIC-NORTHWEST, USA, Plant and soil, 180(1), 1996, pp. 147-158
Ectomycorrhizal mats in forest soils have a wide global distribution a
nd have been noted as potentially important elements in forest soil nu
trient cycling. To elucidate the relationship between ectomycorrhizal
mats and their environment, we undertook field studies and spatial ana
lyses of mat distributions at different spatial scales. We used two ex
perimental approaches to study mat-forming ectomycorrhizal fungi in co
niferous forests of the Pacific Northwest in the United States. In the
first approach, ectomycorrhizal mats and other forest door features w
ere mapped in 2 x 10 m plots and digitized into a geographical informa
tion system (GIS) for spatial pattern analysis. In order to examine la
rger-scale phenomena, a second approach involving other sites was take
n; soil cores were taken along 30-m transects, and distance to the clo
sest living potential host tree was calculated for each core. Mat patt
erns were studied at two scales: (1) within-stand level (i.e. variabil
ity attributed to distribution of other mat species, forest floor attr
ibutes, and understory vegetation); and (2) stand level (i.e. variabil
ity expressed along a successional gradient). Mat distribution was inf
luenced by: (1) the proximity of one mat to another; (2) the distance
from the mat to the closest living tree; (3) the density of living tre
es in a stand; and (4) the successional stage of the stand. Although G
IS analysis indicated that mats of different morphologies did not phys
ically overlap, there was a tendency for clustering of mats. No appare
nt correlations were observed between forest floor features and mats l
ocated within the 2 x 10 m grids. On the scale of tens of meters, mats
decreased with distance from the closest potential host tree. Spatial
patterns of mat distributions in harvested sites suggest that these m
ats may persist at least 2 years after their host trees have been cut.
For Gautieria mats, total mat area, size, and frequency differed with
stand age. This study has demonstrated the importance of both spatial
scaling and forest stand age when the natural distribution of mycorrh
izal fungi is examined. Results suggest the need for mat research dire
cted at higher-order scales (e.g. stand and watershed) that will provi
de accurate information for managing forests to ensure their survival
and normal function.