Peck, J.E. & B. McCune. 1995b. Accumulation of harvestable epiphyte mats in the Hebo District, Siuslaw National Forest, Final Report to the Siuslaw National Forest.
Ten
sites were selected within the Hebo District of the Siuslaw National Forest (see
Figure 1 and Appendix IV for location data). chosen to represent sites that are likely to be commercially harvested
for moss. Twenty-eight hardwood
tree and shrub trunk subsamples with harvestable quantities of epiphytes were
taken at each site, selected using the point-centered quarter method. On each stem, below two meters in vertical height, a randomly
chosen one meter segment was stripped of all harvestable epiphytes. In the 280 sampled epiphyte mats were found 17 mosses, 6 hepatics, 10
lichens, and 2 vascular plants. Species
richness of epiphytes, which ranged from 6 to 24, was lowest in the Isothecium
myosuroides dominated conifer stands. Biomass
was extremely variable, with neighboring sites quite dissimilar and ranged from
120 to 3050 kg/ha (22-78 g/m).
The ordination results reflect the tendency of harvestable mosses to vary
in species composition and abundance along a canopy composition gradient. Older stands with high conifer basal area have the most abundanct
populations of Isothecium myosuroides. Younger stands with high hardwood basal area and many available
substrates have more abundant populations of Antitrichia curtipendula, Claopodium
crispifolium, Dicranum scoparium, Eurhynchium oreganum, Metzgeria
temperata, Plagiothecium undulatum, Rhizomnium glabrescens,
and Rhytidiadelphus loreus. These results also indicate that for epiphyte mats the most
influential factor is not elevation. Rather,
the composition of the canopy and the availability of hardwood substrates
appears to be most important. These
results also indicate that stand age is an important factor for moss mat
development, although the range of ages for these stands (65 to 110 years) is
relatively small. Most species
responded negatively to stand age, except Isothecium myosuroides which
showed the opposite pattern. The
slopes of the 95% Frequency curve and the curve of mean mat mass as functions of
stem age yielded the net periodic growth rates for harvestable mats: 1.6-2.7 g/m/yr.
With a mean mat growth rate of 1.6 g/m/yr, a 5 m vine maple
can be expected to accumulate approximately 8 grams of harvestable material in a
year. The average harvestable
epiphyte mat in this study weighed 125 g/m; by these calculations, to achieve
that mass would take approximately 78 years on average. A vigorously growing mat would achieve that mass within only 46 years.
Given that the average mat weighed 80 g at year 10, on average the growth
rate for those mat on stems less than 10 years of age is 8 g/m/yr. That suggests that while it may take 78 years for the average mat to
reach 125 g/m, two thirds of the material was accumulated in the first 10 years.
In 1995, 165 permanently tagged vine maple that were harvested in August 1994 were remeasured to determine moss regrowth. Cover for each species of epiphyte was visually estimated to the nearest one percent on the upper and lower portions of each unit. A total of 21 taxa were found. Total average cover among all sites was 5.5% (sd 4.8%). Only two species averaged more than one percent cover among all sites: Isothecium myosuroides (2.7%; 2.8% including pendant material) and Neckera douglasii (1.1%; 1.6%). The upper surface of stems typically had a higher cover of epiphytes: 6.44% (sd 5.5%) vs. 4.6% (sd 3.8%) on the lower surface.