Peck, J.E. & B. McCune. 1995a. Diversity and growth of epiphyte mats in the Clackamas and Santiam Resource Areas, Final Report to the Salem District, BLM.
Eighteen sites on the Clackamas and Santiam resources areas of the Salem
District, BLM were surveyed for epiphytic lichens and harvestable epiphytes.
A whole-plot survey was conducted, using standard Forest Health
Monitoring (FHM) methods. The 34.7
m = 114 ft radius circular plot enabled visual sampling of all macrolichens
occurring on woody plants (plus litterfall), excluding the 0.5 m basal portions
of trees and shrubs. Additionally,
20 to 28 hardwood tree and shrub trunk subsamples with harvestable quantities of
epiphytes were taken at each site, selected using the point-centered quarter
method . Harvestable quantities
were defined as quantities of nonadherent species (i.e. no tiny adherent
liverworts or well-embedded species such as Dendroalsia abietina) that a
harvester would consider worth removing. On
each stem, below two meters in vertical height, a randomly chosen one meter
segment was stripped of all harvestable epiphytes and branch age was determined.
Species richness of lichens ranged from 21-36 per FHM plot, and that of
the harvestable epiphytes from 11-18: 110 taxa of lichens were observed, 31 harvestable epiphytic bryophytes,
and 2 vascular plants were found in the harvestable mats. Biomass of harvestable epiphytes ranged from 0 to 212 kg/ha.
Harvestable quantities of epiphytes were found in 9 of the sites, all
below 780 m in elevation. Epiphytes
were present in the remaining sites, but in too low an abundance to fit current
criteria for being "harvestable." The average harvestable epiphyte mat in this study weighed 43 grams (oven
dry weight), and the average stem length was 2.7 m. Thus the average stem in this study, across all sites, held a
total of 116 grams of harvestable material. Several ROD listed lichens and bryophytes were found.
Ordination analysis reflected the tendency of epiphytic lichens to vary
in species composition and abundance along elevational gradients, as well as
with the abundance of conifer and hardwood tree species. High elevation stands with high conifer basal area have more
abundant populations of Alectoria, Bryoria species, Cavernularia
hultenii, Hypogymnia imshaugii, and Platismatia norvegica. In contrast, the following species are most abundant in low elevation
stands with high hardwood basal area: Evernia prunastri, Hypotrachyna
sinuosa, Menegazzia terebrata, Peltigera collina, and Ramalina
farinacea. All high elevation stands were in the western foothills of the Cascades,
while low elevation stands were primarily in the Willamette Valley. Thus the elevational gradient also reflects the differences
in the mountain and valley floras.
The only harvestable epiphyte that was abundant in stands of high conifer
basal area and close proximity to water was Isothecium myosuroides, the
most abundant bryophyte in the entire study. Species most abundant in stands of high hardwood basal area and far from
water include: Cladonia ochrochlora, Claopodium crispifolium,
Homalothecium fulgescens, Homalothecium nuttallii,
Neckera douglasii, and Plagiomnium venustum. These results 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. All but two of
the sites lacking harvestable mats were above 650 meters in elevation. The slopes of the 95% Frequency curve and the curve of mean mat mass as
functions of stem age yielded net periodic growth rates for harvestable mats: 1.0-3.6
g/m/yr. With a mean mat growth rate of 1.0 g/m/yr, a 5 m vine maple can be
expected to accumulate approximately 5 grams of harvestable material in a year.
The average harvestable epiphyte mat in this study weighed 43 grams; by
these calculations, to achieve that mass would take approximately 43 years on
average. A vigorously growing mat
would acheive that mass within only 29 years, with a minimum of 12 years. These findings also reveal that, up to 40 years of stem age, mat mass
generally accumulates.