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OCR for page 205
EXPERIMENTS AND OBSERVATIONS ON EPIPHYTIC LICHENS
AS EARLY WARNING SENTINELS OF FOREST DECLINE
Martha G. Scott Thomas C. Hutchinson
Department of Botany and Institute for Environmental Studies
University of Toronto
Toronto, Ontario, Canada. MSS IA1.
ABSTRACT
Forest declines are now widely reported in Europe and eastern
North America, especially in high elevation areas where fogs,
oxidants and SO2 frequently co-occur. Analyses of cloudwater
indicate that high-altitude fogs are more acidic (x#pH of 3.8)
than ambient precipitation at the same sites and may be present
for up to 50% of the year. A combination of high humidity and
nutrient enrichment normally allows for a prolific, species-rich
epiphytic lichen flora on coniferous trees in the transition zones.
In previous field studies, we have shown that boreal
forest-floor lichens such as Cladina rangiferina respond to seasonal
sprays of simulated, acidic rain of less than pH 3.5 by producing
abnormal morphological and cytological structures. We have,
therefore, selected a number of high-altitude sites showing varying
degrees of forest dieback in Quebec, Vermont and New York
(North America) and in the Black Forest and Hartz Mountains
(Germany) to determine whether similar abnormalities occur in
lichen populations exposed to ambient levels of acidity. We shall
discuss the suitability of two, widely-distributed epiphytic lichens,
Hypogymnia physodles and Pseudevernia sp., as early warning
indicators of forest dieback, based on a combination of
morphological, cytoplasmic and chemical data.
INTRODUCTION
The nature of the forest decline, which is currently affecting tree species in
Europe, Scandinavia and eastern North America, is complicated both by the plethora of
hypotheses which have been advanced to explain the diebacks and by the complexity of
the forest ecosystem itself. A delicate balance exists between above-ground foliar
processes such as gas exchange, cuticular integrity and stomata! mechanisms and less
visible below-ground factors such as soil chemistry, decomposer organisms, mycorrhizal
associations and nutrient availability. Superimposed upon these interrelationships are
disease vectors, climatic variables, community and stand dynamics and
anthropogenically-derived pollutants, all of which may play a vital role in determining the
health of trees within narrowly-defined geographical limits.
In order to understand the dynamics of specific dieback scenarios and the possible
involvement of atmospheric pollutants such as acid rain, acid fogs and oxidants, it is
necessary to document links between known levels of inputs (eg., SO4 and NO3) and
regional declines of specific species. Unfortunately, the long-term monitoring of ambient
205
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206
precipitation chemistry is time-consuming and expensive and, to date, only a handful of
such programmer exist. The CHEF project (Chemistry of High Elevation Fog-
Schemenauer 1986), currently being implemented at two sites in Quebec, and a similar
study at Whiteface Mountain in New York, are two such programmes which provide
accurate information about atmospheric chemistry in high-elevation forests where
significant declines of balsam fir and red spruce are occurring.
This report presents the results of studies conducted both in Germany and at the
high-elevation locations noted above, on two widely-distributed species of lichens,
Hypogymnia physodes and Pseudevernia sp. which show good potential as sentinels of
forest dieback.
2.
Historically, there are distinct advantages in predicting the severity of atmospheric
pollution on the basis of changes in 'simple' organisms such as lichens and mosses, which
have neither roots nor the waxy cuticle which protects higher plants. Traditionally, the
presence or absence of key indicator species has been used as a kind of 'litmus paper' to
map levels of SO2 emitted from point-source industrial processes (Leblanc and Rao 1966.
Seaward 1987~. The disadvantages of this technique lie in the fact that expertise in
lichen taxonomy is required to interpret the data and that the response of a particular
lichen to a gaseous pollutant may be an "all-or-nothing phenomenon," open to a number
of alternative explanations.
However, the acidophilic nature of lichen thalli, in particular of the fungal partner
in the symbiosis, suggests that these organisms may be much more tolerant of acid rain
and fogs than they are of gaseous pollutants (Scott and Hutchinson, 1987~. In fact,
lichen populations epiphytic on declining Norway spruce in Germany are actually
flourishing. Tolerant lichen species which gradually change in some aspect of their
biology over a long period have potential value as bioindicators of tree dieback in
impacted areas.
Accordingly, the objectives of this current study are two-fold:
1. To assess the effect on lichen tissue chemistry of elevated levels of
sulphate, nitrate, ozone and possibly metals. In 1986, the mean fog pH at high
elevation sites in eastern Quebec was 3.S, whereas the mean pH of precipitation at
the same sites was 4.3 (Schemenauer 1986~. Modelling techniques suggest that fogs
and clouds blanket these mountaintops for up to 50% of the year.
To determine whether specific morphological or cellular aberrations exist in species
of Hypogymnia and Pseudevernia epiphytic on declining balsam fir and red spruce at
these sites. Our previous research in a boreal forest ecosystem showed that
branching pattern abnormalities and changes in starch and lipid content of algal
cells could be induced in Claciina species by seasonal sprays of simulated rain of pH
less than 3.5.
METHODOLOGY
Only a brief summary of our experimental design and methodology will be
presented here. Data are preliminary and have not yet been statistically analysed. Our
study sites are listed in the following table. To date, all of the high elevation locations
have been sampled. However, low elevation sites experiencing acidic fogs near the Bay
of Fundy, Nova Scotia and a northern boreal forest site with low pollutant inputs will be
visited in 1988. A range of altitudes is included for each mountain.
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207
Site Elevation
Germany:
Black Forest Region - 4 sites 500 - 1300 m
Hartz Mountains - 2 sites 800 - 1000 m
Czechoslovakian Border - 1 site up to 1200 m
North America:
Mt. Tremblant (Quebec) 100m, 590 m, 860m
Mt. Sutton (Quebec) 845m, 970 m
Whiteface Mountain (N.Y.) SS4m, 1 1 60m
Camelts Hump (Vermont) 884m, 1067m
Low Elevation Sites:
Sudbury, Ontario (near smelting operations) - Ciadina sp.
Burt Lake, Ontario - boreal forest ecosystem
Bay of Fundy, Nova Scotia - low elevation with acidic fog
monitoring station
Two species of lichen were present at most of the study locations. Hypogymnia
physod~es, a foliose epiphyte of conifers, has a ubiquitous distribution and is semi-tolerant
of gaseous pollutants such as SO2. Two species of the subfruticose Pseudevernia (P.
consocians in NA and P. furfuraceae in Europe) were chosen also because of irregular
morphological features noted during preliminary site visits in 1987.
Because of the wide geographical disparities between the study sites, appropriate
control sites were difficult to establish. Although the boreal forest location in northern
Ontario is unaffected by air currents from the southwest, it is a low-elevation site.
However, boreal and high-altitude transitional forests are quite similar in structure and
contain many of the same understory species. Low-elevation sites at the base of the
mountains are inappropriate because the mixed hardwood forests do not support the same
lichen flora and microhabitat factors are completely different. At two elevations on
Mount Tremblant and Mount Sutton, therefore, we selected paired sites of different
exposures to prevailing winds, in order to test the hypothesis that atmospheric inputs
from the SW were more damaging to lichens than inputs from an eastern or northern
source.
At each site, 10 balsam fir and red spruce trees, with a DBH of approximately 50
cm, were selected at random from within a defined area. Crown dieback was rated
subjectively using a scale of 1 to 5, with 1 being healthy (less than 20% dead branches
and chlorotic needles) and 5 being dead. The percentage cover of all lichen species
present on a one-metre segment of the bole of the trees (measured upwards from DBH)
was also recorded. From within this 1 metre zone, even-aged samples of H. physodes
and Pseudevernia were then harvested for laboratory analyses.
The following tests were performed for each collection:
( 1 ) Lichen thalli were examined and photographed using a dissecting microscope. Unusual
branching or lobation patterns were noted, along with abnormal production of sexual and
asexual reproductive structures (Sigal and Nash 1983~. This information will be
quantified.
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208
(2) Tissue, containing both the algal and fungal symbionts, was fixed for TEM using a
previously-published protocol (Scott and Larson 1984~.
(3) Following digestion with nitric acid, the tissue chemistry of unwashed lichens was
analysed using either ICP (inductively-coupled plasma emission spectroscopy) or atomic
absorption spectroscopy. Data were obtained for a number of elements and expressed on
a ug/g dry weight basis (n=5-~.
(4) Pieces of lichen thalli similar in dry weight and exposed surface area were soaked in
double-distilled water for one hour. Aqueous extracts were then filtered and analysed
for cations (Na+, NH4+, K+) and anions (C1-, F-, N03, P04, SOT) using DIONEX (n=6
reps/study site).
RESULTS AND DISCUSSION
Our results clearly demonstrate that both morphological and chemical indicators of
air pollution effects can be seen in lichen epiphytes of declining trees. As seen in Table
1, the percentage cover of the dominant epiphyte H. physodes decreases with increasing
altitude at all but the most northern location (Mt. Tremblant). Ideally, lichen growth
should be extremely vigorous in such a cool, moist habitat. The lowest percentage cover
of dominant lichen species on boles of balsam fir was recorded near the summit of
Whiteface Mountain, where the average crown dieback rating was 4.1, or extremely
severe. On-site observations also indicated that many lichens were white or pinkish in
appearance, a symptom which may be the result of membrane damage resulting in
destruction of chlorophyll.
Table 1. Percentage Cover of llchene on boles (DBH) of Baleam Fir
growing at high elevation sitea in eastern North America.
Site ~ H`fpogy~nnla physotes Total Dominant Total Lichen Crown Dleback
species Cover Ratlug
-
x S.E. x S.E.
Mt. Tremblant:
590 m 26 8 S5 66 27 2 .8
860 m 36 S 77 84 7 2.6
Mt. Sutton:
865 m 29 5 83 103 11 3.3
970 m 26 5 65 94 25 3.1
Whlteface (MY. ):
884 m 35 5 66 90 8 3.3
1160 m 21 5 44 72 15 4.1
Camel'n Hump:
884 m 35 6 71 97 12 3.4
1067 m 29 3 49 89 12 3.2
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209
Micrographs of Cladina rar~giferina (boreal), H. physodes and P. furfuraceae are
presented in Plates 1 and 2. Figures 1-3 show podetia of C. rangiferina which received
periodic sprays of acidic rain (a field simulation experiment) (Hutchinson et al., 1987~.
As compared to the normal situation in which branching occurs close to the tip (Fig. 1),
affecter! lichens produced numerous stunted branches on fully-elongated portions of the
thallus which usually do not initiate new growth (Fig. 2~. These short branches
dichotomize repeatedly and rapidly produce sexual structures (Fig. 3~. In addition, there
is an increase in the number of algal clusters as compared to the volume of the thallus
comprised of fungus. At high elevation sites, thalli of a number of species showed either
branching pattern abnormalities (Figs. 4,5,7) or they produced enormous numbers of
asexual structures. German populations of Pseudevernia furfuraceae from both the
Schwarzwald regions and the Hartz Mountains (acid fog, ozone and S02) produced
club-shaped structures which failed to dichotomize at the growing tips (Fig. 4 arrow).
Asexual structures known as isidia, which contain both the algal and the fungal
symbiont (Fig. 5,6) are the normal reproductive propagule of this genus. However, thalli
harvested from severely declining sites in both Europe and North America produced large
numbers of these highly branched structures with little subsequent elongation of the
'internodal' regions (Fig. 5~. This phenomenon occurred on both large and small
diameter thalli in the populations. Lobes of Hypogymnia physodes (not shown) were also
convoluted and had prolific marginal soralia (another form of asexual structure).
Morphological changes in lichen thalli exposed to air pollution have been reported in the
literature for Parmelia species exposed to high dosages of SO2 near Sudbury, Ontario
(LeBlanc and Rao 1966) and for H. enteromorpha from the heavily-impacted San
Bernardino Mountains in California (Sigal and Nash 1983~. These authors also observed
an abnormally high production per mm2 Of asexual pycnidia. Factors which control
branching patterns in healthy lichenized fungi are very poorly understood. In
non-lichenized Ascomycetes, sources of carbon, nutrients and especially nitrogen (Griffin,
1981) have been reported to control the degree of 6hyperbranching' of hyphae. Since
the stemflow of declining trees may be both acidic and enriched with canopy leachates,
altered nutritional factors may, indeed, play a role in stimulating branch production in
lichens at high elevation sites. A fertilization effect from the nitrate component of the
acidic fogs may also be related to the vigorous lichen growth.
At the cellular level (Plate 2), Figures ~ and 9 show transmission electron
micrographs of C. rangiferina exposed to simulated rains in a boreal forest ecosystem
(Hutchinson et al., 1987). Compared to the normal appearance of the cytoplasm (Fig. 8,
pH 5.6), thalli sprayed with rain of pH 2.5 or 3.0 contained algal cells with huge
peripheral lipid bodies (Fig. 9) and large deposits of intrathylakoidal starch. This
phenomenon has been reported in lichens exposed to high levels of industrial pollution,
including S02 near urban centres in Madrid (Silva-Pando and Ascaso 1982) and in higher
plants exposed to salt stress (Winter 1982~.
In high elevation populations of Hypogymnia and Pseudevernia, starch and lipid are
also accumulated by algal cells (Figs. 10, 13~. This apparent sequestering of
photosynthetic pro~iucts may represent a failure to translocate sugar alcohols to the
fungal partner and might ultimately result in decreased growth of the hyphae and
possibly saprophytism. Within the population of algal cells in an affected lichen, healthy
and senescent algal cells co-occur. However, the most severely declining sites had the
highest percentage of algae with cytoplasmic damage. Deterioration of the chloroplast
and cellular membranes was commonly found, along with extensive cell wall degradation.
The degree of cellular damage to the lichens appeared to be correlated with the tree
dieback rating for the site.
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210
1
_
-
~..
Figure 1. Light micrograph of growing
tips of C. rangiferina from a boreal
forest ecosystem. Podetia sprayed with
'rain' of pH 5.6 had numerous terminal
apothecia (Ap). (Hutchinson et al., 1987~.
Figure 2. Initialtion of numerous small
branches on a mature lower portion of C.
rangiferina sprayed periodically for five
years with artificial rain of pH 2.5.
Figure 3. High magnification of a newly-
initiated branch with a developing sexual
structure (Ap - apothecium). The dark
coloration is a result of numerous, large
algal cell clusters.
Figure 4. Pseudevernia furfuraceae from
the Schwarzwald region (greater than
1 OOOm), West Germany. Note the heavily
isidiate regions (large black arrow),
which failed to dichotomize.
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211
e
Figure 5. Higher magnification of a
portion of the thallus shown in Figure 4.
Isidia (Is) are highly branched.
:~4
Figure 6. A portion of the same species
(P. furfuraceae) from a lower elevation
collection (SOOm) in the Schwarzwald.
The thallus is relatively smooth, with
fewer numbers of isidia
Figure 7. P. furfuraceae from the Hartz
mountains. Branched isidia are short and
thickened. Algal cells (A) are darkened
and necrotic-looking, as is much of the
upper surface of the thallus.
:i~
::~
Figure 8. Cytoplasm of the unicellular
alga, Trebouxia, in C. ran~iferina from
the boreal forest simulation experiment.
this micrograph is representative of
either unsprayed podetia or podetia
sprayed with rain of pH 4.0-5.6. A-
algal layer. PB-pyrenoid body (starch
organizing centre). Ch-Chloroplast. Hy-
Hyphae. (Hutchinson et al., 1987~.
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212
. ..~ Ida .
~ it,
ff<
.:. ~
by. _
L_
P. ~
by: ~
C`_
_
hi.
I.
3.
{,_
Figure 9. Algal cell from the same
species sprayed with simulated rain of pH
2.5. Note the large deposits of peripheral
lipid (Li).
Figure 10. Algal cells of P. consocians
from a high elevation site on Camels
Hump, Vermont. Cells are relatively
normal in appearance, except that they
contain numerous starch grains (St) and
poly-phosphate type bodies (Pp).
Figure 11. Epiphytes (Ep), with well-
preserved cytoplasm are commonly found
on the surface of lichens harvested from
the Hartz mountains in Germany.
Although many of the lichenized "algae
were senescent, there were an abundance
of micro-organisms on the upper cortex.
Figure 12. High magnification of the
thylakoid membranes (Th) in the
chloroplast (Ch) of an alga from H.
ohvsodes (Schwarzwald region). Note the
interthylakoidal starch grains (St) and
the disruption of membrane structure.
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213
-
Figure 13. The alga of H. physodes from a high elevation collection on Whiteface
Mountain, N.Y. Note the large, peripheral lipid bodies (Li) and the accumulation of
starch bodies (arrow).
Two strong patterns emerge from examination of the tissue chemistry data in Table
2. First, at heavily impacted sites such as Whiteface Mountain, there is a general
pattern of loss of important plant nutrients, such as P. Mg and Mn, with increasing
elevation. At sites with intermediate dieback, some of these nutrients, especially Ca,
may be substantially elevated, possibly because of foliar leaching or mobilization of
cations from bark substrates exposed to acidified stemflow. In the case of calcium, two
values are presented for each site, one with all trees included in the sample, and a
separate mean from which values for dead trees were removed. It is apparent that a
tremendous flush of Ca is released from senescent trees, thus substantially elevating the
lichen tissue content of elemental Ca. Even with the dead trees removed, however, Ca
levels are elevated at sites with a SW exposure, compared to sheltered sites at an
equivalent altitude on the same mountain. Calcium content of epiphytic lichens may,
therefore, be a useful marker of tree senescence.
As far as the metals are concerned, lichens from heavily-impacted high-
elevation sites contain high levels of Al, Fe, Pb and Cu (not shown). All of these metals
may, in some way, be related to by-products of industrial processes. Aluminum has been
reported by Scherbatskoy ( 1982) and Scherbatskoy and Klein ( 1983) to occur in cores
taken from declining red spruce at high elevation sites. It is interesting to note the
pattern for Pb which is positively correlated with increasing elevation, with the
exception of sheltered sites which contain only background levels of Pb.
Although the data for anions and cations in aqueous extracts of lichen tissues are
incomplete, the pattern for ammonia is similar to that observed for the metals. Nitrate
and sulfate are also substantially elevated, especially in lichens from the collection near
the Czechoslovakian border.
In conclusion, epiphytic lichens appear to have potential as bioindicators of
forest decline. To be useful as early warning indicators, however, it is important to
identify morphological and chemical markers in advance of severe tree dieback. Both the
growth pattern abnormalities and the accumulation of Ca and metals
OCR for page 214
Table 2. Tissue che~atr' (ug/g) of Hypo~nla ohysodes from high elevation sites.
Site (Elevation) P Ca Al Fe Pb S N
. .
Genuine:
S18CL Forest 2248 8~ 1038 71 ~23 17,4
558 2348
1032 60
Czechoslovakia
(1000- 1200~) 1390 2322 1147 1606 56 2856
1786 16, 300
Mt. ~re~laDt:
100 metros 1323 87,12~) 604 750 26 2630
S90 metrca 884 6409 591 807 67 1947 13,200
(2110)*
860 metros 1285 56SO S07 548 92 1702 14,100
(2347) *
860 m(sheltered) 686 2069 173 184 28 1237 11,300
Mt. Sutton:
845 metros 1422 6597 649 928 138 1996 16,900
(2012)*
845 Sheltered) 1938 3346 715 1025 65 1600 12,300
970 met res 754 10,406 690 818 99 1237 12,100
(3935)*-
Whiteface (N.~. ):
884 metres 1765 6471 608 779 48 1393 9,300
(3468)
1160 metres 8S0 9568 870 1382 87 1720 13,800
(1016)
Camel's Bump (VA):
884 metros 1341
14 ,657
(2409)
1067 Petrel 1836 14,836
( 2665)
890 629 92 1896 11, 100
548 650 78
1478 8,100
occur in species of Hypogymnia and Pseudevernia epiphytic on apparently healthy
conifers. If, in fact, we can demonstrate that good correlations exist between
atmospheric inputs and changes in lichen flora, then these studies may provide a faster,
more economical way to assess ambient air quality in the absence of permanent
atmospheric monitoring stations.
ACKNOWLEDGMENTS
Our thanks are due to Dr. R. Schemenauer of the Atmospheric Environment
Service of Environment Canada for his considerable help and encouragement in initiating
this project. We also thank field workers on the Chemistry of High Elevation Fog
(CHEF) project. Marilyn Feth and Catriona Gordon provided invaluable technical
assistance. The project was funded by the Wildlife Toxicology Fund to whom we are
most grateful. Travel funds were supplemented by the Canadian Forestry Service.
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215
REFERENCES
GRIFFIN, D.H. 1981. "Growth and Development of the Thallus" in Fungal Physiology.
John Wiley and Sons, New York. Pp. 117-130.
HUTCHINSON, T.C., M. SCOTT, C. SOTO, and M. DIXON. 1987. The effect of
simulated acid rain on boreal forest floor feather moss and lichen species. Pp. 411-
426 in Effects of Atmospheric Pollutants on Forests, Wetlands and Agricultural
Ecosystems, T.C. Hutchinson and K.M. Meema teds.), Springer-Verlag Berlin
Heidelberg.
LEBLANC, F., and D.N. RAO. 1966. Reaction de quelques lichens and mousses
epiphytiques a l~anhydride sulfureux dans la region de Sudbury, Ontario. The
Bryologist 69:338-346.
SCHEMENAUER, R.S. 1986. Acidic Deposition to Forests: The 1985 Chemistry of high
elevation fog (CHEF) project. Atmosphere-Ocean (24~4:303-328.
SCHERBATSKOY, T. 1982. Changes in Aluminum and heavy metal concentrations in Picea
rubens wood in Northern Vermont. Cambial Activities Increment 7:2-3.
SCHERBATSKOY, T., and R.M. KLEIN. 1983. Response of spruce and birch foliage to
leaching by acidic mists. J. Environ. Qual. 12:189-195.
SCOW, M.G., and D.W. LARSON. 1984. A correlated light and electron microscope study
of Umbilicaria lichens. Can. J. Bot. 62~9~:1947-1964.
SCOTT, M.G., and T.C. HUTCHINSON. 1987. Effects of a simulated acid rain episode on
photosynthesis and recovery in the caribou-forage lichens, Cladina Stellaris (Opiz.)
Brodo and Cladina rangiferina (L.) Wigg. New Phytologist 107:567-575.
SEAWARD, M.D. 1987. Effects of quantitative and qualitative changes in air pollution on
the ecological and geographical performance of lichens. Pp. 439-448 in The
Response of Forests, Crops and Wetlands to Atmospheric Pollution, T.C. Hutchinson
and K. Meema (eds.) Springer-Verlag. Berlin, Heidelberg.
SIGAL, L.L., and T.H. NASH III. 1983. Lichen communities on conifers in southern
California mountains: an ecological survey relative to oxidant air pollution.
Ecology 64~6~: 1343- 1354.
SILVA - PANDO, F.J., and C. ASCASO. 1982.
~ · · ~.
Modificaciones ultraestructurales de
t~quenes ep~~~tos transplantados a zones urbanas de Madrid. Collectanea Botanica
13(1):351 -374.
WINTER, E. 1982. Salt tolerance of Trifolium alexandrinum L. III. Effects of salt on
ultrastructure of phloem and xylem transfer cells in petioles and leaves. Australian
J. Plant Physiol. 9:239-250.
OCR for page 216
Table 2. Tissue che~atry (ug/g) of Hypo~nla Physodes from high elevation sites.
Site (Elevation) P Ca Al Fe Pb S N
. .
Gerund:
S18CL Forest 2248 8 ~1038 71 ~23 17,4
558 2348
1032 60
Czechosloval~la
(1000- 1200~) 1390 2322 1147 1606 56 2856
1786 16, 300
Mt. ~re~laDt:
100 metros 132387,12~) 604 750 26 2630
S90 metros 8846409 591 807 67 1947 13,200
(2110)*
860 metros 128556SO S07 548 92 1702 14,100
(2347) *
860 m(sheltered) 6862069 173 184 28 1237 11,300
Mt. Sutton:
845 metros 14226597 649 928 138 1996 16,900
(2012)*
845 Sheltered) 19383346 715 1025 65 1600 12,300
970 met res 75410,406 690 818 99 1237 12,100
(3935)*
Whiteface (N.~. ):
884 metres 1765 6471 608 779 48 1393 9,300
(3468)
1160 metres 8S0 9568 870 1382 87 1720 13,800
(1016)
Camel's Bump (VA):
884 metros 1341
14 ,657
(2409)
1067 eetree 183614,836
( 2665)
890 629 92 1896 11, 100
548 650 78
1478 8,100
occur in species of Hypogymnia and Pseudevernia epiphytic on apparently healthy
conifers. If, in fact, we can demonstrate that good correlations exist between
atmospheric inputs and changes in lichen flora, then these studies may provide a faster,
more economical way to assess ambient air quality in the absence of permanent
atmospheric monitoring stations.
ACKNOWLEDGMENTS
Our thanks are due to Dr. R. Schemenauer of the Atmospheric Environment
Service of Environment Canada for his considerable help and encouragement in initiating
this project. We also thank field workers on the Chemistry of High Elevation Fog
(CHEF) project. Marilyn Feth and Catriona Gordon provided invaluable technical
assistance. The project was funded by the Wildlife Toxicology Fund to whom we are
most grateful. Travel funds were supplemented by the Canadian Forestry Service.
Representative terms from entire chapter:
elevation sites
