Message - 7th IAL Symposium

The 7 th International Association for Lichenology Symposium 2012
(5I-O3) Submission ID: IAL0034-00001
BARK ACIDITY AND LICHENS OCCURRENCE IN GOMEL, BELARUS
Tsurykau A. 1 , Khramchankova V. 1
1 Biological, F. Skoryna Gomel State University, Gomel, Belarus
Bark pH might importantly determine the regional occurrence of lichen species, and specific information
on the relationship between lichens and phorophyte bark pH is invaluable for bioindication and monitoring.
We investigated these relationships for an urban area in the city of Gomel, the second largest city in the
Republic of Belarus with a population of c. 480,000 people. We studied the composition of foliose and fruticose
lichens, associated with 11 tree species, and we determined the bark pH. We found that bark acidity in Gomel
exceeds the values recorded for Western European in the 1960s, by 1.5–2.5 pH units, providing new information
on lichen response. Variation in bark acidity was associated with three phorophyte groups: Group 1 (pH
6–8): Physconia distorta and Physconia enteroxantha; Intermediate group (pH 4.5–6.5); Group 2 (pH 4.0–5.5):
Hypogymnia physodes, Evernia prunastri, Melanohalea exasperatula. Regressions to explain lichen occurrence
and bark acidity were calculated for contrasting indicator species: Hypogymnia physodes (y = -7.76x + 52.94; r
= 0.78; p < 0.01) and Physconia distorta (y = 9.38x – 43.89; r = 0.81; p < 0.01). Using the Gomel glass factory
as a site-specific case-study for increased alkalinity, we explore in detail the relationship between lichen species,
their phorophytes, and the functional interaction between phorophyte pH and environmental setting.
(5I-O4) Submission ID: IAL0155-00001
THE RESPONSE OF EUTROPHIC LICHENS TO DIFFERENT FORMS OF NITROGEN IN THE
LOS ANGELES BASIN
Jovan S. E. 1 , Riddell J. 2 , Padgett P. 2 , Nash T. H. 3
1 PNW Research Station, USDA Forest Service, Portland, Oregon, United States
2 Pacific Southwest Research Station, USDA Forest Service, Riverside California, United States
3 Dept. of Botany, University of Wisconsin, Madison, Wisconcin, United States
Epiphytic lichen communities are highly sensitive to excess nitrogen (N), which causes the replacement
of native floras by N-tolerant, “weedy” eutrophic species. This shift is commonly used as the indicator of
“harm” in studies developing empirical critical levels (CLE) for ammonia (NH 3 ) and critical loads (CLO) for N. To
be most effective, empirical CLE/CLO must firmly link lichen response to causal pollutant(s), which is difficult
to accomplish in field studies in part because the high cost of N measurements limits their use. For this case
study we synthesized an unprecedented array of N measurements across 22 long-term monitoring sites in the
Los Angeles Basin, California: gas concentrations of NH 3 , nitric acid (HNO 3 ), nitrogen dioxide, and ozone (n =
10); N in throughfall (n = 8); modeled estimates of eight different forms of N (n = 22); and nitrate accumulated on
oak twigs (n = 22). We sampled lichens on black oak (Quercus kelloggii) and scored plots using two indices of
eutroph abundance to characterize the community-level response to N. Our results contradict two common misconceptions
about the lichen-N response: 1) that eutrophs respond specifically to NH 3 , and 2) that that response
is necessarily dependent upon the increased pH of lichen substrates. Eutroph abundance related significantly
but weakly to NH 3 (r 2 = 0.48). Nitrogen deposition as measured in canopy throughfall was by far the best predictor
(r 2 = 0.94), indicating that eutrophs respond to multiple forms of N. Most N variables had significant correlations
to eutroph abundance (r 2 = 0.36 – 0.62) as well as to each other (r 2 = 0.61 – 0.98), demonstrating the
risk of mistaking correlation for causality in CLE/CLO field studies that lack sufficient calibration data. Our data
furthermore suggest eutroph abundance is primarily driven by N inputs, not pH-- at least at the high pH values
found in the basin (4.8 - 6.1). Eutrophs correlated negatively with trunk pH (r 2 = 0.43), exactly the opposite of
results from virtually all previous studies of eutroph behavior. This correlation is probably spurious and results
because HNO 3 dominates N deposition in our study region.
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