Lecanora barkmaneana, a sorediate corticolous lichen belonging to the Lecanora subfusca group, is described as a species new to science on the basis of numerous sterile collections and two richly fertile collections. It is known so far only from the Netherlands, where it often grows on roadside trees. It seems to be spreading rapidly at nutrient-rich sites.

In the Netherlands a monitoring programme is in operation to map the effects of ammonia pollution with epiphytic lichens. The method is presented here and the results are statistically correlated with abiotic data. The abundance of nitrophytes on Quercus robur appears to be a useful parameter. Detailed spatial patterns of ammonia pollution can be obtained with lichens. To avoid interference, it is important to consider other influences, for example dust, climate, exposure, age of the trees and other pollutants.

The epiphytic lichen floras of different orchards (intensive, semi-intensive apple cultivation and traditional old private garden) in North-West Romania were compared with and without pesticide treatment. Species richness was negatively influenced by the frequency of pesticide treatment.

Epiphytic lichens were recorded on wayside trees in the Netherlands. Four statistical methods were used to detect the relationship between presence and abundance of lichen species and measured atmospheric concentrations of SO2, NO2 and NH3. The observed relationships were compared to published indicator scales of lichen sensitivity to atmospheric pollution. For SO2, a good agreement was found between all scales and calculated sensitivities based on presence or absence of species. For NO2 and NH3 the correspondence was less obvious. The sensitivity to NH3 was inversely related to Wirth's;s acidity indicator positively to NH3 tend to be sensitive to SO2 and NO2.

A survey of epiphytic species on annual increments of Quercus petraea twigs in a west Wales woodland has shown that distribution of lichen species and rates of succession are affected by a range of environmental conditions. Lichen communities were recorded for 1–15 years on randomly sampled twigs along marked woodland boundaries affected by a range of climatic and management conditions. Results show that there is a correlation between environmental condition and lichen communities of twigs, and that indicator species can be used to detect trends towards acidification or eutrophication.

The results from several floristic and bioindication projects in Central Switzerland (1986–1998), focusing on the effects of agriculture, particularly from nitrogen and agrochemical emissions, are summarized. The abundance of nutrienttolerant lichen species and the decreased occurrence of nitrophytic lichens are both correlated with agricultural land use and high atmospheric deposition. The impact could be demonstrated not only by the distribution patterns of nutrient-tolerant species, but also by the high N content of lichens such as Physcia caesia. Positive growth response of Cetraria islandica to application of mineral nutrients and increased CO2 in open-top chambers at high altitudes was also observed. The methods and a survey of the results from studies conducted within the framework of the lichen research programme of the Natural History Museum of Lucerne are presented here. A discussion of the issues shows the need for further studies concerning the influence of introduced nutrients on the biodiversity of lichens.

The effect of deposition of different fertilizers and of lime on lichens was investigated under field conditions. Three terricolous lichens were tested: Cladonia floerkeana, C. furcata and C. portentosa. The lichens were exposed to three types of powdered fertilizer (NPK-, N-, P-fertilizer) and lime. The applied nutrients were recorded in lichen thalli and soil. The influence on lichen growth rate and vegetation cover was estimated over 2 years. The response was a clear change in vegetation cover with an exceptional stimulating effect of NPK on the moss Polytrichum formosum. A lethal effect was observed on Cladonia floerkeana following exposure to lime. NPK and P had the most significant stimulatory effect on C. furcata. Only NPK promoted the growth of C. portentosa and P, N or Ca had a negative effect.

The passive uptake of ammonium ions to extracellular cation binding sites has been demonstrated for a range of lichen species. The possible competitive effect of other cations on ammonium binding is discussed. Binding of uncharged gaseous ammonia to exchange sites was also shown. The rapid loss of exchangeable ammonium from extracellular sites has been demonstrated and, because the greatest losses occur in living material, intracellular uptake is inferred. The labile nature of bound ammonium means that transfer of material to the laboratory for analysis may result in the underestimation of the amount bound.

The sensitivity of Hypogymnia physodes, Lobaria pulmonaria and Peltigera aphthosa to six photosystem II herbicides and to DBMIB was tested in the laboratory by chlorophyll fluorescence and oxygen-exchange measurements. In addition, experiments with freshly isolated photobiont cells from H. physodes and L. pulmonaria were performed. Generally, the lichens were most sensitive to the urea herbicides diuron and isoproturon, whereas the triazines atrazine, terbuthylazine, and simazine and the triazinone metamitron were less inhibitory. Among the three lichen species investigated, H. physodes was the most sensitive to the urea herbicides. For the other agents, no significant differences between lichen species could be found. The highest pI50 values obtained from dose response curves were around 6.5 for isolated photobionts, but most values for lichen thalli were in the range 5–6. Thus, there is no particular sensitivity of green algal lichen photobionts to photosystem II herbicides as compared to other algae, higher plant chloroplasts or protoplasts. In nature, we observed recovery from (damaging) treatment with 10−5 mol diuron 1−1 for H. physodes within weeks. Therefore, damage to lichens from the use of photosystem-II herbicides in agriculture is probably only of very local occurrence.

Paraquat-treatment of Parmotrema reticulatum and high light levels in the habitat of Pamtelia sulcata can cause oxidative stress, which promotes an increase in ascorbic acid contents of thalli. Ascorbic acid was measured by an HPLC method. In P. reticulatum the increase was more pronounced in summer than in other seasons. In P. sulcata, thalli growing in sun-exposed habitats showed a higher ascorbic acid content than shade-growingspecimens.