Measuring nitrogen and sulphur deposition in the Georgia Basin, British Columbia, using lichens and moss

Nitrogen (N) and sulphur (S) in the lichens Platismatia glauca, Parmelia sulcata and Hypogymnia physodes and a moss, Isothecium myosuroides in southwestern British Columbia was studied in a two component program. Firstly, relationships between lichen and moss tissue chemistry and atmospheric loading were explored using data collected at four regional air and precipitation chemistry monitoring sites in an effort to develop predictive models to estimate deposition. Secondly, the regional pattern of atmospheric N and S deposition was studied in a survey of lichen and moss tissue chemistry at fifty-seven locations in the Georgia Basin area. Results of the tissue chemistry was then compared to 1) modelled N and S deposition estimates and 2) lichen community structure response thresholds for N. The calibration component of this study was not successful owing to generally weak relationships between measured deposition and tissue N and S. Additional effort will be needed to define a functional relationship between N or S loading and tissue content. Correlations between the lichen and moss N content and model predictions were generally good. Correspondence between modelled S deposition and tissue content were more variable, but quite good for the dry S component. Nitrogen levels in lichen tissues suggest that lichen communities are probably being affected in urban areas and eastward into the Fraser Valley.