Epiphytic Algae and Lichen Cover in Boreal Forests—A Long-Term Study Along a N and S Deposition Gradient in Sweden
The aim was to describe spatiotemporal patterns of colonization of spruce branches by algae and lichens and the relationship with decreasing deposition of N and S. Coverage was estimated annually over 10 years for four Swedish Integrated Monitoring catchments with varying deposition levels. Initial hypotheses were that algal coverage would be positively correlated with deposition and that lichen coverage would be negatively correlated with S and positively with N deposition. Data were analyzed using regression, ANOVA, and partial least square regression. The results showed a temporal decrease in the coverage of algae but an increase in colonization rates, while lichens showed less uniform patterns. Within catchments, algae and lichen coverages were positively correlated with mainly S deposition. Across catchments, coverage of algae increased, while the coverage of lichens decreased with increasing N and S deposition. Colonization rates of both algae and lichens showed weak correlations with both spatial and temporal trends in N and S deposition. Thus, while N and S deposition had an effect on the colonization and coverage of algae and lichens, other factors are also important.
KeywordsEpiphytes Algae Lichen Nitrogen Sulfur Long-term Indicator
Sven Bråkenhielm, Lage Bringmark and Staffan Åkerblom and Tommy Pettersson are thanked for inventories. The monitoring program is financed by the Swedish Environmental Protection Agency. Brendan McKie and anonymous reviewers gave valuable comment on the manuscript.
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