Long-term effects of nitrogen deposition on epiphytic lichens
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
The main aim of this study was to analyse the long-term effects on epiphytic lichen dry mass development, diversity and community structure after exposure to a simulated nitrogen deposition gradient. A whole tree experiment was set up in a boreal forest in the County of Västerbotten in Sweden, whereby 15 trees were artificially irrigated and nitrogen fertilized during seven consecutive years (2006-2012). The treatments were equal to an additional deposition of 0.6, 6, 12.5, 25 and 50 kg N ha-1 yr-1. Branches from the trees were collected in October 2012 and the lichen material was harvested and further analysed during the spring 2013. The results from this study showed that the lichens were directly affected by the long-term increased nitrogen deposition. Generally, lichen dry mass and species richness declined at high nitrogen loads and the initial positive effects of low nitrogen loads reported in a preceding study had thus depressed with time. The results from this study also showed that the composition of the lichen community changed benefitting nitrogen-tolerant species, probably not because of competition but more likely because of nitrogen-sensitive species disappearance. This study strongly indicates that it takes more than a few years to detect changes in lichen communities exposed to enhanced nitrogen loads. In addition low concentrations seem to have a cumulative impact. Consequently, this study stresses the importance of also considering the cumulative effect of low nitrogen loads when determining critical values. The critical load for lichen communities in boreal forests might be below 6 kg N ha-1 yr-1.
Place, publisher, year, edition, pages
2013. , 20 p.
simulated nitrogen deposition, boreal forest, epiphytic lichens, cumulative loads
IdentifiersURN: urn:nbn:se:umu:diva-72677OAI: oai:DiVA.org:umu-72677DiVA: diva2:626473
Master's Programme in Ecology
Palmqvist, Krisitn, Professor
Byström, Pär, Senior lecturer