Message - 7th IAL Symposium

Lichen: from genome to ecosystem in a changing world
5I-P
(5I-P4) Submission ID: IAL0187-00001
NITROGEN DRIVES LICHEN COMMUNITY CHANGES THROUGH
THE DIFFERENT SPECIES RESPONSES
Johansson O. 1 , Palmqvist K. 1
1 Department of Ecology and Environmental Science ,UMEA University, Umeå, Sweden
Nitrogen (N) deposition has increased globally over the last 150 years and further increase is predicted
in the future. N is an important nutrient for lichens, involved in many processes in both the photobiont and mycobiont.
However, N can also be excessive, with many lichens and lichen communities disappearing with increased
deposition. We initiated a long-term experiment aiming at understanding the underlying dynamic processes that
lead to altered structure and die-back of epiphytic lichen communities with increased N load. The aim was to
study how the N deposition would affect the epiphytic lichen community composition in a naturally N poor boreal
forest. This was done by daily fertilization (during the growing season) of spruce trees with a rich lichen flora at
five N levels (0.6, 6, 12.5, 25 and 50 kg N ha -1 year -1 ) during four consecutive growing seasons (2006-2009),
and yearly monitoring of changes in abundance of crustose, foliose, and pendulous lichens. Change in lichen
abundance on each branch was recorded each autumn and 2005 before the treatments started. The simulated N
deposition caused significant changes for Alectoria sarmentosa, Bryoria spp. and Hypogymnia physodes. A. sarmentosa
increased over time in the lower two levels of N, remained stable at intermediate levels, and decreased
at the higher levels. The abundance of Bryoria spp. showed a positive response to 6 kg N, but negative to 12.5
kg N and higher loads. Hypogymnia spp. decreased over time for all treatments except in 12.5 kg ha -1 , where
it only decreased during the first treatment year and then increased after 2007. The abundance of Platismatia
glauca increased over time, independent of treatment. Our results show that four years of simulated N deposition
caused an alteration of the epiphytic lichen community. As we hypothesized, responses to the treatments
differed among species, reflecting their different N optima. The results indicated that decreased stability of the
lichen thalli, due to altered phytobiont:mycobiont ratio or parasitic fungal attacks, might be causing the decline
of A. sarmentosa, and that competitive interactions were not important for changes in species abundance during
the first four years.
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