Question: Global change is likely to strongly affect alpine and sub-alpine
regions, in which bryophytes are important components. Global change effects
on sub-alpine vegetation, bryophytes in particular, however, have been
addressed in few studies. We ask if global warming and increased nitrogen (N)
deposition, two of the most important components of global change, will have
different effects on bryophyte communities and species in sub-alpine coniferous
and shrubland ecosystems.
Location: Eastern slope of the Tibetan Plateau.
Methods: We established a warming by N deposition experiment, using a
2 9 2 factorial design, replicated three times, in each of two sub-alpine ecosystems.
Effects on bryophytes at the community and species levels were evaluated
after 4 (shrubland) and 5 (coniferous forest) years of warming and N deposition
treatments.
Results: Bryophyte cover increased in the first two growing seasons and thereafter
decreased until the end of the experiment in all treatments, most strongly
in warming plots in both ecosystems and in N deposition plots in the coniferous
forest. At the species level, the pleurocarpous bryophyte Pleurozium schreberi was
resilient to warming but sensitive to N deposition, while the acrocarpous bryophytes
Rhizomnium tuomikoskii and Racomitrium japonicum were resilient to N
addition but sensitive to warming.
Conclusions: Effects of warming and increased N deposition on bryophytes
were species- and to some extent also ecosystem-specific in the experiment in
the sub-alpine region, indicating that bryophytes do not respond to global
change as one single functional group. The observed species replacements in
response to warming and N depositionmay affect ecosystemprocesses.