Warming and nitrogen addition effects on bryophytes are species- and plant community-specific on the eastern slope of the Tibetan Plateau

QuestionGlobal 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. LocationEastern slope of the Tibetan Plateau. MethodsWe established a warming by N deposition experiment, using a 2x2 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. ResultsBryophyte 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. ConclusionsEffects 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 deposition may affect ecosystem processes.