The two sessions of S10 presented a wonderful synopsis of the current state of long-term biodiversity monitoring in mountains across the major biomes from the tropics to the subarctic. It combined new results out of the global GLORIA network that commenced at the beginning of the century with longer timelines of approaches dealing with revisitations of historical study sites dating back to more than 50 to almost 200 years. Fifteen presentations showed a broad spectrum of studies in the well-attended sessions. Enthusiastic and stimulating discussions followed the presentations throughout.
A pan-European GLORIA study, presented by Klaus Steinbauer, showed significant differences in both vascular plant species diversity as well as temperature sums among aspects, being most apparent in the temperate biome and most striking between eastern and western slopes. The study, based on 123 summit sites, is the largest so far on aspect differences in alpine environments. A subset of sites with resurvey data, further, showed that the highest species turnover during the past decade coincided with the warmest slopes. This suggests that processes of species colonization as well as disappearance run at faster rates under warmer conditions.
Stephan Halloy presented the first continental-scale study (Cuesta et al.) of Andean tropical alpine flora, based on 50 GLORIA summit sites (with elevations ranging from 3250 to almost 5500m) distributed from northern Argentina to Venezuela. Data collected through a standardized sampling design remarkably showed pronounced differences in species composition between the Puna and Páramo biomes and among their regional subgroups. Both geographical proximity as well as environmental variables defining the habitat conditions were explaining the differences in biodiversity patterns.
Historical data sets and observation sites are invaluable for assessing longer-term changes associated with global climate warming. Unfortunately, such data are not or hardly available in many mountain regions on a global level. The long research tradition in the European Alps, however, left a rich legacy. Sonja Wipf et al. were resurveying an impressing number of 124 historical sites in Switzerland and initiated a Europe-wide revisitation-initiative. Species richness was strongly increasing over the past century through upward shifts of range limits, a process that was clearly accelerating during the past decades. Comparisons with historical sites in the Slovak Tatry mountains, as shown by Robert Kanka, yield in principal consistent results, however, with striking declines in some genera such as Hieracium. Results from historical sites in the Pyrenees, presented by Christian Rixen, also indicate an overall increase in species numbers which was followed by a concurrent floristic homogenization. Further, summits with a higher frequency of visitors showed a smaller increase in species numbers.
Jan Salick and Robbie Hart showed the first resurvey comparison based on the remarkable setting of GLORIA summit sites ranging from the central to the eastern Himalaya system. Alpine summit sites between 4000 and 5000m a.s.l. were especially rich in species and exposed to adversely wet conditions during most of the growing season. The first repeat surveys were conducted in Hengduan Shan, the eastern part of the vast mountain system and showed a rapid increase in species richness as well as in community composition, being most apparent on southern exposures. Changes involved many species restricted to the mountain system. The rate of species shift, however, appeared to be too low to keep pace with the rate of global warming in the region.
A study dealing with biodiversity changes on GLORIA sites and LTER sites in glacier foreland and plots with grazing exclosures in alpine grassland and dwarf shrub heath in the Tyrolean Alps was presented by Brigitta Erschbamer. Grazing exclusion showed a decrease in species numbers and frequency, contrary to the other sites. A thermophilization trend is indicated by an increase in Landolt temperature indicator values. Strikingly, floristic changes were unexpectedly high in dwarf shrub communities as well as in habitats of the subnival zone.
Continued in Session 8.