Long-term vegetation changes in bogs exposed to high atmospheric deposition, aerial liming and climate fluctuation

Abstract

Questions: Is vegetation composition of ombrotrophic bogs with an undisturbed water regime resistant or sensitive to ongoing high atmospheric deposition and climatic changes? Location: The Sudeten Mountains (Czech Republic). Methods: Species composition of bryophytes and vascular plants was sampled in 25 permanent plots in suboceanic bogs of the Jizerské hory Mountains and in 26 permanent plots in subcontinental bogs of the Hrubý Jeseník Mountains. The permanent plots were established and first sampled in 1991. These plots were re‐sampled after 14 and 17 years, respectively. We also used historical vegetation plots (1947–1949; 1980) from the same localities in order to reveal possible changes that might start earlier. Water chemistry was analysed annually, usually three times a year. Compositional changes were analysed by PERMANOVA, β‐diversity changes by PERMDISP and other changes by t‐test and Fisher's exact test. Results: At the community level, no statistically significant changes were detected in permanent plots (PERMANOVA, PERMDISP), either in hollows or in hummocks, but the vegetation composition changed between the oldest (historical) and the newest data sets. At the level of functional groups, cover of Cyperaceae significantly decreased and cover of other herbs (excluding graminoids) and Sphagna increased in the Hrubý Jeseník Mountains, whereas no changes were detected in the Jizerské hory Mountains. Cover of ericoid dwarf shrubs has not changed in either area. At the level of particular species, the frequency of Sphagnum magellanicum, Carex limosa, Scheuchzeria palustris and Vaccinium myrtillus decreased, while the frequency of Straminergon stramineum, Sphagnum recurvum agg., Eriophorum angustifolium and Luzula sylvatica increased. These changes were more evident when recent and historical data were compared. Conclusions: When water regime is not affected, the bog vegetation seems to be rather resistant to high atmospheric deposition and climate fluctuation. A significant change of the species composition occurs only in the long‐term perspective. Particular species could, however, decrease or increase their frequencies more rapidly. For some of these species a positive or negative response to nitrogen availability was also found in other studies, whereas for other species further research is needed in order to separate the effects of atmospheric deposition and internal ecosystem dynamics.

Persistent versus transient tree encroachment of temperate peat bogs: effects of climate warming and drought events

“…The peat bog vegetation proved resilient to transient drought effects despite positive effects of increased tree cover on vascular plant transpiration and N mineralization as well as the negative effects on moss growth under drier and shaded conditions. Vegetation monitoring in some European peat bogs also suggested resilience to drought events (Gunnarsson & Flodin, ; Hajkova et al ., ). Gunnarsson & Flodin () observed reductions in tree cover and increases in Sphagnum cover during 6 years with normal precipitation that followed the dry 1995–1997 period, which suggests recovery after drought events as in our simulations.…”

Influence of Interspecific Competition and Landscape Structure on Spatial Homogenization of Avian Assemblages

“…PERMDISP compares variation in measures of assemblage similarity between groups, with low dispersion indicating more homogeneous assemblages across sites within that group whereas groups with more variable assemblage similarity measures have more heterogeneous avian assemblages, with greater β diversity. PERMDISP has previously been used to analyze various biotic communities such as vegetation communities [35], soil fungal communities [36], soil seed-bank communities [37], and marine benthic communities [38], [39]; although the method appears to have not been used for the analysis of biotic homogenization of avian communities. PERMDISP tests the homogeneity of multivariate dispersions within factor groups based on deviations from the group centroid.…”

Do we need soil moisture measurements in the vegetation–environment studies in wetlands?

“…Conversely, the study of permanent plots in our study area found that the species composition of ombrotrophic bog vegetation is relatively stable, even if environmental conditions, including water level, fluctuate considerably (Hájková et al. ).…”