Holocene vegetation history of the Jeseníky Mts: Deepening elevational contrast in pollen assemblages since late prehistory
2018
Dudová, Lydie | Hájek, Michal | Petr, Libor | Jankovská, Vlasta
QUESTIONS: How did the vegetation of a Central European mountain region with a fragmented alpine zone develop during the Holocene? When did human land use start to alter summit grasslands? Which gradient in pollen assemblages was strongest and was it consistent through time? LOCATION: Jeseníky Mountains, Czech Republic. METHODS: Sixteen pollen records were subjected to DCA in order to explore patterns of compositional similarities in the fossil pollen data. Because only the last 6,000 years were recorded in the study sites from mountain summits, we restricted further analysis to this period. Twelve radiocarbon‐dated pollen records were subjected to DCCA constrained by modelled calibrated age. Responses of individual pollen types to the principal DCCA gradients were tested with GAMs. RESULTS: In the DCA, Early Holocene samples were located close to recent ones due to abundant pollen of herbs, Poaceae, Betula, Pinus sylvestris type and rare pollen of climax deciduous trees. In the DCCA for the last 6,000 years, the sorting of sites along the first unconstrained axis correlated with altitude, which is a complex factor corresponding to temperature and geomorphology (flat summits vs alluvia of mountain rivulets). This elevational differentiation became more pronounced after 2,250 cal BP when summit peatlands started to contain more Vaccinium, Calluna vulgaris, Amaranthaceae, Plantago lanceolata and Rumex acetosa type pollen. In contrast, mid‐elevation pollen spectra started to contain more meadow herbs (Caltha, Potentilla type, Cirsium/Carduus). Picea pollen was surprisingly more associated with mid‐elevation than high‐elevation sites, unlike Fagus. CONCLUSION: Increasing contrast between summits and middle elevation alluvia seems to be a major feature of vegetation development over the last 6,000 years. While alluvial areas were encroached by Alnus–Picea forests, and later locally transformed into wet grasslands, grazing and forest burning at summits gradually increased abundance of acidophytic dwarf shrubs and peatlands, especially since the Iron Age. Human impact might facilitate beech expansion at high elevations, with Picea‐dominated forests being restricted to alluvia and around mid‐elevation basin peatlands prior to establishment of modern Picea plantations.
显示更多 [+] 显示较少 [-]