A lake-bog succession vs. climate changes from 13,300 to 5900Â cal. BP in NE Poland in the light of palaeobotanical and geochemical proxies

This paper presents and discusses the influence of climatic and edaphic factors on vegetation succession of the postglacial Lake Czarne (LC) located in NE Poland. On the basis of pollen, macroscopic plant remains, non-pollen palynomorphs (NPPs), and geochemical analyses, we reconstructed the transition from a clear oligotrophic lake to an ombrotrophic mire from 13,300 to 5900 cal. BP. Climatic events/periods that may have affected the lake/mire succession were as follows: (i) relatively warm conditions in the younger part of the Younger Dryas (ca. 12,220 cal. BP) that led to water eutrophication recorded as blooms of Scenedesmus ellipticus, whose response preceded that of woodland vegetation by ca. 200 years, (ii) the warming of the Late Glacial-Holocene transition and early Holocene that caused the final melting of dead ice block(s) and led to the deepening of the water body and/or an increase in the water level, the retreat of submerged macrophytes, and the enrichment of waters with sulphur, (iii) the global cold period between 8600 and 8000 cal. BP that contributed to a rise in the water level during the phase of sedge swamp and enabled the reappearance of Nymphaeaceae and blooms of S. ellipticus (ca. 8570-8500 cal. BP), and (iv) the global climate cooling 6500-5900 cal. BP that still remains enigmatic in terms of palaeobotanical patterns; however, geochemical markers point to an increase in the water level and enhanced erosion in the LC catchment ca. 6200-6000 cal. BP. Lake terrestrialization resulted in the concurrent appearance of microhabitats suitable for mosses with contrasting ecological preferences, e.g., Warnstorfia exannulata (acidic) and Scorpidium revolvens (alkaline), or Straminergon stramineum (acidic), Meesia triquetra (alkaline) and S. revolvens (alkaline).