Can we expect pristine mountain peatland ecosystems in Central Europe? Evidence from multi-proxy palaeoecological studies on the Holocene peatland development

The Holocene climate shifts had a significant impact on the development of ombrotrophic peatland ecosystems located in various biogeographic zones. Disturbances of the plant communities at peatlands ecosystems took place also due to intensified human activities in the past several centuries, that include peat excavation, fires, as well as deposition of dust and pollutants on peatland surfaces. This merger of natural and human impacts has led to direct hydrological and biochemical disturbances that triggered changes in plant populations, e.g. often leading to the decline of some species, such as Sphagnum austinii in Great Britain.

The knowledge about the development of peatlands across mountain ranges in Europe is still poor. Determining the resilience of peatland vegetation to disturbance is an important and significant task to aid further protection and management of the entire range of ombrotrophic peatlands found in the European mountains, from destroyed or restored to pristine. We carried out high-resolution, multi-proxy studies including plant macrofossils, pollen, testate amoebae, geochemical analyses (XRF and stable carbon isotopes), micro- and macro-charcoal, supported by radiocarbon dating, on replicate peat cores from five well-preserved ombrotrophic peatlands across Europe where peat-forming process is active. The studied peatlands are located along an east west gradient in the Central and Western Europe: Eastern Carpathian Mts. (Calimani-Gurghiu-Harghita, Romania; Bieszczady, Poland), Harz Mts. and Schwarzwald Mts. (Germany), and Vosges Mts (France). In our palaeocological studies we aimed to: i) reconstruct long-term local (mainly Sphagnum populations) and regional (forest communities) vegetation changes at and around selected bogs; ii) reconstruct long-term palaeohydrological shifts; iii) assess mountain peatland ecosystems resilience to Holocene climate shifts and disturbance by fire events and human impact (deforestation, dust and pollution).

Based on our results, we found that: i) despite human activites (pollutants and dust deposition, drainage) some of the mountain peatlands remained in a pristine state, however some plant communities had changed; ii) plant communities composed mainly by Sphagnum species, could repeatedly self-regenerate via autogenic processes following a decline in stressors; iii) recent climate warming has stimulated the spreading of some species indicative of more dry habitats; vi) lack of macrocharcoal in the peat layers indicate that fires did not play a significant role in the development or evolution of local peatland communities. Results from our studies show that palaeoecological records play an important role for the determination of present peatland ecosystem stage and reference conditions for the restoration of damaged ombrotrophic peatlands in European mountains.

The research has received support National Science Centre (Poland) grant No UMO-2016/23/B/ST10/00762 (PI: Mariusz Gałka).