Reborn from fire: the history of subalpine grasslands in the Central European mountain range

Biodiversity of subalpine grasslands in European mountain ranges is threatened by land-use changes, forest encroachment and climate warming, raising questions about which ecosystem states should be maintained or restored. Addressing biodiversity loss requires long-term evidence on the past dynamic and drivers of treeless vegetation above the timberline. Using a high-resolution, multi-proxy record from the peat bog in Eastern Sudetes, this study reconstructs Late-Holocene dynamics of subalpine vegetation, fire regimes and peat bog development from 800 BC to the present, and relates them to historical land use and climate. The results show that extensive subalpine grasslands already existed in the Iron Age, before significant human influence, indicating a long-term persistence of natural alpine vegetation. A major charcoal layer around 730 AD marks an extensive fire that triggered the onset of peat accumulation distinct after evapotranspiration decrease. From the High Middle Ages, repeated burning and grazing above the timberline drove the expansion of grasslands and a peak in exceptional fire frequency in the 16th–17th centuries. Peat bog vegetation and geochemical proxies indicate a generally stable environment with distinct wet phases aligned with cool, pluvial episodes of the Little Ice Age and recent drying coupled with dwarf-shrub expansion. The findings demonstrate that long-term development of subalpine grasslands in the Eastern Sudetes results from interactions among climate, fire and pastoralism, and suggest that prescribed burning combined with other types of active management may be needed to sustain these communities under ongoing climate change.