Subfossil trees from Sweden – a Holocene archive of climate, hydrology, and ecosystem change: review and new perspectives

Subfossil trees preserved in lakes, peatlands, and submerged coastal environments represent one of the most valuable high-resolution archives for reconstructing Holocene climate and environmental variability. Sweden hosts an exceptional diversity of such archives, spanning from subalpine lake systems in northern Lapland to raised bogs and submerged Baltic landscapes in the south, yet no comprehensive synthesis of Swedish subfossil dendrochronological research has previously been undertaken. We reviewed the published dendrochronological literature on subfossil trees from Sweden and adjacent Fennoscandian regions, focusing on studies that employed tree-ring analysis to reconstruct past climate, hydrology, or ecological change. Electronic database searches were supplemented by screening of reference lists in key publications. Studies were evaluated with respect to species, depositional environment, geographic location, chronology length, and principal environmental signal. Swedish subfossil archives are dominated by Scots pine (Pinus sylvestris), with additional contributions from oak (Quercus spp.) and Norway spruce (Picea abies). Existing chronologies span much of the mid- to late-Holocene, with the longest records extending back approximately 8,000 years. These archives have yielded important reconstructions of summer temperature variability, peatland hydrology, and moisture dynamics, and show statistical coherence in several cases with chronologies from Germany, Denmark, Finland, and the British Isles, underlining their value for pan-European palaeoclimate networks. Nevertheless, significant temporal and geographic gaps remain, particularly for the early Holocene. Emerging methodological approaches – including blue intensity measurement, stable isotope analysis, wood anatomy, and machine-learning-assisted ring detection – offer promising possibilities for expanding both the spatial coverage and climatic interpretability of Swedish subfossil archives.