The Eemian (the Last Interglacial; ca. 129–116 thousand years ago) presents a testbed for assessing environmental responses and climate feedbacks under warmer-than-present boundary conditions. However, climate syntheses for the Eemian remain hampered by lack of data from the high-latitude land areas, masking the climate response and feedbacks in the Arctic. Here we present a high-resolution (sub-centennial) record of Eemian palaeoclimate from northern Finland, with multi-model reconstructions for July and January air temperature. In contrast with the mid-latitudes of Europe, our data show decoupled seasonal trends with falling July and rising January temperatures over the Eemian, due to orbital and oceanic forcings. This leads to an oceanic Late-Eemian climate, consistent with an earlier hypothesis of glacial inception in Europe. The interglacial is further intersected by two strong cooling and drying events. These abrupt events parallel shifts in marine proxy data, linked to disturbances in the North Atlantic oceanic circulation regime.

Fossil pollen, conifer stomata, and charcoal records for the last 10,000 years were studied from three small hollow sites (Larix Hollow, Mosquito Hollow,\ud and Olga Hollow) located at the modern western range limit of Siberian larch (Larix sibirica) in northwestern Russia to investigate the role of forest fires\ud in stand-scale dynamics of taiga vegetation. Wavelet coherence analysis was utilized to reveal the significance of fire on the vegetation composition at\ud different timescales by assessing the phase and strength of the relationship between forest fires and most common boreal tree taxa in a time–frequency\ud window. Pollen and stomata data show that all of the modern-day common tree taxa, including Norway spruce (Picea abies) and Siberian larch, have been\ud present in the study region since the early Holocene. The absence of charcoal layers at Mosquito Hollow suggests that this site has acted as a fire-free\ud refugium with continuous dominance of spruce throughout the Holocene. Meanwhile, the Larix Hollow record indicates frequent local fire events and as\ud a consequence, a more variable tree species composition. The wavelet coherence results show that the impact of forest fires on vegetation varies from\ud short-term (<200-year periods) changes in individual tree taxa to long-term (400–800 years) changes in forest composition, such as the expansion of\ud spruce population after local high-intensity fires around 7500–7000 cal. yr BP and the increase in abundance of birch and alder during periods of high fire\ud frequency. Our results suggest that Holocene fire histories can be markedly different within a small geographical area, demonstrating the importance of\ud site-specific factors in the local fire regime in the unmanaged taiga forest

In 1927, the first pollen diagram was published from the Bohemian/Bavarian Forest region of Central Europe, providing one of the first qualitative views of the long-term vegetation development in the region. Since then significant methodological advances in quantitative approaches such as pollen influx and pollen-based vegetation models (e.g., Landscape Reconstruction Algorithm, LRA) have contributed to enhance our understanding of temporal and spatial ecology. These types of quantitative reconstructions are fundamental for conservation and restoration ecology because they provide long-term perspectives on ecosystem functioning. In the Bohemian/Bavarian Forests, forest managers have a goal to restore the original forest composition at mid-elevation forests, yet they rely on natural potential vegetation maps that do not take into account long-term vegetation dynamics. Here we reconstruct the Holocene history of forest composition and discuss the implications the LRA has for regional forest management and conservation. Two newly analyzed pollen records from Prášilské jezero and Rachelsee were compared to 10 regional peat bogs/mires and two other regional lakes to reconstruct total land-cover abundance at both the regional- and local-scales. The results demonstrate that spruce has been the dominant canopy cover across the region for the past 9,000 years at both high- (>900 m) and mid-elevations (>700–900 m). At the regional-scale inferred from lake records, spruce has comprised an average of ~50% of the total forest canopy; whereas at the more local-scale at mid-elevations, spruce formed ~59%. Beech established ~6,000 cal. years BP while fir established later around 5,500 cal. years BP. Beech and fir growing at mid-elevations reached a maximum land-cover abundance of 24% and 13% roughly 1,000 years ago. Over the past 500 years spruce has comprised ~47% land-cover, while beech and fir comprised ~8% and <5% at mid-elevations. This approach argues for the “natural” development of spruce and fir locally in zones where the paleoecology indicates the persistence of these species for millennia. Contrasting local and regional reconstructions of forest canopy cover points to a patchwork mosaic with local variability in the dominant taxa. Incorporation of paleoecological data in dialogues about biodiversity and ecosystem management is an approach that has wider utility.

Fire disturbance is considered paramount for regeneration and biodiversity in the boreal forest with prescribed\ud burning widely advocated in present day forest management. Palaeoecological knowledge is beneficial\ud in understanding the role of fire as a driver of past vegetation dynamics. We use a sedimentary\ud pollen and charcoal record to reconstruct 5000 years of fire and vegetation history from a small forest\ud hollow (approximate area 12 m2) in the Vesijako Strict Nature Reserve, currently one of the few remaining\ud old-growth forest stands in southern Finland. Results indicate three distinct periods in the environmental\ud history (1) 5000–2000 cal. yrs. BP; semi-natural low frequency (430 year return period), low\ud intensity fires in a diverse mixed stand with little evidence of anthropogenic disturbance and an expanding\ud Picea abies (Norway spruce) population (2) 2000–750 cal. yrs. BP; anthropogenic-driven high frequency\ud (180 year return period), high intensity stand-replacing fires in a low diversity stand with\ud evidence of slash and burn cultivation and a decline of Picea population, (3) 750 cal. yrs. BP to present\ud day; fire absence through a reduction in human-induced fire or active fire suppression and the expansion\ud of the currently dominant Picea forest. The changing fire frequency has had a major influence on the forest\ud composition during the last 5000 years. The loss of floristic diversity is associated with an increase in\ud the human use of fire and without this human interference the previously high biodiversity in the stand\ud may have remained up until the present day. If fire remains absent in Vesijako then it is likely that the\ud Picea population will continue to dominate in the stand supporting a negative feedback mechanism that\ud will result in lower frequency, higher intensity fires in the future

Questions We investigated the changing role of climate, forest fires and human population size in the broad‐scale compositional changes in Holocene vegetation dynamics before and after the onset of farming in Sweden (at 6,000 cal yr BP) and in Finland (at 4,000 cal yr BP). Location Southern and central Sweden, SW and SE Finland. Methods Holocene regional plant abundances were reconstructed using the REVEALS model on selected fossil pollen records from lakes. The relative importance of climate, fires and human population size on changes in vegetation composition was assessed using variation partitioning. Past climate variable was derived from the LOVECLIM climate model. Fire variable was reconstructed from sedimentary charcoal records. Estimated trend in human population size was based on the temporal distribution of archaeological radiocarbon dates. Results Climate explains the highest proportion of variation in vegetation composition during the whole study period in Sweden (10,000–4,000 cal yr BP) and in Finland (10,000–1,000 cal yr BP), and during the pre‐agricultural period. In general, fires explain a relatively low proportion of variation. Human population size has significant effect on vegetation dynamics after the onset of farming and explains the highest variation in vegetation in S Sweden and SW Finland. Conclusions Mesolithic hunter‐gatherer populations did not significantly affect vegetation composition in Fennoscandia, and climate was the main driver of changes at that time. Agricultural communities, however, had greater effect on vegetation dynamics, and the role of human population size became a more important factor during the late Holocene. Our results demonstrate that climate can be considered the main driver of long‐term vegetation dynamics in Fennoscandia. However, in some regions the influence of human population size on Holocene vegetation changes exceeded that of climate and has a longevity dating to the early Neolithic.

We report pollen‐stratigraphical evidence for an abrupt, episodic and widespread population decline of alder (Alnus), one of the most common boreal tree genera, during the medieval period in northern Europe. Decline of alder pollen values was observed both in forest hollow pollen records reflecting local vegetation of pristine forests and in pollen percentage and pollen accumulation data from lake sediments. The event began roughly at AD 600 and the recovery took place at AD 1000. Human impact is an unlikely cause because the decline is specific to alder and there is no evidence for a concurrent episode of human impact. It is possible that the decline was caused or influenced by a severe drought. Another potential cause is a sudden, widespread pathogen outbreak, especially as alder is known to be sensitive to the impacts of fungal pathogens such as the oomycete Phytophthora.

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The relative importance of climate, forest fires and human population size on long‐term boreal forest composition were statistically investigated at regional and local scales in Fennoscandia. We employ pollen data from lakes, reflecting regional vegetation, and small forest hollows, reflecting local vegetation, from Russia, Finland and Sweden to reconstruct the long‐term forest composition. As potential drivers of the Holocene forest dynamics we consider climate, generated from a climate model and oxygen isotope data, past forest fires generated from sedimentary charcoal data and human population size derived from radiocarbon dated archaeological findings. We apply the statistical method of variation partitioning to assess the relative importance of these environmental variables on long‐term boreal forest composition. The results show that climate is the main driver of the changes in Holocene boreal forest composition at the regional scale. However, at the local scale the role of climate is relatively small. In general, the importance of forest fires is low both at regional and local scales. The fact that both climate and forest fires explain relatively small proportions of variation in long‐term boreal vegetation in small forest hollow records demonstrates the complexity of factors affecting stand‐scale forest dynamics. The relative importance of human population size was low in both the prehistorical and the historical time periods. However, this is the first time that this type of data has been used to statistically assess the importance of human population size on boreal vegetation and the spatial representativeness of the data may cause bias to the analysis.