The southernmost spruce–lichen woodlands in the Parc des Grands‐Jardins, Québec, Canada, are situated 500 km south of their usual range in the northern lichen woodland zone. Their co‐occurrence within a spruce–moss forest matrix suggests the existence of alternative stable states. We investigate the possibility of these spruce–lichen woodlands as an alternative stable state along with the factors contributing to their origin and spatiotemporal distribution. Analysis of plant macrofossils, charcoal, head capsules of defoliating insects, and pollen were used along with vegetation surveys to reconstruct the past and present disturbance dynamics along an east–west transect, corresponding to a precipitation and fire frequency gradient. At each site, spruce budworm head capsules were found preceding the charcoal layer delineating the shift to spruce–lichen woodland, demonstrating the compound disturbance (insect–fire) origin of the lichen woodlands. Moss forests previously occupied all lichen woodland sites, with the oldest record starting ca. 8300–9400 yr BP. A change to a higher fire frequency around 2500 yr BP was evident in the lichen woodland zone of the park. A lower fire frequency west of the lichen woodland zone likely is a result of orographic precipitation. While the spruce budworm affects the entire region, lichen woodlands are found exclusively within an increased fire frequency zone. Thus, it is the superimposition of these two disturbance factors that is responsible both for their creation and spatial distribution. Lichen woodland inception dates range between 580 and 1440 yr BP, demonstrating that these lichen woodlands have maintained their open structure with time and have not transformed into closed forests. Their persistence, along with their previous moss forest histories and current occurrence adjacent to closed moss forests, indicate that they are an alternative stable state to the spruce–moss forests and not a successional stage. In contrast to other examples of reported alternative stable states, this one is a result of natural disturbances inherent to the system and not anthropogenic impacts.

A 3.86 m core of peat and organic lake mud from a polygonal peatland in the Lena River valley of Siberia was radiocarbon dated and analyzed for pollen, plant macrofossils, chrysophyte stomatocysts, stable isotopes, and charcoal. At around 7200 BP, a shallow lake or open-water wetland supported diverse aquatic macrophytes. The site had transformed initially into a richer fen with Carex, Comarum palustris, and Drepanocladus and later a poorer fen with Sphagnum which persisted until around 3000 BP. Fire may have been responsible for silt being blown onto the peatland, which changed the hydrological and geochemical conditions for development of the poor fen. Ice accretion led to an increase in the height of the centre of the polygon and expansion of Sphagnum peatland . 18O values become progressively more enriched, which reflects more direct input of summer precipitation waters and less groundwater during this period. Finally, the peatland surface was elevated sufficiently to limit water and nutrient supply, thereby allowing Ericaceae and Betula to grow at the coring site. Fire burned the peatland surface and may have exaggerated the extremely slow rate of peat accumulation. Fire may also be a factor in maintaining the open Larix dahurica forest in the region today, while climate may be contributing to reducing postfire regeneration. Fire and climate together may be controlling the character and composition of forests near tree line in the Lena River valley of this part of Siberia.

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Holocene occurrences of conifer needle endophytes have not previously been reported. We report the fossil remains ofLophodermium piceae(Fckl.) Hoehn., a fungal endophyte of black spruce (Picea mariana(Mill.) B.S.P.) needles, in macrofossils dating back to 8000 cal yr BP. Spruce budworm head capsules andL. piceaeremains were found preceding charcoal layers delineating the transformation of four spruce−moss forest sites to spruce−lichen woodland. AsL. piceaeis found solely on senescent needles, its increased presence during these transformation periods likely indicates that the forests were in decline due to the spruce budworm (Choristoneura fumiferana(Clem.)) when they burned. Future paleoecological studies incorporating needle fungi observations could be used to investigate the historical occurrence of tree disease and the role of fungi in forest health and decline.

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