Holocene dynamics of an eastern hemlock (Tsuga canadensis) forest site at the northern range of the species limit

Abstract

Eastern hemlock (Tsuga canadensis) is a shade-tolerant tree of the temperate conifer-hardwood forests of northeastern North America whose northern limit of distribution coincides with the St Lawrence River around Québec City (Canada). We have analyzed the structure and dynamics of one of the very few old-growth hemlock stands in this area to evaluate its successional status at the Holocene scale. To document the origin and long-term development of the hemlock site, we have used conventional forest surveys and macrofossil analysis of woody debris and charcoal pieces at the soil surface and buried in the mineral soil. The 'Rivière-du-Moulin hemlock forest' is an old-growth forest, at least 1000 years old, whose structure has been rejuvenated by recurrent surface fires killing most plants of the shaded forest floor and facilitating hemlock regeneration. According to the number of fires and the corresponding fire intervals, the hemlock site experienced a sustained fire regime since the mid-Holocene, first in a developmental context of hardwood forests where beech (Fagus), butternut (Juglans), and birch (Betula) were growing, and then for the last 2400-2100 years as conifer forests where hemlock prevailed throughout or during a large part of the period. Our data highlight the influence of fire on the dynamics of hemlockhardwood stands, a forest ecosystem generally viewed as being controlled by local light and medium canopy-gap disturbances. Soil charcoal analysis of conifer-hardwood forests may be used concurrently with canopy-gap analysis to decipher the influence of stand-scale disturbances and to calculate better forest turnover at several time scales.

Lakes cannot burn and buried charcoals cannot fly: Reconciling lake- versus soil-based reconstructions of past forest dynamics

“…As such, SMCA was often selected for inferring ecological histories of small and isolated marginal populations located at the limit of a species range (de Lafontaine et al, 2014;Payette, 2011, 2012;Jules et al, 2018;Dumont et al, 2023;Minchev et al, in prep. ;Mondou Laperrière et al, submitted;Payette et al, 2015Payette et al, , 2017Payette et al, , 2018aPayette et al, , 2018b. Furthermore, it has been seen as complementary to lake sediment proxies because the strengths of one approach might compensate for the weaknesses of another (Gavin et al, 2014).…”

Reconstructed high-resolution forest dynamics and human impacts of the past 2300 years of theParc national de Mont-Orford, southeastern Québec, Canada

“…Lavoie et al (2013) found four major charcoal peaks above background in the most recent 2600 years from a peat bog core at Covey Hill (45°00′29″N, 73°49′36″W -130 km to the west, located in the sugar maple-bitternut hickory forest domain), which corresponds well to Étang Fer-de-Lance. Payette et al (2015Payette et al ( , 2016 dated soil microcharcoal pieces and found that fire has been a part of T. canadensis and Acer stands in the eastern sugar maple-basswood forest domain throughout the last 2000 years. We conclude from our pollen and charcoal records that while fires are a re-occurring part of the Mont-Orford forest landscape, this fire regime likely did not play a major role in vegetation dynamics prior to significant land clearing by European settlers.…”

“…Blarquez et al, 2018;Clark and Royall, 1996;Clifford and Booth, 2013;Lafontaine-Boyer and Gajewski, 2014;Paquette and Gajewski, 2013;Stager et al, 2016), but not in densely-populated southeastern Québec. There has also been limited research determining in situ forest fire dates using macrocharcoal from soils from two sites in the southern mixed forest of Québec (Payette et al, 2015(Payette et al, , 2016. Given the many forest types of southern Québec (Ressources Naturelles Québec, 2003), there is a need for continuous high-resolution lacustrine paleo-fire studies from each forest type to better understand the natural fire-vegetation relationship, which can only be studied using paleo-methods because of modern fire suppression.…”

Anthropogenic Disturbances Create a New Vegetation Toposequence in the Gatineau River Valley, Quebec

“…While hemlock is today associated with maple, during the period in which this landscape was originally surveyed, it was associated with white pine. A recent study showed that this type of association dominated by long-lived trees that have self-pruning stems and a thick bark was able to evolve following a regime of recurrent surface fires [63].…”