The relation between geomorphology and forest community types of the Haut-Saint-Laurent, Quebec

Abstract

The highly disturbed community types of the Haut-Saint-Laurent in southern Quebec were classified using an hierarchic approach with three levels: geomorphology, pedology and vegetation. Considered as distinct entities were, on the one hand, the herbaceous and shrub species that made up ecological groups as defined by Meilleur et al. (1992), and, on the other hand, individual tree species. Great importance was given to geomorphological variables because they are one of the most stable ecological factors of the region. We identified 47 community types from 452 sites sampled, based on a TWINSPAN analysis of the vegetation data. Binary Discriminant Analysis (BDA) showed the importance of disturbance on community composition, especially for sites included in the forest mosaic. Other important abiotic parameters included morphogenic features, topography and drainage. The BDA showed that 24 community types were found to be significantly associated with at least one morphogenic feature. The results indicate that the Beech-Hemlock association is a more stable state for mesic sites than the often cited Sugar Maple with Hickory. On glacial deposits, the presence of Thuja occidental& is significantly associated with grazing practices. The other 23 community types are not significantly associated with any morphogenic features. On one hand, these types tend to be ubiquitous on different deposits with the same drainage class and reveal that their composition was altered through disturbances. On the other hand, some community types are more associated with microclimates as is the case of Sugar Maple with Striped Maple, or with their ecological amplitude limits as is the case of Sugar Maple with Ironwood and Aspen or Sugar Maple with Red Maple and Black Ash. A classification of the stands, given the high number of disturbed communities within the territory, appears difficult to use as a basis for ecological units.

Can plantations develop understory biological and physical attributes of naturally regenerated forests?

“…Naturally established, mature mesic forests in both regions are normally dominated by Acer saccharum in association with Fagus grandifolia, Tilia americana and Ostrya virginiana, and also with Carya cordiformis in the Upper St. Lawrence. Fraxinus americana, A. rubrum, Populus tremuloides and Betula populifolia are found on disturbed sites (Meilleur et al, 1994;Brisson and Bouchard, 2003). Small gaps created by tree senescence are characteristic of the natural disturbance regime in the region, while some large scale disturbances such as ice storm and wind throw are occasional events (Bouchard and Brisson, 1996).…”

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“…Even in the Lower Mississippi River Valley in southeastern Missouri where there are more competing species than further north, native elms were the most frequently recorded floodplain trees after Liquidambar styraciflua in General Land Office Surveys from the 19 th century (Hanberry et al 2012). Before DED arrived, U americana was sometimes also codominant in swamps in northeastern North America often with Fraxinus nigra Marshall and Acer rubrum L., (e.g., Barnes 1976, Meilleur et al 1994. From this literature review we can conclude that before the spread of DED, U. americana was a codominant or even the most dominant canopy tree species in many floodplain forest stands across northeastern North America and westwards along the major rivers of the prairies.…”

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“…Mesic sites are generally dominated by sugar maple, along with bitternut hickory or American beech (Fagus grandifolia Ehrh.). However, an increasing proportion of sites presenting various degrees of disturbance are colonized by red maple, grey birch and trembling aspen (Meilleur et al 1994). …”