Phytocoenotical behaviour of boreal plant species in broadleaved-forest zone communities

Phytocoenotic behaviour of 11 species of boreal vascular plants and mosses is analyzed within the broadleaved-forest zone in comparison with that in different subzones of the boreal-forest zone, based upon the set of 1417 relevés made in European Russia in 1996–2017. The significance of differences in species cover is estimated by means of the one-way ANOVA. The cover of species like Vaccinium myrtillus, V. vitis-idaea, andHylocomium splendens in broadleaved / spruce forests of zonal types is constantly decreasing southwards. On the contrary, the cover of Luzula pilosain Scots pine forests and Pleurozium schreberi and Dicranum polysetum in paludified Norway spruce forests is subject to southward increase. Finally, Oxalis acetosella and Equisetum sylvaticum demonstrate maximae of their cover in forests of zonal types in the southern-boreal and hemiboreal subzones. The dark-coniferous boreal forest “cortege” of species is breaking down into several different floristic elements in the broadleaved-forest zone. These are: “vaccinietal” species p. p. sensu Yu. D. Kleopov (like Vaccinium myrtillus), “quasi-boreal” species sensu V. B. Sochava (Oxalis acetosella, Maianthemum bifolium, Trientalis europaea), hygromesophytes with aged areas (Equisetum sylvaticum), associated species with European-Ancient-Mediterranean nemoral (Luzula pilosa) or East-Asian boreal-montane (Rubus saxatilis) origins. Phytocoenotical behaviour of species is not always different in the intrazonal and the zonal community types but is rather similar in many cases like those of Vaccinium vitis-idaea and Equisetum sylvaticum. The more distinct differences in species positions are found in the extrazonal communities. The statistically proved differences are lacking in phytocoenotical behaviour of Maianthemum bifolium and Trientalis europaea in different zones and subzones due to either florogenetical, or purely methodical reasons, the latter connected with low abundance but high constancy of these species. Disintegration of vegetation “corteges” and individualization of coenotic patterns of species previously growing together are usually observed at the climatically determined (zonal / subzonal or altitudinal) distribution limits.

Seven Ways a Warming Climate Can Kill the Southern Boreal Forest

The southern boreal forests of North America are susceptible to large changes in composition as temperate forests or grasslands may replace them as the climate warms. A number of mechanisms for this have been shown to occur in recent years: (1) Gradual replacement of boreal trees by temperate trees through gap dynamics; (2) Sudden replacement of boreal overstory trees after gradual understory invasion by temperate tree species; (3) Trophic cascades causing delayed invasion by temperate species, followed by moderately sudden change from boreal to temperate forest; (4) Wind and/or hail storms removing large swaths of boreal forest and suddenly releasing temperate understory trees; (4) Compound disturbances: wind and fire combination; (5) Long, warm summers and increased drought stress; (6) Insect infestation due to lack of extreme winter cold; (7) Phenological disturbance, due to early springs, that has the potential to kill enormous swaths of coniferous boreal forest within a few years. Although most models project gradual change from boreal forest to temperate forest or savanna, most of these mechanisms have the capability to transform large swaths (size range tens to millions of square kilometers) of boreal forest to other vegetation types during the 21st century. Therefore, many surprises are likely to occur in the southern boreal forest over the next century, with major impacts on forest productivity, ecosystem services, and wildlife habitat.

Strategic analysis of forest vulnerability to risk related to fire: an example from the coniferous boreal forest of Quebec

As fire is a major disturbance in boreal forests, it is now recognized that it has to be taken into account in forest management planning. Moreover, as the time of exposure to fire is related to stand productivity, combining information on productivity and fire should help in assessing the potential to sustainably manage forests. We present a method to assess potential vulnerability to the risk of fire and illustrate it in the boreal coniferous forest of Quebec. This method takes into account some sources of uncertainty related to the estimation of productivity and fire risk. Spatialization of stand productivity from growth and yield curves allowed us to compute the area comprised of productive stands of each district with or without considering fire risk. Results showed that productive area is generally decreasing with decreasing degree-days, increasing elevation, or in relation to surficial geology. Furthermore, districts with moderate to good productivity were found to be vulnerable to fire when burn rates were greater than 0.333%·year–1. Our innovative approach allowed us to assess the vulnerability of the districts to fire and could be helpful in many regions in the context of a projected increase in future area burned under climate change.

Immediate tree uprooting after retention-felling in a coniferous boreal forest in Fennoscandia

We studied the immediate effects of retention-felling on the occurrence of tree uprooting in two different types of boreal spruce forest in Finland to determine whether susceptibility to uprooting is dependent on the biotope. During the first post-treatment year, 7.1% of the trees in the paludified forest type and 1.8% in the upland forest type were uprooted. During the 2 following post-treatment years, uprooting percentages increased considerably (39.3% in the paludified type and 11.5% in the upland type in year 2; 48.3% in the paludified type and 15.2% in the upland type in year 3). Norway spruce (Picea abies (L.) Karst.), the dominant species in both forest types, was the species most susceptible to uprooting. The high uprooting rate in the paludified groups was probably caused by an interaction between the rocky ground and moist overlying peat layer with the shallow root system of P. abies. As paludified forest biotopes are generally recognized to have high biodiversity, the use of green-tree retention in these biotypes may enhance the continuum and survival of sensitive species. Moreover, because of the high level of uprooting, green-tree retention in paludified forest types can quickly and more naturally help restore levels of coarse woody debris.

Successional pathways on different surficial deposits in the coniferous boreal forest of the Quebec Clay Belt

To infer successional pathways on different surficial deposits in northwestern Quebec, we combined the chronosequence approach to the study of within-stand species' vertical distribution. The deposits sustained different frequencies of postfire stand composition types and successional trajectories. After fire, Picea mariana (Mill.) B.S.P. dominated all stands on organic deposits, while shade-intolerant species dominated the canopy in over 30% and 60% of stands, respectively, on fine- and coarse-textured deposits. In the absence of fire, P. mariana eventually dominates the canopy of all stands on every deposit. However, as the frequency of Larix laricina (DuRoi) K. Koch and Abies balsamea (L.) Mill. in old stands (>100 years) are, respectively, positively and negatively correlated with the deposits' paludification potential, changes in composition in this landscape appear to be driven by the species' tolerance to shade and paludification. Structural changes were characterized by the replacement of closed dense stands by open stands. The diversity of P. mariana stand structures within the youngest age-classes suggests that fire severity may also explain the diversity of stand structures within this landscape. As among-stand structural diversity decreases with increasing time elapsed since fire, converging structural development pathways may be occurring in this landscape.