by Audrey Verreault | 21 October 2024
Published in Environmental Reviews 30(2): 8. https://doi.org/10.1139/er-2021-0074
Over the past few decades there has been increasing concern that boreal forests could convert from a carbon sink to a carbon source, thus accentuating the effects of climate change. Although forest fires are generally regarded as mainly responsible for causing boreal forests to transition to a carbon source, other factors, such as the activity of exotic earthworm species, could also play an important role. Invasive and exotic species of earthworm can affect nutrient cycling, biodiversity, and forest dynamics. In this context, greater knowledge of the distribution of exotic species of earthworm could help researchers to understand the likely changes in the ecosystems that they have colonized. Herein, we report the results of an exhaustive literature review of the presence of exotic species of earthworm in the Canadian boreal forest and taiga zones. We identified 230 sectors containing 14 earthworm species (11 exotic, two native, and one putative native) in six provinces and three territories across Canada’s boreal forest and taiga zone. We also report 23 as-yet unpublished observations from the province of Quebec. We noted the presence of earthworms in environments (acid soils, harsh climate) that were historically considered inadequate for their survival. This suggests that the portion of Canada’s boreal forests suitable for the presence or colonization of exotic species of earthworm is larger than was previously believed. This study represents the first compilation of locations with exotic species of earthworm in this large northern area. Factors that could affect their distribution and potential effects on boreal ecosystems are also discussed. We also report that several earthworm species seem to be overcoming the previously assumed limitations of temperature and soil pH.
by Audrey Verreault | 10 September 2024
Published in Agricultural and Forest Meteorology 358: 110219. https://doi.org/10.1016/j.agrformet.2024.110219
Large-scale modes of climate variability influence forest fire activity and may modulate the future patterns of natural disturbances. We studied the effects of long-term changes in climate upon the fire regime in the red pine forests of eastern North America using (a) a network of sites with dendrochronological reconstructions of fire histories over 1700–1900 A.D., (b) reconstructed chronologies of climate indices (1700–1900), and (c) 20th century observational records of climate indices, local surface climate and fire (1950s-2021). We hypothesized that (H1) there are states of atmospheric circulation that are consistently associated with increased fire activity, (H2) these states mark periods of increased climatological fire hazard, and (H3) the observed decline in fire activity in the 20th century is associated with a long-term decline in the frequency of fire-prone states. At the annual scale, years with significantly higher fire activity in the reconstructed and modern fire records were consistently associated with the positive phases of the Pacific North American pattern (PNA), either independently or in combination with the positive phase of the El Niño-Southern Oscillation index (ENSO). During years with both ENSO and PNA in their positive state, the region experienced positive mid-tropospheric heights and temperature anomalies resulting in drought conditions. The fire-prone climate states identified in the reconstructed records became less frequent in 1850 but re-emerged in the 20th century. While our study did not demonstrate a direct influence of climate on the observed decrease in fire activity in the 20th century, it does reveal a clear climate signal embedded within the fire history reconstruction of the region over the past centuries. This study underscores the importance of considering large-scale climatic patterns in understanding historical fire regimes and highlights their role for future fire dynamics in the region and shaping ecological effects of future fires.
by Claire Morin | 9 September 2024
This document outlines the threats facing this species, which is likely to be designated as threatened or vulnerable in Quebec, and presents the actions that the Ministry intends to pursue and undertake with its collaborators to halt the species’ decline over the coming years.
by Audrey Verreault | 30 August 2024
Published in Canadian Journal of Forest Research (e-First). https://doi.org/10.1139/cjfr-2024-0009
Commercial thinning is a silvicultural treatment that has been practiced for centuries in Europe. However, in Eastern Canada, its application to naturally regenerated stands is much more recent, and long-term monitoring of this treatment realized in an operational context is rare. We monitored 135 paired sample plots (thinned and control) over a 20-year period. The plots are in stands dominated by either black spruce (Picea mariana (Mill.) B.S.P.), jack pine (Pinus banksiana Lamb.), or balsam fir (Abies balsamea (L.) Mill.) and distributed throughout the boreal and temperate forests of Québec (Canada). Twenty years after treatment, thinning increased quadratic mean diameter (QMD) for balsam fir (1.7 cm) and jack pine (0.7 cm), while for black spruce the change in QMD varied according to the QMD before treatment. Periodic annual increment in gross merchantable volume of thinned and control plots was similar for balsam fir and jack pine but was less in thinned black spruce plots during the first 5 years. Thinning did not affect mortality, which remained low until 15 years after treatment. As commercial thinning should gain popularity over the next years, our study provides a benchmark of the expected effects when the treatment is performed in an operational context.
by Audrey Verreault | 20 August 2024
Published in The Forestry Chronicle 100(2): 1-12. https://doi.org/10.5558/tfc2024-023
Repeated diameter-limit cutting in mixedwood forests often leads to altered stand composition, quality, and regeneration, hence decreasing productivity and value over time. We studied the evolution of stand characteristics after diameter-limit cutting on a 15-year period, beginning from 11 to 43 years after cutting. We used 415 sample plots (200 m2) and three criteria: (i) ≥9.0 m2/ha overstory (trees ≥9.1 cm dbh [diameter at breast height, 1.3 m above ground]) acceptable growing stock (AGS, i.e. basal area of vigorous trees with sawlog potential), (ii) ≥3.0 m2/ha pole timber AGS (9.1 cm-23.0 cm dbh) and (iii) ≥60% sapling (dbh 1.1-9.0 cm) stocking of desired species. Stand initial quality was determined in function of overstory AGS at the beginning of the monitoring period: good quality (AGS≥9.0 m2/ha), impoverished (7.0≤AGS< 9.0 m2/ha), degraded (AGS <7.0 m2/ha). After 15 years, 47% of stands satisfied at least two criteria, but most stands (65%) had insufficient sapling regeneration. Stands in good quality and impoverished categories had sufficient basal area and AGS to support a new partial cutting cycle, contrary to stands in the degraded category. A conceptual model based on these three criteria is presented to guide silvicultural rehabilitation of uneven-aged mixedwood stands altered by past cutting practices.
