by Audrey Verreault | 30 January 2019
Published in Phytoprotection 90: 117-120
A trial involving the mass propagation of Argania spinosa cuttings was established following two protocols: in mini-bouturathèques without mist and in a greenhouse under mist. Symptoms of petiole necrosis, foliar yellowing and abundant black acervuli were observed under both protocols. These symptoms were responsible for a 90% mortality rate in the mini-bouturathèques while under the mist treatment premature fatal necrosis of the apical buds resulted in 100% mortality. The disease’s causal agent, Pestalotiopsis clavispora, was identified on the basis of its morphological characteristics and by molecular analysis. Alternating weekly teatments of systemic and contact fungicides resulted in a 41% success rate in controlling this pathogen, described for the first time on argan cuttings.
by Marie-Claude Boileau | 30 January 2019
Published in Canadian Journal of Forest Research 40: 894-903
We present the effects, 10 years after treatment, of different cutting intensities (removal of 0%, 35%, 50%, 65%, and 100% of basal area (BA)) on the response of residual trees in a 60-year-old mixed aspen–conifer stand in Québec, Canada. While decennial mortality reached 170 stems.ha–1 under natural conditions (control, 24 m2.ha–1 BA), the removal of mature trembling aspen (Populus tremuloides Michx.) trees reduced hardwood losses to 125, 105, and 0 stems.ha–1, respectively, in the 35%, 50%, and 65% cuttings, without affecting losses of coniferous species (<25 stems.ha–1). The growth response of conifers was generally higher than that of broad-leaved species. For hardwoods, the decennial gains in merchantable BA decreased with respect to the control (3.2 m2.ha–1), to 1.2 m2.ha–1 in the 35% cut and to 0.9 m2.ha–1 in the 50% cut, but increased under the 65% cut (2.5 m2.ha–1). For conifers, gains were proportional to removal in partial cuts (2.6–4.9 m2.ha–1) and lower in the control (1.7 m2.ha–1). As a whole, our results suggest that partial cutting may be an effective means of increasing growth of the softwood proportion occupying the intermediate and suppressed strata in a mixed aspen-dominated stand.
by Audrey Verreault | 30 January 2019
Published in American Midland Naturalist 163(1): 95-105
Eastern red-backed salamander (Plethodon cinereus, RBS), known to be one of the most common vertebrates within its geographical range, is an amphibian species commonly used as indicator of forest ecosystem health. Its suitability in this role is based in part on previous studies showing that it is sensitive to changes in habitat such as increased acidity. The occurrence and body sizes of RBS were examined under coverboards, over a 5 y period, in a northern hardwood forest of Québec (Canada) having a highly acidic forest floor (pH = 3.7 ± 0.4). During this period, 565 RBS were captured. Encounter rate (29%) of salamanders under coverboards was considered very high, as compared to similar studies. Also, 87% of youngs of the year and 83% of adults were found under coverboards that had a forest floor pH £ 3.8, representing 79% of all coverboards. Weight and length of RBS measured in this forest ecosystem are among the highest values reported in the scientific literature for this species. Both the relatively high body parameter values and occurrence of RBS in this acidic environment contradict previous studies that demonstrated the negative influence of soil pH on the occurrence and health of RBS. These observations indicate that a highly acidic habitat may support a healthy RBS population. Moreover, the studied forest seems to have the lowest pH yet reported for a habitat known to support this salamander species. Given that RBS has been widely used as an indicator for monitoring forest ecosystems in recent years, this new information on microhabitat tolerance should be considered for correctly using this species as indicator of forest health and soil acidity.
by Audrey Verreault | 30 January 2019
Published in Canadian Journal of Forest Research 31: 1968-1980
ln production tunnels, time domain reflectometry (TDR) was used to manage irrigation and leaching by controlling water content in the rhizosphere of air-slit containerized white spruce (Picea glauca (Moench) Voss) seedlings (1+0). Seedlings were exposed to four irrigation regimes (v/v: IR-60%, IR-45%, IR-30%, and IR-15%) during the first growing season to assess IR effects on growth, gas exchange, nutrient uptake, carbohydrates, root architecture, and leaching. ln the province of Québec, seedling producers generally maintain a high substrate water content (> 50%, v/v) during aIl growth phases. The accuracy and feasibility of using TDR to decrease irrigation without affecting the material attributes of the seedlings at the end of the first growing season was confirmed. However, seedlings grown under IR-15% had significantly lower height, root collar diameter, shoot and root dry masses, root surface, root length, net photosynthesis, and nutrient contents than seedlings grown under IR-30%, IR-45%, and IR-60%. ln comparison with IR-30% and IR-45%, the application of IR-60% produced no increase in shoot or root growth, mineral nutrition, and carbohydrates. Seedlings grown under IR-15%, IR-30%, and IR-45% used approximately 28, 37, and 46%, respectively, of the amount of water applied under IR-60%. Nutrient losses including anions and cations under IR-60% were higher in comparison with the other IRs. Maintaining a water content in the rhizosphere that changes with the stage of seedling development is suggested to optimize growth and to avoid excess irrigation and leaching.
by Audrey Verreault | 30 January 2019
Published in Nativeplants 9(1): 41-44
In a simple evaluation we found that a portable refrigerator/freezer unit, powered by the 12v DC connection in a vehicle, maintained a constant and colder temperature than a similarly sized recreation-style cooler filled with ice. Such a device may have utility for preserving the quality of seeds and cuttings collected in the field.
