by Audrey Verreault | 10 April 2020
Published in Journal of Applied Ecology 56(3): 758-768
It has recently been reported that changing precipitation patterns increase tree mortality and reduce biomass accumulation in northern temperate and boreal forests. Functional diversity can mitigate the impacts of climate extremes in different types of ecosystems, but few studies have focused on tree functional diversity in forest ecosystems. It is critical to identify functional traits that could help anticipate the impact of drought on tree mortality, and how these affect above-ground tree biomass productivity at the ecosystem level.
We tested how three functional traits (ratio of dry leaf mass per unit area [LMA], xylem pressure at which 50% of stem xylem conductivity is lost through cavitation [Ψ50] and leaf area to sapwood ratio) influence severe drought impacts on stand mortality and productivity. We used structural equation modelling to compare the effect of a latent variable composed of these three traits between plots that had suffered drought and plots that had not, on the mortality and productivity of northern temperate and boreal forests of Québec, Canada.
A latent variable composed of LMA and Ψ50 significantly explained drought-induced tree mortality, but did not explain stand productivity response to severe drought. Therefore, even if these traits relate to the ability of species to survive drought (drought tolerance) at the tree level, they did not affect the maintenance of plant productivity during drought events (drought resistance) at the stand scale. We hypothesize that the effect of tree mortality on productivity was likely compensated by the formation of canopy openings that stimulate the growth of surviving trees.
Synthesis and applications. Our results show that mitigation of water loss and xylem resistance to cavitation contribute similarly to severe drought tolerance in trees within northern temperate and boreal forests. Therefore, including drought-resistant trees in fine-scale mixtures might mitigate the impacts of drought on forest productivity due to the survivors’ response to released resources.
by Marie-Claude Boileau | 3 February 2020
More than 80 fish species are found in the freshwater and brackish waters of the St. Lawrence River and evaluation of the status of these fish stocks is complex. In order to paint a current picture of our understanding of the fish communities and aquatic habitats of the St. Lawrence, and to judge the evolution of these elements over the last 25 years, different status indicators were used: (1) Index of Biotic Integrity, (2) status of the stock of certain species subject to recreational and commercial fishing, (3) status of species under threat, (4) coastal zone fish biodiversity index and (5) relative abundance index for submerged aquatic vegetation. Analysis of these indicators highlights what are sometimes very different findings between species and sectors. Several rapid changes that have arisen during the last two decades in the characteristics of aquatic habitats and in the structure of fish communities testify to an evolving ecosystem that is tending to degrade in certain sectors. Over the years, several exploited fish stocks have seen periods of decline. While certain species have been able to re-establish themselves thanks to restrictive management measures, others have been slow to recover due to several factors other than pressures from fishing.
by | 10 January 2020
The Eastern Habitat Joint Venture (EHJV) is a group of partners from six Canadian provinces, namely Ontario, Québec, New Brunswick, Nova Scotia, Prince Edward Island and Newfoundland-and-Labrador. In each of these provinces, government departments, non-government agencies, landowners and many other organizations with an interest in conservation work together on initiatives designed to support the North American Waterfowl Management Plan. This document presents a summary of the EHJV in Québec and includes examples of wetland protection and restoration projects carried out over a 30-year period (1989 to 2019).
by Marie-Claude Boileau | 3 July 2019
The upstream migration of Bérard River Arctic charr was subject to monitoring to establish its reference state. A total of 1,823 anadromous Arctic charrs were recorded at the counting fence from August 8 to
September 8, 2017, of which 83 were randomly selected during this period to characterize different biological parameters.
by Marie-Claude Boileau | 4 April 2019
Forestry research paper No. 7
This report demonstrates the suitability of using multiple regression and principal component analyses for growth prediction and phytosociological studies in black spruce forests of eastern Canada.
The data come from 125 black spruce stands located in the Boreal forest of Canada from Newfoundland to western Ontario. The observed factors in this study are: dominance of species and species groups, stand density, soil moisture regime and site index.
The prediction of site index is satisfactory using the dominance of species and species groups in multiple regression. Principal component analysis shows some possibilities of application for the identification of broad site quality classes. Further study is needed to perfect the vectorial ordinations before this method can be used for prediction purposes.
The classification of forest stands as to types and associations seems to be relatively simple with the component analysis. For application to field conditions each region should be studied separately in order to increase the precision of the vectorial ordinations.
