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Daniel Gagnon


Office: LB 243
Phone: 306-337-2971
Fax: 306-337-2410

Research interests
Forest ecology, Plant Conservation Biology,
Hardwood Reforestation and Restoration, Hybrid poplar riparian buffers and agroforests

Hardwood Reforestation and Restoration

One of my major research interests is the ecology of reforestation with valuable native hardwoods (oaks, ashes, walnuts, etc.). An example of this research is a study analysing data from 7 year-old plantations, of 7 species on 5 different soils, to identify which soil factors are optimal for the growth of each species (Cogliastro et al., 2003. Forest Ecology & Management 177: 347-359). We tested the feasibility of restoring the presence in forests of formerly abundant tree species in a study of the 8-year growth of 4 species planted under partial forest cover of 4 forest types and in 2 open environments (Truax et al., 2000. For. Ecol. Manag. 137: 155-169). This study showed that red oak can be established under partial forest cover, without the problems associated with open field plantings, and without the use of herbicide. With Dr. Benoit Truax, a former Ph.D. student, I am currently developing forest zoning management in privately owned forests of southern Quebec. This type of forest management had originally been developed for public forests. The zoning includes 3 zones, a "forest conservation zone", an "ecosystemic forest management zone" and an "intensive production zone" (see hybrid poplar section below). Within the ecosystemic forest management zone, species poor or degraded forests (young forests on abandoned fields or forests depleted from overharvesting), may lack important forest species which were more common in the past. Restoration underplanting of valuable hardwoods, such as red oak, and of white pine is a part of ecosystemic forest management. This research is being done in collaboration with the Eastern Townships Forest Research Trust(PDF) (D. Gagnon and B. Truax are trustees). Please see Forest zoning on private lands: reconciling conservation, restoration and production(PDF), an article for the general public that describes this ongoing forest zoning management project.

Hybrid poplar riparian buffers and agroforests

Another of my major research interests is hybrid poplar plantation research. Dr. Benoit Truax and I have developed the largest network of hybrid poplar plantations in Eastern Canada on private land and farmland. We have shown that hybrid poplar riparian buffers (a type of temperate agroforestry) have a high capacity to capture carbon, nitrogen and phosphorus, thus mitigating non-point source agricultural pollution of streams (Fortier et al., 2010. Agriculture, Ecosystems & Environment 137: 276-287). For hybrid poplar agroforests on uplands, we published growth results at 8 years in plantations along gradients of elevation and soil fertility, producing extremely strong predictive equations of wood volume and biomass for 5 clones, and a multiple regression model that explains 78% of yield with 3 ecological factors (Truax et al., 2012. For. Ecol. Manag. 267: 228-239). This predictive equation allows for the selection of the most productive future plantation sites. We are now using the hybrid poplar riparian buffers and agroforests to investigate their capacity to store carbon in their below ground biomass and their soil. Hybrid poplars can rapidly produce wood or biomass for energy, as well as provide several ecosystem services. Hybrid poplars can also be used to rapidly create “forest” corridors (in 10 years) that share many understory attributes with natural second growth forests (Boothroyd-Roberts et al., 2013. For. Ecol. Manag. 287: 77-89). Such corridors could be used for reconnecting the highly fragmented natural forests of agricultural landscapes, without waiting for abandoned fields to return to young natural forests, a process that can take in excess of 50 years. High yielding hybrid poplar plantations can also be a vital part of a forest zoning management system on private land, when planted in the intensive production zone, by subsidizing the creation of forest conservation zones, and sustainable harvesting in the ecosystemic forest management zone with their high wood production.

Plant Conservation Biology

I am also interested in the conservation biology of plants, more specifically the population dynamics of understory forest herbs, mainly endangered and threatened species. Using our own published transition matrices to incorporate environmental stochastic variability in population dynamics modelling, we evaluated the effects of harvesting on populations of wild leek (vulnerable in Québec) and American ginseng (endangered in Canada) (Nantel  et al., 1996. Conservation Biology 10: 608-621). This research provided solid evidence against the sustainability of harvesting wild plants (non-timber forest products) when the plant is harvested whole. Research in my lab has lead to the legal conservation designation of 12 species of plants in Québec, among the 59 species designated to date. At the Canadian level, the Species at Risk Act protects 6 species that we have studied (Panax quinquefolius, Juglans cinerea, Viola pedata, Eurybia divaricata, Woodsia obtusa, Asplenium scolopendrium). Recently, we studied the butternut canker infection rate in butternut (Juglans cinerea; endangered in Canada) in natural forests, along ecological gradients in southern Quebec, in order to detect resistant individuals. This rapidly declining tree is being killed by a fungal pathogen introduced from Asia. Other conservation biology projects also involve the study of the ecological effects of introduced invasive plant species, such as the shrub Rhamnus frangula.

Juniper dendroclimatology project

A dendroclimatology research project, led by Dr. Jacques Tardif (University of Winnipeg), is ongoing with old red cedar (Juniperus virginiana) trees growing on the steep south-facing slopes of the Eardley Escarpment, in Gatineau Park, southern Quebec. Red cedar, a wide ranging eastern North American tree, reaches its northern distribution limit in Gatineau Park. This tree is easily killed by fire and therefore survives in habitats were there is little fuel accumulation and fires are not destructive (steep slopes with lots of bare rock, flat limestone pavements (no soil), dune systems). Red cedar tolerates very dry soils, can grow very slowly, and its wood is extremely resistant to decay (used to make cedar chests and closets, as well as fence posts). The growth rings of red cedar provide an excellent record of early summer precipitation (by their width), because the trees grow on sites with very low water availability. Some live red cedar trees attain 400 years of age, but trees that have died several hundred years ago leave behind nearly sound trunks. By interdating the growth rings of dead and live trees, a continuous chronosequence of more than 800 years may be produced. Using available recorded climate data (last 100 years) the rainfall "signal" registered by the growth ring width can be interpreted for the entire chronosequence, informing us on rainfall over the last 800 years. We can then see how frequently droughts have occurred in the past and how severe they were. We can also determine if the recent decade has had a higher frequency or severity of droughts than in the past.