Recruitment of boreal forest trees in poplar plantations on mine waste rock slopes

1 Hugo Bouchard, research institute in mines and the environment - UQAT

2 Marie Guittonny-Larcheveque, The Research Institute in Mines and Environment - UQAT

3 Suzanne Brais, Forest Research Institute - UQAT

Mine wastes provide harsh substrate conditions for the reestablishment of trees in forested regions, especially waste rock dumps where slopes are prone to erosion. Fast- growing tree plantations on a respread topsoil may be used to stabilize the waste rock slopes and modify the microenvironment under their canopy. An efficient design of plantation could then help to overcome the limiting factors for forest tree recruitment and catalyze plant succession. An experimental setup was designed to test this facilitation technique on waste rock slopes, on the Canadian Malartic mine site, located in Northwestern Quebec. Two hybrid poplar plantations established on a 10 or 50-cm overburden topsoil layer are being examined to assess how spacing and planting stock type affect 1) understory light, humidity and temperature conditions; 2) litter accumulation; and 3) understory vegetation cover. These microenvironmental parameters are studied in order to measure their respective effects on seed germination and seedling development of forest tree species. Preliminary results tend to suggest that a 2 × 2 m poplar spacing in a two-year-old plantation provides more favorable soil humidity conditions for the reestablishment of boreal tree species. Additional data are being collected during a second sampling season this summer 2015. Our findings will have practical implications for the development of innovative revegetation techniques on waste rock slopes in forested regions.