Abstract Detail

Ecological impacts and restoration of industrial sites: roles of bryophytes and graminoid vascular plants 

Guittonny-Larchevêque, Marie [1], Bouchard, Hugo [1], Remaury, Arnaud [1].

Do herbaceous species used for mine waste revegetation facilitate or compete with tree establishment?

Seeding of agronomic herbaceous species is routinely used in mine revegetation to rapidly cover mine wastes and limit their erosion. When mines are established in forested landscapes, the evolution of the created grassland towards forest should be desired to limit environmental impacts and restore traditional uses of sites. However, the used agronomic species are known to be very competitive to trees in contexts different from mine reclamation, for example tree plantations on abandoned hay fields. Recent studies tend to show that plant interactions change from negative (competition) to positive (facilitation) when stress exposure increases (stress gradient hypothesis). Mine wastes are known to expose plants to severe abiotic stresses, such as low nutrients, salinity, trace elements, and inadequate soil structure. In such habitats exposed to stresses, seeded herbaceous species could rather facilitate tree establishment by decreasing the level of some stresses in their vicinity. The effect of seeded herbaceous species on abiotic parameters that influence tree establishment was studied in two mine revegetation situations: 1) seeding of waste rock slopes covered with soil, 2) direct seeding of mine tailings. Both mine wastes came from a gold mine and contain low sulfur and trace metals. Waste rocks are the rocks that surround the ore but contain too low resource to be of commercial value. They are removed by explosion then piled on tens of meters. Planted tree growth and tree natural recruitment were followed two years after revegetation and compared in seeded vs non seeded plots. The seeding mix contained agronomic graminoid and leguminous species. Since temperature, humidity, and light at the ground level greatly influence tree recruitment, these variables were measured in plots with or without seeded herbaceous species. Herbaceous aerial and root biomasses were also measured in all plots because they could influence planted trees growth. Mine tailings consist in the crushed ore from which the commercial resource was removed. They are transported with water and deposited in tailing facilities. Under controlled conditions, we studied the root development of five agronomic graminoid species in mine tailings and their associated effect on tailings density and macroporosity. Both parameters showed values in the studied mine tailings before seeding that could limit tree root development.

Related Links:
Research institute in mines and the environment website

1 - Université du Québec en Abitibi-Témiscamingue (UQAT), Research institute in mines and the environment (RIME), 341, rue Principale Nord, bureau 5004, Amos, QC, J9T 2L8, Canada

Keywords:
mine afforestation
plantation trees
seedling recruitment
Abiotic stress
agronomic herbaceous species
waste rocks
mine tailings
plant interactions.

Presentation Type: Symposium Presentation
Session: SY07
Location: Hall C/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 10:45 AM
Number: SY07007
Abstract ID:1194
Candidate for Awards:None