Plant interactions with oxygen barrier covers used to reclaim mine waste storage areas: a functional ecology approach.

点击翻译按钮获取中文摘要

Under humid climates, the functioning of oxygen barrier covers relies on a nearly water-saturated part through which oxygen diffusion to the underlying reactive wastes is limited (covers with capillary barrier effect CCBE, covers with elevated water table EWT). Oxygen barrier (OB) covers may rapidly be colonized by plants coming from adjacent ecosystems. Inaccurate evaluation of plant effects on OB cover functioning, ie cover hydrogeological properties, can result in cover failure to achieve its mission, at the cost of environmental pollution. The prediction of plant contribution to cover functioning is often inaccurate. First, a major deficiency is the omission of root growth as a dynamic process that affects the movement of water in the cover. Second, experiments focused on the mining context are needed to improve the predictions. Thus, long-term objective is to integrate vegetation driven ecosystem processes to OB covers functioning to improve the prediction of their performance at the long-term. The research will both use field-scale and controlled laboratory monitoring and rely on a clear quantitative, experimental approach. A functional ecology approach grounded on plant traits will allow to study plant effects on OB cover hydrogeological properties, and relate them to environmental variations, ie abiotic filters.***Three shorter-term objectives will be addressed: 1) Measure plant root effects on OB cover functioning and integrity. The relation between plant root traits, saturated hydraulic conductivity (ksat) and porosity of the moisture retaining layer (MRL) of a CCBE will be studied in situ. Tree uprooting and associated erosion risk will be related to root traits on in situ analogues of covers with EWT made of tailings; 2) Predict the control of abiotic factors on root traits that impact CCBE functioning. Mesocosms reproducing a CCBE will be planted with boreal woody species and submitted to water and nutrient stress to precise the desired range of environmental variations that control root effects on cover functioning; 3) Study the contribution of topsoil development to the decrease of abiotic stress exposure and OB cover functioning. The effect of topsoil or organic matter presence on the top of the cover will be related to soil and woody species water relations, nutrition, and root traits in mesocosms reproducing a CCBE and a monolayer tailings cover with EWT. ***The outcomes will constitute a knowledge base for application to other waste confinement technologies and could result in eco-engineering developments to control plant effects on cover hydrogeological properties. Three HQP will acquire interdisciplinary skills and will be able to design reclamation technologies responding to industrial, government, and communities' needs.**