Methods
A greenhouse study was conducted to evaluate how woody plants grow in this tailings material. Beaked willow (Salix bebbiana) was planted in tall pots containing tailings on the bottom and topped with different reclamation soils at varying capping depths (0, 5, 10 and 20 cm). The different soil types used were forest floor mineral mix (FFMM), a typically upland forest soil that is rich in minerals; peat mineral mix (PMM), an organic based wetland or lowland soil; and a 50/50 mixture, containing 50% FFMM and 50% PMM. Clay was used as the subsoil for the control to reproduce similar physical properties as the tailings. A second sub-experiment (see figure 5-b) used biochar as an amendment, added to a 50/50 mix soil at a rate of 10T/ha, and a saline solution was added to another clay control treatment to produce similar salinity to the tailings. In total there were 11 treatments for the first experiment (see Figure 5-a), each with 6 replicates, for a total of 66 willow plants in a completely randomized design. The sub-experiment had 4 treatments for a total of 24 willow plants. Pots were rotated twice per week. The greenhouse was kept at 25 degrees Celsius during the day and 18 degrees at night. The plants were grown from seed, with seedlings planted on April 26th, 2018 and grown for four months. Final height, stem diameter and above-ground biomass (dry) was measured at the end of the study.
Figure 5-a. Diagram of treatments used for sub-experiment 1.
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Figure 5-b. Diagram of different treatments for sub-experiment 2.
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Figure 6. Photos of the Willow trees and the research greenhouse at Northern Forestry Centre.
Statistical Analysis
Statistical analysis was done using multi-factor Analysis of Variance (ANOVA) in R-Studio. To answer the first two research questions, interactions between yield, capping depth and treatment were investigated (BIOMASS~TREAT*CAP), as well as analysing differences between treatments (BIOMASS~TREAT) and differences between capping depths (BIOMASS~CAP). To answer the third research question, a one-way ANOVA was conducted, comparing the biomass of different treatments, which all had a 10 cm capping depth (BIOMASS~TREAT). A log transformation was conducted to all of the data to meet assumptions of homogeneity of variance.
Statistical analysis was done using multi-factor Analysis of Variance (ANOVA) in R-Studio. To answer the first two research questions, interactions between yield, capping depth and treatment were investigated (BIOMASS~TREAT*CAP), as well as analysing differences between treatments (BIOMASS~TREAT) and differences between capping depths (BIOMASS~CAP). To answer the third research question, a one-way ANOVA was conducted, comparing the biomass of different treatments, which all had a 10 cm capping depth (BIOMASS~TREAT). A log transformation was conducted to all of the data to meet assumptions of homogeneity of variance.