The role of microtopography in vegetation colonization and early forest development on mine reclamation sites
Creators: Aasberg, Sophie
Publisher: name: University of Alberta Library
Year: 2023

<p>Microsite heterogeneity is an important variable that drives biodiversity in forests. Current forest reclamation practices often do not incorporate site heterogeneity in their practices which might pose a challenge to the reclamation goals of restoring disturbed sites to resilient and sustainable forests. The goal of this thesis is to explore whether increasing variation of microtopographical features and substrates types have positive impacts on forest restoration efforts. Specifically, I am interested in the benefits of implementing microsite variability by increasing the microtopographic variation to the establishment and performance of tree seedlings (naturally regenerated and planted) and the colonization of the vegetation community. <br>
In this operational scale study, I examined the effect of increased microsite heterogeneity on planted and naturally regenerated trees and the vegetation community by comparing a contoured (levelled (least heterogeneous and current practice)) treatment, a treatment that produced small parallel ridges (ridged), and a treatment (most heterogeneous) that used large loose piles of different material types pushed into alternating rows (hilled). I hypothesized that increased microsite heterogeneity would have a positive impact on tree establishment and growth and produce a more diverse plant community. <br>
Overall, increased microtopographical along with coversoil heterogeneity improved tree establishment and growth as well as contributed to greater native species richness (33% increase in hilled and 43% increase in ridged treatment) compared to the more homogenous levelled treatment. Furthermore, the hilled treatment produced the greatest positive response in tree growth and native vegetation diversity. In the hilled treatment, the improved growth was especially observable for trembling aspen (43% height increase) and jack pine seedlings (29% height increase) when compared to the levelled treatment. Increased microtopography also encouraged natural regeneration of trembling aspen with a 60% and 31% increase in individuals in both the hilled and ridged treatments, respectively. Natural balsam poplar regeneration was 24 times higher in the hilled treatment than the levelled treatment. Interestingly, the hilled treatment had fewer non-native agronomic competitors and maintained more open mineral soil conditions, likely providing an advantage of reduced competition for planted and natural seedlings during establishment. The greatest positive responses of these microtopographical treatments appear to be gained when applied in areas that have stressful conditions (e.g. south facing slopes). The differences between the levelled and the hilled treatment of planted seedlings and natural regeneration were much greater when applied on a south-facing slope compared to an east-facing slope. The results of this study support the positive impact of heterogeneity on early forest establishment and growth and suggest that greater use of site reconstruction techniques that increase topographical and soil variability might be beneficial for forest reclamation sites. </p>