The development of protocols to restore the globally at-risk limestone barrens ecosystem

Restoring ecosystems and habitats in human-altered landscapes is challenging where reference sites to guide restoration can be limited or absent. The current shift in restoration theory to a dynamic reference alleviates some of this concern, acknowledging systems are not static. However, historical references are still useful as restoration targets when relatively intact. I applied this principle here, focusing on the limestone barrens of Newfoundland (Canada), an ecosystem that represents a biodiversity hotspot and hosts endemic plant species, e.g. the endangered Braya longii; human activities have degraded its critical habitat. Historical aerial photographs were used to depict landscape topography prior to substrate removal, and identify intact reference sites. Identified reference sites were characterized in terms of substrate, nutrient and vegetation composition, and topography through field observations and measurements. To test protocols to restore the complex small-scale disturbance regime, substrate manipulation experiments were constructed and monitored for frost heave and cycles. Experiments were also seeded with native flora, including B. longii to determine an effective means of re-introduction following restoration. Limestone barrens occur sparsely on the landscape atop ancient beach ridges. Low potential habitat (10%) was observed at the study site in 1948, of which slightly less than half was degraded by quarry activity and road construction by 1995. Remnant high quality habitat identified in aerial photos and described through field surveys is characterized by frost heave and sorting, high silt/clay and bare ground cover, and low organic content. Degraded sites and overburden material differed from the reference iii site in terms of vegetation, substrate and nutrient composition. In addition, substrate treatments to restore small-scale disturbance that lacked added overburden material demonstrated similarities to the reference site in terms of the average number of frost cycles and duration suggesting partial recovery of cold-soil processes. The seeding experiments with native flora, including the endangered endemic B. longii, resulted in low percent emergence. However, more seeds are expected to germinate in subsequent years given germination syndromes. This thesis emphasizes the need for human intervention, rather than a non-intervention expecting regeneration given the absence of vegetative and natural disturbance recovery towards limestone barrens. It also recommends that overburden material not be used to restore soil and substrate as it will hinder progression along the target limestone barrens trajectory. Overall, the recommendations provide a baseline methodology to restore limestone barrens habitat in degraded quarry sites, addressing the Federal Recovery Strategy’s target to expand and restore critical habitat, natural freeze-thaw disturbance, and B. longii within its historical range