Department of Biology
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Browsing Department of Biology by Author "9b2a8970376f5cb8ba311b5f93d9784e"
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Item Open Access Evaluating the Success of Deciduous Forest Restoration in Southwestern Ontario, Canada(Heritage Resources Centre, University of Waterloo, 2000) McLachlan, S.M.; Bazely, DawnForest fragmentation has resulted in reduced richness of native species in northeastern North America. Despite recent large-scale increases in forest cover, studies indicated that understorey herbaceous plant communities may take decades to recover. In 1994 and 1995, we assessed the effectiveness of restoration by comparing the understorey plant composition of 28 former cottage and road sites with less disturbed reference sites at Point Pelee National Park, Ontario, Canada. Sites were restored over a 35-year period. We took into account the effects of selected environmental and landscape variables. There was a significant increase in similarity between restored and reference sites as time-since-restoration (TSR) increased. Overall, there were no signifcant differences in the diversity of native species between restored and relatively undisturbed reference sites suggesting recovery of restored sites may have been unsucessful. However, there was still significant among-site variation in the composition of the native species component of these plant communities. When only restored sites were examined, variation in native species composition was associated with time since restoration, soil moisture, canopy cover, and distance to continuous forest. Native species were assigned vulnerability rankings according to their relative occurence in reference and restored sites. Spring-flowering herbs such as Hepatica acutiloba, Dicentra cucullaria, and Allium tricoccum, with ant or gravity dispersed seeds, were absent from restored sites and were defined as highly vulnerable. In contrast, summer and fall-flowering herbs, with verterbrate and wind-dispersed seeds, dominated restored sites and were assigned lower vulnerability rankings. Species assigned low and intermediate vulnerability rankings had colonized restored sites successfully. These intermediately ranked species should function as indicators of recovery. In contrast, species with high vulnerability rankings had not recovered at all and, because of their limited disperal ranges, may only recolonize restored sites if they are actively reintroduced.Item Open Access Shedding Light on the Problem of Deer Overgrazing in Carolinian Forests(Centre for Wildlife and Conservation Biology, Acadia University, 2002) Hynes, Kim E.; Koh, Saewan; McLachlan, S.M.; Timciska, M.; Bazely, DawnIn nearly a decade of research we have carried out a multi-faceted study of the impact of deer grazing in three major Carolinian parks: Point Pelee National Park, and Rondeau and Pinery Provincial Parks. This research has had a direct impact on management policy. We will review key findings of the research program and highlight what we consider to be our most general research finding, namely that the state of the overhead canopy in Carolinian forests appears to have a major impact on the composition of understorey plant communities. We suggest that deer overgrazing has initiated a process that has signiticantly altered understorey light conditions. Our hypothesis is that increased canopy gaps, initially caused by deer preventing forest regeneration, have led to trees being more susceptible to wind throw. This further opens the canopy, leading to increased light levels in the understorey, which in turn drive changes in the vegetation. Non-native, invasive species can take advantage of the increased light conditions and appear to replace and suppress native woodland species, which are adapted to shade. The forest may then switch to some alternative stable state. Currently, analysis of long-term data sets is aimed at evaluating this hypothesis. Our current research aims to quantify the relationship between understorey light levels and the plant community, and it will establish whether there is some threshold light level beyond which many vulnerable native understorey species cannot survive, and are suppressed by exotics. In this respect it is of general interest to anyone working in a degraded, highly disturbed forest, with an interest in habitat restoration.