At present, forest cover in southwestern Ontario, Canada, remains at less than 5% due to intensive agricultural and urban land use. Although much of the extant forest is increasingly protected by legislation, remnants continue to be degraded by the spread of non-native plant species, overgrazing, and recreational use. Some parks in the region have adopted management programs aimed at mitigating this degradation. Over the last 35 years, cottages and roads at Point Pelee National Park have been removed and sites either passively restored (i.e. road or cottage eliminated and vegetation allowed to regenerate) or actively restored (i.e. road or cottage eliminated, exotic vegetation removed, and native species planted). In 1994 and 1995, the overall eï¬€ectiveness of the restoration program was evaluated by comparing the understory plant communities in 28 restored sites with those in less disturbed reference sites. There was found to be a signiï¬cant increase in the similarity of understory plant communities between restored and reference sites as time-since-restoration increased. Soil moisture, canopy cover, distance to continuous forest, and site-shape all signiï¬cantly aï¬€ected plant species composition. Former road sites recovered signiï¬cantly more rapidly than former cottage sites, and the former lawns of passively restored cottage sites were the slowest to recover. Five years following active restoration, non-native ruderal species continued to dominate restored sites. The observed recovery of understorey plant communities in restored sites is attributed to their proximity to natural vegetation, and its function as a seed source. In some sites, recovery is substantial and, assuming present trajectories of change are maintained, we predict that recovery could occur in many mesic sites within the next 20 years. Restoration activity facilitates forest recovery and would appear to have a valuable function in mitigating ongoing conï¬‚icts between conservation and human use in this region.
Point Pelee National Park, Point Pelee Drive, Leamington, ON, Canada, 41.96277200000001, -82.51844
Country or Territory:
Temperate Forest - Mixed
Primary Causes of DegradationAgriculture & Livestock, Deforestation, Fragmentation, Invasive Species (native or non-native pests, pathogens or plants), Urbanization, Transportation & Industry
Agricultural and urban land-use dominate the landscape of southwestern Ontario, the most densely populated region of Canada. Forest cover is less than 5% and remnants tend to be small, isolated, and privately owned. Currently, 40% of Ontario’s rare plant species are restricted to this ecoregion, known as the Deciduous or Carolinian Forest Zone. Although conservation efforts have focused on habitat protection, either through the creation of parks and conservation areas or, when privately owned, through trust and stewardship agreements, these protected areas are, and continue to be, degraded. Causes of this degradation are the spread of non-native species, deer overgrazing, as well as recreational land use. Historically, land uses in this area were commercially driven, either for wood production or the reduction of soil erosion. But, as with most production forests, the understory has not been viewed only through the prism of undermining tre productivity and regeneration, and thus has been controlled with herbicides, cultivation, and mowing. The project was conducted at Point Pelee National Park in southwestern Ontario, which had been subjected to extensive human use and disturbance in the past. Prior to be designated a park in 1918, Point Pelee was cleared of white pine and is now dominated by hackberry and to a lesser extent, black maple and white ash. Agriculture peaked in the 1950s when 40% of the park was allocated to orchard, crop, and vegetable production. By 1960, 600 cottages and numerous roads were situated in the park and 500,000 people visited each year. At this time, park managers initiated an intensive naturalization program and over the past 35 years most of the cottages and roads have been removed.
Reference Ecosystem Description
Geography and the moderating effects of Lake Erie have allowed southern plants and animals to flourish at Point Pelee. The vast forest of deciduous trees is the northern end of a broad belt which extends from the coastal zone of the Carolinas, northward between the Mississippi River and the Appalachian Mountains, to southern Ontario. The Canadian Carolinian Zone stays much warmer than similarly situated areas because of Lake Erie and the lake effects that result from the cushioning of temperature peaks. This area has tremendous variety and endemism, with more rare species than any other region in Canada.
The specific goals of this project were: 1) to assess the impact of 40 years of habitat restoration on understory plant communities; 2) to compare the composition of understorey communities in restored and relatively undisturbed, reference deciduous forest sites at Point Pelee and Fish Point; 3) to relate changes in species composition to environmental variables expected to affect rates of forest recovery; and 4) to compare the relative effectiveness of passive and active restoration. The project hypothesized that restored sites would show an increased similarity to reference sites over time, and that active habitat restoration aimed at accelerating desirable vegetation change would be more effective than passive restoration.
The project does not have a monitoring plan.
Forest restoration in southern Ontario has centered on the planting of trees on marginal farmland since the turn of the century. These plantations have the potential to generate additional forest habitat, provide buffer zones for pre-existing habitat, and increase connectivity among remnant patches of forest. However, in practice, they have tended to be management-intensive, have remained largely isolated from surrounding natural or restored habitat, and have born little resemblance to adjacent pre-existing forest. Even when unmagaged, however, the understory flora may take decades, if not centuries to recover without some form of intervention. Many recent forest restoration efforts in southern Ontario have taken more comprehensive approaches, these efforts increasing the scale from individual tree species to that of the ecosystem or landscape, involving a diverse set of stakeholders, and incorporating adaptive management strategies.
Description of Project Activities:
While restoration efforts had been ongoing, both active and passive, since the 1960s this project sought to quantitatively assess the results of those efforts. Starting in 1994, 28 former road and cottage sites were identiï¬ed throughout Point Pelee using aerial photographs, park blueprints and input from long-time park employees. Sites were categorized according to their date of restoration and a preliminary visual assessment of soil moisture. Because of the long history of widespread disturbance in Point Pelee, three relatively undisturbed reference sites (10 m x 80 m) were located at Fish Point. In 1995, three additional reference sites (10 m x 80 m) were identiï¬ed in relatively undisturbed upland forest at Point Pelee, using park records to ensure that these sites had never been used as cottages or roads and that they had been distant from past recreational areas. The herbaceous plant community in all sites was measured in June and September 1994 and May 1995, with the exception of the reference sites at Point Pelee, which were measured in May and September 1995. In addition, for comparison purposes, eight quadrats were located in part of an actively restored site that had been inadvertently left unchanged. For each quadrat, the maximum cover value for each species was selected from the multiple sample dates. Depending on site area and habitat heterogeneity, between 13 and 22 1 m x 1 m quadrats were randomly located in each of the 34 sites, approximately 10 m apart. Pins were used to mark the SE corner of each quadrat. The percent cover of all herbaceous species, and woody species less than 40 cm in height, was recorded. Species nomenclature followed Morton and Venn (1990) and voucher specimens were deposited in the Point Pelee herbarium. Non-native species were deï¬ned as having been introduced to Point Pelee since European settlement (c. 1700) according to Jellicoe and Rudkin (1984). Environmental data collected at all sites in both Point Pelee and Fish Point included soil moisture, canopy cover, and topography. Eight soil samples were taken from each site within a two-day period in both September 1994 and June 1995, and analyzed for moisture content. Samples were dried at 100 C for 24 h before weighing. Percent canopy cover was estimated for all quadrats in all sites. Surface topography was qualitatively assessed and sites were classiï¬ed as 0 (ï¬‚at), 1 (rolling), or 2 (hilly). Historical forest data for restored sites at Point Pelee were collected from aerial photos taken in 1933, 1955, 1968, and 1973, using the set that most closely preceded the restoration date. Cottages and roads restored since 1983 were initially described using the most recent aerial photo and corroborated by ground truthing. Measurements estimated from aerial photos were (1) the size of the forest gap in which the cottage or road had been situated, (2) site area of the cottage or road, (3) distance to continuous forest, (4) proportion of the site, boundary that was adjacent to forest, (5) whether sites had formerly been cottages or roads, (6) whether sites had been actively or passively restored, and (7) shape index. Although reference sites in Point Pelee had not been used previously as cottages or roads, the high overall disturbance level in the park led project managers to believe that all in-park habitat had been disturbed or degraded at some time. This accounts for the use of Fish Point as an endpoint, partly because it provided the most conservative measure of forest recovery.
Ecological Outcomes Achieved
Eliminate existing threats to the ecosystem:
Overall, the results of the study indicate that these disturbed forest sites are recovering from their former use as cottages and roads, that restoration is having a desirable eï¬€ect, and, should recovery continue, that mesic sites that are relatively close to continuous forest will be largely similar to the high quality reference sites, perhaps within 50 years. Project researchers used an increasing similarity between restored sites and high-quality reference sites as the primary gauge of forest recovery. Although a dependence on the use of "˜"˜reference'' sites has been questioned, the objective for this project, unlike many restoration studies, was never to deï¬ne recovery as the return to pre-existing site-conditions, nor even to deï¬ne the reference sites at Fish Point as the goal of recovery. Rather, the goal was to assess whether the observed, and inevitable, changes regarding plant species composition in restored sites at Point Pelee indicated that recovery was occurring along a desirable, management-deï¬ned trajectory. Researchers used the nearby relatively undisturbed Fish Point sites to assess the direction and degree of change. That the three Fish Point sites were the most similar to one another and that the least disturbed (i.e. reference) sites at Point Pelee sites were the most similar to sites at Fish Point sites of all the Point Pelee sites, suggests that Fish Point was a suitable choice for reference sites. Researchers deliberately used Fish Point as the end point, rather than reference sites at Point Pelee, in large part because of the low, historical levels of disturbance at Fish Point. This, then, represents a more conservative means of estimating recovery than would comparisons between the reference and restored sites within Point Pelee. These results may seem to contrast with some other studies of restoration of disturbed natural habitats that have estimated recovery periods of many decades, or even centuries. These studies frequently describe larger-scale disturbance, such as forest clearing and ï¬‚ooding. This study and others that indicate relatively rapid site recovery seems to involve smaller-scale disturbances, as only one restored site (Tav) was greater than 80 m from standing, continuous forest. However, recovery was far from consistent across all the study sites.
Factors limiting recovery of the ecosystem:
The relatively small distances appeared to be too great for some dispersal-restricted species that remained absent from restored sites. For example, ant-dispersed Dicentra cucullaria (Dutchman's britches) failed to establish in one restored site (MarsC), despite the presence of a large population 20 m away on the other side of a road. Instead, restored sites were dominated by wind and vertebrate dispersed species that tend to have dispersal distances of two to three orders of magnitude higher than dispersal-restricted species. Although one restored site at Point Pelee (PostH) was more similar to reference sites at Fish Point sites than were the reference sites at Point Pelee, it too still lacked typical understory species such as Trillium grandiï¬‚orum (trillium), Arisaema triphyllum (Jack-in-the-pulpit), and Dicentra cucullaria. Their absence from restored sites is associated with restricted seed dispersal and early-season ï¬‚owering phenology traits, and the apparent inability of ephemerals to compete with ruderal species in these disturbed environments. Spring ephemerals were recorded in only one restored site, MarsC. Their presence could be attributed to a number of contiguous, remnant populations of Arisaema triphyllum and Hydrophyllum appendiculatum present at the edges of the site. Thus, the availability of propagules appears to be a major factor aï¬€ecting recovery rates in this study. Long-term disturbance at Point Pelee has resulted in a species-poor seedbank, dominated by non-native species. Therefore, species availability in restored sites was largely dependent on seed immigration from surrounding forest. As time since restoration increased and opportunities for seed immigration continued, native species richness of the seedbank increased. Forest recovery appeared to occur more quickly in road than in cottage sites at Point Pelee, in contrast to other studies showing that soil compaction on logging roads tends to impede forest regeneration. Although roads in this study were smaller and showed less use than most logging roads, many had been extensively used since at least 1933. Seed availability might also be greater for road sites as they had comparatively high shape index and proportion-of-adjacent-forest and low distance to continuous forest. Converted cottage sites also were dominated by former lawn species that can inhibit vegetational change. Researchers had anticipated that active restoration would result in greater and more rapid forest recovery. However, the beneï¬ts were still equivocal 6 years after restoration. Most actively restored sites had higher non-native diversity and were dominated by ruderal, often non-native, species, unlike passively restored sites that were often associated with herbs characteristic of recovered and reference sites. In general, actively restored sites had been more recently converted and were subjected to relatively intense disturbance events such as bulldozing and planting and, thus, active restoration became an eï¬€ective measure of disturbance. After six years, the impact of active restoration, however benign in intention, was no diï¬€erent, in eï¬€ect, from any other intense, localized disturbance. The long-term eï¬€ects and beneï¬ts of active restoration have yet to be determined.
Socio-Economic & Community Outcomes Achieved
Economic vitality and local livelihoods:
Most protected areas located in human-dominated landscapes are subject to intensive human use. Although this tends to contribute to the degradation of the extant natural habitat, such areas still have considerable conservation and educational value. In many cases managers are attempting to mitigate this degradation by adopting "˜"˜naturalization'' programs similar to those conducted at Point Pelee. However, there may be signiï¬cant associated costs beyond those of the restoration activity itself. As parks become less amenable to recreational and residential use, visitor numbers often decrease; at Point Pelee, visitation is approximately half of what it was two decades ago when recreation was dominated by cottage and beach use. Decreases in government funding and park services, and the resistance to increases in entrance fees, may force some parks to choose between conservation and recreation priorities. In contrast, this study shows that these priorities may not be incompatible. We found that highly degraded areas can be successfully restored as long as there are viable seed sources. Although some use-associated degradation is inevitable, it is likely to be temporary and can be mitigated by restoration. Forest restoration practices at Point Pelee have changed signiï¬cantly over the last 40 years. Simple removal of cottages and roads and natural regeneration has been largely replaced by active restoration, whereby non-native species are removed, topography returned, and park-grown shrubs and trees planted extensively. Despite being dominated by ruderals six years after site conversion, apparent beneï¬ts for actively restored sites include an increase in aesthetic value associated with increases in canopy cover and topography, a decrease in the dominance of succession-inhibiting former lawn species, and an increase in education value and awareness. Future restoration eï¬€orts should also include vulnerable ephemeral and dispersal-restricted herbaceous species that largely remain absent from restored sites. Regardless of the type of restoration activity undertaken and the limited recovery of a number of vulnerable species, the results of our study strongly suggest that restoration has facilitated the recovery of a protected area that continues to be degraded by human use, overgrazing by deer, and invasion by non-native plant species, and that this activity should be continued in the future.
Sources and Amounts of Funding
This project was funded by Parks Canada, Wildlife Habitat Canada, and the Natural Sciences and Engineering Council of Canada.