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Item Open Access Interactions between deer and vegetation in southern Ontario, Canada: Monitoring and restoration of overgrazed plant communities in Pinery and Rondeau Provincial Parks.(Biology Department, York University, 1995-03) Pearl, David L; Koh, Saewan; Bazely, Dawn; Voigt, Dennis R; Tang, Maxine; Soo, WymanExecutive Summary: One of the main goals of this report was to lodge a single record of our numerous research activities on deer-plant interactions in southern Ontario. Table 1 summarizes the project's components and illustrates its wide scope. Not all of the results from these studies are presented in this report; some results are in other reports, while some data, specifically that on stand composition, soil seed bank composition, and woody browse availability, still await analysis. With the large database that we have amassed, we are now well placed to accurately monitor and assess changes in plant communities as vegetation recovers following the deer herd reduction in Rondeau and to place the ongoing degradation of grazed vegetation at Pinery into both a spatial and historical context. In spring 1994 it was clear that there was more herbaceous vegetation at Rondeau than at any time since 1991. This rapid recovery in deer grazed areas was expected based on the results of exclosure studies. Preliminary results from our studies of plant community composition showed that the plant community at Rondeau changed following protection from deer grazing in 1991 and 1978 exclosures. In 1994, both the grazed and ungrazed sites at Rondeau were distinguished from the Pinery sites in having a higher percent cover and a greater abundance of herbaceous species, typical of a mature, undisturbed Carolinian forest (e.g. Viola spp.). However, in 1992 these same Rondeau sites were distinguishable from other less heavily grazed location in southern Ontario because they had a higher percent cover of grazing tolerant species (e.g. Aster spp.). We do not yet know whether the plant community will return to its condition before disturbance by deer grazing or whether the "recovered" community will be fundamentally different - only time will tell. In 1995 we will be analyzing data sets from Rondeau for 1991, 1992, 1994 and 1995 to determine how the plant community has changed with time. We had success with the use of plant species as indicators of overall vegetation recovery following grazing, although only two of the five species which we assessed were suitable. In addition to Trillium grandiflorum (Koh et al., 1995), Circaea quadrisulcata and Polygonatum biflorum were good indicators of grazing pressure and habitat protection at Rondeau. Plant sizes observed throughout the park were determined more by deer grazing, which imposes homogeneity across grazed sites, than by habitat variation (e.g. soil type). The three other candidates for indicator species did not respond to release from deer grazing pressure as well, and their heights appeared to be related more to other factors than deer grazing. In 1995 appropriate indicator species will be determined for Pinery. While some rare plants such as Showy Orchis flowered for the first time in years in Rondeau, in general we found that effective monitoring of the recovery of rare species within the park required greater effort than was possible from two or three individuals doing sporadic searches. Due to the many negative results (failure to find species) we must develop a stringent protocol for quantifying search effort. As a consequence, S. Koh, D. Bazely, and A. Woodliffe (OMNR) will be designing a protocol which accounts for search effort and will make use of the potential volunteer base from Rondeau's visitors. Exotic and invasive plant species are of concern in any habitat which has been released from strong grazing pressure. It appears unlikely that the lower grazing pressure at Rondeau will result in as wide a distribution of weedy, invasive species as at Point Pelee National Park (e.g. Alliaria officinalis) because of the robust seedbank which contains many native species (Koh & Bazely, 1994). The greater crown cover at Rondeau (Koh, pers. comm.), in contrast to Point Pelee which is more open, will not provide as suitable a habitat for these weedy species with respect to light availability. However, in disturbed areas within Rondeau (e.g. along roadsides) some weedy species appear to be spreading. Treatment and monitoring programs initiated in 1994 will continue for A. officinalis in 1995. Berberis thunbergii (woody exotic) may have spread throughout Rondeau due to their thorns which defend them against grazing. This species may be less competitive against native shrubs now that grazing pressure has been reduced. We recommend that treatment programs be continued, and monitoring programs be established for this species. Since a herd reduction has not taken place at Pinery and has only recently occurred at Rondeau, it is vital to have a comprehensive baseline dataset against which to compare continuing habitat degradation or recovery. Such a database is in the process of being created for the woody stand structure and woody-browse, and herbaceous plant communities in both Pinery and Rondeau. Each year, data collected from the parks over the duration of the project can be compared against this baseline to monitor changes over time and grazing pressure. A report after the 1995 field season will provide the first indication of what changes can be expected in the long-term recovery process.Item Open Access Interactions between deer and vegetation in Southern Ontario: Monitoring and restoration of overgrazed plant communities in Rondeau and Pinery Provincial Parks(Biology Department, York University, 1997) Bazely, Dawn; Carr, L W.; Koh, Saewan; Carnie, John; Greenberg, Amy; Isaac, Leigh Anne; Falkenberg, Nancy; Hunt, Andrea M.; Sykes, Catherine A.; Carleton, Terry J.; Voigt, Dennis R.; Carleton, S. M.Executive Summary: 1. In 1994 the Science Technology Transfer Unit of the Ontario Ministry of Natural Resources initiated a 5-year project in collaboration with the Department of Biology, York University, Toronto, to monitor and assess southern Ontario forests affected by deer herbivory. 2. In 1995, we obtained the Cornell Ecology Detrended Correspondence Analysis (DECORANA) and Canonical Correspondence Analysis (CANOCO) computer programmes. These allowed multivariate analysis of changes in the herbaceous plant communities at Rondeau and Pinery Provincial Parks, as well as the relationship between these two parks and 8 other study locations. We have analysed Rondeau data for 1995 and compared 1992 to 1995. This period covered a 1993 herd reduction. Plant community composition changed significantly in grazed areas from 1992 to 1995, but did not change significantly over the same period in deer exclosures built in 1991. We concluded that we either missed a very rapid change that occurred in exclosures from 1991 to 1992 (we have the data to check this) or the overall composition of intensely grazed plant communities in Rondeau is very slow to change to pre-overgrazed conditions. In 1995, the plant community composition was significantly different between the Bennett and Gardiner exclosures, built in 1978, and the grazed areas and also the 1991 exclosures. We suggest that these differences may be due in part to the different shade conditions in these habitats. We also suggest that intense deer grazing has radically altered subcanopy light conditions, and has subsequently affected the recovery of herbaceous communities. We will be testing this hypothesis in 1997. If it is valid then herbaceous (understorey) plant communities may only recover when overstorey woody plant communities recover from the detrimental effects of deer grazing. 3. A range of species were found to be suitable indicators of grazing pressure and vegetation recovery at both Rondeau and Pinery Parks. Plants that survived deer grazing at Rondeau increased in height from 1994 to 1995. However, a 1996 study of Arisaema triphyllum by Dennis (1996) suggested that increasing deer numbers may again have started to have an adverse affect on this species. Plant heights need to be examined in 1997 in order to confirm these trends. 4. Exotic and invasive species are of concern in Rondeau and Pinery because of their ability to invade and dominate disturbed areas. Alliaria petiolata, Garlic Mustard, populations have expanded significantly in Rondeau from 1994 to 1996. The effectiveness of control programmes for Garlic Mustard, which were initiated in 1994, could not be evaluated due to the unusual population dynamics of Garlic Mustard in which plants go through alternate years of high and low flowering populations. 5. Berberis thunbergii, Japanese Barberry, is an exotic shrub common in Rondeau. If a removal policy for B. thunbergii is to be adopted, then the most effective method is cutting the bushes and then painting the stumps with herbicide. 6. The structure and composition of woody plant communities at Pinery and Rondeau Parks have been altered by intensive vertebrate grazing, resulting in lower shrub densities and the presence at both parks of unpalatable woody species. Intensively grazed sites such as Rondeau and Pinery had smaller trees (lower diameters at breast height - DBHs) than other forest locations. We suspect that there may be higher mortality rates of larger trees at Rondeau and in some Pinery habitats due to increased windthrow. This process could be initiated when intense deer grazing reduces the sub-canopy shrubs and saplings to the point where recruitment of saplings to the canopy does not occur. When recruitment declines, canopy gaps will increase in size, subsequently increasing the likelihood of windthrow of larger trees. In 1996, Catherine Sykes (M.Sc. student) revisited 1980 plots in Rondeau and found that in some of them over 50% of the large trees were gone and many of the smaller trees were also missing. These data, along with lower DBHs, suggest that regeneration rates at Rondeau are not high enough to fill existing canopy gaps. In addition, the relatively low shrub densities in Bennett and Gardiner exclosures indicate that recovery is proceeding slowly. Overall, these results are alarming because they suggest that the Rondeau forest will continue to decline as long as trees are no longer recruited to the overstorey. We strongly recommend that the loss rates of large trees and rates of creation of canopy gaps be monitored at Rondeau (this is included as part of our 1997 research programme), and that the impact of altered understorey light conditions on plant communities be assessed. This will indicate whether some form of drastic management intervention might be justified to replace and/or protect large trees. 7. Available woody browse (current annual growth - CAG) was sampled in Rondeau and Pinery in the Fall of 1994 and 1995. In both parks the availability of woody browse was extremely low in 1995 (< 1 g dwt CAG /m2), with the bulk of CAG from species traditionally considered to be less palatable to deer.Item Open Access Overgrazed Ecosystems: Do Plant Communities Recover?(Parks Research Forum of Ontario (PRFO) Heritage Resources Centre University of Waterloo, Waterloo, Ontario, Canada, 1998) Koh, Saewan; Bazely, Dawn; Watt, Trudy A.Large herbivores, such as white-tailed deer (Odocoileus virginianus), are major determinants of the structure and composition of forest plant communities. Previous studies of herbivory have examined plant community response by focusing primarily on diversity indices or single plant species. Few studies have shown whether statistically significant changes in species composition have occurred. In this study we used ordination analyses (DCA, CCA and RDA) to examine the effect of biomanipulations including exclosures and removal of deer on plant species composition and the dynamics of southern Ontario forests in the Canadian region of the North American Eastern Deciduous Forest or Carolinian Zone. In 1992, 1995 and 1996, plant communities in forest stands with high deer densities (50 deer/km2) were compared with adjacent plots closed-off to deer in 1978, 1991 and other long-term ungrazed sites. Stands where deer were reduced in 1993 from 10 to 50 individuals/km2 were also examined. Ordination showed that older exclosures were similar to ungrazed sites and dominated by native plant species. Both differed significantly from grazed sites, which were dominated by non-native species. Newer exclosures and stands where deer densities were reduced differed from both grazed and long-term ungrazed sites. This suggested an intermediate or alternate recovery trajectory with implications for management decisions about plant species conservation and reestablishment. Herbivore-mediated changes in light regimes at-the forest subcanopy may be a factor in preventing native plant communities in overgrazed sites from recovering and may also be determining the trajectory of some plant communities over time.Item Open Access Recovery of Red Cedar Savanna and Oak Savanna Plant Communities: Report to Pinery Provincial Park & Point Pelee National Park for the 1999 Field Season(Biology Department, York University, 2001-06) Tagliavia, Cecilia; Koh, Saewan; Bazely, DawnExecutive Summary: 1. Southwestern Ontario is the most densely populated, urbanized, industrialized and intensively farmed part of Canada. The remaining natural habitat cover is 5-10%, and much of this has been subjected to intense human-induced disturbance in the past Conservation and habitat restoration is, to put it mildly, a huge challenge. 2. This report explains the 1999 fieldwork results of two projects, part of which comprises the research of Cecilia Tagliavia a York University M.Sc. student. The work done at Point Pelee by Ms. Tagliavia, followed up on the M.Sc. research of Nancy Falkenberg. 3. The overall aim of the research was to determine how best to restore Carolinian plant communities, specifically Oak Savanna and Red Cedar Savanna. 4. Both communities are to some degree a fire-dependent. Rare and endangered species (e.g. Wild Lupine and Karner Blue Butterfly) are present and oak savanna itself is considered to be extremely rare in Ontario and globally imperiled. 5. For Oak Savanna communities at Pinery Provincial Park, our goal was to assess the effects of restoration efforts (deer herd reductions and deer exclusion) on plant community composition. 6. Intensive deer herd reductions, and removal of planted pines at Pinery Provincial Park are allowing the Oak Savanna plant communities to move away from the species composition of the early to mid-1990s, towards communities characterized by prairie and savanna species. We support the proposals to continue deer herd reductions and to carry out prescribed burns at Pinery for the foreseeable future. 7. In the future, the recovery rates of these Oak Savanna communities will depend on the presence of a suitable seedbank and the dispersal rates of individual plant species from local seed sources. 8. For Red Cedar Savanna communities at Point Pelee National Park our goal was to assess the effects of restoration efforts (prescribed burns in 1997 and 1999, soil disking and manipulation of red cedar tree densities) on plant community composition. 9. At Point Pelee, there was a significant increase from 1997 to 1999 in the cover of species native to Red Cedar Savanna at one of the two experimental plots (De Laurier), while at the Nature Reserve the cover of native species declined, but this was not significant compared with 1997. Overall, the communities changed in opposite directions at the two experimental sites, most likely because the native seedbank and availability of seed sources varied. 10. We recommend that prescribed burns in Red Cedar Savanna sites be maintained and that desired species be actively reintroduced if no or low levels of local seed sources are available, in order for these species to compete more effectively with non-native species present at these sites.Item Open Access Response of Vegetation to Grazing Pressure by White-Tailed Deer, Odocoileus virginianus: Progress report on studies carried out in l992 at Point Pelee and at other sites in Southern Ontario(Biology Department, York University, 1993) Koh, Saewan; Bazely, DawnItem Open Access Responses of Vegetation to Grazing by White-Tailed Deer, Odocoileus virginianus, Progress Report #2: Studies carried out from 1992-1993 at Point Pelee National Park and at other sites in Southern Ontario(Biology Department, York University, 1994-06) Bazely, Dawn; Koh, SaewanItem Open Access A study of prescribed burns, tree and shrub layer in oak savanna plant communities in Southern Ontario: Pinery Provincial Park, Rondeau Provincial Park and Point Pelee National Park(Heritage Resources Centre, University of Waterloo, 2002) Tagliavia, Cecilia; Bazely, Dawn; Koh, SaewanOak savanna is a rare plant community in Ontario, which has been intensely overgrazed by white-tailed deer in the study areas. The goals of the study were to: 1) assess vegetation recovery after deer herd reduction and prescribed burns at Pinery Provincial Park, 2) monitor savanna remnants at Rondeau Provincial Park and Point Pelee National Park. In the Pinery sites deer exclosures were built in 1994 in order to test for deer grazing. Following burning some of the sites at Pinery and at Rondeau has shown an increase in species such as Big Bluestem (Andropogon gerardii). In the unburned site at Rondeau native savanna species are present. In Pelee the Oak savanna remnants appear to be in an advanced stage of succession with closer canopy and forest type species. The tree and shrub density are similar, except for the tree density in the Point Pelee sand dune.