up:: [[CKLA400 - Ecology and Sustainable Landscapes]] tags:: #source/course #on/design #on/landscape_design # CKLA400 M4 - High Park Black Oak Savannah High Park, spanning approximately 160 hectares, retains about one-third of its area in a fairly natural state despite extensive human use. Originally acquired by the City of Toronto in 1836, the park underwent various developments from the 1950s to the 1980s, transitioning towards landscape restoration in the late 1980s to preserve its natural ecosystems. ## Characteristic Species Composition of Black Oak Savannahs [[Black Oak Savannahs]] are characterized by the dominance of Black Oak trees, accompanied by various other species such as White Oak, Red Oak, and shrubs like Sassafras and Black Cherry. Grasses like Big Bluestem and Little Bluestem, along with herbaceous perennial flowers like Wild Lupine and Cup-plant, are also typical. *The composition of species in these savannahs depends on factors like soil moisture and the frequency of cool fires*. In a Black Oak savannah, tree canopies are usually widely spaced, with occasional denser areas, classified as Black Oak Woodland. In High Park, the typical species associated with Black Oak savannahs are present, but there are notable differences. The Black Oak population consists mostly of *mature to over-mature individuals due to decades of maintaining grass lawns under the trees*. Seedlings and saplings have been added in recent years to address the gap in age structure. Some typical *associated tree species are present in low numbers or absent*, while atypical species like Green Ash and European Buckthorn are present. Grasses may be thin in some areas, with Kentucky Blue Grass being common. *Herbaceous flowering plants have restricted distribution and are absent in certain areas*, with atypical species like Dandelion and Ragweed present. Controlled fire, crucial for controlling atypical species, has only recently been reintroduced to High Park, with its full beneficial impact yet to be achieved. **Key Points:** - Black Oak savannahs are dominated by Black Oak trees with accompanying species like White Oak, Red Oak, and various shrubs and grasses. - High Park exhibits characteristics of a Black Oak savannah but with notable differences, including a predominantly mature Black Oak population due to past grass lawn maintenance. - Some typical associated tree species are present in low numbers or absent, while atypical species like Green Ash and European Buckthorn are found. - Herbaceous flowering plants have restricted distribution, with atypical species like Dandelion and Ragweed present. - Controlled fire, necessary for managing atypical species, has only recently been reintroduced to High Park, with its full benefits yet to be realized. ## Edaphic (Soil) Conditions High Park's soil conditions are *predominantly sandy to sandy loam*, forming part of a glacial deposit that stretches northeast from the park, eventually looping eastward across Toronto before arching back down towards Lake Ontario. The terrain in High Park *slopes southward towards the lake, featuring a slightly rolling topography*. These sandy soils are typically acidic, deep, with a low water table, and contain little organic matter and nutrients. Consequently, *water retention is poor, providing an advantage to trees and shrubs with strong tap roots or deep lateral roots*, especially during drought conditions. Black Oak Savannahs, including those in High Park, are subject to periodic disturbances, *primarily drought and fire*. These disturbances play crucial roles in maintaining the resilience and characteristic species compositions of these ecosystems. Adaptations such as deep root systems and thick insulating bark enable trees to survive cool fires with minimal damage, while epicormic buds allow for rapid regeneration. [[Herbaceous]] species, including grasses and flower perennials, possess traits that aid in recovery from drought and fires, such as *impermeable seed coatings and the ability to resprout quickly after damage*. Fire also releases nutrients from dead organic matter, facilitating their rapid redeployment into living plant tissues. Drought conditions further prevent nutrient leaching from the sandy soil, reinforcing the synergistic relationship between drought and fire in maintaining the ecosystem's species composition and nutrient cycling. **Key Points:** - High Park's soil is sandy to sandy loam, with poor water retention and low nutrient content. - Black Oak Savannahs experience periodic disturbances of drought and fire. - Adaptations such as deep root systems and thick bark enable tree survival during fires. - Herbaceous species have traits that aid in recovery from disturbances, such as impermeable seed coatings and the ability to resprout quickly. - Fire liberates nutrients from dead organic matter, facilitating their rapid redeployment into living plant tissues. - Drought conditions prevent nutrient leaching from the soil, reinforcing the ecosystem's resilience. ## Species Composition Influence on Resilience The Black Oak Savannah of High Park comprises remnant patches of varying sizes and configurations, often isolated from one another by roads and other ecosystems. This spatial arrangement results in extensive ecotones between the Savannah patches and surrounding environments. These [[Ecotones]], characterized by the encroachment of various species, including invasive ones like White Mulberry, European Buckthorn, Manitoba Maple, and Tartarian Honeysuckle, are gradually encroaching into the Savannah patches. Despite attempts at controlled burning, these efforts have not been sufficient to suppress the development of ecotones. The gradual reduction of Black Oak Savannah patches due to [[Ecotone Encroachment]] poses a threat to their resilience. As the ratio of interior area to perimeter length decreases, the patches may lose their ability to sustain characteristic species in viable populations with sufficient genetic diversity. This decline in resilience makes the Savannah less capable of withstanding sudden shocks or disturbances. **Key Points:** - The Black Oak Savannah patches in High Park consist of remnant areas of varying sizes, isolated by roads and other ecosystems. - Ecotones, characterized by invasive species like White Mulberry and European Buckthorn, are encroaching into the Savannah patches, despite attempts at controlled burning. - The gradual reduction of Savannah patches due to ecotone encroachment threatens their resilience by diminishing the interior area and genetic diversity necessary for sustaining characteristic species. - This decline in resilience makes the Savannah less capable of surviving sudden shocks or disturbances. ## Spatial Structures The Black Oak savannahs of High Park exhibit distinctive spatial characteristics compared to typical Black Oak Savannahs. The canopy in High Park is *notably variable*, with some areas featuring merging canopies of several trees while others have extensive open spaces. There is a scarcity of younger Black Oak trees and saplings, with the few present belonging to non-typical species, contributing to an overall *atypical spatial structure* for a Black Oak Savannah. Furthermore, the ecotones surrounding the Black Oak Savannahs in High Park differ significantly from the norm. These areas are characterized by the presence of *invasive species such as White Mulberry and European Buckthorn, along with a notable presence of Manitoba Maple*. The ecotones are extensive relative to their coverage area due to fragmentation, and their depth suggests prolonged ecotone development without the moderating influence of regular cool fires. Overall, the absence of regular cool fires as a disturbance phenomenon has led to skewed spatial structures and ecotone development in the Black Oak savannahs of High Park, deviating from what is typical of such ecosystems. **Key Points:** - The Black Oak savannahs of High Park exhibit unique spatial characteristics compared to typical Black Oak Savannahs. - The canopy in High Park varies significantly, with some areas densely populated with merging trees and others featuring extensive open spaces. - Younger Black Oak trees and saplings are scarce, with those present belonging to non-typical species, resulting in an atypical spatial structure. - The ecotones surrounding the Black Oak Savannahs in High Park contain invasive species like White Mulberry and European Buckthorn, along with a notable presence of Manitoba Maple. - Ecotones are extensive and deep, indicating prolonged development without the moderating influence of regular cool fires. - The absence of regular cool fires has contributed to skewed spatial structures and ecotone development in High Park's Black Oak savannahs. ## Flows with Adjacent Ecosystems The Black Oak Savannah in High Park *boasts a high perimeter-to-area ratio*, allowing for extensive boundaries where various flows occur. While larger mammal species are scarce, the park is abundant with *dogs, raccoons, squirrels, chipmunks, and humans*, with occasional sightings of deer and coyotes. *Songbirds, including Red Tail Hawks and Seagulls, thrive in this environment*, favoring ecotone habitats. They play a *crucial role in spreading seeds of ecotone berry plants* like White Mulberry and European Buckthorn, as well as herbaceous plants such as Burdock. Prevailing wind patterns and diurnal breezes aid in dispersing wind-borne seeds of herbaceous species like goldenrods, asters, milkweeds, and Dog-Strangling Vine into the Savannah. Localized water-mediated *soil erosion occurs along footpaths*, especially in drier or sloped areas of the park. This erosion, coupled with the movement of various species by seed, particularly weed species, takes advantage of the disturbed conditions linked to soil erosion. **Key Points:** - Black Oak Savannah in High Park has a high perimeter-to-area ratio, facilitating various flows within its boundaries. - Songbirds, including Red Tail Hawks and Seagulls, thrive in ecotone habitats, aiding in seed dispersal of various plant species. - Localized water-mediated soil erosion occurs along footpaths, especially in drier or sloped areas. - Movement of various species by seed, particularly weed species, takes advantage of disturbed conditions linked to soil erosion. ## Influence of Human Behaviours The Black Oak Savannahs in High Park have faced significant impacts from intensive human use, particularly between 1950 and 1990. During this period, *the removal of understorey species and introduction of mown lawns drastically reduced diversity and disrupted spatial structure*. This loss of appropriate age structure in tree and shrub populations, notably the Black Oak, has been long-lasting and irreparable. *Efforts to introduce younger trees and shrubs cannot fully replace the lost age cohorts, leading to diminished reproductive potential and genetic diversity*. The development of recreational facilities has further fragmented the once vast continuous ecosystem of Black Oak Savanna into smaller fragments, isolating populations and reducing reproductive potential. *Trail use, particularly by bicyclists, disrupts regenerative processes*, necessitating periodic closures of severely affected areas. Controlled burning has been reintroduced to regenerate characteristic species and spatial structure, but more episodes over larger areas are needed to address creeping ecotones and invasive species. Reintroducing genetically robust and age-diverse populations remains a challenge, alongside funding issues hampering necessary monitoring efforts. **Key points:** - Removal of understorey species and introduction of mown lawns reduced diversity and disrupted spatial structure. - Loss of appropriate age structure in tree and shrub populations, especially the Black Oak, has been long-lasting. - Fragmentation due to recreational facility development isolates populations and reduces reproductive potential. - Trail use, particularly by bicyclists, disrupts regenerative processes, requiring periodic closures of affected areas. - Funding issues hinder necessary monitoring efforts to ensure ecosystem persistence.