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Ecological Integrity at Hendrie Valley Nature Sanctuary

November 9, 2023

By Tys Theijsmeijer, Sr. Director Ecosystem Stewardship, Royal Botanical Gardens

The Cootes to Escarpment Ecological Corridors Pilot Project (Ecocorridors) provides Royal Botanical Gardens the opportunity to work on forest protection and restoration at a larger scale than we have in the past. One of the 2023 special project sites is in Hendrie Valley Nature Sanctuary. For RBGs Hendrie Valley Nature Sanctuary the challenges are many with Invasive Plants, particularly Eurasian trees seeding into the forest ecosystem as a top priority for actionThe status and integrity of the forest ecosystem is summarized in the Hendrie Valley 2018 Forest Status Report with several invasive trees species abundant enough to occur in standardized monitoring plots with the most abundant invasive species including the Norway Maple (Acer platanoides), Horse Chestunt (Aesculus hippocastanum) and the Tree of Heaven (Ailanthus altissima) – see table below.  Other invasive plants species also continue to creep in, including the regionally very abundant shrubs Amur Honeysuckle (Lorincia maackii) and Common Buckthorn (Rhamnus cathartica), abundant throughout southern Ontario in old hedge rows and in regenerating former pastures. The overall list of invasive plants is very long and is daunting to think about. The Cootes to Escarpment Ecopark System collaboration for the Lower Grindstone Heritage Lands Management Plan details the local ecological threats and actions that are needed to maintain and restore ecological integrity of places such as Hendrie Valley. 

In the fall of 2023 in Hendrie Valley Nature Sanctuary a removal project for highly invasive trees is continuing. The resources available through EcoCorridors Pilot project will dramatically increase the RBG restoration work for forest protection. The primary focus is removal of up-and-coming Norway Maple and Tree of Heaven tree species, but with a number of other invasive species included. Several thousand small trees and shrubs will be removed. In addition, the large individual invasive trees found around the edges of the valley, the source of the seeds and numbering several dozen, will also be removed. The removal process will be through best practices to ensure minimal impact on the sensitive habitat. The end goal is to facilitate recovery of the declining forest habitat, reduce the supply of nonnative tree seeds, and provide light to the forest floor again for locally native tree species seedlings such as oak and maple to regenerate.   

Table: The main identification of Norway maple in comparison to give species that may appear similar (lookalike). Key identification features that seperate the lookalikes from Norway maple are in bold.

Table: The main identification of Norway maple in comparison to give species that may appear similar (lookalike). Key identification features that seperate the lookalikes from Norway maple are in bold.

The topic of ecological integrity and invasive plant species is a daunting one. Initiatives to remove invasive plants from environmental protection areas as well as home gardens and landscaping is a rapidly growing area of activity with thousands of initiatives across southern Ontario alone.  Centralize resources for information support are forming in several areas including the Ontario Invasive Species Centre, the Canadian Council on Invasive Species, the Nature Conservancy of Canada and Carolinian Canada to just name a few.  Local leaders include the Royal Botanical Gardens, the Hamilton and Halton Conservation Authorities, the Hamilton Naturalist Club and the Bruce Trail Conservancy. All of these groups are undertaking projects to remove invasive plants on their individual portions of lands along the Niagara Escarpment World Biosphere in support of longer-term environmental sustainability.  Many residents of the area have also joined in, both volunteering at the above organizations as well as removing plants from their own properties.  Land owner support and resources are available on this theme and as a starting point it is recommended to review Canada’s National Strategy on Invasive Species as well as the resources assembled at the bottom of the RBG’s Invasive Species webpage. The National strategy is a product of the signing of the United Nations Convention of Biological Diversity by Canadians in 1994 providing a framework for all to participate in.

Table: 2018 Hendrie Valley tree abundance summary for the six 20x20m forest monitoring plots, sorted by relative abundance; non-native species are bolded.

Species Relative Abundance (%) Density (trees/ha) Basal Area (m2) Percentage Basal Area (%)
Red Maple, Acer rubrum 25.74 108 16.66 9.14
Red Oak, Quercus rubra 23.76 100 149.35 81.94
Black Cherry, Prunus serotina 12.87 54 4.08 2.24
Norway Maple, Acer platanoides 8.91 38 3.3 1.81
Black Maple, Acer nigrum 5.94 25 2.27 1.25
White Oak, Quercus alba 4.95 21 3.87 2.12
Sugar Maple, Acer saccharum 1.98 8 0.26 0.14
Horse Chestnut, Aesculus hippocastanum 1.98 8 0.03 0.02
Green Ash, Fraxinus americana 1.98 8 0.05 0.03
Black Oak, Quercus velutina 1.98 8 1.24 0.68
White Birch, Betula papyrifera 0.99 4 0.03 0.02
Bitternut Hickory, Carya cordiformis 0.99 4 0.01 0.00
Shagbark Hickory, Carya ovata 0.99 4 0.25 0.14
White Ash, Fraxinus americana 0.99 4 0.03 0.02
Black Walnut, Juglans nigra 0.99 4 0.02 0.01
Ironwood, Ostrya virginiana 0.99 4 0.01 0.01
White Pine, Pinus strobus 0.99 4 0.22 0.12
Large-tooth Aspen, Populus grandidentata 0.99 4 0.08 0.04
Bur Oak, Quercus macrocarpa 0.99 4 0.38 0.21
Hemlock, Tsuga canadensis 0.99 4 0.14 0.08
Species Richness 20

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