October 14th, 2005
Why salmonberries? Or Garry oaks or oceanspray or pearly everlasting for that matter? What reasons are there to promote the retention and replanting of native species?
Native plants are plants that historically grow in a given locality, under certain conditions. The water regime, the type of soil and its fertility, the slope, the position relative to the sun, prevailing winds, temperature, even the underlying bedrock are all factors that determine the evolution of plant communities. In addition, the frequency of disturbances such as fire and flooding, further contribute to the makeup of an ecosystem. Within all these many and varied constraints, native plants have evolved over thousands of years, to take best advantage of their situation.
Salmonberries, for example, thrive in reliably moist, rich soil conditions, often along streambanks and they tolerate fluctuating groundwater tables, something most plants find deadly. They are often found in flood and erosion prone areas along creeks and streams. They have strong roots which are invaluable in these conditions because they hold the soil during heavy floods and their suckering ability quickly repopulates an area with new plants, if necessary. They provide food, in the form of nectar, pollen, leaves and berries to a wide variety of insects, birds and animals. In fact, their very early flowers are an important energy source to the first hungry pollinators and humming birds that arrive in the spring.
If you were to plant rhododendrons or other less adapted plants in place of the salmonberries, it would disturb the interactions among the various species. There would be no early flowers, of the right size and shape for the starving rufous humming birds. There would be no regeneration after a heavy late winter flood, because rhodos don’t have shoot producing roots and cannot quickly form colonies; the earth would fall into the stream, silting over gravel beds which might harbour cutthroat trout eggs, because rhododendrons, although beautiful, did not evolve to occupy this particular set of circumstances and associations.
Whether in development projects or around your own property, retaining native plants is the best option, replanting with appropriate native species a passable second and replanting with non-native plants a poor third, even when they are adapted to the site conditions, such as wet or dry soils. Broom, for instance is adapted to our dry summers with sun-baked soils, but it has been found deficient in other regards. It has very aggressive survival techniques with which it displaces native species, so that there are fewer types and reduced abundance of plants, insects and animals in areas where broom has secured a foothold.
Purple loosestrife is a flamboyantly beautiful plant that has been planted in wet garden areas across North America. It outcompetes virtually all other plants in favourable areas, successfully invading wetlands across the continent, again reducing diversity. Yes, a red-winged blackbird can use it for a nest site, but soon there will be less food for the blackbird to eat as the insect species that depend on a variety of plants to survive move on to more diverse, wetlands comprised of their natural plant communities.
Like everyday gardening, understanding the site specific needs of a plant, determines its location. If you have a salmonberry growing on the edge of a lightly shaded stream and transplant it to the top of a sunny rocky bluff only fifteen metres away, although it is a native plant, it will not flourish, in fact, it will most likely die, because it is outside its ecological comfort zone. Conversely, if you were to transplant a clump of creamy grey stonecrop from its cliff hanging, sunny habitat into the midst of an alder swamp, it too would not prosper. In other words, the plants are dependant on the conditions in which they have evolved.
This evolution has included not just the plants, but the insect, bird and animal worlds as well. The natural diversity of plants also determines the variety of insect species, which in turn influences the bird and animal species that will inhabit the area. There will be different birds, ants, beetles and flying pollinators, for each type of plant community, the mix and abundance dependant on the environment.
Salmonberries, with their myriad ecological values, and their striking rich magenta flowers, have an important role to play in a sustainable environment. Like all native species, they perform diverse roles within their community, some of which we can appreciate with a bit of knowledge and some which are likely as yet undiscovered.
Monday, October 13, 2008
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