Coastal Forest Karst Ecosystems
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Several environmental factors favour the development of karst on BC's coast:

  • geology--large units of very pure carbonate bedrock,
  • heavy rainfall--a plentiful and steady supply of water,
  • steep topography--creates higher energy sinking stream systems for underground drainage development,
  • tectonic activity--uplifting, tilting, faulting, and folding limestone beds cause weaknesses and fractures in the rock for exploitation by infiltrating water,
  • vegetation cover--extensive forests provide a high level of organic matter, increasing CO2 in the soil as it decomposes,
  • glacial history--deglaciation released great quantities of water to dissolve susceptible bedrock. (Photo by P. Griffiths.)

Photo of a sinkhole
Surface stream flowing into sinkhole
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Most of the karst on the coast occurs within the coastal western hemlock biogeoclimatic zone where the major tree species are western hemlock and amabilis fir, with some western redcedar, Sitka spruce, and yellow-cedar. These coastal forest karst ecosystems are often characterized by large mature trees, diverse plant and animal communities, highly productive aquatic systems, well-developed subsurface drainage, and extensive surface karst and underlying cave resources.

Coastal forest karst ecosystems are commonly more productive than similar forest sites on non-karst terrain. This increased productivity can be largely attributed to well-drained soils and the nutrient cycling associated with karst. As carbonate bedrock is dissolved by penetrating water, it releases CO2, calcium carbonate, and micro-nutrients into the soil, encouraging plant growth and development. The level of productivity appears to be directly related to the extent of surface and subsurface connections.

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