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Karri forest is tall open forest of Eucalyptus diversicolor (karri), one of the tallest hardwoods in the world.
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Karri forest occurs only in the south-west corner of the Southwest Botanical Province of Western Australia, in the Warren biogeographic region. The Warren region is also known as the Karri Forest Region, but this is a misnomer, as only about half of the region is vegetated with karri forest.
Historically, karri forest supported timber and firewood industries from the 1880s, when access to the forest was improved by a network of railway lines. Small settlements such as Karridale, Deanmill and Pemberton were established around timber mills, and have since become townships despite the closing of some of the mills.
Some of the remaining areas of karri forest are now protected in reserves such as Brockman National Park, Warren National Park, Beedelup National Park and Gloucester National Park.
Karri forest
Ecology of the karri forest
Karri forest is found on loamy soils, but may include wetlands, river edges, heathland and rocky outcrops. Leaf litter (i.e. twigs, leaves and branches which fall from trees to the ground) plays a substantial role in nutrient recycling and has been measured at 9.45 tonnes per hectare in mature forest. Leaf litter fall and nutrient cycling of calcium, potassium and magnesium in mature forest is the highest reported for any eucalypt forest.
The understorey of karri forest is dense and may reach a height of 10m, according to the conditions of the site and time since fire. Understorey leaf material contributes between 30 and 70% of the nutrients by weight, and is particularly important in the cycling of major plant nutrients nitrogen and sulfur, and micro-nutrients copper and zinc.