On Wednesday, May 28, 1997 Thor Hjarsen wrote: >I got my hands on an article with the interesting title: "An Assessment > of the Allelopathic Potential of Eucalyptus" (May and Ash (1990): Austr. J. > Bot, 38: 245-254). This paper conclude (on the background of realistic > ecological studies), that Eucalyptus is effective in surpressing ground > vegetation, especially in drier climates!!!! Well, that was another way of > looking at allelopathy. Many tree species have mechanisms for suppressing ground vegetation, the most common being shade. In a closed canopy forest, hundreds of species that require more light are suppressed. There are also many species that exude chemicals from their leaves that are toxic to understory vegetation. In British Columbia the western red cedar, Thuja plicata, our provincial tree and the most important tree to the aboriginal people, is strongly allelopathic, much more so than eucalyptus spp. It is important to recognize that there are over 600 species of eucalyptus, each with different properties. Also, there are a wide variety of silviculture methods. When I toured eucalyptus plantation in Brazil there were many plantations where the understory vegetaion was very lush. The poorest understory vegetation was where plantations were established on land that had long been cleared for agriculture, perhaps the seed source for understory plants was diminished during the farming phase. Also, if you go to Australia where all the eucalypts are from, you will see a lush understory beneath most forests. It is true that in very dry areas the understory is mostly grasses but this is due to competition for water, not allelopathy. I think this paper has been referenced before but I will point to it again as it is very thorough: http://www.esd.ornl.gov/bfdp/reports/euc-braz/toc.html Cheers Patrick Moore, Greenspirit 4068 West 32nd Avenue Vancouver, BC, CANADA V6S 1Z6 e-mail pmoore@rogers.wave.ca 604-221-1990 ph. 604-221-1990 fax web http://www.greenspirit.com May the Forest be With You visit http://www.forest.org
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