The biology of southern bracken in the anthropogenic ecosystem in the San Francisco valley of South Ecuador

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Bracken covers about 40% of the pastures in the San Francisco valley and it is still spreading. Preliminary results suggest that “bracken” is composed of 2 species Pteridium arachnoideum and caudatum and several genetically differing lines. The taxonomic composition of bracken in the research area will be analysed using morphological characters, allozyme analysis and DNA-microsatellites. In a firetriggered succession, bracken outcompetes the pasture grass Setaria. This process is simulated by a model which is based on field measurements (ecological, ecophysiological, radiation data) assuming competition for light as the decisive factor. An extra module simulates the effect of burning on the competition. The model shall be extended to a third plant life form, the bush Baccharis latifolia, which is very common in the bracken-infested pastures. It shall also be applied to the effects of grazing and of bracken control measures which have been running for 2.5 years. The bracken control experiment has meanwhile merged in a repastorization experiment which shall be continued. Invasion and spreading of bracken since 1975 will be traced from Landsat scenes and the current appearance and further spreading of a bracken blight disease, a potential means of biocontrol shall be followed with QuickBird scenes.