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

Bracken覆盖了旧金山山谷约40%的牧场，而且还在蔓延。初步研究结果表明，蕨类植物由蜘蛛蕨属和尾蕨属2个种和几个不同的遗传品系组成。对研究区蕨类植物的分类组成进行了形态特征、等位基因分析和DNA微卫星分析。在激烈的演替中，蕨类胜过牧草狗尾草。这一过程由一个基于野外测量(生态、生态生理、辐射数据)的模型模拟，该模型假定对光的竞争是决定因素。一个额外的模块模拟燃烧对比赛的影响。该模型应扩展到在蕨类出没的牧场中非常常见的第三种植物--宽叶灌木。它还应适用于放牧和已经运行了2.5年的蕨类控制措施的影响。同时，蕨菜防治试验已并入复牧试验，将继续进行。自1975年以来蕨类的入侵和传播将从陆地卫星场景和目前出现和进一步传播的蕨类枯萎病进行追踪，一种潜在的生物防治手段应在QuickBird场景之后进行。

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.