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

蕨类植物覆盖了旧金山山谷约40%的牧场，而且还在不断蔓延。初步结果表明，“蕨菜”是由蜘蛛翼蕨（Pteridium arachnoideum）和尾蕨（Pteridium caudatum）两种植物和几个遗传差异系组成。利用形态学特征、同工酶分析和dna微卫星分析对研究区蕨类植物的分类组成进行了分析。在火灾引发的演替中，蕨类植物胜过了草尾草。这一过程是通过一个基于野外测量（生态、生态生理、辐射数据）的模型来模拟的，该模型假设对光的竞争是决定性因素。一个额外的模块模拟燃烧对比赛的影响。该模型应扩展到第三种植物生命形式，灌木巴克利斯latifolia，这是非常常见的蕨类植物出没的牧场。它还应适用于放牧和已实施两年半的蕨类控制措施的影响。与此同时，蕨类植物控制实验已合并为再温化实验，该实验将继续进行。自1975年以来，蕨类植物的入侵和传播将从Landsat图像中追踪，目前蕨类植物枯萎病的出现和进一步传播，一种潜在的生物防治手段将通过QuickBird图像进行跟踪。

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.