Land-use change in the form of extensive Pinus plantations is currently altering the natural vegetation cover at the forest–steppe ecotone in northern Patagonia. Providing recommendations for conservation efforts, with respect to this recent and earlier land-use changes, requires a longer time perspective. Using pollen analysis, we investigated to what degree the colonization of the area by Euro-American settlers changed the forest composition and the vegetation cover, and to explore the spread of the European weed Rumex acetosella. This study is based on short sediment cores from six lakes in the Araucaria araucana forest region, across the vegetation gradient from the forest to the steppe. Results document that although Araucaria araucana has been extensively logged elsewhere, near the investigated sites, populations were rather stable and other elements of the vegetation changed little with the initiation of Euro-American settlements. A reduction of Nothofagus dombeyi-type pollen occurred at some sites presumably due to logging Nothofagus dombeyi trees, while toward the steppe, Nothofagus antarctica shrubs may have been removed for pasture. The appearance of Rumex acetosella pollen is consistent with the initiation of land use by Euro-American settlers in all cores, probably indicating the onset of animal farming. The rise of the Rumex acetosella pollen curve during the 1950s marks more recent land-use change. These observations indicate that the spread and local expansion of the weed requires disturbance. Overall, the study shows that the initial colonization of the area by Euro-American settlers had little effect on the natural vegetation structure, while developments since the 1950s are strongly altering the natural vegetation cover.

中文翻译：

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巴塔哥尼亚北部 Araucaria araucana 森林近期土地利用变化的影响

以广泛的松树种植园形式出现的土地利用变化目前正在改变巴塔哥尼亚北部森林-草原交错带的自然植被覆盖。就近期和较早的土地利用变化提供保护工作的建议需要更长的时间。通过花粉分析，我们调查了欧美定居者对该地区的殖民在多大程度上改变了森林组成和植被覆盖，并探索了欧洲杂草 Rumex acetosella 的传播。本研究基于来自南洋杉林区六个湖泊的短沉积物核心，跨越从森林到草原的植被梯度。结果表明，虽然南洋杉已被广泛采伐，但在调查地点附近，随着欧美定居点的开始，人口相当稳定，植被的其他元素几乎没有变化。某些地点的山毛榉型花粉减少可能是由于采伐山毛榉树而导致的，而在草原附近，可能已移除了南极山毛榉灌木用于放牧。Rumex acetosella 花粉的出现与欧美定居者在所有核心土地使用的开始一致，可能表明畜牧业的开始。1950 年代 Rumex acetosella 花粉曲线的上升标志着最近的土地利用变化。这些观察表明杂草的传播和局部扩张需要干扰。全面的，