Late and postglacial vegetation and fire history in Southern Patagonia and Tierra del Fuego
Late and postglacial vegetation and fire history in Southern Patagonia and Tierra del Fuego
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DOI：
10.1016/j.palaeo.2010.08.013
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发表时间：
2010-11
期刊：
影响因子：
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通讯作者：
V. Markgraf;Ulli M. Huber
中科院分区：
文献类型：
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作者：
V. Markgraf;Ulli M. Huber
在火地岛（哈伯顿，54°54′S）和巴塔哥尼亚南部（里奥鲁本斯，52°4′48″S）的低海拔地区发现了两个17,000年前的泥炭沼泽记录，通过对火地岛（Paso Garibaldi，54°43′S）上树线的14，000个calyr BP记录的花粉、木炭和植物宏体化石进行分析，分别重建了区域和当地植被、火灾频率和沼泽水文的变化。过去的环境变化，在低地记录和上部树线记录解释的有效水分的变化。在晚冰期，有效的水分变化，在低海拔和高海拔地区进行了解释，从可比的变化之间的中草药丰富的草原和干旱的Empetrum石南或灌木草原丰富的干扰指标。晚冰期有效水分变化主要是由温度变化驱动的。在全新世早期，开放Nothofagus林地在低地在今天的茂密的森林地区的扩张是与一个显着的降水增加。然而，降水量必须保持高度可变的长达一个世纪的夏季干旱增加的时间，证明了反复的间隔时，沼泽干涸和火灾频率很高。在11，000和9000 calyr BP的Nothofagus森林-安第斯苔原交错带的上坡位移似乎也反映了降水量的增加。然而，降水量的变化，一定没有影响到上层树线环境，因为没有火灾记录和现在的Nothofagus森林已成为9000 calyr BP后建立。8000 ~ 7000年和2500 ~ c年的上层树线明显低于现在。400calyr BP。在这段时间里，低海拔的环境没有发生变化，这表明上部的树线可能受到了低温的影响。在c之后。5000 calyr BP火灾在低地变得罕见，这表明转变到一个均匀的降水制度，只有轻微的夏季干旱的间隔。在上树线没有记录到同时发生的变化。因此，晚冰期和全新世早期的上部和下部的树线环境显然类似的主要水分变化。只有在全新世中晚期，高海拔和低海拔的环境变化不同，这表明不同的气候信号，在低地降水和高海拔温度的响应。
Two 17,000-yr-old peat bog records from low-elevation sites in Tierra del Fuego (Harberton, 54°54′S) and southern Patagonia (Río Rubens, 52°4′48″S) and one c. 14,000calyr BP record from the upper treeline in Tierra del Fuego (Paso Garibaldi, 54°43′S) were analyzed for pollen, charcoal, and plant macrofossils to reconstruct changes in regional and local vegetation, fire frequency, and bog hydrology, respectively. Past environmental changes in both lowland records and in the upper treeline record are interpreted in terms of variations in effective moisture. During the late-glacial period, effective moisture changes at both low and high-elevation sites were interpreted from comparable shifts between mesic herb-rich grasslands and arid Empetrum heath or shrub–grassland with abundant disturbance indicators. The late-glacial effective moisture changes were primarily driven by temperature changes. During the early Holocene, expansion of open Nothofagus woodlands in the lowlands in present-day areas of dense forest was related to a marked precipitation increase. However, precipitation must have remained highly variable with century-long periods of increased summer drought, as evidenced by repeated intervals when bogs dried out and fire frequency was high. Up-slope shifts of the Nothofagus forest — Andean tundra ecotone at 11,000 and 9000calyr BP also appear to reflect precipitation increases. Precipitation variability, however, must not have affected the upper treeline environments as no fires were recorded and the present-day Nothofagus forest had become established after 9000calyr BP. Upper treeline apparently was below present from 8000 to 7000 and 2500 to c. 400calyr BP. During those times low-elevation environments did not register change which suggests that the upper treeline may have been affected by lower temperatures. After c. 5000calyr BP fires became rare in the lowlands, suggesting a shift to an equable precipitation regime with only minor intervals of summer drought. No simultaneous change was recorded at the upper treeline. Thus, for the late-glacial and early Holocene the upper and lower treeline environments apparently responded similarly to primarily moisture changes. Only during the mid- and late Holocene environmental changes at high and low elevations differed, suggesting responses to different climate signals, precipitation in the lowlands and temperature at high elevation.