A late Holocene pollen record from proglacial Oblong Tarn, Mount Kenya.
A late Holocene pollen record from proglacial Oblong Tarn, Mount Kenya.
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DOI：
10.1371/journal.pone.0184925
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发表时间：
2017
期刊：
影响因子：
3.7
通讯作者：
Rosqvist G
中科院分区：
文献类型：
--
作者：
Courtney Mustaphi CJ;Gajewski K;Marchant R;Rosqvist G
高海拔生态系统，如肯尼亚山的生态系统正在经历重大变化，20世纪冰川冰的加速消失为高山植物的生长创造了新的空间。这些生态系统对气候变化反应迅速，在冰川退缩的几十年里，非洲高山先锋分类群稳定了贫瘠的土地，促进了土壤的发育，促进了高山植被的复杂斑块。冰缘湖泊沉积物记录可用于研究高寒和山地植被组成的百年和千年尺度变化。在这里，我们提出了一个5300年的复合花粉记录来自一个高山tarn（海拔4370米）在肯尼亚山的Hausberg谷。总体而言，记录显示花粉组合随时间变化不大，有丰富的山地森林类群来自中海拔，特别是高丰度的喜风性Podocarpus花粉。非洲高山分类群包括炼金属、蜡菊属和树endrosenecia型，反映了当地的植被覆盖情况。整个记录中都有来自白垩系带的花粉，禾科花粉的比例很高，与东非其他高海拔花粉记录相似。长形Tarn记录了晚全新世（~4000 calyr BP-present）以来Podocarpus和Podocarpus科植物的花粉组合组成和丰度，与附近埃尔贡山和乞力马扎罗山等高山中高海拔遗址的花粉记录相似。这些结果表明，花粉的上坡运输量很大，而局部分类群的差异很小。根据3100 calyr BP的花粉组合估算，高山和白垩系分类类群对全球晚全新世变冷的长期响应呈轻微下降趋势，对区域水文气候变率的响应呈逐步下降趋势。花粉组合主成分轴值的变化与独立的中高程温度重建相一致，支持了山地森林植被上坡花粉运输的强烈影响以及温度与山地植被动态之间的关联。花粉积累速率表现出一定的变异性，与湖泊的成矿沉积物输入有关。长形Tarn花粉记录表明，肯尼亚山的植被在5300-3100 calyr BP之间有所减少，而中高海拔森林的山地分类群在百年尺度上有较小的变化。该记录突出了利用前冰期湖泊沉积物来研究突出山体上植被变化的潜力、挑战和机遇。
High-elevation ecosystems, such as those on Mount Kenya are undergoing significant changes, with accelerated glacial ice losses over the twentieth century creating new space for alpine plants to establish. These ecosystems respond rapidly to climatic variability and within decades of glacial retreat, Afroalpine pioneering taxa stabilize barren land and facilitate soil development, promoting complex patches of alpine vegetation. Periglacial lake sediment records can be used to examine centennial and millennial scale variations in alpine and montane vegetation compositions. Here we present a 5300-year composite pollen record from an alpine tarn (4370 m asl) in the Hausberg Valley of Mount Kenya. Overall, the record shows little apparent variation in the pollen assemblage through time with abundant montane forest taxa derived and transported from mid elevations, notably high abundances of aerophilous Podocarpus pollen. Afroalpine taxa included Alchemilla, Helichrysum and Dendrosenecio-type, reflecting local vegetation cover. Pollen from the ericaceous zone was present throughout the record and Poaceae percentages were high, similar to other high elevation pollen records from eastern Africa. The Oblong Tarn record pollen assemblage composition and abundances of Podocarpus and Poaceae since the late Holocene (~4000 cal yr BP-present) are similar to pollen records from mid-to-high elevation sites of nearby high mountains such as Mount Elgon and Kilimanjaro. These results suggest a significant amount of uphill pollen transport with only minor apparent variation in local taxa. Slight decreasing trends in alpine and ericaceous taxonomic groups show a long-term response to global late Holocene cooling and a step decrease in rate of change estimated from the pollen assemblages at 3100 cal yr BP in response to regional hydroclimatic variability. Changes in the principal component axis scores of the pollen assemblage were coherent with an independent mid-elevation temperature reconstruction, which supported the strong influence of uphill pollen transport from montane forest vegetation and association between temperatures and montane vegetation dynamics. Pollen accumulation rates showed some variability related to minerogenic sediment input to the lake. The Oblong Tarn pollen record provides an indication of long term vegetation change atop Mount Kenya showing some decreases in local alpine and ericaceous taxa from 5300–3100 cal yr BP and minor centennial-scale variability of montane taxa from mid elevation forests. The record highlights potentials, challenges and opportunities for the use of proglacial lacustrine sediment to examine vegetation change on prominent mountain massifs.
影响因子：
1.6
作者：
Aeschbacher, J;Liniger, H;Weingartner, R
通讯作者：
Weingartner, R