Sensitivity of East African savannah vegetation to historical moisture-balance variation
Sensitivity of East African savannah vegetation to historical moisture-balance variation
复制标题
东非草原植被对历史水分平衡变化的敏感性
DOI：
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
D. Verschuren
中科院分区：
文献类型：
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作者：
I. Ssemmanda;V. Gelorini;D. Verschuren
抽象的。化石花粉记录为了解陆地生态系统对气候变化的敏感性提供了关键的见解。然而，追踪植被对相对温和的历史气候波动的反应往往是复杂的压倒一切的签名人为景观干扰。在这里，我们使用高分辨率的花粉数据从一个~200年的湖泊沉积物记录在开放的树木繁茂的大草原伊丽莎白女王国家公园（乌干达西南部），以评估敏感性的热带低地草原森林过渡到历史，十年尺度的水分平衡波动。具体来说，我们跟踪植被响应的三个事件较高的平均降雨量可追溯到19世纪20年代至19世纪30年代，约。1865-1890年和1962年到2000年左右。我们的花粉数据确实揭示了三个湿润期的序列，被两个干燥期隔开。在推断的更潮湿的插曲，我们发现增加的百分比花粉丰富的树木和灌木从潮湿的半落叶林（Allophylus，Macaranga，Alchornea，Celtis），河岸森林（凤凰reclinata）和树木繁茂的萨凡纳（铁苋菜属，Rhus-type vulgaris，使君子科/木贼科）以及当地裂谷草原常见的类群（金合欢属、榕属），共同造成禾本科花粉的暂时性大幅减少（减少至陆地花粉总和的45-55%）。在干旱期间，禾本科花粉达到65- 75%的价值，旱地草本植物，如鸭跖草，正义型odora和藜科扩大了在Asteraceae，Solpendi型，Swertia usambarensis型，（适度）荨麻科的费用。注意到树栖类群的整体丰富度仍然很高，但它们的综合丰度低，我们得出结论，在过去的200年里，奇布韦拉湖周围的景观一直是一个开放的树木繁茂的萨凡纳，历史上的水分平衡变化对当地的树木覆盖（主要是丰富的金合欢和榕树）和潮湿的土壤地区促进凤凰reclinata的发生产生适度的影响。真正的森林树木在潮湿的情节强大的明显扩张，可以解释部分通过增强花粉输入通过一个临时激活的高地流。从20世纪70年代起，外来树木和文化指标的花粉出现了，但它们的综合影响未能掩盖花粉记录中自然植被动态的特征。
Abstract. Fossil pollen records provide key insight into the sensitivity of terrestrial ecosystems to climate change. However, tracing vegetation response to relatively modest historical climate fluctuations is often complicated by the overriding signature of anthropogenic landscape disturbance. Here we use high-resolution pollen data from a ~200-year lake-sediment record in open wooded savannah of Queen Elizabeth National Park (southwestern Uganda) to assess the sensitivity of the tropical lowland grassland–forest transition to historical, decade-scale moisture-balance fluctuations. Specifically we trace vegetation response to three episodes of higher average rainfall dated to the 1820s–1830s, ca. 1865–1890 and from 1962 to around 2000. Our pollen data indeed reveal a sequence of three wet periods, separated by two drier periods. During the inferred wetter episodes we find increases in the percent pollen abundance of trees and shrubs from moist semi-deciduous forest (Allophylus, Macaranga, Alchornea, Celtis), riparian forest (Phoenix reclinata) and wooded savannah (Acalypha, Rhus-type vulgaris, Combretaceae/Melastomataceae) as well as taxa common in the local rift-valley grasslands (Acacia, Ficus), together creating strong temporary reductions in Poaceae pollen (to 45–55% of the terrestrial pollen sum). During intervening dry periods, Poaceae pollen attained values of 65–75%, and dryland herbs such as Commelina, Justicia-type odora and Chenopodiaceae expanded at the expense of Asteraceae, Solanum-type, Swertia usambarensis-type, and (modestly so) Urticaceae. Noting that the overall richness of arboreal taxa remained high but their combined abundance low, we conclude that the landscape surrounding Lake Chibwera has been an open wooded savannah throughout the past 200 years, with historical moisture-balance variation exerting modest effects on local tree cover (mostly the abundance of Acacia and Ficus) and the occurrence of damp soil areas promoting Phoenix reclinata. The strong apparent expansion of true forest trees during wet episodes can be explained partly by enhanced pollen input via a temporarily activated upland stream. Pollen from exotic trees and cultural indicators appears from the 1970s onwards, but their combined influence fails to mask the signature of natural vegetation dynamics in the pollen record.
影响因子：
4
作者：
Isabelle Matthias;T. Giesecke
通讯作者：
Isabelle Matthias;T. Giesecke
影响因子：
4.3
作者：
Mills, K.;Ryves, D. B.;Tyler, J. J.
通讯作者：
Tyler, J. J.