DOI: 10.5194/cp-10-2067-2014
Scopus记录号: 2-s2.0-84913596090
论文题名: Sensitivity of East African savannah vegetation to historical moisture-balance variation
作者: Ssemmanda I. ; Gelorini V. ; Verschuren D.
刊名: Climate of the Past
ISSN: 18149324
出版年: 2014
卷: 10, 期: 6 起始页码: 2067
结束页码: 2080
语种: 英语
Scopus关键词: disturbance
; ecotone
; forest dynamics
; moisture content
; paleoclimate
; paleoecology
; palynology
; pollen
; savanna
; shrub
; Queen Elizabeth National Park
; Uganda
英文摘要: 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. © Author(s) 2014. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/49204
Appears in Collections: 气候变化与战略
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Recommended Citation:
Ssemmanda I.,Gelorini V.,Verschuren D.. Sensitivity of East African savannah vegetation to historical moisture-balance variation[J]. Climate of the Past,2014-01-01,10(6)