Vegetation controls on weathering intensity during the last deglacial transition in southeast Africa

Sarah J. Ivory, Michael M. McGlue, Geoffrey S. Ellis, Anne Marie Lézine, Andrew Cohen, Annie Vincens

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Tropical climate is rapidly changing, but the effects of these changes on the geosphere are unknown, despite a likelihood of climatically-induced changes on weathering and erosion. The lack of long, continuous paleo-records prevents an examination of terrestrial responses to climate change with sufficient detail to answer questions about how systems behaved in the past and may alter in the future. We use high-resolution records of pollen, clay mineralogy, and particle size from a drill core from Lake Malawi, southeast Africa, to examine atmosphere-biosphere-geosphere interactions during the last deglaciation (∼18-9 ka), a period of dramatic temperature and hydrologic changes. The results demonstrate that climatic controls on Lake Malawi vegetation are critically important to weathering processes and erosion patterns during the deglaciation. At 18 ka, afromontane forests dominated but were progressively replaced by tropical seasonal forest, as summer rainfall increased. Despite indication of decreased rainfall, drought-intolerant forest persisted through the Younger Dryas (YD) resulting from a shorter dry season. Following the YD, an intensified summer monsoon and increased rainfall seasonality were coeval with forest decline and expansion of drought-tolerant miombo woodland. Clay minerals closely track the vegetation record, with high ratios of kaolinite to smectite (K/S) indicating heavy leaching when forest predominates, despite variable rainfall. In the early Holocene, when rainfall and temperature increased (effective moisture remained low), open woodlands expansion resulted in decreased K/S, suggesting a reduction in chemical weathering intensity. Terrigenous sediment mass accumulation rates also increased, suggesting critical linkages among open vegetation and erosion during intervals of enhanced summer rainfall. This study shows a strong, direct influence of vegetation composition on weathering intensity in the tropics. As climate change will likely impact this interplay between the biosphere and geosphere, tropical landscape change could lead to deleterious effects on soil and water quality in regions with little infrastructure for mitigation.

Original languageEnglish (US)
Article numbere112855
JournalPLoS One
Volume9
Issue number11
DOIs
StatePublished - Nov 18 2014

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Weathering
weathering
Rain
rain
vegetation
Kaolin
Lake Malawi
Erosion
Drought
smectite
Malawi
kaolinite
Climate Change
Droughts
Climate change
Lakes
woodlands
summer
tropics
drought

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Vegetation controls on weathering intensity during the last deglacial transition in southeast Africa. / Ivory, Sarah J.; McGlue, Michael M.; Ellis, Geoffrey S.; Lézine, Anne Marie; Cohen, Andrew; Vincens, Annie.

In: PLoS One, Vol. 9, No. 11, e112855, 18.11.2014.

Research output: Contribution to journalArticle

Ivory, Sarah J. ; McGlue, Michael M. ; Ellis, Geoffrey S. ; Lézine, Anne Marie ; Cohen, Andrew ; Vincens, Annie. / Vegetation controls on weathering intensity during the last deglacial transition in southeast Africa. In: PLoS One. 2014 ; Vol. 9, No. 11.
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