wetland vegetation dynamics in the semi-arid amboseli...
TRANSCRIPT
1,4 1 1 2Colin Courtney-Mustaphi *, Rob Marchant , Esther Githumbi , Veronica Muiruri ,2 2 3,1 4 4Stephen Rucina , Rebecca Muthoni , Suzi Richer , Paul Lane , Anna Shoemaker
1 University of York Institute for Tropical Ecosystems, UK2 National Museums of Kenya, Nairobi, Kenya3 Dept. of Archaeology, University of York, UK
4 Dept. of Archaeology and Ancient History, University of Uppsala, Sweden* Email: [email protected]
Wetland vegetation dynamics in the semi-arid Amboseli landscape of southern Kenya
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Depth (cm)
ESAM2c
ESAM2b
ESAM2a
ESAM1
Podocarpus
0 20
Juniperus
0 20
Celtis
0 20
Croton
0 20
Olea
0 20
Schefflera
0 20
Acacia
0 20
Balanites
0 20
Capparis
0 20
Commiphora
0 50
Cordia
0 50
Terminalia
0 20
Acanthaceae
0 50
Acalypha
0 20
Aloe
0 50
Apocynaceae
0 20
Asteraceae
0 100
Amara/chenop
0 20
Brassicaceae
0 20
Cadaba
0 20
Cucurbitaceae
0 50
Impatiens
0 20
Indigofera
0 50
Justicia
0 50
Liliaceae
0 20
Rhus
0 20
Rumex
0 50
Salvadora
0 50
Tapura
0 20
Umbelliferae
0 100
Urticaceae
0 20
Poaceae>60µm
0 100
Poaceae
Pinus
0 50
Nymphaea
0 100
Cyperaceae
0 100
Typha
0 2000
Charco
al>1
25µm
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cal yr BP
AFROMONTANE WOODLAND SHRUB/GRASSLAND AQUATIC
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% terrestrial pollen sum % aquatic sum -3No. cm
sumof
squares
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40 60 80 100
Cyp
erac
eae
0 10 20
Typha
0 1
Ludw
igia
0 5
Hyd
roco
tyle
0 2
Polyg
onum
Pavon
ia
0 10 20
Com
mel
ina
0 2
Justicia
Cuc
urbita
ceae
0 15
Poace
ae
0 15
Aster
acea
e
0 10 20
Amar
a/Che
no
0 10 20
Solan
um
Acant
hace
ae
0 1
Syzyg
ium
Borag
inac
eae
0 10
Tribulus
0 3
Eupho
rbia
0 8
Acacia
0 10
Com
mip
hora
0 4
Cap
parid
acea
e
0 10
Mae
sa
Acalyp
ha
Ipom
oea
Poute
ria
Phylant
hus
0 3
Mal
vace
a
Ole
aJu
nipe
rus
Podoc
arpu
s
Artem
isia
Stoeb
e
Ericac
eae
Aquatics Herbaceous Semi-arid savannah Semi-arid Shrubland-Woodland Montante forest Ericaceous
Introduction
Methods
Results and discussion
Amboseli, near the Kenya-Tanzania border, is a relatively flat landscape, punctuated by volcanic cone fields and intermittent palustrine wetlands (Figs1-3).Water is primarily sourced from orographic precipitation on Mt Kilimanjaro that sustains the swamps (Fig4).Since the 1980s, the swamps have been increasingly converted to agriculture, except those in the National Park (Fig3).The wetlands are a critical link for wildlife and pastoralist corridors between national parks.Recent changes to precipitation on Mt Kilimanjaro and the impacts of occasional drought are a major threat to socio-ecological resilience.
Amboseli basin
Mt Kilimanjaro
Chyulu H
ills
Tsavo
NP
Enkongu
Namelok
Ormakau
Esambu
Kimana
Amboseli National Park
Fig1: Location in Africa Fig2: Amboseli region, international border in red.
KenyaTanzania
Fig3: Intermittent wetlands fed by springs and river channels.
Geo-h
ydro
clim
atic
pro
cess
es
Isolatedconvective precipitation
Orographic precipitationEvapotranspiration
Lithosphere
Biosphere
Atmosphere
Groundwater
SurfaceSprings
KilimanjaroAmboseli Plains
Lower M
ontane
Upper M
ontaneAlpine
Saturated zone
Phreatic zone
Vadose zone
Volcanic cones
Water table
Large volcanic cones
La
nd
sca
pe
fe
atu
res
Ch
an
ne
l
Sw
am
p
Sw
am
pfo
rest
Sava
nnah
Dryla
nd
Volcaniccones
Pool
Ephemeral
Endorh
eic b
asin
Rip
aria
n
fore
st
Mo
un
tain
Rech
arg
e z
one
Fig4: Mt Kilimanjaro, the orographic water tower.
Cyperaceae wetlandCyperaceae wetland Wetlands and surrounding moist soils Savannah Semi-arid scrub and woodland Arid scrub and volcanic ejecta
Water channeling Walled spring source areas Intensive agriculture
Land c
ove
rLand u
ses
To examine long-term variability of the wetlands, we cored multiple sites using a Russian corer, and radiocarbon dated the stratigraphies.Pollen analysis and macrocharcoal has been completed on 5 sites.
All coring sites dated <5000 cal yr BP, suggesting that their sediments have been accumulating since to termination of the African Humid Period.Pollen data show that woody compositions near the swamps varies spatially and temporally, evidence of the heterogeneity and complexity of the landscape.Archaeological evidence in the area suggests extensive hunter-gatherer livelihoods until the recent and unprecendented land use changes.
Esambu pollen record
Enkongu pollen record
Ongoing work continues to analyse the pollen and charcoal data alongsidearchaeological survey and pits acrossAmboseli.