Lisa Schüler & Hermann Behling

Studies on late Quaternary environmental dynamics on Mt Kilimanjaro - �rst results

Department of Palynology and Climate Dynamics

Corresponding author: Lisa Schülerlisa.schueler@biologie.uni-goettingen.de

Göttingen Center for Biodiversity & Ecology

This project is funded by:

Introduction Study Site

Method

First Results

References:1 Hemp 2006 4 Verschuren et al. 20092 Hemp 2006 5 Marchant et al. 20063 Feagri & Iversen 1989

NORTH SOUTH

6000m

5000m

4000m

3000m

2000m

1000m

100

200

Depthcm

0

10000

20000

30000

2200±96

6100±86

7400±47

8900±100

10600±65

13800±144

18900±224

21700±365

32700±335

14C ages (yr B

P)

%

0

Savanna

0

Submontane Forest

0 10

Afromontane Forest

0 10 20

Ericace

ous Belt

0 10 20

Alpine Grassl

and

0 10 20 30 40 50 60 70

Herbs

0

Aquatics

0 10 20 30

Fern Spores

0 10 20

Fungal Spores

0

Euphorbia

0

Abrus

0

Leonitis

0

Cissampelos

0

Ulmace

ae

0

Vitex

0

Araliace

ae

0

Ilex

0

Senecio hadienese

0

Olea

0

Podocarp

us

0

Clematis

0

Artemisi

a

0 10

Erica

0 10

Myrsine

0 10 20

Ranunculus

0 10

Alchemilla

0

Iridace

ae

Main Taxa

Mt Kilimanjaro is an inactive stratovolcano located in NE Tanzania. It rises from savanna plains at 700m to an ice-capped summit at 5895m asl. It was formed in the spreading zone of the East African Rift System.Our study site, Maundi Crater, is located at 2780m asl on the SE side of Mt Kilimanjaro in the transition between upper montane forest and the subalpine heathland zone. The climate is tropical diurnal and influenced by the Asian Monsoon penetrating into East Africa and causing two pronounced wet seasons. Annual mean temperature is 10°C and annual precipitation is around 1900mm1.

Fig 1: The study site, Maundi Crater, surrounded by Erica bush Photo: Rob Marchant

In our project, we study pollen, charcoal and chemical composition derived from peat and sediment cores from different key areas at Mt. Kilimanjaro in order to reconstruct former and to predict future landscape dynamics. We would like to better understand local and regional ecosystems, climate and fire dynamics in a larger context as well as ecosystem dynamics and their reaction on environmental changes. Further, we would like to investigate their role for the development of the biodiversity hot spots in East Africa. Here, we are presenting the results of the pollen analysis of our first study site, the Maundi Crater.

We sampled every 10cm of the 6m long sediment core derived from the center of the Maundi Crater. The samples were prepared applying the standard method3. So far, we have determined and counted 100 pollen grains of the uppermost 32 samples which are dated back to ~38000 14C yrs BP. We assigned every pollen taxa to a vegetation zone known from the present and calculated percentages.

Our first results reveal that the vegetation belt composition, classified as savanna, submontane forest, Afromontane forest, Ericaceous belt, and alpine grassland, has remained rather stable during the past 38,000 yrs. The taxa composition within the vegetation types has varied. The increase in Ericaceous vegetati-on in the late Holocene indicates more frequent (anthropogenic?) fire events. Three phases with no pollen records may be related to droughts that disabled pollen preser-vation. The high percentage of herbs and Ericaceous vegetation inbetween these periods also suggest dry conditions causing a decline of montane forest vegetation.The dry period between 6200 and 7400 14C yr BP coincides with low lake level stands recorded from a lake at the foot of Mt Kilimanjaro4. The increase of aquatics and spores during the late Holocene proposes increasingly humid conditions.

Conclusion and Future Perspective Based on our pollen analytical results, we assume that the ecosystems on Mt Kilimanjaro have been rather stable during the past 38,000 yrs. Despite pronounced past climate events which impacted other parts of the African continent, such as Heinrich Events and African Humid period, we can notice very little change in vegetation composition at our study site. This leads to the conclusion that this East African Mountain system must be predominantly influenced by a different climate driver, possibly the Asian Monsoon activity and its associated precipitation intensities and patterns5.We will analyse further pollen, charcoal and chemical composition to investigate more samples of the Maundi core, and follow-up cores along the slopes of Mt Kilimanjaro. Modern vegetation and pollen rain data will help us calibrate, interpret and model our results.

Mt Kilimanjaro

Fig 2. Ericaceous vegetation at 3200m asl on the S slope of Mt Kilimanjaro

Fig 3. Alpine grassland vegetation at 4000m asl with Poaceae species and Dendrosenecio.

Fig 4. Afromontane Forest between 1500 and 3000m asl

Fig 5. Submontane forest between 1100m and 1500m asl

Fig 6. Savanna vegetation composed of many grass species (Poaceae) and drought resistent trees such as Acacia (Acacia sp.) and Baobab (Adansonia digitata)

Fig 7. The vegetation belts on Mt Kilimanjaro. Due to the moist air of the SE Asian Monsoon, the vegetation belts are shifted downslope on the N side. At the foot of the mountain savanna vegetation dominates the landscape. On the southern slope, agricultural plants such as bananas or coffee are cultivated. Further uphill, we find submontane forest between 1100 to 1500m asl (S slope) with different species depending on the exposition of the slope. From 1500m to 3000m asl (S slope) the vegtation is composed of Afromontane Forest species. Above ~3000m asl on (S slope), occasional frost and decreasing precipitation only allow Ericaceous shrubland to grow; in the areas higher than 4000m asl, exclusively afroalpine grassland can be found up to the rock and snow line2 (after Hemp 2006).

Fig 8. Percentage pollen diagram of the samples from the Maundi Crater peat core. Pollen and spore percentages are plotted against core depth (cm) and age (14C yr BP). The pollen taxa are grouped into vegetation zones found today at Mt Kilimanjaro. The main taxa composing the different vegetation zones are shown in more detail.

Artemisia sp.

Senecio hadiense

Alchemilla sp.

Hagenia abyssinica

Helichrysum spec.Helichrysum sp.

Erica spec.Erica sp.

PoaceaePoaceae

Podocarpus spec.Podocarpus

Mt Kilimanjaro

no pollen record

no pollen record

no pollen record

Source: NASA