Abstract
East and West Usambara Mountain blocks are unique based on three characteristics. Firstly, they are connected blocks; secondly, they have an oceanic-influenced climate; and thirdly, the rain seasons are not easily discernible due to their close proximity to the Indian Ocean and Equator. Sediment cores were collected from peat bogs in Derema (DRM) and Mbomole (MBML) in East Usambara and from Madumu (DUMU) in West Usambara. The multiproxy record provides an understanding on climate and vegetation changes during the last 5000 years. DRM and MBML cores result in radiocarbon ages and age-depth curve which showed hiatus at 20 cm and 61 cm and huge inversion for DUMU core at 57 cm. Period 5000–4000 14C yr BP for DUMU core revealed increased Montane forest indicative of relatively moist conditions. Periods 3000–2000 and 2000–1000 14C yr BP, DUMU core demonstrated increased submontane and lowland forests. Period 1000–200 14C yr BP, DUMU core signified increased coprophilous fungi while DRM and MBML cores signified fluctuating herbaceous pollen spectra (wet-dry episodes). Period 200 14C yr BP to present, all cores demonstrated stable recovery of forest types especially dominance of submontane forests. Abundant coprophilous fungi indicated increased human impacts including forest fires, cultivation, and grazing.
Highlights
The Eastern Arc Mountains comprise thirteen separate blocs with their location stretching from south-east Kenya through south-central Tanzania (Figure 1)
Sediment cores were collected from peat bogs in Derema and Mbomole (East Usambara) and Madumu (West Usambara)
This period deals with DUMU core in which it is characterized with higher proportions of montane forest and local vegetation which can be indicative of relatively moist conditions at the higher altitude areas of East and West Usambara
Summary
The Eastern Arc Mountains comprise thirteen separate blocs with their location stretching from south-east Kenya through south-central Tanzania (Figure 1) They are situated between 3∘20 to 8∘45S latitude and 35∘37 to 38∘48E longitude covering an area of around 3300 km of submontane, montane, and upper montane forests, which is less than 30%, or some 1440 km, of the estimated original forested area [1]. Their unique characteristic geological formation of isolation and connectivity played a crucial role in shaping the current distribution of species diversity within and between the mountain blocs. The vice versa is true for the isolated mountain blocs; these include Nguu, Nguru, Ukaguru, Rubeho, Mahenge, Malundwe, and Uvidunda in Tanzania; Taita hills are an isolated bloc, the only mountain bloc in Kenya with an estimated remnant forested area of 6 km (Figure 1)
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