Estimation of Carbon Sequestration Potential under Different Vegetation Types in the Borana Rangelands, Ethiopia

Publikations-Art

Kongressbeitrag

Autoren

Pfister, J., Asch, F., Said, M., Giese, M.

Erscheinungsjahr

2013

Veröffentlicht in

Agricultural development within the rural-urban continuum

Herausgeber

Tielkes, E.

Verlag

Cuvillier Verlag , Göttingen

Seite (von - bis)

326

Tagungsname

Tropentag 2013

Tagungsort

Hohenheim

The Borana rangelands in southern Ethiopia used to be among the most productive pastoralareas in East Africa. However, over-utilisation and over-grazing have resulted in decliningrangeland conditions and woody-species encroachment. Payment for environmental services(PES) based on carbon sequestration has been proposed as additional livelihood option to offeran incentive for an improved and sustainable management which in turn is expected to increasethe carbon sink in such semi-arid ecosystems. Nevertheless, information on basic above- andbelow-ground biomass and carbon pool inventories providing reference data for common veg-etation types of the Borana rangelands is missing.Within four representative vegetation types (grassland (GL), tree savannah (TS), bush-tree sa-vannah (BT) and bushland (BL)), we repeatedly determined above- and below-ground biomass(AGB, BGB) using destructive sampling methods and allometric equations (for woody biomass).Total mean AGB (herbaceous + woody biomass) was highest in TS (24.2±7.6 t ha−1) and low-est in GL (1.0±0.4 t ha−1). Regarding the sum of all herbaceous biomass fractions (green,standing dead, litter), AGB decreased from 1.94 t ha−1(BL) to 1.02 t ha−1(GL) in June 2012(after the rain season) and from 2.83 t ha−1(BL) to 0.30 t ha−1(GL) in Oct. 2012 (after the dryseason). In contrast, below-ground biomass (BGB) of the herbaceous layer ranged from 3.20 tha−1(BT) to 2.45 t ha−1(GL) and did not show this pattern among vegetation types. Dynamicsampling indicates AGB minima before and maxima after the rainy season, but only for thevegetation types GL and BT, while BL and TS did not show a pronounced seasonal dynamic.Our data provide a first multi-seasonal quantification of above- and below-ground biomass andcarbon stock estimates for common vegetation types in the Borana rangelands. We hypothe-sise that differences in biomass and carbon pools of the herbaceous layer between vegetationtypes are mainly based on above-ground vegetation dynamics, while below-ground biomassallocation does not reflect the above-ground pools. Thus, a first step to building a database asreference for PES systems and sustainable rangeland management has been taken.