Stijn Cleemput, Bart Muys, Christoph Kleinn, Marc J.J. Janssens:
Biomass Estimation Techniques for Enclosures in a Semi-Arid Area -- A Case Study in Northern Ethiopia


1Georg-August-Universität Göttingen, Institute of forest Yield and Management, Germany
2Katholieke Universiteit Leuven, Laboratory for Forest, Nature and Landscape Research, Belgium
3University of Bonn, Institute of Horticulture, Germany

For centuries, land degradation triggered by deforestation has occurred in Ethiopia, in particular in the northern regional state Tigray, the area under study. In order to change this situation, the local government started to establish enclosures. In these sites, grazing is no longer permitted so that forest can naturally regenerate. In order to develop sustainable yield planning for forest rehabilitation areas in Tigray, one needs to know the effect of closing areas on biomass accumulation. In an enclosure, aboveground dry weight of herbaceous and woody species was estimated at 1,84 ton/ha. A combination of destructive and non-destructive methods was tested. The non-destructive study was rejected because of a non-accurate wood density estimation, and low correlation coefficients for the weight predicting models. Best fit-least square regression models were developed using diameter at 30 cm height as the independent variables and dry weight as the dependent variable. Coefficients of determination for the selected total biomass models non-destructive study. Equations for foliage biomass generally had lower coefficients of determination than the equations for either stem or total biomass of the woody species. Non woody biomass was measured in different enclosures in order to estimate the biomass production in function of the management technique. 98% of the total herbaceous biomass of the sampled grass plots belonged to Hypperrhenia hirta, while in the grazing land nearby it was only 11%. The correlation coefficient between grass biomass and basal area of the woody vegetation was -0.11. Based on this study this enclosure is not adopted for fuelwood collection.

Keywords: Biomass yield, closed areas, destructive study, Hyparrhenia hirta, non-destructive study

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Contact Address: Stijn Cleemput, Georg-August-Universität Göttingen, Institute of forest Yield and ManagementBuesgenweg 2, 37077 Göttingen, Germany, e-mail:
Andreas Deininger, September 2004