Woody plant secondary succession along the gradients of fallow periods in traditional shifting cultivation system of Quara district, North West low land Ethiopia

Abstract

Traditional shifting cultivation is a common land management practice widely used in the northwest low lands of Ethiopia and in Quara district in particular. It is considered as an important factor in determining the woody plant diversity, composition and structure in the area. Particularly, no studies have been attempted to examine the resilience capacity of woody plant species after shifting cultivation along the fallow period gradients by comparing with the old-age natural forest adjacent to the fallow lands. This study was conducted at three sites of Bambaho, Gelegu and Chercher (Quara woreda) to examine the diversity, structure and regeneration status of woody plant secondary forest in traditional shifting cultivation system. To investigate the woody plant diversity, structure and regeneration status, a total of 57 quadrates (20 x 20 m 2 ) were laid out randomly along different fallow period gradients of 2-4 year, 5-7 year, 8-10 year, 11-13 year, 14-16 year and 17-20 year fallow period gradients considered as a treatment separately. Major quadrates were sub-divided in to four, each 100m 2 (10 x 10 m) subplots for the counting of sapling and seedling counting. From each treatment of the fallow period 12% sampling intensity was taken per hectare. Thus, the measured vegetation parameters were then compared along the fallow period gradients and the adjacent old-growth natural forest using multi variant analysis in R soft ware version 3.4.3 and Microsoft excel. The highest vegetation similarity coefficient was observed between fallow period one and three. Whereas the least similarity coefficient was observed between fallow period two and old-age natural forest. No statistically significant difference was observed in Shannon’s diversity index (P=0.08), wood plant regeneration status (P=0.94) and species evenness (P=0.89) among the fallow period gradients and old-age natural forest, while species richness (P=0.004), tree density (p=0.001) and basal area (P=0.0000) showed significant difference among the fallow period gradients and old-age natural forest. Over all this study shows that secondary woody plant succession after traditional shifting cultivation has the resilience potentials in the district. But the succession was dominated by Acacia seyal and Acacia polycantha species along the fallow period gradients compared with adjacent old-age natural forest. Therefore to ease the present human influence on the woody plant species there should be a progressive study to determine an optimum fallow period to the local community to use woody plants in sustainable manner and sequester carbon instead of emit to the atmosphere.