Measuring Extent of Restoration Using Coffee (Coffea arabica L.) as a Bioassay Plant Species

Abstract

This study was undertaken as part of the ongoing biological restoration with the objective of measuring extent of restoration over a degraded landscape using coffee plants (Coffea arabica L.) as bioassay organisms. The coffee plants were established beneath Acacia abyssinica Hochst.ex.Benth., Croton macrostachyus Hochst. ex Del. and Euclea divinorum Hiern. stands which were established 9-11 years ago in a degraded landscape. All the vegetative and reproductive data were collected on randomly selected 3- to 5-year-old coffee plants. The results showed that mean number of lateral stem branch, leaves, leaf area and internodal lengths were significantly (P<0.05) greater for those established beneath the shades of E. divinorum for 3-4 years, compared to those beneath the C. macrostachyus and A. abyssinica shades. Further, key biological indices such as mean number of fruiting nodes, berries per node, mature red berries harvested per plant, fresh weight of berries, size and weight of beans, bean to berry weight ratio, weight per 1000 beans and coffee bean yield (g/tree) were all significantly (P<0.05) higher for coffee plants established under the shade of A. abyssinica than those established under the shades of C. macrostachyus and E. divinorum, and on less-restored area. The levels of available phosphorous, total nitrogen and organic carbon were significantly (P<0.05) 54, 39 and 56 % higher, respectively, in the sites that were in the process of restoration than adjacent, non-restoring sites. This study showed that restoring native plants over degraded landscapes restores essential nutrient elements and favorable environmental conditions for the successful development productivity of economically useful crops such as C. arabica.

Keywords: coffee reproductive traits, degraded landscapes, Ethiopia, indigenous trees, restoration bioassay