Species diversity and stand structural diversity of woody plants predominantly determine aboveground carbon stock of a dry Afromontane forest in Northern Ethiopia

Abstract

Aboveground carbon (AGC) stock in forests is affected by several biotic and abiotic factors. Understanding those factors is crucial in managing forests for climate change mitigation and other ecosystem services. This study examined effects of diversity attributes (species and stand structural diversity of woody plants) and topographic attributes (altitude and slope) on AGC stock of a dry Afromontane forest. Data from individual woody plants for estimating AGC were collected from 252 plots (20 × 20 m) established in a systematic grid (2 × 2 km) covering the entire forest area. Woody plant diameter diversity and woody plant height diversity were used as proxies for stand structural diversity. Structural equation modelling was applied to test the effects of the selected attributes on AGC stock, and together they explained 71% of the variation. Stand structural diversity was the most important driving factor for the AGC stock. Woody plant species diversity had both direct and indirect effects on AGC stock, but the indirect effect through its influence on stand structural diversity was more pronounced. Altitude and slope were both negatively but weakly associated with AGC stock. Our results provide insight on the effects of diversity and topographic attributes on AGC stock, which can assist future management of the forest. Enhancing stand structural diversity by means of selection cutting systems and woody plant species diversity by means of enrichment planting can be effective treatments. When considering dry Afromontane forests’ widespread distribution, the potential contribution in carbon sequestration and thereby mitigating climate change is substantial. Hence, the results and management suggestions from the present study may have practical interest for the management of dry Afromontane forests not only in Ethiopia but also in Africa at large.