Impact of site protection mechanisms on natural regeneration potential along a degradation gradient in Miombo Woodland region of the Democratic Republic of the Congo

Abstract

For several decades, the Miombo woodland located in Lubumbashi plain in the Democratic Republic of the Congo (DRC), has experienced significant changes in its floristic composition due to increasing human activity on the landscape, which has greatly impacted its potential for natural regeneration. Various human interventions have been implemented to protect this ecosystem, including the adoption of set-aside mechanisms with varying levels of protection. The objective of this study was to assess the effects of site protection mechanisms on the regeneration potential of vegetation, along a disturbance gradient, in the Miombo woodland of the Democratic Republic of the Congo. A study was conducted at Upper Katanga region in the Miombo woodland in the Lubumbashi Plain, involving a total of 60, 10 m x 10 m plots with 20 plots per site established across three sites, namely Kibundu, Kiswishi and Mikembo. Each plot was subjected to different levels of protection that is conservation with fence, without fence and forest communities-based management. A total of 1,230 individual trees were inventoried, representing 65 species, 45 genera and 20 families. Vertical spatial structure analysis revealed that the understory harbours greater species diversity than the upper canopy. The most represented families in the strata were Fabaceae, Apocynaceae, Phyllanthaceae and Ochnaceae. Additionally, Coefficient of Variation (CV) across the sites indicated uneven spatial distribution of three crowns within strata. Kibundu, with a CV of 102.9% in the upper canopy against 73.6% in Kiswishi and 18.4% in Mikembo, was found to influence the absolute density of individuals in the understory (CV =32.4, 61.5, 72.3% for Kibundu, Kiswishi and Mikembo, respectively). Interestingly, there was a high correlation between site disturbance rate of the potential of landscape regeneration (r =0.85, 0.055 and 0.77 at Kibundu, Kiswishi and Mikembo, respectively). Despite human pressures, regeneration indices were greater than unity, indicating a state of equilibrium in the vegetation of the Miombo woodland.