The association between rainforest disturbance and recovery, tree community composition, and community traits in the Yangambi area in the Democratic Republic of the Congo

Abstract

Despite their key role in biodiversity conservation, forests in the Congo Basin are increasingly threatened by human activities, but it remains challenging to assess the impact of forest degradation under a more or less intact canopy. Likewise, forest recovery following agricultural abandonment remains poorly understood in the Congo Basin. Here, we surveyed 125 vegetation quadrats across 25 forest inventory plots in the Yangambi area. We aimed to find associations between both selective logging and forest recovery, and a range of forest community and tree community trait characteristics, as compared to reference undisturbed old-growth forest. We found that plots in undisturbed old-growth forest harboured both more tree individuals and tree species with a higher wood density as compared to plots in disturbed old-growth forest. In addition, their tree community composition was significantly different, whereas species diversity recovered since relatively recent agricultural abandonment (< 60 years), community composition and forest structure remained significantly different from the plots in undisturbed old-growth forest. Our study provides some insights into the rate of forest recovery in the Congo basin after agricultural abandonment and highlights the need of proper conservation of the remaining relatively undisturbed old-growth forests. Finally, we stress the need for more extensive vegetation surveys in the Congo Basin to further unravel the effects of anthropogenic disturbance.

Genetic diversity and structure in wild Robusta coffee (Coffea canephora A. Froehner) populations in Yangambi (DR Congo) and their relation to forest disturbance

“…Previously, Depecker et al (2022) established 25 forest inventory plots of 125 × 125 m (1.56 ha), covering an area of ca. 50-by-20 km, just North of the Congo River (Fig.…”

“…These founder effects can result in major genetic changes, including loss of genetic diversity and increased genetic differentiation among populations, with associated fitness consequences (Born et al 2008;Vandepitte et al 2012). Whereas ample research has already been done on species diversity and community composition in regrowth tropical forests (e.g., Oberleitner et al 2021;Makelele et al 2021;Depecker et al 2022), studies on the genetic diversity of tropical tree species in regrowth forests in the tropics are still scarce, especially in Africa.…”

Genetic diversity and structure in wild Robusta coffee (Coffea canephora A. Froehner) populations in Yangambi (DR Congo) and their relation with forest disturbance

“…Previously, Depecker et al (2022) established 25 forest inventory plots of 125 m × 125 m (1.56 ha), covering an area of ca. 50-by-20 km, just North of the Congo River ( Fig.…”

“…We adopted their classification of the plots into three different forest categories: (i) Plots in regrowth forest (8 plots) located on historical agricultural land. Depecker et al (2022) estimated that these agricultural lands were abandoned somewhere between 1962 and 1980, and since then overgrown. (ii) Plots in disturbed old-growth forest (7 plots), with clear indications of small-scale selective logging through the presence of tree stumps Genomic DNA extraction and Genotyping-by-Sequencing (GBS) 20-30 mg leaf material was homogenised with a Retsch TissueLyser II (Mixer Mill MM 500 Nano; Retsch®).…”

“…We hypothesised that anthropogenic disturbance leads to decreased population genetic diversity, specifically due to selective logging (Depecker et al 2022). However, we found no evidence of reduced genetic diversity in plots in disturbed old-growth forest, as compared to plots in undisturbed old-growth forest.…”