Restoration of Degraded Landscapes Along the Urban-Rural Gradient of Lubumbashi City (DR Congo) by Acacia auriculiformis Plantations: Spatial Dynamics and Impact on Plant Diversity

Résumé fourni par la source

With the liberalization of the mining sector, a considerable demographic explosion is witnessed in Lubumbashi city (southeastern of the D.R. Congo). The resulting spatial urban expansion is unplanned, reducing the vegetation cover abundance within and around the city. To address this situation, Acacia auriculiformis, an alien species, has been planted without planning and monitoring. We quantify the spatio-temporal pattern dynamics of A. auriculiformis along the urban-rural gradient from the digitisation of Google Earth images from 2006, 2014 and 2021, and evaluate tree diversity through floristic inventory. Results showed that the plantation of A. auriculiformis, belonging to park, street trees and green spaces-types, increased in patch number and acreage, mostly in urban zone. The values of the patch which were highest in 2006 decreased in 2021, especially in the urban zone. Thirty-nine trees species were founded on A. auriculiformis plantations, with Albizia lebbeck, Albizia alba and Leucaena leucocephala being the most common. However, results showed that 20 species out of 39 species found are exotic, half of which are invasive species. However, 19 trees species are indigenous, mainly found in peri-urban zones. Although most tree species were observed in urban zones, the average diameters were greater in the peri-urban zone. Overall, obtained results appear to suggest that the sustainability of A. auriculiformis within the urban and peri-urban zones of Lubumbashi city appears uncertain since a considerable number of attracted species are found to be alien invasive trees that pose a threat to biodiversity conservation. There is an urgent need for adoption of a master plan for sustainable integration and monitoring of trees plantations for limiting erosion of indigenous phytodiversity and the spread of alien invasive species populations in the adjacent rural area.

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