Assessing the Landscape Pattern and Population Status of the Timber Species Mansonia altissima A. Chev. For Restoration Purposes in Moist Semi-Deciduous Forest

Abstract

Abstract Mansonia altissima A. Chev., a redwood producer species in tropical Africa, occurs as one small, isolated population in a highly anthropized landscape in Republic of Benin. We accessed the landscape pattern and population status to inform restauration action for the species. We established 20 one-ha permanent plots divided in 320 subplots (25 m × 25 m) in-situ and counted and measured M. altissima plants with diameter ≥ 1cm at base and 1.30 m above ground (DBH) in February 2017, 2018 and 2019. Based on the main disturbance factors, such as fire, human-caused damage to seedlings, harvesting of wood for fuel, and agriculture, we assigned the plots to one of three disturbance levels: poor, moderate, and strong. We grouped the plants into four life stages according to diameter size (cm): seedling (1 ≤ DBH < 5), sapling (5 ≤ DBH < 10), premature (10 ≤ DBH < 20), and mature (DBH ≥ 20). We used Landsat data of years 1986, 2002 and 2017 to quantify and analyze landscape changes and fragmentation. Results showed that the landscape was dramatically changed and fragmented between 2002 and 2017 due to disturbance increase. Semi-deciduous forest (SDF) containing M. altissima decreased, whereas woodlands and savannas increased. SDF was severely fragmented and disaggregated. In plots with strong disturbance, mortality rate was higher, whereas in plots with poor disturbance, it was lower and recruitment was highest. Mortality rate differed significantly among life stages and disturbance levels. Experimental restoration is required to identify locations where the species can establish young viable populations. Fire and other anthropogenic disturbance have to be controlled to ensure this natural population can provide seeds for restoration and conservation projects.