& Key message Mansonia altissima A. Chev. has an aggregated distribution at the juvenile life stage that becomes random at the mature life stage. Ceiba pentandra (L.) Gaertn could play the role of nurse plant in the management of M. altissima populations providing them a moderate forest shade in large gaps for early growth. M. altissima and Triplochiton scleroxylon K. Schum. displayed independent distribution patterns. & Context M. altissima is a species with economic value found in moist semi-deciduous forests of tropical Africa. The analysis of spatial distribution patterns can help to understand the ecology of this species in forest stands dominated by emergent pioneer tree species like C. pentandra and T. scleroxylon. & Aims To assess the spatial distribution patterns of M. altissima and spatial relationships with C. pentandra and T. scleroxylon in their natural habitat. & Methods We investigated the spatial patterns of the three species during three life stages; juvenile (immature trees), premature (trees with minimum flowering diameter) and mature (trees with minimum fruiting diameter). Diameter at breast height (DBH) was measured and geographical coordinates of trees were recorded within ten one-ha plots, divided into sixteen subplots (625 m 2 ). We computed the L(r) function, normalized from Ripley's K(r) function to detect aggregated, random or regular distribution patterns. & Results Aggregations were detected in juvenile and premature M. altissima. Size and scales of spatial aggregation were inversely proportional to the DBH size. M. altissima and C. pentandra displayed interspecific association patterns at the similar life stages. Both species were positively associated within a radius ≥ 3 m. No positive association was detected between M. altissima and T. scleroxylon. & Conclusion Interspecific association patterns between M. altissima and C. pentandra suggest that C. pentandra could be used as a nurse tree in reforestation and management practices of M. altissima populations.

No abstract

No abstract

AbstractMansonia 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.

Le karité (Vitellaria paradoxa) est un arbre indigène d'Afrique sub-saharienne d'intérêt écologique, alimentaire et économique. L'étude a pour but d'identifier les contraintes qui pèsent sur la domestication du karité au Bénin et d'évaluer l'effet de la provenance des graines et de la fertilisation sur la croissance juvénile des plants de karité. Le karité est vulnérable selon l'UICN et semi-domestiqué compte tenu des contraintes qui entravent sa domestication. Il s'agit entre autre de la lenteur de sa croissance juvénile et la longueur de son cycle végétatif. L'étude menée en pépinière a porté sur la croissance des plantules obtenues des graines issues de deux provenances à savoir Parakou et Banikoara. Ces deux provenances présentent une différence climatique et appartiennent à deux différents parcs à karité-néré du Bénin. Au total quatre traitements (témoin, engrais NPK avec deux doses (10 g/pot/mois, 20 g/pot/mois) et déjection de boeuf) ont été appliqués sur les plantules des deux provenances pour évaluer leurs croissances aériennes. Les résultats issus de cette étude montrent que la provenance n'a pas d'effet sur le diamètre au collet des plantules et sur la longueur des feuilles (P>0,05), mais l'on note une différence significative entre les provenances en ce qui concerne la hauteur et le nombre de feuilles (P<0,05). La fertilisation a un effet significatif sur la croissance des plantules (P<0,05); mais l'impact de l'engrais NPK sur la croissance des plantules de karité n'est pas substantiel.