Papers by DIBI N'DA HYPPOLITE
Forests, Mar 12, 2019
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International Journal of Biodiversity and Conservation, 2015
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Trees, 2016
Key messageThe paper demonstrates the prospects and applications of dendrochronology for understa... more Key messageThe paper demonstrates the prospects and applications of dendrochronology for understanding climate change effects on riparian forests in the savanna landscape. AbstractRiparian trees in savannas have a potential for dendro-climatic studies, but have been neglected hitherto. We examined ring-width series of Afzelia africana (evergreen) and Anogeissus leiocarpus (deciduous) to study the influence of climatic factors on the growth of riparian trees in the humid (HS) and dry (DS) savanna zones of the Volta basin in Ghana. A total of 31 stem discs belonging to A. africana and A. leiocarpus were selected from HS and DS to establish species-specific local chronologies of tree growth. Each individual of A. africana and A. leiocarpus from the two savanna sites showed distinct growth rings. Cross-dating of individual tree-ring patterns was successful using standard dendrochronological techniques. The mean annual growth rates of A. africana in the HS (1.38 ± 0.09) and DS (1.34 ± 0.08) were not statistically different. Furthermore, mean annual growth rate of A. leiocarpus in the DS (3.75 ± 0.27) was higher than in the HS (2.83 ± 0.16) suggesting that species in drier environment can have higher growth rates when sufficient soil moisture is available. The growth rates of both species at the same sites were different, which might indicate different water use strategies. High correlations of individual tree-ring series of A. africana and A. leiocarpus trees at HS and DS suggest a strong climatic forcing controlled by the seasonal movement of the inter-tropical convergence zone. The annual growth of A. africana and A. leiocarpus at both the HS and DS was significantly correlated with local temperature and precipitation. The negative correlations of the growth of the two tree species to global sea surface temperatures were however, indications that the growth of riparian forests can be impacted during El Niño-Southern Oscillation years. The result of our study shows that riparian trees in the humid and dry savanna zones of West Africa can be successfully used for dendrochronological studies.
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Climate Change Management, 2016
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Journal of Geoscience and Environment Protection
The Azagny Ramsar site has been the scene of very strong agricultural pressures for several decad... more The Azagny Ramsar site has been the scene of very strong agricultural pressures for several decades. In Côte d’Ivoire, management policies, previously developed and implemented in wetlands, remain very sensitive and vulnerable to environmental changes. It is to overcome these environmental management difficulties that this study was carried out to assess the impacts of mainly industrial agricultural activities on the wetland. To achieve this goal, we mapped the land use dynamics of the study area by a series of Landsat imagery from 1988, 2002, 2008, and 2019 and obtained 11 classes. The spatial analysis of the dynamics of land use from these images has shown that the increase in agricultural operations around the protected area has favored the reduction of several ecosystems of natural plant formations (forests, savannas, mangroves) amounting to 36.34% to the benefit of artificial plant formations such as rubber, oil palm and coconut trees (42.73%). However, these losses of natural plant formations are more accentuated outside the Ramsar site (peripheral zone) than in the Ramsar site with the example of mangroves which have lost 3.27% of their area in the Ramsar site against 33.80% in the peripheral zone between 1988 and 2019. These changes are less accentuated in the Ramsar site than on the periphery thanks to the vigilance of the Ivorian Office of Parks and Reserve (OIPR) and natural barriers (watercourses) that surround it.
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Open Journal of Ecology, 2016
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Climate Change Management, 2016
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Trees, 2016
Key messageThe paper demonstrates the prospects and applications of dendrochronology for understa... more Key messageThe paper demonstrates the prospects and applications of dendrochronology for understanding climate change effects on riparian forests in the savanna landscape. AbstractRiparian trees in savannas have a potential for dendro-climatic studies, but have been neglected hitherto. We examined ring-width series of Afzelia africana (evergreen) and Anogeissus leiocarpus (deciduous) to study the influence of climatic factors on the growth of riparian trees in the humid (HS) and dry (DS) savanna zones of the Volta basin in Ghana. A total of 31 stem discs belonging to A. africana and A. leiocarpus were selected from HS and DS to establish species-specific local chronologies of tree growth. Each individual of A. africana and A. leiocarpus from the two savanna sites showed distinct growth rings. Cross-dating of individual tree-ring patterns was successful using standard dendrochronological techniques. The mean annual growth rates of A. africana in the HS (1.38 ± 0.09) and DS (1.34 ± 0....
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Arid Land Research and Management
ABSTRACT Understanding the impacts of agricultural land use is desired for proper management of r... more ABSTRACT Understanding the impacts of agricultural land use is desired for proper management of riparian forests buffers (RFs) in savannas. In this light, we analyzed the relationship between woody plant diversity and soil properties of RFs in farmlands (FAs) and protected areas (PAs) along Afram (Guinean zone) and Tankwidi (Sudanian zone) Rivers located within the Volta sub-basin of Ghana. ALOS-AVNIR imageries were used to map RFs to facilitate sampling of soil and woody vegetation (dbh ≥5 cm) using stratified randomized design (72 plots; size: 500 m2 each) for the analysis of soil physical and chemical properties and Shannon-Wiener plant species diversity. Although the fractions of sand, silt, and clay varied between the PAs and FAs, they were predominantly categorized as sandy loam. Along the Afram River, there were no significant differences in the concentrations and nutrient stocks of soil C, N, P, and K as well as the pH, moisture content, and bulk density between PA and FA. For the Tankwidi River, the concentrations and nutrient stocks of C and K significantly decreased from PA to FA while N, P, pH, bulk density, and moisture content were not different. Of the soil attributes measured C, N, P, pH, ground slope, and soil moisture had significant relationships with the diversity and density of the riparian woody plants. Controlling agricultural activities in riparian forests could preserve soil properties similar to that found in protected areas.
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Papers by DIBI N'DA HYPPOLITE