Tree formations in relation with soil and grasses in a dry savanna in Mali, West Africa

Abstract

The relationship between trees, grass and soil in a dry savanna in Mali was investigated, to identify variables that are most relevant to assess vegetation units. A 65 ha plateau was inventoried using a systematic square grid sampling pattern. Thirteen soil or topography variables, and tree and grass characteristics were measured at each sampling point. Multivariate analysis was used to separately analyse soil, tree and grass data, and to characterize tree-grass and tree-soil relationships. Four units of soils, four units of tree formations, and four units of grass formations were identified. There was a correspondence between these groups, indicative of four vegetation units: thicket, bare land, shrub savanna and tree savanna. Soil depth and soil texture were the soil variables that best related to tree vegetation. A negative correlation was found between tree basal area and grass dry biomass. Finally, vegetation units, as identified from tree species composition, had contrasted diameter structures and densities. RésuméLa relation entre les arbres, les herbes et la terre dans une savane sèche du Mali fut enquêtée, afin d'identifier des variables qui sont plus pertinentes dans l' évaluation des unités végétales. Un plateau de 65a fut recensé utilisant un modèle d'échantillon systématique par quadrillage. Treize variables de terre ou topographie, ainsi que les caractéristiques des arbres et des herbes furent mesurées à chaque point échantillon. Des analyses multivariées furent employées afin d'analyser individuellement les données venant de la terre, des arbres et des herbes, et afin de caractériserles rapports arbre-herbe et arbre-sol. Quatre unités de terre, quatre unités de la formation des arbres, et quatre unités de la formation de l'herbe furent identifiées. Il existait une harmonie entre ces groupes, indicative de quatre unités de végétation: broussailles, terre dénudée, savane arbrisseau, et savane forestière. La profondeur et la texture de la terre furent les deux variables qui agissaient le plus surla végétation arboricole. Une corrélation négative fut trouvée entre la taille de l'étendue basale de l'arbre et la biomasse d'herbes sèches. Finalement, les unités végétales, identifiées par la composition d'espèces d'arbres, déployaient des structures de diamètre et de densité contrastantes.

Defining units for savanna management in Sudano-sahelian areas

“…The role of soil depth in this Sudanese savanna is therefore confirmed (Picard et al, 2005), whereas, no relationship between soil properties and vegetation characteristics has been found in other savannas (Dezzeo et al, 2004). Large-scale differences in soil depth were observed in the Commune of Zan Coulibaly, with plains being associated with deep soils and plateau with shallow soils.…”

The effect of land use on the recruitment and population structure of the important food and fodder plant, Dobera glabra (Forssk.) Poir., in northern Afar, Ethiopia

“…Spatial patterns and relative abundance of both woody and herbaceous plants in rangelands have been intensively studied in many areas (Huntley and Walker, 1982;Walker, 1987;Belsky, 1994;Picard et al, 2005). Because of cultural traditions, however, management of arid and semi-arid areas in one region differs considerably from that practiced in other regions, and results from one study area are not necessarily applicable to other areas (e.g., Smet and Ward, 2006).…”

“…Major factors determining the spatial distribution of plants include topography, geomorphology, soil moisture (Picard et al, 2005), soil nutrients (Walker, 1987;Belsky et al, 1989;Isichei and Muoghalu, 1992;Belsky, 1994), soil structure (Picard et al, 2005), fire (Walker, 1987;Hochberg et al, 1994), herbivory (HilleRisLambers et al, 2001;Moe et al, 2009) and human activities (Lykke, 1998). The influence of these factors varies, however, depending on the particular plant species and local utilization levels.…”

Changes of woody plant interaction and spatial distribution between rocky and sandy soil areas in a semi-arid savanna, South Africa

“…The composition, structure, and spatial arrangement of vegetation are influenced by the amount of available soil moisture and nutrients. These factors in turn are influenced by soil characteristics (Cole, 1982), such as soil depth or the proportion of soil rock fragments (Fournier and Planchon, 1998;Maestre and Cortina, 2002;Picard et al, 2005). We studied the growth and spatial distribution of woody plants in an area with a high amount of rock fragments and in a sandy soil area without rocks.…”