Variation in growth, wood stiffness and density, and correlations between growth and wood stiffness and density in five tree and shrub species in the Sahelian and Sudanian ecozones of Mali

Wood stiffness is a key functional trait of woody plants, but variation in wood stiffness has not been studied in native tree and shrub species in Africa. We investigated variation in growth (height, stem diameter, height/diameter ratio, ring width), wood stiffness (dynamic modulus of elasticity in longitudinal and tangential axes), specific wood stiffness (dynamic modulus of elasticity divided by air-dry density) and air-dry density of Balanites aegyptiaca, Combretum glutinosum, Guiera senegalensis, Piliostigma reticulatum and Ziziphus mauritiana related to region, land use type, soil type, terrain type, latitude, longitude, elevation and mean annual rainfall, and correlations of growth with wood stiffness, specific wood stiffness and wood density in the Sahelian and Sudanian ecozones of Mali. Growth variables, wood stiffness and wood density differed significantly among some of the species, but specific wood stiffness did not differ significantly among any of the species. There were few consistent effects of the environmental variables on growth and wood variables of the five species. Geographical coordinates generally had stronger effects than mean annual rainfall on growth and wood variables of the species. Positive correlations between growth and wood density were significant in three of the species. Correlations between height and wood stiffness and/or specific wood stiffness differed in sign among some of the species. Results illustrate that different species may respond differently to environmental factors in the Sahelian and Sudanian ecozones of West Africa.