The long-term performance of 35 tree species of sudanian West Africa in pure and mixed plantings

The rapidly growing human population in sudanian West Africa has generated increasing demand for agricultural land and forest products so that most of the original vegetation cover has disappeared and the remainder is highly degraded, meaning that it is urgent to draw up a long-term assessment of the potential of local species to be promoted in pure and mixed plantings as contribution to global forest restoration efforts. We inventoried the survival and growth of 5817 trees belonging to 35 species planted more than 25 years ago in pure and mixed plantings. For a subset of individuals, we estimated heights and volumes of standing timber. We found that (i) the long-term survival (from 50 to 99%.yr(-1)) and diameter growth (from 1 to 10 mm.yr(-1)) are highly diverse between species and not correlated to each other, (ii) the annual increase in biomass per tree averages 2.22 kg while the annual increase in stand biomass may be over 6 Mg. ha(-1) for three highly-productive species (Khaya senegalensis, Pterocarpus erinaceus and Anogeissus leiocarpa) (iii) the effect of mixture on annual growth is significantly positive with an across-species gain of 0.7 mm.yr(-1) while there is no effect on the survival probability. Considering a potential productivity of 10 m(3) of timber wood per hectare at 30 years, 13 species have been retained in the list of woody species of interest for planting in the Sudanese zone of West Africa.