Abstract

Western Niger lateritic plateaux formally occupied by tiger bush are mainly secondary ecosystems affected by crusting and soil compaction that impedes infiltration and induces intense erosion, which hampered lowlands millet fields. Restoration of these plateaux is essential, but, failure is frequently reported about early species establishment. It’s therefore necessary to examine the mechanisms and factors of early plants recovery which are important for vegetation restoration. Vegetation data have been recorded in 31 plots, at four sites with similar environmental characteristics and different land use histories: Unrevegetated area, 1-3-years old revegetated area, 6-years old revegetated area and 14-years old revegetated area. We also measured 16 environmental variables in each plot to examine the driving forces of succession and the vegetation-environment relationships. TWINSPAN results revealed that plant species could be classified into six plant communities representing 4 succession stages. The DCA confirm TWINSPAN classification and indicated two gradients of succession: land condition and successional age. According to the CCA and the Monte Carlo tests, the determinants of succession are succession age, covers of gravel crusts, erosive crusts, barren soil, plants and litter, soil pH, soil contents of organic carbon, organic matter, available phosphorus, calcium, magnesium, total of basic cations and Cation exchange capacity. The chronological changes in plant communities associated with environmental variables contribute to plant assemblage and vegetation development. Since, the environmental variables are able to change with succession age, succession pathways can be divergent, but in the present study it becomes convergent at late stage. As each stage can be structured by more than one plant community, the model of restoring degraded lateritic is closer to alternative stable states model.

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