Effects of substrate coarseness and exposure on plant succession in uranium-mining wastes

Species turnover and speed of primary revegetation on uranium-mining spoils are described from the Centre-West part of Spain. Four 21-yr-old successional seres differing in substrate-grain size (broken/unbroken waste) and slope orientation (North/South) are compared. Qualitative and quantitative changes in species composition and the time required for recovery of a terminal stage are analysed, using an undisturbed pasture as reference. Revegetation succession is faster on the broken waste and on the North slope. Moreover, there is a combined effect of both abiotic factors on the pattern and duration of revegetation succession. 195 plant taxa are recorded showing one of four patterns of change: (1) 'pioneer'; (2) 'intermediate'; (3) 'late coloniser'; (4) 'fluctuating'. Multivariate analysis allows us to identify species following each of these patterns on each substrate.