Can compost improve Quercus pubescens Willd establishment in a Mediterranean post-fire shrubland?

The aim of the study was to evaluate the effects of sewage sludge compost (control, 20 kg m−2, 40 kg m−2) supplied to Quercus pubescens Willd seedlings planted in a post-fire calcareous site in Provence (France). Changes in soil properties, seedling survival, growth and nutrition were monitored 7 months, 1.5 years and 2.5 years after amendment, and possible trace metal contamination of soil and seedlings by compost was also evaluated. Compost improved overall soil fertility by increasing organic matter, cation exchange capacity, total N and exchangeable P, K, Mg and B concentrations, but 40 kg m−2 induced a more significant and more durable effect than 20 kg m−2. However, the compost had no effect on seedling survival and growth, but increased foliar P and B concentrations at 40 kg m−2. No foliar contamination of seedlings by trace metals occurred, although amendment increased exchangeable Cu and Zn concentrations in soil. Compost P and exchangeable Cu and Zn concentrations could induce eutrophication and water pollution, and limit rates that can be applied without environmental hazard.