Effect of substrate treatments on survival and growth of Mediterranean shrubs in a revegetated quarry: An eight-year study

Loss of soil is a major problem that restoration actions must solve in Mediterranean quarries. Soil replacement by a low-quality substrate is often inadequate for revegetation and limits plant establishment and growth in these degraded areas, which are also subject to drought recurrent stress.In 1998, a field experiment was performed in a limestone quarry at Outão (Serra da Arrábida, SW Portugal) to test different types of substrate improvement: NPK fertilizer, water-holding polymer, mycorrhizal inoculum, and combinations of these. Two-year old plants of three native woody species were planted - carob (Ceratonia siliqua), wild-olive tree (Olea europaea var. sylvestris) and mastic (Pistacia lentiscus). Reports concerning the short-term results showed some differential effects of the assayed treatments on plant growth and physiology. The monitoring program was maintained, and here we report on the survival and growth of the introduced plants over eight years after planting. This prolonged study showed that, with the limited exception of fertilization, none of the assayed treatments added major advantages for plant survival or growth. Regardless of the tested substrate treatment, mortality was low and these native species became established in the revegetated area.