Restoration through trenches does not demand organic fertilization and sawdust coverage on plant establishment

Abstract

Forest restoration in post-open pit mining areas is complex and faces the challenge of “recreating” the soil under horizontal disruption, representing strong barriers to root growth. Hence, trenches (paths opened by digging) for planting are an alternative to improve root development conditions and plant growth. This study aimed to evaluate growth of six tree species planted in trenches under three treatments: Topsoil or control (TS), Sawdust (SD) and Cow manure (CM). The trenches (1 m in height and length by 40 m long) were filled with topsoil. In the 6-m space between trenches, two treatments were performed: soil covered and not covered by sawdust to test natural regeneration. Six tree species (250 individuals) in pits over trenches where Mean Annual Increment in height (MAIHt,), diameter (MAIDSH), crown area (MAICA), and survival were assessed. After 18 months, mortality was 2.4%, Clitoria fairchildiana, Tachigali vulgaris, and Croton matourensis showed highest MAIHt and MAIDSH, and the C. fairchildiana presented the highest MAICA with no statistical differences among treatments. Sawdust coverage had no effects on litter amounts and on tree species from the natural regeneration. Herbs and grasses covered 45.5% and 57.2% of the soil with and without sawdust. Based on growth and mortality, C. fairchildiana, T. vulgaris, and C. matarensis can be recommended for initial restoration after kaolin mining.