Biodegradação de madeiras de espécies tropicais afetam o desenvolvimento vegetal.

Abstract

In order to implement and conduct hydroelectric plants, highways or mining activities, it is necessary to suppress native vegetation. In these situations, wood biodegradation products generated in the log storage yards and wood residues interact with water from precipitations or volatilize and may impact the environment and hamper future efforts to recover degraded areas. The objective of this work was to verify if the biodegradation of tropical wood stored in different conditions affects the soil properties and the initial growth of seedlings of the pioneer species Schizolobium parahyba var. amazonicum (Huber exDucke) Barneby. The woods of four tropical species were selected: timborana (Pseudopiptadenia suaveolens (Miq.) J.WGRIMES); yellowwood (Euxylophora paraensis Huber); clover (Aegiphila integrifolia (Jacq.) Moldenke); and para-pará (Jacaranda copaia (Aubl.) D.Don) collected in the storage yard of a bauxite mining company. The chemical, anatomical and physical characterization of the wood was carried out before and after storage in the soil for 75 days, in three conditions: buried wood, positioned horizontally and positioned vertically (partially buried), in relation to the substrate contained in the pot. For the soil, pH, cation exchange capacity, organic matter content, base saturation, aluminum saturation and macronutrients were determined. In the germinated seedlings, biometric properties and biomass production were analyzed. The seedling development test was conducted in a greenhouse. Mass losses were 2.7%, for Euxylophora paraensis and 13.1%, for Pseudopiptadenia suaveolens, both high density woods, and 8.7% for Aegiphila integrifolia and 18.4%, for Jacaranda copaia, woods low density. The woods with the highest biodegradation rate also showed higher levels of water-soluble extracts (8.4% and 5.4%). Longer fiber length (1172.96 μm), vessel length (768.67 μm) and wall thickness (5.92 μm) were observed for the species with the lowest biodegradation rate and largest lumen diameter (21.64 μm) and vessel diameter (255.67 μm) for species with the highest rate of biodegradation. The biodegradation of all species has negatively modified soil properties causing reductions in pH, organic matter content, macronutrients and increased H + Al content. In addition, there was a reduction in growth in Schizolobium parahyba plants of 28%, 18%, 46%, 34% and 57% for height, stem diameter and dry weight of root, stem and leaves, respectively, when grown in soil in the presence of biodegradation of tropical woods. It is concluded that the intensity of biodegradation depends on the species and varies depending on its anatomical and chemical properties, but it does not depend on the storage position in the soil. Biodegradation negatively affected soil properties and, consequently, the development of Schizolobium parahyba var. amazonicum. This work indicates that the maintenance of wood in the storage yard of mining areas can impair the recovery of degraded areas.