Restoration and Revegetation of Abandoned Ex-Stone Quarry Lands with Tree Species in Southeast Nigeria

Abstract

A Randomized Complete Block Design with three replicates was used to study the revegetation and restoration of abandoned quarry lands using three tree species (Adenanthera pavonina, Gmelina arborea and Acacia auriculiformis) in Ihube, Okigwe Local Government Area, Imo State, Nigeria. The abandoned stone quarry site chosen measured 45.5m x 45.5m (0.20 ha). The area planted up was 22.5m x 30m. At the site, each of the tree species occupied an area of 7.5m x 30m and was treated as a block. The trees were planted in each block at 2.5m x 2.5m, which gave 12 rows of trees making a total of 36 trees per block and 108 trees of the entire experimental layout. Inorganic fertilizer N.P.K. (20:10:10) treatments were used to enhance tree growth and were applied at the rates of 0, 160, 320, 480 kg/ha. The growth parameters of the tree seedlings investigated were total plant height, stem girth, basal area, canopy cover and canopy sectional area. Data collected were subjected to analysis of variance (ANOVA), and means segregated using Least Significance Difference (LSD). The study showed that Acacia auriculiformis had the best plant revegetative attributes of total plant height, canopy cover and canopy sectional area on the abandoned quarry site. The study also showed that Acacia auriculiformis had significantly the highest plant height (71.62 cm). Gmelina arborea had significantly the highest stem girth (2.62 cm) and stem basal area (3.39 cm²) in almost all the treatments used.  Acacia auriculiformis gave significantly the highest canopy cover (386.93 cm²) and canopy sectional area (3115.40 cm²).  The results obtained from the soil analysis based on the effect of the tree species seedlings on the soil showed that   Adenanthera pavonina tree seedlings increased the percentage sand content, silt content, base saturation, nitrogen, organic carbon and organic matter. The soil calcium, sodium and ECEC were recorded to have been increased by Gmelina arborea. Acacia auriculiformis tree seedling increased the soil magnesium while the potassium (K), phosphorus (P), EA and soil pH was not increased by the tree species seedlings. Based on the findings of the study, Adenanthera pavonina tree seedling is the best tree species for the reaffoerestation of Ihube abandoned quarry sites and 320 kg/ha inorganic fertilizer application regime is the best level for the establishment of the tree species.