Deep ripping after topsoil return affects root proliferation and floristic diversity in a restored biodiverse forest after bauxite mining

摘要

This study aimed to determine whether deep ripping following the placement of overburden and topsoil materials significantly reduced in-situ soil strength, encouraged root penetration/proliferation and altered floristic diversity in a rehabilitated bauxite mine pit. Three plots located within an area that was deep-ripped after overburden and topsoil return were compared with three plots within the same mine pit that received the conventional pit floor ripping/topsoil scarification treatment. All plots were reseeded with > 150 plant species from the local biodiverse forest. Topsoil ripping produced no significant overall effect on soil strength because the materials in the pit were very friable and had low soil strength regardless of topsoil treatment. Root abundance generally correlated better with depth than with penetration resistance. There was interaction between soil depth and ripping treatment with respect to root abundance, indicating that the vegetation responded differently in terms of root proliferation to depth depending on whether the topsoil was deep-ripped. Roots were significantly more abundant in the top 10 cm of scarified profiles, but in those that received the topsoil ripping treatment, root abundances were significantly higher between 50 and 60 cm depth. This differential response was also highlighted by multivariate analysis of floristic data, which revealed that community composition and structure differed between topsoil ripping treatments. After 12 years, scarified plots had greater species richness, total abundance and plant density on average, but the vegetation was larger in topsoil-ripped plots. The benefits conferred by topsoil ripping appear to be highly dependent on the physical properties of the soil materials but may affect floristic diversity of the restored forest. From this the conclusion is there is a direct link between the physical treatment of soils and rehabilitation success.