An application of space-for-time substitution in two post-mining chronosequences under rehabilitation

Abstract

Long-term monitoring of post-mining rehabilitation is inherently difficult and cannot be replicated, making the application of traditional experimental and statistical approaches for quantitative assessment of rehabilitation progress unattainable. An alternative approach to monitoring through time is space-for-time substitution; a technique used to infer a temporal trend from a study of different aged sites. In this investigation, space-for-time substitution was applied to two chronosequences of coal discard sites to determine the applicability of this approach to show the long-term effect of rehabilitation age on microbial communities. Sites at different stages of rehabilitation at separate locations (space) were identified to obtain a chronosequence of ages (time). Two chronosequences of rehabilitation ages from 1-11 and 6-17 years, respectively, were included, each with its own management regime. The long-term effect of the management regimes on soil microbial communities was investigated in terms of community function (enzymatic assays) and structure (phospholipid fatty acid profiles). Results showed no trends consistent with the rehabilitation ages of the respective sites for any of the investigated parameters. However, multivariate statistical analysis indicated a clear distinction between the chronosequences based on management regimes. This study shows the value of alternative statistical approaches in monitoring to elucidate long-term effects of management that might otherwise not be apparent.