Shannon tree diversity is a surrogate for mineland rehabilitation status

Abstract

Mineland rehabilitation is performed to reduce the overall impacts of mining operations. Thus, statistically validated and easily measurable indicators are necessary to monitor the environmental status along time, enhance the rehabilitation process, and increase institutional tractability. The objective of this study is to derive an effective indicator to assess the environmental quality of iron mining waste piles undergoing rehabilitation in the Carajás National Forest, eastern Amazon, Brazil, from a curated set of field-surveyed environmental variables related to vegetation structure, invertebrate and vegetation compositions, diversity, and ecological processes. Data were collected from a chronosequence that included non-revegetated areas, areas in different rehabilitation stages and natural reference sites. All variables were integrated to produce a single estimate of rehabilitation status using a multivariate approach. Individual variables largely differed in their response ratios; nevertheless, the data integration showed that more than 50% of the predisturbance ecosystem structure, diversity and functioning were restituted after only seven years, which highlights the potential of rehabilitation activities to effectively reduce mining impacts. Among all 27 variables, the Shannon index of tree diversity had the highest predictive power for overall rehabilitation status, qualifying this metric as the most effective indicator for the use in future comprehensive monitoring activities in waste piles undergoing rehabilitation in the Carajás National Forest. The positive relationship between tree diversity and mineland rehabilitation status in the examined areas emphasizes the importance of diverse tree communities in increasing rehabilitation success and ecosystem and soil functioning over short time periods.