Vegetation convergence during early succession on coal wastes: a 6-year permanent plot study

Abstract

AbstractQuestion: Does the course of succession on a coal mine restored by hydro-seeding converge with a reference community in terms of species compositionandvegetationstructure?Whatistherateofsuccessiononrestoredareas?Howdoesthebalancebetweenlocalcolonizationandextinctionrateschangeduringsuccession? Which species group (native or hydroseeded) determines thesuccessional process?Location: Large reclaimed coal mine in the north of Palencia province, north-ern Spain (42150 0 N, 4138 0 W).Methods: Between 2004 and 2009 we monitored annually vascular plantspecies cover in nine permanent plots (20m 2 each) at a restored mine; theseplots were structured to account for site aspect (north, south and flat). Threeidentical permanent plots were established in the surrounding referencecommunity and monitored in 2004 and 2009. We used detrended correspon-dence analysis to assess successional trends and rates of succession, generalizedlinear mixed models to derive patterns of vegetation structural changes andturnover through time, and Huisman–Olff–Fresco modelling to illustrateresponse of individual species through time.Results: The three restored mine areas exhibited a successional trend towardsthe reference community through time, although speed of convergencediffered. However, after 6 years the restored sites had diverged considerablyand this was greater than the dissimilarity reduction with respect to thereference community. Richness, diversity and native species cover increasedlinearly through time, whereas hydroseeded species cover decreased. Successof hydroseeded species initially differed in the three areas, and this wasnegatively related with native species colonization rates. Response patternsthrough time of ten hydroseeded and 20 most common native species aredescribed.Conclusions: Vegetation structural parameters rapidly converged with thereferencecommunity,whereascompositionalconvergenceneededmuchlonger.At the same time, successional composition trajectories and rates were relatedto site properties (here aspect).IntroductionOpencast mining is a major environmental disturbancethat often leaves a landscape with no vegetation and verypoor soil-forming material on which an ecosystem candevelop (Herath et al. 2009). In such damaged systems,the aim of the ecological restoration should be to create ahealthy, self-sustaining ecosystem, which is similar to thesemi-natural or natural ecosystems that were presentbefore the mining operations. As restoration proceeds,thereisanexcellentopportunitytostudythesuccessionaldynamics of vegetation development in these newly