Spontaneous succession on opencast mining sites: implications for bird biodiversity.
Remediation of lands devastated by industry includes various forms of restoration, such as technical reclamation and spontaneous succession. These management approaches are debated regarding conservation strategies for postindustrial landscapes. Mining areas consisting of early- to late-developmental stages of both reclaimed and unreclaimed sites offer an opportunity to examine the roles of restoration strategies in a complete successional series for biodiversity and disentangle the contributions of particular biotopes available at postindustrial sites. Using linear models and multivariate analysis, I tested the effects of (a) developmental stages from early successional sites to mature forests, combined with (b) the initiation process at the sites, which was either technical reclamation or spontaneous succession, and (c) vegetation cover on (i) species richness, (ii) rarity and (iii) species composition of bird communities on 60 plots (100×100 m) within opencast mining areas in the lignite basin of north-western Czech Republic. Bird communities were consistently more species rich on spontaneously developed sites compared with reclaimed sites throughout all stages of the succession series. Species richness increased with site age due to increasing habitat heterogeneity. The conservation value of bird communities was generally lower on reclaimed sites than on spontaneously developed sites and decreased with site age. The most valuable communities developed on early successional sites and native shrublands, because these were inhabited by specialists that were scarce in the surrounding landscape. By contrast, technically reclaimed sites resulted in impoverished communities, usually with narrow spectra of common species. Synthesis and applications. The results highlight the importance of spontaneously established sites and complete succession series for developing valuable bird communities in postindustrial areas such as opencast mining sites. In particular, early successional sites and shrublands create refuges for early successional specialists disappearing from the common landscape and these should be promoted at the expense of reclaimed sites wherever possible. My results support an effort for systematic implementation of early successional sites into conservation practice.