Natural Seed Limitation and Effectiveness of Forest Plantations to Restore Semiarid Abandoned Metal Mining Areas in SE Spain

Marta Bindang Oná,Marta Goberna,Jose Antonio Navarro-Cano

doi:10.3390/f12050548

Marta Bindang Oná, Marta Goberna + Show 1 more

Open Access

https://doi.org/10.3390/f12050548

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Abstract

The natural regeneration of forests in mining areas is typically hampered by edaphic stress. Semiarid conditions add a climatic stress that challenges the restoration of these harsh ecosystems. This is the case of Tetraclinisarticulata (Vahl) Masters mixed forests in the Western Mediterranean region colonizing mining structures abandoned three decades ago. We studied the factors controlling the natural establishment of nine shrub and tree species key in these forests in eight metal mine tailings in SE Spain. In addition, we assessed the success of reintroducing 1480 individuals of the nine species 15 months after planting in one of the tailings. Specifically, we analyzed the effect of (i) species identity in terms of sapling survival, growth, nutritional status and metal bioaccumulation, and (ii) adding organic amendments into the planting holes on the same parameters. Our results indicated that natural colonization is a recent process, with seedling cohorts that vary up to two orders of magnitude among species and a practical absence of adult plants in most species excepting T. articulata. We identified seed limitation as a key factor controlling seedling density, which was significantly explained by the distance from the border of the tailing to the closest adult out of the tailing. Soil metal concentration did not have any explanatory power on the density of naturally-established seedlings, whereas soil fertility was relevant only for Rhamnus lycioides L. Overall survival of planted individuals was over 80%, survival and growth remarkably differing among species. Organic amendments had neutral or negative effects on plant survival, but significantly increased the growth of survivors despite their modest effects on leaf nutrient contents. Most species showed high metal bioaccumulation, which was exacerbated by organic amendments. We discuss how biodiversity conservation programs can benefit from the affordable and successful plantation of stress-tolerant local species, but come at the expense of potential metal transfer through trophic webs.

Highlights

IntroductionIn Europe, mining industry is responsible for 60% of contaminated lands, and only in 5% of all cases restoration or rehabilitation programs have been carried out [2]
We reduced the soil properties within the tailings to two main variables by performing two principal component analyses (PCA) that respectively included variables related to soil fertility (TOC, N, P and K) and metal(oid) content (As, Cd, Cu, Fe, Mn, Zn and Pb)
They were followed by P. angustifolia and T. articulata whereas species such as O. europaea, C. humilis or Q. coccifera had densities below 2 seedlings·ha−1

Summary

Introduction

In Europe, mining industry is responsible for 60% of contaminated lands, and only in 5% of all cases restoration or rehabilitation programs have been carried out [2]. That is the case of mining areas in drylands. Metal mining generates barren substrates of high soil toxicity, physical instability, as well as water and temperature stress. These factors hamper biological colonization and the promotion of basic ecosystem functions, such as organic matter decomposition and nutrient cycling driven by decomposer activity [4] or the resistance to disturbances and ecosystem stability provided by the plant cover [5]

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