Mid‐term effects on ecosystem services of quarry restoration with Technosols under Mediterranean conditions: 10‐year impacts on soil organic carbon and vegetation development

Vicenç Carabassa,Josep M Alcañiz,Xavier Domene,Elisa Díaz

doi:10.1111/rec.13072

Abstract

The use of Technosols for the restoration of limestone quarries overcomes the usual “in situ” scarcity of soil and/or its poor quality. The use of mine spoils, improved with mineral and/or organic amendments, could be an efficient and environmentally friendly option. Properly treated sewage sludge from urban wastewater treatment plants could be a suitable organic amendment and fertilizer (rich in N and P) whenever its pollutant burden is low (heavy metals and/or organic pollutants). Its appropriate use could improve essential soil physical and chemical properties and, therefore, promote key ecosystem services of restored areas, such as biomass production and carbon sequestration, as well as biodiversity and landscape recovery. However, the mid‐term impacts of these restoration practices on soil functioning and their services have rarely been reported in the available literature. In this study we assess the mid‐term effects (10 years) of the use of sewage sludge as a Technosol amendment on soil organic carbon (SOC), nutrient status, and plant development in several restored quarries. Soils restored using sewage sludge showed a threefold increase in SOC compared to the corresponding unamended ones, despite the moderate sludge dosage applied (below 50 tonnes/ha). Plant cover was also higher in amended soils, and recruitment was not affected by sludge amendment at these doses. This study demonstrates that, used at an appropriate rate, sewage sludge is a good alternative for the valorization of mine spoils in quarry restoration, improving some important regulatory ecosystem services such as carbon sequestration, without compromising woody plant encroachment.

Highlights

Quarrying activities produce severe impacts on important ecological functions that provide ecosystem services contributing to human well-being
These differences were even stronger in the case of N, where sludge-amended Technosols had more than three times higher contents compared to unamended ones, which were extremely poor in N, especially when only mine spoils were used as mineral substrate
Regarding the N:P ratio, controls were deficient in available P and highly unbalanced, mainly when rocky debris without including topsoil were used for Technosol construction

Summary

Introduction

Quarrying activities produce severe impacts on important ecological functions that provide ecosystem services contributing to human well-being. In most of the scenarios, restoring ecosystem services after finishing the exploitation implies the recovery of vegetation in sites where soil fertility levels have been depleted (Moreno-Peñaranda et al 2004). Carbon sequestration in quarry Technosols quarry restoration is a management option that contributes to the valorization of mine spoils and sludge from urban wastewater treatment plants (Sopper 1993), in agreement with the EU principles for a more circular economy (Mosquera-Losada et al 2017). Sewage sludge is an interesting option for valorizing mine spoils due to its fertilizing properties (Van-Camp et al 2004) and its known positive effects on soil aggregate stability (Caravaca et al 2002; Ojeda et al 2008), soil water retention (Ojeda et al 2010, 2011), and vegetation recovery (Moreno-Peñaranda et al 2004; Ortiz & Alcañiz 2006; Carabassa et al 2018). Sewage sludge application requires strong supervision and monitoring due to certain environmental risks related to its potentially harmful heavy metals and persistent organic pollutant content (Düring & Gäth 2002; Carabassa et al 2010a)

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Conclusion