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In summer 2018, Central Europe was hit by an extreme drought event that widely impacted ecosystems and markedly increased tree mortality in forest ecosystems across the continent. As climate models predict an increase in frequency and severity of such events, there is an urgent need to adapt forests in order to maintain the diverse benefits they provide. Soil processes play an essential role in this context and are key for a plethora of terrestrial ecosystem functions, but they are strongly dependent on water availability. Here, we investigated how tree species richness (TSR), composition, and identity in a 13‐year‐old temperate tree diversity experiment influenced selected ecosystem functions (as important representatives of different ecosystem processes) during the 2018 summer drought. We focused on the stability of soil microbial biomass and standard litter decomposition, as well as tree species‐specific mortality rates. Contrary to our expectations, TSR did not generally increase the resistance of soil functions or decrease tree mortality rates. However, the resistance of these functions was determined by tree species identity and community composition. For the resistance of both soil functions (microbial biomass and litter decomposition), we found that TSR effects depended on the presence of certain tree species. Moreover, we found that the performance of a specific tree species in monoculture, Norway spruce, was a poor predictor of its response to drought in tree species mixtures. Taken together, the results of our study demonstrate that the species composition of tree stands determines tree mortality and the resistance of soil functions under drought. This indicates that enhancing multiple ecosystem functions under environmental disturbance requires maintaining diverse forests. [ABSTRACT FROM AUTHOR]

Solar energy is increasingly used to produce electricity in Europe, but the environmental impact of constructing and running solar parks (SP) is not yet well studied. Solar park construction requires partial vegetation removal and soil leveling. Additionally, solar panels may alter soil microclimate and functioning. In our study of three French Mediterranean solar parks, we analyzed:(1) effects of solar park construction on soil quality by comparing solar park soils with those of semi‐natural land cover types (pinewood and shrubland) and abandoned croplands (former vineyards); and (2) the effect of solar panels on soil microclimate, CO2 effluxes, and vegetation. We measured 21 soil properties of physical, chemical, and microbiological soil quality in one solar park and its surroundings to calculate integrated indicators of soil quality. We surveyed soil temperature and moisture, CO2 effluxes, and vegetation below and outside solar panels of three solar parks. Soil aggregate stability was reduced by SP construction resulting in a degradation of soil physical quality. Soil chemical quality and a general indicator of soil quality were lower in anthropogenic (SP and abandoned vineyards) than in semi‐natural (pinewood and shrubland) land cover types. However, differences between abandoned vineyards representing the preconstruction land cover type and solar parks were not significant. Solar panels reduced the soil temperature by 10% and soil CO2 effluxes by 50% but did not affect early successional plant communities. Long‐term monitoring is needed to evaluate the effects of solar panels on vegetation. [ABSTRACT FROM AUTHOR]

Soil is important as a critical component for the functioning of terrestrial ecosystems. The largest part of the terrestrial biodiversity relies, directly or indirectly, on soil. Furthermore, soil itself is habitat to a great diversity of organisms. The suitability of soil to host such a diversity is strongly related to its physico-chemical features and environmental properties. However, due to the complexity of both soil and biodiversity, it is difficult to identify a clear and unambiguous relationship between environmental parameters and soil biota. Nevertheless, the increasing diffusion of a more integrated view of ecosystems, and in particular the development of the concept of ecosystem services, highlights the need for a better comprehension of the role played by soils in offering these services, including the habitat provision. An assessment of the capability of soils to host biodiversity would contribute to evaluate the quality of soils in order to help policy makers with the development of appropriate and sustainable management actions. However, so far, the heterogeneity of soils has been a barrier to the production of a large-scale framework that directly links soil features to organisms living within it. The current knowledge on the effects of soil physico-chemical properties on biota and the available data at continental scale open the way towards such an evaluation. In this study, the soil habitat potential for biodiversity was assessed and mapped for the first time throughout Europe by combining several soil features (pH, soil texture and soil organic matter) with environmental parameters (potential evapotranspiration, average temperature, soil biomass productivity and land use type). Considering the increasingly recognized importance of soils and their biodiversity in providing ecosystem services, the proposed approach appears to be a promising tool that may contribute to open a forum on the need to include soils in future environmental policy making decisions. [ABSTRACT FROM AUTHOR]

Abstract: We studied the effect of topsoil removal, a nature management technique used in The Netherlands and other countries in North Europe to restore heathland vegetation. Sandy soils under original heathland vegetation were compared with sites that were transformed to farmland in 1950 and sites where after the transformation topsoil removal took place in the 1990s. All soils were sandy and acidic. Topsoil removal led to an 88–94% reduction in the C storage. Therefore, the C storage and the buffer function of the soils have drastically decreased. The N and P storages in the soils where topsoil was removed have also greatly reduced. In the topsoil removed soils no re-colonization of earthworms had occurred and microbial activity has significantly reduced. The soil biological properties were similar between the reference site and the topsoil removed soils. The high bulk density and the typical abiotic soil structure are most likely the results of a combination of management using heavy machinery and no recolonization by earthworms. These changes in soil properties negatively influenced several soil functions which are relevant in nature and environmental protection, e.g. C-storage, filtering and buffering. We therefore conclude that removal of topsoil cannot be recommended as a nature management technique due to its negative effects on soil quality. [Copyright &y& Elsevier]

Abstract: Nationally and internationally there are an increasing number of legal initiatives to protect the ecological processes in soil. This article describes the legal situation concerning the protection of natural functions of soil in Europe (mainly The Netherlands (since 1987) and Germany (since 1998)). Examples of processes to be protected comprise the element cycles, the degradation of pollutants, and the conversion of organic matter. These processes are performed by organisms, and therefore, there is a growing consensus that protection of soil biodiversity is necessary for the survival of humans and the above-ground ecosystems. It is discussed that protection of soil ecosystems needs requires definitions and aims for the ecological quality of soil (as already provided for aquatic ecosystems). Taking into account that most soils are privately owned, legal initiatives are necessary to clarify responsibilities and to direct research toward the implementation of reproducible and standardized methods to determine the ecological quality of soil. [Copyright &y& Elsevier]

Soil quality is fundamental for ecosystem long term functionality, productivity and resilience to current climatic changes. Despite its importance, soil is lost and degraded at dramatic rates worldwide. In Europe, the Mediterranean areas are a hotspot for soil erosion and land degradation due to a combination of climatic conditions, soils, geomorphology and anthropic pressure. Soil organic carbon (SOC) is considered a key indicator of soil quality as it relates to other fundamental soil functions supporting crucial ecosystem services. In the present study, the functional relationships among SOC and other important soil properties were investigated in the topsoil of 38 sites under different land cover and management, distributed over three Mediterranean regions under strong desertification risk, with the final aim to define critical SOC ranges for fast loss of important soil functionalities. The study sites belonged to private and public landowners seeking to adopt sustainable land management practices to support ecosystem sustainability and productivity of their land. Data showed a very clear relationship between SOC concentrations and the other analyzed soil properties: total nitrogen, bulk density, cation exchange capacity, available water capacity, microbial biomass, C fractions associated to particulate organic matter and to the mineral soil component and indirectly with net N mineralization. Below 20 g SOC kg−1, additional changes of SOC concentrations resulted in a steep variation of all the analyzed soil indicators, an order of magnitude higher than the changes occurring between 50 and 100 g SOC kg−1 and 3–4 times the changes observed at 20–50 g SOC kg−1. About half of the study sites showed average SOC concentration of the topsoil centimetres <20 g SOC kg−1. For these areas the level of SOC might hence be considered critical and immediate and effective recovery management plans are needed to avoid complete land degradation in the next future. • SOC was an important indicator of soil quality in areas under desertification risk. • A critical limit of 20 g SOC kg−1 was found for soil quality in the analyzed areas. • Soil properties rapidly changed for a variation of 1% SOC below critical limit. • MAOC represented most of the organic C pool <50 g SOC kg−1. [ABSTRACT FROM AUTHOR]