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Primary forests, defined here as forests where the signs of human impacts, if any, are strongly blurred due to decades without forest management, are scarce in Europe and continue to disappear. Despite these losses, we know little about where these forests occur. Here, we present a comprehensive geodatabase and map of Europe's known primary forests. Our geodatabase harmonizes 48 different, mostly field-based datasets of primary forests, and contains 18,411 individual patches (41.1 Mha) spread across 33 countries. When available, we provide information on each patch (name, location, naturalness, extent and dominant tree species) and the surrounding landscape (biogeographical regions, protection status, potential natural vegetation, current forest extent). Using Landsat satellite-image time series (1985–2018) we checked each patch for possible disturbance events since primary forests were identified, resulting in 94% of patches free of significant disturbances in the last 30 years. Although knowledge gaps remain, ours is the most comprehensive dataset on primary forests in Europe, and will be useful for ecological studies, and conservation planning to safeguard these unique forests. Measurement(s) Geographic Distribution Technology Type(s) digital curation Factor Type(s) country Sample Characteristic - Environment primary forest Sample Characteristic - Location Europe Machine-accessible metadata file describing the reported data: https://doi.org/10.6084/m9.figshare.14540625 [ABSTRACT FROM AUTHOR]

The conservation of semi-natural habitats represents a primary challenge for European nature conservation due to their great species diversity and their vulnerability to ongoing massive land-use changes. As these changes rapidly transform and phase out semi-natural habitats, conservation measures should be prompt and specifically focused on a sound assessment of the degree of conservation. Here we develop a methodological strategy for the assessment of the degree of conservation of semi-natural grasslands based on well-defined criteria rather than on expert opinion. Through mixed effect models, we tested ten potential indicators, encompassing proxies of species composition, habitat structure, and landscape patterns, against a measure of compositional change from habitat favourable condition, i.e., an inverse proxy of conservation status. This measure derives from the re-visitation of 132 sampling units historically sampled between 1966 and 1992 along the Apennines. The compositional change was quantified as the dissimilarity between historical habitat species pools and the composition of current communities. The compositional change was significantly related to the number of habitat diagnostic species and the relative cover of woody species with opposite sign (positive and negative, respectively). We classified and combined the classes of these two indicators in each sampling unit to assess the habitat degree of conservation at the plot and at the Natura 2000 site level. At the plot level, our assessment was in good agreement with the occurrence of species of conservation concern. On the other hand, at the site level, our assessment was not always harmonic with the habitat conservation assessment officially reported for the site investigated. [ABSTRACT FROM AUTHOR]

Assessing the contribution of forest soils to carbon (C) and nutrient dynamics is extremely complex due to the high spatial variability of soil properties, at fine to very broad scales. Improving our understanding of soil variability is necessary to scale up sample-based inventory data for the estimation of regional contribution of forest soils to C dynamics. We analyzed the topsoil spatial variability of organic carbon (OC) and matter (OM), nitrogen (N), C/N ratio, texture, and pH in 11 southern European old-growth beech stands. Our aim was to assess the within- and among-stand topsoil variability, and to determine the drivers underlying this variation. For each stand, we sampled the topsoil in 25 quadrats in a 1-ha regular grid where we recorded overstorey structural and compositional attributes, deadwood quantity and quality, microtopography and site conditions. Soil parameters varied highly at both scales: When considering all the topsoil properties together through multivariate analysis, most of the variability occurred at the within-stand scale (mostly due to shifts in organic matter content, C/N, and litter depth); the opposite was true when considering soil properties singularly, with pH, soil texture, and N concentration varying greatly among stands. Most of the among-stand variability depended on climate and on the direct and indirect effects of parent material. Fine-scale variation, instead, depended mainly on overstorey composition and microtopographical variation. Surprisingly, we found no direct influence of overstorey structure on topsoil parameters, likely because soil parameters respond to changes in stand structural features only after a substantial time lag. [ABSTRACT FROM AUTHOR]

The importance of harmonizing the group of terms used to indicate ‘natural’ forests is reported in several studies. In a recent paper the term virgin forest is proposed as a unifying concept for forests which are not influenced by man in their development. In response to that paper my aim is to clarify the terms virgin and old-growth. My response focuses on two points: the term virgin forest is generally used to indicate forests that have not been influenced by people even in the distant past, therefore something different from what described by the authors; the definition drawn up for the proposed term substantially overlaps with the definition of old-growth forest resulting from a long history of studies on this theme. I think that the overlap between the two analyzed terms can ultimately only increase the existing confusion on this group of forest terms. [ABSTRACT FROM AUTHOR]