Exploring the limits of Norway Spruce: Presence/absence data at the species' southernmost edge

Abstract

Norway spruce (Picea abies (L.) Karst.) is a keystone species of European forests. Its latitudinal range extends from Scandinavia to the Balkans. The southern Rhodopes population (Greece) represents the species' global southernmost limit. This rear-edge population is critically important for assessing resilience to climate-driven range contraction and calibrating Species Distribution Models (SDMs), yet remains undocumented in continental data resources - notably the EU-Forest dataset which contains no records for this region.To address this gap, we present a georeferenced polygon-level presence-absence dataset synthesized from information from local forest management plans of the period 1970-2019. Covering 110694 hectares of topographically complex terrain, our protocol for data-collection integrated division of the territory into 1912 homogeneous stands followed by field surveys, forest inventories and recurrent validation of species presence-absence. Key results confirm Norway spruce occupies 26415 hectares across 500 stands. This includes the previously undocumented Trachoni population, within which the species' southernmost occurrence was recorded at 24°45' E, 41°21' N. Compiled as a polygonal OGC GeoPackage file, this dataset provides the first comprehensive spatial registry of the species at its biogeographic boundary. It significantly expands existing resources such as EU-Forest data set by (i) documenting presence of a new nuclei, (ii) serving as a vital baseline for monitoring climate-induced responses, (iii) provides critical input for improving SDMs.