Are the remnants of both ancient and mature forest relevant to inspire close-to-nature forest management and efficient biodiversity conservation?

Primary and old-growth forests have been identified as high priority for biodiversity conservation and their study could provide benchmarks for forest managers who wish to promote biodiversity-friendly forestry. However, can the remnants of primeval and old-growth forests in any case provide these services? This study shed light on these issues by considering a large French region where almost all old-growth forest patches have been identified and accurately located. The Pyrenees still contain remnants of ancient forests, some of which are also mature (hereafter AMFs), i.e. present oldgrowth forest attributes. The location of AMFs and their environmental conditions are likely not random. This study aims to (i) identify factors that explain the current location of AMFs; (ii) assess the potential of these AMFs as reference ecosystems; (iii) discuss the relevance of the current AMF network for the conservation of forest-dwelling taxa. We used a set of 10,344 virtual 1 ha-plots described by 10 variables for both abiotic conditions and the socio-economic context to compare AMFs, ancient but not mature forests, and recent forests. AMFs significantly differed from other forests for most of the variables tested, but effect size is rather weak, except for the number of days with late frost, exposition and ownership type. The current AMF network cannot fully ensure conservation of biodiversity associated with the Pyrenean forests since it is too patchy, covers too little surface area and is not sufficiently representative of the range of abiotic conditions that prevail on the Northern slope of the Pyrenees