Historical ecology and ancient forests: Progress, conservation issues and scientific prospects, with some examples from the French case

Abstract

Forest area has dramatically increased since the beginning or middle of the 19th century in European countries. At least half of the forests present today have grown on formerly cultivated lands, pastures or heathlands. However, net forest expansion largely masks a slow but irretrievable erosion of ancient forests. Meanwhile, forest resource harvesting (biomass, litter) has fundamentally changed during the last two centuries, moving from intensive biomass removal to increased growing stocks in different European countries. This article reviews the current knowledge on the longterm legacies of past land use and forest management practices and their effects on the functions, diversity and composition of understory vegetation of current forest ecosystems. First, we define the concepts of forest continuity and ancient forest. Then, based on the French case, we present the advances in historical sources, which make it possible to better reconstruct the change in land use and forest management practices over the last two hundred years. We review how understory plant communities and their traits respond to forest continuity and to different types of former agricultural uses, both at local and landscape scales. We then address three important issues for conservation and management: the conservation value of ancient forests, the impact of forest management on the ecological integrity of ancient forests, and the under-explored legacies of former forest management practices on soil and understory vegetation. Lastly, we propose five main fronts for future research efforts: (a) explore all types of cartographic, written sources and environmental markers; (b) develop modelling approaches to understand how past land use shapes plant communities; (c) better define the conservation value of ancient forests in conservation and management policies; (d) investigate how drivers of global change interact with forest management and land use legacies and (e) explore land use legacies in mountain and Mediterranean socio-ecological systems.

From taxonomic to functional dark diversity: exploring the causes of potential biodiversity and its implications for conservation

“…Our results confirmed that recent woodlands, even after decades of forest re-establishing, do not 397 fully recover communities like those of ancient forests in terms of species identity, whether for 398 plants (Bergès & Dupouey, 2020;Hermy & Verheyen, 2007) or spiders (Morel et al, 2019). Dark 399 diversity showed that recent forests mainly lacked some generalist species they could recruit (e.g.…”

“…Terrestrial ecosystems currently experience many land-use changes, which raises important 158 questions about their impacts on biodiversity and natural habitats (Newbold et al, 2015). In 159 particular, how communities of ancient forests differ from those of recent woodlands is an old but 160 persistent issue of ecology (Bergès & Dupouey, 2020), which offers an ideal opportunity to make use Here, we developed the first method to estimate functional dark diversity, and we applied this 184 method to evaluate how passive rewilding (i.e. spontaneous afforestation) may reshape the 185 biocenosis of forest ecosystems.…”

Mapping Mature Post-Agricultural Forests in the Polish Eastern Carpathians with Archival Remote Sensing Data

“…Post-agricultural forests develop on former farmlands and differ in species composition from those with no record of agricultural use [1][2][3]. Nowadays, in many regions around the world, post-agricultural forests constitute a significant part of the total forest area [1,4,5].…”

“…Post-agricultural forests often seem to form uniform complexes with old forests, but the differences between them are significant for the natural environment [12,13]. For instance, forests with long continuous history are characterized by a higher biodiversity and occurrence of ancient forest species [2,13].…”

“…One of the main factors influencing the dispersal of forest species and affecting the regeneration is the connectivity with the ancient forest [1,2,10]. Mapping post-agricultural forests and old-woods (forests that most likely have never been cleared for agriculture) enables to further analyze the connectivity and, thus, the possibility of spreading species between them.…”