Ecological classification of land based on Potential Natural Vegetation: a new quantitative & multivariate approach to map ecosystems. The case study of Campobasso Functional Urban Area

Nature and biodiversity make life possible, provide health and social benefits and support our economy. In Europe and many other countries worldwide, ecosystems and services they provide are under pressure from urban sprawl, intensive agriculture, pollution, invasive species and climate change, resulting in widespread degradation since more than 80% of habitats are in poor condition (1). The Nature Restoration Law aims to put Europe’s biodiversity on the path to recovery by 2030 to benefit people, climate and the planet. It is acknowledged that protecting biodiversity is essential to reforming ecosystems that host it. Restoring wetlands, rivers, forests, grasslands, marine ecosystems, and the species they host is imperative. Effective land management and biodiversity conservation rely on a thorough comprehension of ecosystems, which makes it necessary to describe, characterise, and spatially locate them (2). The ecological classification of land can help delineating ecosystems through a hierarchical approach that defines homogeneous portions of territory, or Land Units (LU), based on their homogeneity according to physical and biological features at various scales (3,4). A valid approach to classify LU is associating the physical factors with the corresponding Potential Natural Vegetation, a mature vegetation stable in time, developing in sites under undisturbed conditions. Vegetation-based landscape classifications thus reflect combinations of different vegetation types, promote understanding of landscape patterns and support ecological restoration (5). Potential vegetation approaches also enable the classification of currently transformed landscapes, representing a fundamental tool for selecting species suited for these environments in ecosystem restoration actions or as a guide for nature-oriented agricultural and silvicultural management (6). To provide a standard methodology useful for fine-scale research on urban and peri-urban areas, we propose an updated ecological classification of land based on PNV-LU relationships that has been tested for the Functional Urban Areas (FUA) of Campobasso (Italy, Molise Region). We applied a deductive process, dissecting wholes into parts based on environmental discontinuities (concerning climate, lithology and geomorphology features), and leading to the hierarchical delineation of LU within which phytosociological surveys were homogeneously stratified in woodland patches, followed by vegetation analyses based on clustering and Indicator Species Analyses. Therefore, relationships between recognised vegetation typologies and environmental variables were investigated through multivariate analyses, leading to the estimation of threshold values for each diagnostic feature. In conclusion, a detailed PNV/Environmental Land Unit map of the study area was obtained, improving the cartographic products already available at the regional/national level. This tool enriches the basic knowledge on mature forest ecosystems and may support effective restoration actions for the specific case study, but can be also transferred and generalised for wide-scale research on urban biodiversity (such as that on the overall Italian FUAs promoted by the National Biodiversity Future Center). 1) Nature and biodiversity - European Commission. https://environment.ec.europa.eu/topics/nature-and biodiversity_mt 2) Capotorti, G., Guida, D., Siervo, V., Smiraglia, D., & Blasi, C. (2012). Ecological classification of land and conservation of biodiversity at the national level: The case of Italy. Biological Conservation, 147(1), 174-183 3) Bailey, R. G. (2004). Identifying ecoregion boundaries. Environmental management, 34(Suppl 1), S14-S26. 4) Klijn, F., & de Haes, H. A. U. (1994). A hierarchical approach to ecosystems and its implications for ecological land classification. Landscape ecology, 9, 89-104. 5) Konrád, K. D., Bede-Fazekas, Á., Molnár, Z., & Somodi, I., (2022). Multilayer landscape classification based on potential vegetation. Preslia, 94(4), 631-650. 6) Bourdouxhe, A., Wibail, L., Claessens, H., & Dufrêne, M. (2023). Modeling potential natural vegetation: A new light on an old concept to guide nature conservation in fragmented and degraded landscapes. Ecological Modelling, 481, 110382.