Effects of multi-scale drivers on plant diversity and forage quality in traditional wood-pastures of Transylvania (Romania)

Traditional wood-pastures are agroforestry systems shaped by long-term low-intensity management. However, the relative importance of drivers of plant diversity and forage quality operating at different spatial scales in these systems remains poorly understood. We investigated 30 traditional wood-pasture sites in Transylvania (Romania) by integrating drivers i) at the large-scale: historical Corona satellite imagery from 1964, contemporary land-cover data, and CHELSA climatic data; ii) at the intermediate-scale: tree and woody configuration; and iii) at the fine-scale: soil surveys. We evaluated the interaction among landscape structure, site factors, plant diversity and forage quality. We analysed long-term changes in land use and woody cover across multiple spatial scales within wood-pasture mosaics. Using linear models and variation partitioning, we assessed the multi-scale environmental determinants on plant taxonomic and functional diversity, and forage quality of the wood-pastures. Landscape composition remained largely stable over six decades, although woody cover declined at most sites, indicating fine-scale structural change within a persistent land-cover mosaic. Climatic conditions such as annual precipitation was positively associated with forage quality and functional richness of specific leaf area, while mean annual temperature and pasture loss were negatively associated with functional richness of plant height. Current forest cover was related to functional richness related to leaf economics and seed mass, whereas soil carbon showed a positive relationship with species richness and leaf-trait diversity. Woody cover was linked to higher species richness but lower forage quality, suggesting a structural trade-off between biodiversity and palatability. Current land use explained the largest proportion of variation in forage quality and species richness, whereas climate and land-use change were more strongly associated with functional composition. These results support hierarchical environmental filtering, whereby regional climate and local habitat structure constrain community assembly more strongly than landscape composition. Our findings about this traditional multifunctional landscape highlight that conserving and restoring wood-pasture functionality requires combined management practices that optimise woody cover, grazing intensity, and soil quality.