Monitoring Variations in Forage Production and Grazing Capacity Across Grasslands in Different Altitudinal Zones in Northwestern Greece Using Remote Sensing Techniques

Grasslands in Greece are vital for biodiversity, ecosystem services, and extensive livestock production due to their forage resources. This study examined the seasonal variations and differences between two years in terms of grazeable forage production and grazing capacity across semi-mountainous, mountainous, and subalpine grasslands in the Regional Unit of Florina, located in northwestern Greece. Field measurements collected during two consecutive years were combined with satellite-derived vegetation data to estimate forage productivity and create spatially explicit maps of grazing resources. Grasslands were mapped through supervised classification using the Maximum Likelihood algorithm (MLA), utilising NDVI and OSAVI as auxiliary spectral indices. The results revealed clear seasonal and altitudinal patterns in forage production. Subalpine grasslands served as highly productive reservoirs for summer forage, yielding up to 1698.90 kg DM ha−1, whereas lower-elevation grasslands provided greater forage availability in spring but experienced a marked decline of approximately 37% by autumn as the growing season progressed. Although subalpine grasslands had the highest seasonal mean forage productivity, mountainous grasslands supported the greatest grazing capacity, exceeding 11,000 animal units, due to their larger grazing area and longer grazing season. The generated maps effectively illustrated seasonal changes in forage availability across the altitudinal gradient, and the spatial patterns derived from remote sensing were consistent with the field measurements. These results highlighted the importance of integrating field observations with remote sensing to quantify seasonal forage resources, thereby enhancing adaptive and sustainable grazing management in Mediterranean mountain grasslands.