Habitat quality assessment of Atlantic wet heathlands in Serra do Xistral, NW Spain

Abstract

The assessment of habitat quality, especially in semi-natural managed systems, provides a powerful tool for monitoring short and long-term conservation actions. The Erica mackayana Atlantic wet heathlands of the Serra do Xistral protected area in Galicia, NW Spain, represent a dynamic system with high conservation value associated to traditional management through grazing of free-ranging cattle and wild ponies. Here, we aimed to develop a spatially-explicit, quantitative method for Habitat Quality Assessment, defining an optimum state and the alternative states that may arise from habitat degradation. Vegetation structure, grass-shrub cover ratio, gorse cover, presence of bracken, exotic species such as pine trees and saplings, erosive events and altered hydrological dynamics were identified as the main indicators of habitat degradation. A heterogeneous vegetation structure with a dominant shrub cover of c.0.5 m height and constant gaps among shrubs, with a limited cover of gorse and absence of pine trees, bramble and bracken, and absence of erosive events was recognized as the optimum state. We applied the Habitat Quality Assessment (HQA) method to a pilot area within the Xistral protected site. Wet heathland was the dominant habitat, covering 37.1% of the area. 7.0% of the assessed heathlands were recognized as in the optimum state for habitat quality. Recommendations are made for habitat management to revert low scores, mainly by the adjustment of livestock numbers and the removal of exotic pine trees.