Ungulate damage on Scots pines in Mediterranean environments: effects of association with shrubs

The spatial structure of plant communities as well as the quality and abundance of neighbours can strongly influence the intensity of herbivory suffered by a plant. In this paper, we study the effect of the association with shrubs on the ungulate herbivory suffered by Scots pine (Pinus sylvestris var. nevadensis Christ., Pinaceae) saplings in two isolated, fragmented populations in southeastern Spain. For this, we monitored herbivory on saplings with regard to the microhabitat in which they grew. We distinguished pines growing in open interspaces, on the edge of shrubs and within the canopy of shrubs, and also we distinguished four functional types of shrubs: thorny shrubs, nonthorny shrubs, thorny scrubs, and nonthorny scrubs. Our results show that association with shrubs increases the damage inflicted on Scots pine saplings. In fact, saplings growing in the open patches, far from the shrubs, escaped from herbivory more frequently and incurred less damage than did saplings growing close to shrubs. However, herbivory was also reduced when pine saplings were completely surrounded by shrubs, since then they served as a mechanical barrier. The type of neighbouring shrub did not affect the overall damage suffered by pines, despite the fact that the ungulates damaged the nonthorny scrubs more intensely than the other kinds of shrubs. Consequently, saplings have an advantage when growing within the canopy of shrubs; these constitute key microsites for pine recruitment in these Mediterranean forests.