Abstract
We investigated the relationship between feeding selection by goats and changes in plant species abundance in the shrubland of a pine forest in Doñana Natural Park along three years. The abundance of the shrub species was measured using the point-intercept method. Goat preferences for shrub species were determined through direct observation. Goats showed selective feeding, since their browsing behavior was not related to species abundance. Myrtus communis was the overall preferred species (almost half of the bites belonged to this species, despite its low abundance) throughout the monitored years and seasons. Half of the species were selected some years while discarded others; two species were never grazed (Daphne gnidium and Thymus mastichina) and nine others were always ingested below their abundance. Within a year, species were consumed in certain seasons but not in others. The detected changes in species abundance were not related to the feeding preferences of the goats. The influence that grazing selectivity exerts on vegetation composition and abundance has long been recognized, but our study suggests that the mechanical effect of grazing herbivores on vegetation (pawing, scratching, and lying) may portrait a more important role than attributed to date.
Highlights
Along with burning, grazing is the greatest vegetation disturbance activity in terms of area and biomass loss [2], significantly influencing current vegetation composition and structure [3]
We recorded 88,395 goat bites along the study period; goats browsed the leaves, stem shoots and flowers of all species except Daphne gnidium and Thymus mastichina, which were never consumed (Table 1). They browsed the fruits of Cistus salviifolius (Cs). salviifolius, H. halimifolium, M. communis, P. lentiscus, and Quercus coccifera, and grazed the pasture
During three years of study, goats showed a selective feeding, since they did not browse species according to their abundance; they are selective grazers
Summary
Along with burning, grazing is the greatest vegetation disturbance activity in terms of area and biomass loss [2], significantly influencing current vegetation composition and structure [3]. Grazing selectivity has been considered to greatly influence species composition and abundance, through the control that it exerts over the population dynamics of plant species [4]. It is accepted that goats (Capra hircus) have modified, through selective feeding [5,6,7,8], the structure and composition of Mediterranean rangelands, which they have traditionally grazed. The aim of this study was to determine if changes in the abundance of the understory shrub species of a pine forest grazed by goats were related to diet selection of goats. We analyzed the potential relationship between the diet of a herd of goats during three years and changes in shrub species abundance along this period. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
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