The impact of goats grazing on understory vegetation of cork oak woodlands

Abstract

The aim of this study is to evaluate the effects of high grazing pressure for short, intermittent periods (1–2 h per day) on fuel load management in cork oak (Quercus suber L.) forests in the north-eastern region of Portugal. This evaluation aims to understand the effectiveness of targeted grazing as a forest management tool, specifically in reducing fuel load accumulation and thereby potentially reducing wildfire risk. In addition, this study extends its analysis to examine the time required for vegetation recovery in the absence of grazing, with the aim of determining the optimal grazing interval. Changes in herbaceous and shrub cover, herbaceous biomass and phytovolume were compared between grazed and ungrazed plots over a period of thirty-four months. Using a stocking rate of 400 goats per hectare for 21 cumulative hours over 12 days resulted in a 93.43% reduction in shrub phytovolume and a 76.2% reduction in shrub cover. Herbaceous biomass also decreased from 53.80 ± 7.82 g m⁻² to 17.76 ± 6.29 g m⁻² in the grazed areas. Twenty-two months after cessation of grazing, no significant differences in plant and shrub cover or herbaceous biomass were observed. The results highlight the effectiveness of targeted grazing in managing fuel loads in cork oak woodlands, with pronounced short-term benefits. However, the rapid recovery of vegetation in the absence of grazing highlights the need for a strategic and continuous management approach to maintain the benefits of fuel reduction.