Ungulates Mitigate the Effects of Drought and Shrub Encroachment on the Fire Hazard of Mediterranean Oak Woodlands

Study Description

Climate change urges us to assess interactions between increased drought and wildfire frequencies, and ungulate browsing. We used a long-term browsing exclusion experiment to explore the combined effects of drought and deer browsing on shrub mortality and fire hazard in a Mediterranean oak woodland (Portugal). Drought increased the proportion of dead shrubs, total fuel loading, and fire hazard (modeled) in browsed and un-browsed plots. However, in spite of a higher shrub mortality and plant flammability in browsed plots, deer drastically reduced shrub biomass, decreasing the fire hazard in these plots. Our study highlights ungulate effects on ecosystems under climate change.

Photo 1. Mediterranean oak woodlands in the study site, in southeast Portugal, are composed of cork (Quercus suber) and holm oak (Q. rotundifolia) with an understory dominated by the shrub gum rockrose (Cistus ladanifer) interspaced with grassland patches. White dots are C. ladanifer flowers (enlarged photograph). Photo credit: Miguel Bugalho.

Photo 2. Deer browsing, in addition to drought, increases shrub mortality outside fenced plots, with a higher accumulation of dead woody biomass and potential effects on wildfire hazard. Herbs and other fine fuel are also lower outside the fence due to deer grazing. Photo credit: Miguel Bugalho.

Photo 3. Red deer (Cervus elaphus), such as this female and calf, together with fallow deer (Dama dama) are the main browsers in the study area and contribute to reduce shrub encroachment and fuel accumulation. Photo credit: Miguel Bugalho.

Photo 4. Red deer (Cervus elaphus) also use the areas with high C. ladanifer cover for hiding. Tall shrubs, reaching the tree canopy, increase the likelihood of canopy fire. By reducing shrub height through browsing, deer contribute to decrease fire hazard. Photo credit: Miguel Bugalho.

These photographs illustrate the article “Ungulates mitigate the effects of drought and shrub encroachment on the fire hazard of Mediterranean oak woodlands” by X. Lecomte, M. N. Bugalho, F. X. Catry, P. M. Fernandes, A. Cera, and M. C. Caldeira published in Ecological Applications. https://doi.org/10.1002/eap.2971