The impact of browsing intensity on argan trees in the Essaouira region of Morocco

Abstract

Pastoralism is a cornerstone of the argan forest ecosystem in Morocco, where the argan tree supports food production and livelihoods. However, overbrowsing threatens this ecosystem, underscoring the need for sustainable management strategies. This study assessed the impact of three browsing intensities on argan trees in the Essaouira region: no-browsing, moderate-browsing (managed browsing or the Agdal system), and heavy-browsing systems. Measurements of argan physiological and biochemical traits and soil parameters revealed significant differences among the three-browsing intensities. Heavily browsed argan trees exhibited reduced photosynthetic efficiency, stomatal conductance, photosynthetic pigments content, and leaf area index, while no-browsing system maintained optimal performances. The Agdal strategy significantly enhanced plant health compared to heavy browsing, improving physiological indicators and soil quality. Soil traits including electrical conductivity, moisture, and organic matter and total nitrogen content were notably better under managed browsing, promoting healthier argan ecosystems. Additionally, browsing intensity affected leaf biochemistry: overbrowsing induced a decline in protein content, while it enhanced total soluble sugars, malondialdehyde, and hydrogen peroxide content, and antioxidant enzymes activity (catalase, peroxidase, and polyphenoloxidase), reflecting heightened stress responses. Overall, even if the non-browsed trees performed best, the moderate-browsing system (Agdal) may be the most suitable of the three browsing systems, since it will be able to meet goats’ feed needs while ensuring the sustainability of the argan forest ecosystem.