Livestock browsing affects the species composition and structure of cloud forest in the Dhofar Mountains of Oman

Questions: It is frequently reported that overstocking of camels, cattle and goats is degrading the Anogeissus cloud forest, which is endemic to a 200 km stretch of coastal mountains in southern Arabia. However, livestock impacts on the vegetation have not been assessed. Furthermore, we have a limited understanding of the impacts of large-bodied browsing livestock, such as camels, in woodland and forest rangelands. Therefore, in this study, we examine the effects of livestock browsing on the species composition, density, and hytomorphology of woody vegetation in the Anogeissus cloud forests in the Dhofar Mountains of Oman.

Location: Data was collected at 30 sites in the Jabal Qamar mountain range in western Dhofar, Oman.

Methods: The point-centered quarter method was used to sample the composition, density and structure of woody vegetation. Constrained correspondence analysis was used to quantify the effects of livestock browsing on woody plant species composition, whilst effects on plant density were analysed using mixed effects models. Standardised major axis regression was used to examine differences in height-diameter allometry (stunting) under different stocking rates.

Results: Fog density, topographic position and long-term stocking rates were found to be important factors affecting woody species composition. We found lower species diversity and plant density, and higher frequencies of unpalatable species, under higher stocking rates. Juveniles showed a stronger response to stocking rates than adults, and several common species exhibited stunted morphology under high stocking rates.

Conclusions: Browsing by large-bodied livestock, such as camels and cattle, can substantially alter the species composition, structure, and phytomorphology of woody vegetation in semi-arid woodlands and forests. Juveniles are particularly susceptible to browsing which alters woody vegetation demography and inhibits regeneration potential. Our results support previous suggestions of overstocking in Dhofar and highlight the importance of swift measures to reduce livestock browsing pressure in the Anogeissus cloud forests.