Cattle grazing potentially benefits a key organic carbon producer in a water limited ecosystem

Cattle grazing serves as a principal land management tool in drylands worldwide, substantially affecting major soil properties and processes, such as soil organic carbon, soil moisture, and biotic components. The mechanisms of many of these effects remain elusive, although they hold particular significance, as they play a vital role in determining carbon-, water- and nutrient-related habitat conditions, ultimately affecting the aboveground environment. In addition, trees in drylands serve as ecosystem engineers that can modify soil functionality to a large degree. To examine the combined effects of grazing and trees on soil properties and functioning, a field experiment was carried out in the at the dry edge of the distribution of Quercus calliprinos, a dominant woody species in the eastern Mediterranean region. Large exclosures were installed around Q. calliprinos trees in 2013, preventing cattle from grazing in their vicinity. After eight years (2021), we sampled soil from two habitat types, under the oak canopy and in adjacent herbaceous-dominated space. We found that cattle trampling under the tree canopy accelerated the incorporation of the soil organic and litter layers into the mineral soil, leading to increased soil moisture, microbial activity and nutrient availability. Additionally, beneath the oak canopy, the soil had more soil organic carbon, higher soil moisture, higher availability of some of the nutrients, and the soil detritivore community exhibited an elevated trophic level. Our study showed that cattle grazing has the potential to create fertile soil hotspots under Q. calliprinos, thereby profiting the trees. The study further promotes the idea of Q. calliprinos as a keystone species at the edge of the desert which has a profound impact on the carbon and water relations of the ecosystem.