Beneficial effects of livestock exclusion on tree regeneration, understory plant diversity, and soil properties in semiarid forests in Iran

Zagros forests in western Iran have been impacted by severe fuelwood removal, traditional agricultural systems, non‐timber products removal, and livestock grazing. These conditions have led to the forest area diminishing from 10 to 6 million hectares over the last six decades. This study was conducted to understand the consequences of livestock exclusion on understory plant diversity, forest tree regeneration, and soil physicochemical properties in semiarid forests. We selected four neighbouring areas, including those subject to livestock exclusion and to grazing, in the Zagros oak forests of Iran. Ten randomized sampling plots (400 m2) were established, and all plant species were recorded in each area. A soil physicochemical analysis indicated a significant improvement in soil nitrogen, phosphorous, potassium, and organic matter in the livestock exclusion area compared to the grazing area. The Shannon–Wiener diversity and species richness was also significantly higher in the livestock exclusion areas compared to the grazed. Grazing tolerant species like Poa bulbosa were abundant in grazing areas, while palatable and nitrogen‐fixing species disappeared. The tree regeneration rate was significantly higher in the exclusion areas compared to the grazing areas, and its values were 0.079 and 0.006 per square metre in the exclusion and grazing areas, respectively. The results of the present study provided evidence that exclusion had a significant effect on improving soil chemical properties, understory plant diversity index, and sapling regeneration. However, the regeneration rates were still low, and therefore, livestock exclusion alone may not be enough to promote forest restoration. Therefore, to better understand plant diversity and tree regeneration in the Zagros forests, livestock exclusion and other factors such as soil seed bank and socio‐economic status of people should be considered.