The type of land cover and management affect differently soil functional indicators in a semi-arid ecosystem

One of the intrinsic features of the soil is its function, which relates to the land cover and management. However, the effect of land use/cover changes and management systems on indicators of soil functionality, especially in semi-arid regions is less known. Hence, in the present study soil samples were collected from five typical land cover types in a semi-arid mountainous area of northern Iran: (1) a natural forest (Carpinus orientalis and Quercus macranthera), (2) rangeland (Crataegus melanocarpa and Crataegus microphylla - Berberis integerrima), (3) 30-yearold walnut orchard, (4) agriculture (Hordeum vulgare) with moldboard plowing, and (5) agriculture (Hordeum vulgare) with disk plowing. For each type of land cover, three 1-ha areas spaced 4-6 km apart were chosen in order to avert pseudo-replication. Both physical and biochemical soil properties were assessed at a depth of 0-10 cm from the four corners of the plots in August, comprising a total of 60 samples (5 land covers x 12 samples for each study site) Additionally, soil biological properties were determined in August and November, making a total of 120 samples. Our results showed that available soil nutrients in the forest site were 1.5-2.5 times higher than in the agricultural (disk) site. The highest and the lowest levels of enzymatic activities were found in the forest site and agricultural (disk) site, respectively. In the autumn season, the highest soil biota abundances, except for bacteria and fungi, were observed in the forest site. Also, the biomass of earthworms in the forest site was almost 80 % higher than in the agricultural site. Overall, land covers were classified based on the degree of effect on soil functional indicators as follows: forest > rangeland > orchard > agriculture (moldboard) > agriculture (disk). Taken together, our findings illustrate that preserving natural vegetation is essential for maintaining soil quality on a high level and contributing to the development of fertile areas in mountainous semi-arid ecosystems of northern Iran. The ground vegetation is a key factor affecting the soil functions, and any alteration in the land use, such as switching from forest to agriculture can have a detrimental effect on the quality and productivity of the soil in the long-term.