Effects of Haloxylon spp. of Different Age Classes on Vegetation Cover and Soil Properties on an Arid Desert Steppe in Iran

摘要

In arid regions,afforestation has been considered as a method for ecological revival in terms of vegetation enrichment and soil amelioration.In this study,the effects of afforestation with Haloxylon spp.on vegetation cover and soil properties were measured<3,3,6,and 25 years after planting in an arid desert in Iran.Soil samples were collected at two depths(0-30 and 30-60 cm)under and between shrub canopies.Afforestation succession significantly affected plant community characteristics.In total,16 species from 8families and 15 genera were observed along the afforestation successional gradient.Plant species richness and diversity and vegetation cover increased slowly during the succession,and reached the maximum values in the area where Haloxylon had been planted for25 years.Soil nutrient values gradually increased during the succession,and the levels of organic matter,total nitrogen,available potassium,and available phosphorus were significantly higher under Haloxylon canopies than between them.Afforestation reduced soil pH under and between Haloxylon canopies during the succession,while soil electrical conductivity followed an opposite pattern.Haloxylon planting increased the silt content in the 0-30 cm soil layer.Our results suggest that Haloxylon establishment plays an important role in the reestablishment of desertified ecosystems in arid regions.