Effect of shrub type on species diversity and richness of soil seed bank in semiarid regions (case study: Chenarnaz rangelands, Khatam city, Yazd province)

Soil seed bank can facilitate natural regeneration of rangeland ecosystems. This bank is usually influenced by local plant species. This study was conducted to investigate the effect of canopy cover of three shrubs (Amygdalus scoparia, Daphne mezereum and Ebenus stellata) on the diversity and richness of soil seed bank under their canopies in Chenarnaz rangelands, Khatam city, Yazd province. Fifteen individuals of each shrub were selected and one soil sample including 10 cores was taken from each sub-canopy along with a control treatment outside the canopy from 0-5 cm soil depth by auger, 5 cm in diameter. Diversity and richness of soil seed bank in soil samples were estimated using germination method in the greenhouse located in Faculty of Natural Resources, Tarbiat Modares University. Species richness was obtained by counting the number of plant species in each sample as well as the Margalef and Manhinick indices. Species diversity was calculated using the Simpson and Shannon-Weiner indices. The results of one-way ANOVA showed that the mean values of richness and diversity under the canopy of A. scoparia, D. mezereum and E. stellata were significantly higher than outside the canopies. The highest values of Margalef (2.12) and Manhinick (1.48) richness indices and, Simpson (0.72) and Shannon-Weiner (1.59) diversity indices were observed under the cover of E. stellata. We can conclude that the positive effect of upper canopies of woody plants on soil seed bank depends not only on the presence of woody species but also on the type of species in the rangelands. In addition, this canopy of woody plants is important due to its role in soil seed bank reservoir for recovery of herbaceous species with higher potential in E. stellata.