The effect of earthworms on plant diversity and soil properties under different landuses

Earthworms have significant effect on vegetation and soil physical and chemical properties. The relationship between earthworms and biodiversity is important in ecological researches. Therefore, the effects of earthworm on plant diversity and various indices of diversity and richness, as well as physical and chemical properties of soil in shrub, grass and bare vegetation types on exclosure and grazing sites of Miankaleh Mazandaran biosphere reserve is investigated in this work. Accordingly, sampling was carried out randomly-systematically in three different vegetative types (shrubs, grass and bare soil) at 0 to 20 cm depth. Each vegetative types was placed on three transects of 100 m, 10 plots at a distance of 30 m. Earthworm and soil were sampled from the center of each plot of 25 cm × 25 cm. The Simpson and Shannon-Wiener indexes and Margalef and Menhinick richness indices were used to evaluate diversity and richness of species at different grazing intensities. Stepwise regression was used to study the relationship between diversity and richness indices with different earthworm parameters. The results showed that there was significant difference of potassium and nitrogen in vegetation types of both exclosure and grazing sites at P ≤ .01. Furthermore, the organic carbon, organic matter and potassium in the exclosure site and nitrogen and soil moisture in the grazing site are increased by earthworm abundance.