Abstract

Important factors in rangeland ecosystem suitability are quality and quantity of herbage products.  Negative or positive trend of plants cover in the rangeland is shown by plants evening and plants diversity indexes. In this research, the effects of some soil properties on range evening were studied. In this research to decrease the effects of environment factors on plants evening, three sites consisting of shrub land, grass-shrub land and grass land were selected with the same elevation range and geographical directions. In order to show the evening value in each site, Pit evening index was used and soil elements including Calcium, Magnesium, Phosphorus, Potassium, CaCO_3, Ammonium, Nitrate, Organic Matter, Acidity, EC, Moisture, and Soil Texture were measured in the sites. Plant samples were taken in the key areas along the three transects according to number of plant species one by one. Principal component analysis (PCA) was utilized to find the environment gradient. Duncan and variance analyses were used to compare plants evening in the three sites. Results showed that chemical properties such as organic matter and potassium and physical properties such as soil moisture and silt content caused soil fertility to increase and consequently increased ecologic habitats in the soil. This led to the growth of rare species of plants. Because these rare species need high level of soil fertility and consequently causing a decrease in canopy evening.  This study reveals that the site with weak soil fertility has more plants evening than the other sites.

Key words: Rangeland, soil, principal component analysis, fertility, Iran.