Evaluation of Interception in Astragalus parrowianus, (Case Study: Gonbad Rangeland of Hamadan Province, Iran)

Vegetation cover is the first barrier for the raindrops resulting to the interception and infiltration loss. Interception as one of the main components of ecohydrology equation plays a major role in the water balance of rangelands. However, few studies have been done on the interception of rangeland plants in Iran. This study was carried out to find the interception rate in Astragalus parrowianus through the rainfall portable simulator devices. In addition, the relationship between plant structural factors such as height, large and small diameters, volume and surface of cover and rangeland physiographic factors including altitude, slope percentage and slope in the interception rate was evaluated. Data were collected and analyzed based on simple linear regression models and multivariate analysis (stepwise approach and descending). Results showed that in first group with a volume of 0.002 to 0.02 m3 and canopy cover of 642 m2, 4.421% of total amount of rainfall interception was happened while in second group with volume of 0.02 to 0.087 m3 and canopy cover of 1640 cm2, the interception rate was 1.85% out of total precipitation. In the first group, the interception rate showed a significant correlation (P≤1%) with large diameter (r=-0.73) and the canopy cover at 5% level (r=-0.51). Interception rate in the second group at 1% significant correlations with canopy cover (r=-0.93), diverse small diameter (r= -0.874), large diameter (r=-0.76) and plant volume size was calculated (r=-0.83). From the regression equations obtained in each group, the interception rate can be measured in Astragalus parrowianus without clipping and weighing.