Negative impacts of gully erosion in marly areas are severe due to improper landuse practices such as irrigation, tillage, overgrazing and degradation of vegetation cover. The objective of this research was to evaluate gully thresholds related to plant vegetation cover and landuse change in the Agriculture (AG), Fair Rangeland (FR) and Weak Rangeland (WR) areas of Ghaasr-e-Shirin, Kermanshah, Iran in 2015. The topographical parameters and vegetation cover were measured in the field. Furthermore, nine flumes were performed to determine the critical values of hydraulic parameter and sedimentation. Results revealed that cross-section, width, depth and gully branches length in the FR were significantly lower than those for AG and WR (p<0.05) affected by plant canopy and litter. The significant differences were found between three sits for soil organic carbon (SOC), electrical conductivity (EC) and hydraulic characteristics (inlet discharge, velocity, loaded sediment). Higher vegetation cover in the FR was attributed to the increased hydraulic thresholds and adversely limited cross-section enlargement. Finally, the sediment concentrations in AG, FR and WR were 15163, 9560 and 12000 ppm, respectively. Lower SOC was found in WR and AG due to higher concentration of load sediment. Hence, it was concluded that bare soil, poor vegetation and lower SOC are considerable reduction factors in gully thresholds and subsequently, off-site sedimentation and SOC loss in the study area. تفاصيل المقالة

One of the fundamental difficulties in Iranian rangelands is the existence of wide area of poor condition rangelands that their grazing capability is low due to continuous livestock grazing pressure. Astragalus flexilipes is one of the palatable plant species of rangelands in Iran, while its distribution is being decreased due to improper grazing. The aim of this study was to evaluation the sowing season and cultivation methods of Astragalus flexilipes in dryland farming using split plot design based on completely randomized block with three replications in Meleh-Kabud, Gahvareh, Kermanshah, Iran over two years of 2016-17. The first factor was sowing seasons (spring and autumn) and the second one was cultivation methods (row sowing and scatter sowing). Data were collected for seedling emergence, survivor rate and growth condition in the second year. Result showed significant effect of cultivation method on seedling emergence and survival rate and significant effect of sowing date on growth condition (P<0.01). The sowing date by cultivation method interaction was significant for seedling emergence and survival rate (p<0.05). The highest values of the latter traits were obtained in spring season coupled with row cultivation method. In autumn sowing the highest growth scores of 3.74 and 3.15 (out of 5) for row sowing and scatter sowing, respectively. It was concluded that the highest establishment was achieved in spring cultivation, but the vigorous plants was observed in the autumn cultivation. Thus, early spring cultivation of Astragalus flexilipes using row-sowing method was recommended for rehabilitation of the poor condition rangeland in similar climate area having relatively lower temperature. تفاصيل المقالة