To assess the effects of livestock grazing on soil compaction (density changes), the trampling action of livestock was simulated. The research field was located to the south west of Nazarabad in Savojbolagh district, south west of Tehran Province. Samples were annually collected based on a completely randomized design. From the triple regions (reference, key and critical) 36 cylindrical cores were taken they were 8 and 15 cm in diameter and depth respectively. Sampling was done at the end of each grazing season (early fall) in 2004-2005, pot experiments being composed of 9 treatments in 4 replicates. Collected data were analyzed in a completely randomized block design using ANOVA. The means were compared using Duncan Test. The results show that during conversion from critical to key and reference situations, germination rate and the height in critical condition, critical to key and critical to reference conditions have increased. The organic matter for these conversions were 0.033, 0.07 and 0.23 respectively, among which significant statistical differences are observed (P?0.05). In conversion of key to critical and reference conditions, germination rates (in pot environments) for key, key to critical and key to reference conditions were reduced respectively. The organic matter contents were 0.052, 0.026 and 0.107 gr. While the heights being 51.19, 27.69 and70.62 cm respectively. Stipa barbata shows significant differences in germination rate as well as height. With decrease of bulk density and compaction in the first treatment, and with reverse conditions for the second one, in both treatments, germination rates were decreased. In converting reference to key and critical conditions, germination rates for pots of reference, reference to key and reference to critical conditions were 50, 56.25 and 29.69% respectively. The heights and organic matter were reduced and while in all treatments significant differences being observed (P?0.05).
Keywords: Bulk density, Trampling, Germination, Organic matter, Height, Stipa barbata