S. Ezzati , A. Najafi,
Volume 16, Issue 61 (10-2012)
Abstract
Increase in soil bulk density and reduces in porosity and infiltration rate are the most common disturbances during timber harvesting and ground-base skidding. The present study was conducted to study soil physical properties e.g., soil bulk density, moisture, porosity and soil hydrological properties e.g., soil infiltration from ground-base skidding in twenty years since logging. After initial survey, four abandonment skid trails were selected with similar pedologic, climatic conditions and physiographic and different age in Necka-Zalemrod catchment in east of Mazandaran province. Results indicated that impacts of machinery traffices in high traffic intensity have remained yet 20 years since logging. Means soil bulk density, porosity and void ratio were 42.4 greater, 24.6 and 46.7 percent, respectively, lower than the undisturbed areas. The least infiltration rate was recorded in 1-5 years old skid trail, so the reduction of water was not considerable within 18 minutes after experiment into soil in inner ring in this skid trail. Results in each skid trail firmed that in low traffic intensity soil physical and hydrologic properties was tent to “normal” recover in compare to the undisturbed areas.
A. R. Vaezi, H. Hasanzadeh,
Volume 20, Issue 75 (5-2016)
Abstract
Knowledge of variation in soil properties from each event to another is very important for the determination of critical periods during which soil is susceptible to erosion processes. This study was carried out to investigate soil loss in sequential rainfall events in Zanjan Province. Toward this, ten soil textures samples were taken and were transported to small plots (60 cm×80cm) with 20-cm depth) on a 8% slope land at three replications. The plots were exposed to ten simulated rainfalls with an intensity of 55 mm h-1 for 30-min and 5-day intervals. A total of 300 simulated rainfall trials were carried out at the plots. Results indicated that soil moisture, runoff production and soil loss were significantly affected by rainfall events (P< 0.001). Increasing soil moisture and consequently decreasing soil infiltration capacity were the most crucial element in increasing runoff production and soil loss in the sequential rainfall events, in a way that about 84% of soil loss variation in the rainfall events could be explained based on antecedent soil moisture. After the fifths rainfall event, no significant differences was found in soil infiltration capacity as well as runoff production because of soil moisture reaching to the water-holding capacity. Nevertheless, an increasing trend was observed in soil loss after fifth event which could associate with presence of more erodible soil particles on the surface and consequently increasing the concentration of surface flows.
