Response of Runoff and Sediment on Skid Trails of Varying Gradient and Traffic Intensity over a Two-Year Period

Abstract

Compacted soil has lower water infiltration and hydraulic conductivity, which contributes to increased runoff and erosion on slopes. The aim of the present study was to assess runoff and sediment on three skidding trail longitudinal gradients (15%, 25%, and 35%) and different levels of machine traffic (low, medium, and high), over a two-year period following the impact in the Hyrcanian forest, Iran. The results show that trail gradient and traffic intensity have a significant effect on soil bulk density and total porosity on the skid trails. The average runoff amount varied significantly among trail gradients and ranged from 1.59 mm on the 15% trail gradient and 2.76 mm on the 25% trail gradient, to 4.76 mm on the 35% trail gradient in the low traffic intensity. Average sediment also increased significantly with increasing trail gradient. Average sediment was 0.01 kg m −2 , 0.03 kg m −2 , and 0.05 kg m −2 on the low traffic intensity in the first year for the 15%, 25%, and 35% trail gradients, respectively. The largest runoff and sediment occurred in the first year and stressed the need for applying forestry Best Management Practices such as the use of brush mats during harvesting operations, as well as the installation of water diversion structures or seeding immediately after initial soil compaction and disturbance, in order to protect the bare soil from heavy rainfall.

Variation in runoff and sediment loss in fallow and abandoned farmland in Agoi- Ekpo, Cross River State, Nigeria

“…The canopy gaps (open canopy structure) on the 5-year fallow did not provide adequate cover for controlling soil erosion, as it gives way for raindrop to strike directly on the topsoil. This again corroborates the findings of Solaimani et al, (2009), Su et al, (2010 and Jakab et al, (2017) that sites with sparse surface cover (vegetation and herbaceous cover) can increase soil erosion.…”

“…The 5-year plot yields the highest erosional losses (runoff, sediment and nutrient loss), while the 10-year plot has the lowest. The variation in runoff, sediment and nutrient loss among the plots lends support to earlier and related studies, like those of Puigdefabregas (2005), Vásquez-Méndez et al, (2010), Ai et al, (2017) and Jakab et al, (2017) that land area covered with vegetation helps to reduce runoff and sediment loss. This therefore means that the increase in tree density and vegetal cover during nutrient restoration in fallows results in the decrease in soil erosion and its associated losses.…”

“…In tropical Africa, soil erosion remains a serious problem (Lal, 1989). The degrading strength of soil erosion is dependent on several factors like type of soil, landscape, rainfall, type of vegetation, system of farm management and topographic characteristics (Ezemonye and Emeribe, 2012;Jourgholami et al, 2017). In the tropics, the erosive force of soil erosion is largely caused by rainfall; as such, geomorphologists have used several attributes of rainfall such as kinetic energy, frequency of fall, drop size, intensity of rainfall and rainfall duration among others to study soil erosion (Daura, 1995;Ezemonye and Emeribe, 2012) and reference was made to vegetation cover alone neglecting other vegetation components such as ground cover (undergrowth), girth, basal cover, litter depth, herbaceous composition among others that could have significant effect on soil erosion.…”

“…High density of plant and the establishment of closed canopy cover in the different phases of ecological succession play a vital role in facilitating the canopy hydrological performance of plant communities to reduce the of velocity runoff. In areas where vegetation mostly ground cover is sparse and scanty, the amount of sediment and nutrient element loss may possibly be massive, which may delay the time of optimum nutrient accretion in the soil (Iwara, 2013;Ai et al, 2017;Jakab et al, 2017).…”

“…Literature is rich on soil erosion, sediment and nutrient loss, but majority of the studies available were carried out on cropping system, plantations and under individual species in vegetation patches (Daura, 1995;Zhenhong, 2004;Vásquez-Méndez et al, 2010;Haridjaja, 2012;Ai et al, 2017;Jakab et al, 2017). However, information on runoff and sediment loss during the process of nutrient restoration on abandoned farmlands of different fallow ages is poorly documented in the literature of forest ecology.…”