The impact of vegetation on hydraulic conductivity of sandy soil

The objective of this study was to assess the impact of vegetation on the hydraulic conductivity of sandy soil at the locality Mláky II at Sekule (southwest Slovakia). The measurements were taken on the surface of a meadow (Meadow site), a 30-year old Scots pine (Pinus sylvestris) forest (Forest site) and a glade (Glade site). In the glade, the measurements were also taken in the depth of 50 cm (Pure sand) to reduce the influence of vegetation on the soil properties. It was found that the unsaturated hydraulic conductivity kr(-2 cm) as reduced due to the soil water repellency increased in the same order: Forest soil < Glade soil ≍ Meadow soil < Pure sand, similarly as decreased the water drop penetration time tp: Forest soil > Glade soil ≍ Meadow soil > Pure sand, which could refer to an inverse proportionality between the capillary suction and hydrophobic coating of the soil particles. The saturated hydraulic conductivity Ks increased in the following order: Meadow soil < Glade soil ≍ Forest soil < Pure sand; more than two-times higher Ks at both the Forest and Glade sites than that at the Meadow site could be the result of both the patchy growth of vegetation with some areas of bare soil at the Glade site and the macropores (dead roots) in more homogeneous humic top-layer at the Forest site. The share Br of flux through the pores with radii r longer than approximately 0.5 mm decreased in the order: Forest soil » Meadow soil > Glade soil » Pure sand, revealing the prevalence of preferential flow through macropores (dead roots) in the Forest site and a negligible share of macropores in the Pure sand.