Soil water repellency (SWR) it is recognized to be very heterogeneous in time in space and depends on soil
type, climate, land use, vegetation and season (Doerr et al., 2002). It prevents or reduces water infiltration, with
important impacts on soil hydrology, influencing the mobilization and transport of substances into the soil profile.
The reduced infiltration increases surface runoff and soil erosion. SWR reduce also the seed emergency and
plant growth due the reduced amount of water in the root zone. Positive aspects of SWR are the increase of soil
aggregate stability, organic carbon sequestration and reduction of water evaporation (Mataix-Solera and Doerr,
2004; Diehl, 2013). SWR depends on the soil aggregate size. In fire affected areas it was founded that SWR was
more persistent in small size aggregates (Mataix-Solera and Doerr, 2004; Jordan et al., 2011). However, little
information is available about SWR spatial distribution according to soil aggregate size. The aim of this work
is study the spatial distribution of SWR in fine earth (<2 mm) and different aggregate sizes, 2-1 mm, 1-0.5 mm,
0.5-0.25 mm and <0.25 mm. The studied area is located near Vilnius (Lithuania) at 54 42’ N, 25 08 E, 158
masl. A plot with 400 m2 (20 x 20 m with 5 m space between sampling points) and 25 soil samples were collected
in the top soil (0-5 cm) and taken to the laboratory. Previously to SWR assessment, the samples were air dried.
The persistence of SWR was analysed according to the Water Drop Penetration Method, which involves placing
three drops of distilled water onto the soil surface and registering the time in seconds (s) required for the drop
complete penetration (Wessel, 1988). Data did not respected Gaussian distribution, thus in order to meet normality
requirements it was log-normal transformed. Spatial interpolations were carried out using Ordinary Kriging. The
results shown that SWR was on average in fine earth 2.88 s (Coeficient of variation % (CV%)=44.62), 2-1mm
1.73 s (CV%=45.10), 1-0.5 mm 2.02 s (CV%=93.75), 0.5-0.25 mm 3.12 s (CV%=233.68) and in <0.25 mm 15.54
mm (CV%=240.74). This suggests that SWR persistence and CV% is higher in small size aggregates than in the
coarser aggregate sizes. The interpolated maps showed that in fine earth SWR was higher in the western part of
the studied plot and lower in the central area. In the 2-1 mm aggregate size it was higher in the southwest and
lower at north and northwest area. In the 1-0.5 mm aggregate size it was lower in the central area and higher in the
southwest. In the 0.5-0.25 mm aggregate size it was higher in the west part and lower in the north of the plot and.
In the <0.25 mm no specific pattern was identified and the SWR was heterogeneously distributed. This suggests
that the spatial distribution of SWR is very different according to the aggregate size. Future studies are needed in
order to identify the causes and consequences of such dynamic.
Acknowledgements
The authors appreciated the support of the project “Litfire”, Fire effects in Lithuanian soils and ecosystems
(MIP-048/2011) funded by the Lithuanian Research Counci