INFLUENCE OF DIFFERENT VEGETATION ON SATURATED HYDRAULIC CONDUCTIVITY IN
ALLUVIAL LANDSCAPE.
Andrej Halabuk
Institute of Landscape Ecology, Slovak Academy of Sciences Bratislava, Branch Nitra, Akademická 2,
949 01 Nitra, Slovak Republic. E-mail: andrej.halabuk@savba.sk
Wetland areas and grasslands represent specific landscape features that may have significant
importance for water regime in landscape. Their character, especially soil physical properties and
vegetation may cause a well-known influence on hydrological processes, e.g. evapotranspiration,
infiltration or water retention (Bullock et Acreman, 2003). We focused on their influence on transport of
water in alluvial landscape. Saturated hydraulic conductivity of topsoil was chosen as an indicator of
water transport process. Vegetation performs a multiple influence on transport of water in soil (Kutilek,
1978). Specifically, roots can affect saturated hydraulic conductivity in topsoil directly, inducing the
preferred flow through macropores (Lichner et al., 1994) or indirectly, by their influence on soil
structure. Therefore, we also analysed relationships between root content, bulk density and saturated
hydraulic conductivity. Bulk density was chosen as it is considered to be a complex indicator of soil
physical characteristics (Hrasko et Bedrna, 1988). Root content can indicate basic characteristics of
root development of the respective vegetation type. The main approach of this study was based on the
comparative analysis of saturated hydraulic conductivity among wetlands, mown grasslands and
arable land in alluvial landscape. Reed marshes and tall sedges represented wetlands; mown
grasslands were represented by regularly cut alluvial foxtail meadows. Adjacent arable lands with corn
were added for comparison. The crucial step allowing a correct interpretation of results was the
selection of study sites and sampling design. Therefore we looked for study sites with the closest soil
properties, but at the same time with different vegetation. In real natural conditions, such selection is
quite complicated, because soil parameters are usually those influencing vegetation and vice versa.
According to that, we selected relatively homogenous sites from physical-geographical point of view
with the mosaics of different vegetation within relatively short distances. Arable land with close
proximity to meadows was included as well. Soil texture classes were considered as one of the key
properties that may vary significantly within small locations and distances. Field survey and further
laboratory assessment of textural classes identified soils of the area as mollic fluvisols with prevailing
presence of loam. Finally, we chose 3 representative study localities for experimental survey and
sampling in the small agricultural catchment in southwestern part of Slovakia (Pariz creek catchment).
Random sampling was realised on such mosaics with 64 sample sites in total. This randomisation had
to be applied in order to obtain correct statistical interpretation (Webster et Oliver, 1990). To minimize
the seasonal variability of saturated hydraulic conductivity we made whole field sampling in a relatively
short period of July 2004. Soil samples were taken after careful removal of the aboveground
vegetation and litter. Standard methodologies of estimation of bulk density and saturated hydraulic
conductivity using falling head technique on 250 cm 3 soil cores were used (Fiala, 1999). Root content
was estimated after the sample had been sluiced through 0.5 mm sieve and oven dried. The influence
of vegetation was explored by one-way analysis of variance with a different type of vegetation as the
factor. A mutual comparison of means using Scheffe’s test was used additionally. Due to the identified
lognormal distribution of saturated hydraulic conductivity and root content, a logarithmic transformation
was used because of assumptions of statistical analysis used. Analysis of variance showed significant
effect of vegetation on saturated hydraulic conductivity (p< 0.001).
Mutual comparison revealed significant mean
Tab. 1: Breakdown statistics of the soil
difference in saturated hydraulic conductivity only
characteristics (N=64)
of wetlands in respect to grasslands (a 20% higher
wetland grassland arable land mean values in wetlands) and of wetlands in
respect to arable lands (a 10% higher mean
mean
6.20
1.47
0.79
KSAT
values). Descriptive statistics of all studied soil
median
4.01
0.52
0.14
-1
(m.day )
characteristics are shown in Table 1, followed by
std. deviation 6.57
2.08
1.26
graphically demonstrated mean comparison of
mean
1.09
1.26
1.46
Bulk
saturated hydraulic conductivity in Figure 1.
density median
1.09
1.29
1.46
Results have shown significantly higher values of
(g.cm-3) std. deviation 0.14
saturated hydraulic conductivity in wetlands (6.20
0.18
0.16
m.day-1 on average) compared to mown
mean
1.84
1.88
0.70
Root
grasslands (1.47 m.day-1) and arable land (0.78
content median
1.44
1.56
0.31
m.day-1).
(g)
std. deviation
1.81
1.15
1.10
Tab.2: Correlation matrix of the soil
characteristics
log Root
content
log Root
content
log KSAT
Bulk density
log KSAT
0.32*
0.32*
-0.50*
Bulk
density
-0.50*
-0.72*
-0.72*
N
64
64
64
*marked correlation significant at 0.01
level
As it was expected, the lowest bulk density was in
wetlands, what may indicate a big porosity and total
organic matter of the soil. The highest root content was in
grasslands, what together with the above statement may
imply that the total organic mater influences specific soil
structure in wetlands more than the root content does.
High content of organic matter in wetlands is caused
mainly by specific site hydrology and prevailing reduction
conditions. Furthermore, we analysed relationships
between studied soil characteristics.
Correlation
matrix,
using
Pearson
Bulk density (g.cm-3)
correlation coefficients (Tab. 2) and
scatter plots (Fig. 2) of analysed variables
describe these relationships. The results
have shown that both root content and
bulk density correlate significantly with the
log KSAT (m.day. -1)
saturated hydraulic conductivity. However,
the stronger negative correlation was
indicated between bulk density and
saturated hydraulic conductivity what
again proves that soil structure affected
log Root content (g)
water transport processes more than the
root content itself did.
To conclude, results of this study indicate
a specific significance of wetlands for
water transport processes in alluvial
landscape. Thus, in catchment scale, Fig.2: Scatter plots of analysed soil characteristics
wetland areas may positively influence
relevant hydrological functions like infiltration, percolation, and base flow support. Additionally, more
interest should be devoted to the exploration of an interactive effect of organic matter and roots on
water transport processes in natural conditions.
Key words: saturated hydraulic conductivity, topsoil, vegetation, wetland, grassland, alluvial landscape
Reference list:
Bullock, A. et Acreman, M. (2003): The Role of Wetlands in the Hydrological Cycle. Hydrology and
Earth System Sciences 7 (3), 358-389.
Fiala, K., ed. (1999): Zavazné metody rozborov pod. VUPOP, Bratislava.
Hrasko, J. et Bedrna, Z. (1988): Aplikovane podoznalectvo. Priroda, Bratislava.
Kutilek, M. (1978): Vodohospodarska pedologie. STNL/ALFA, Praha.
Lichner, L., Majercak, J., Slabon, S., et Stekauerova, V. (1994): Prenos rozpustenych latok v pode.
VEDA, Bratislava.
Webster, R. et Oliver, M.A. (1990): Statistical methods in soil and land resource survey. Oxford
University Press, New York.