EXECUTIVE SUMMARY - UNESCO World Heritage

Pre-proposal No 2 SPATIAL VARIABILITY OF SOIL DEPTH AND TRANSPORT
PROPERTIES AS THE PRINCIPAL INDICATORS OF ENVIRONMENTAL SOIL FUNCTIONS
Description
A soil acts as a physical, chemical and biological reactor {Richter 1987), which determines the functionality of ecosystems. Some of the most
important forest soil functions include the biomass production, regulation of ecosystem processes and environmental interaction, i. e. mainly
accumulation, filtration and transformation. Individual functions are most often approximated through certain attributes and their indicators,
which are parameters relatively easily available from soil survey or mapping, such as textural composition, structure, pH and others. More
complex indicators, termed as pedotransfer functions represent combinations of several variables and are based on various types of correlation
analysis with the aim to extract transformation relationships. As important forest soils quality indicators, organic matter content, porosity
and infiltration intensity have recently been proposed by international working groups. The most frequently used indicators however provide
only a rough and little reliable approximation of soil functions, as they are based on intensity variables, instead of the capacity ones.
The estimation of forest soil functions based on the intensity-capacity approach requires a sufficient knowledge on the spatial variability of the
forest soils depth, which is one of he least studied processes due to inherent technical difficulties. This problem is often solved by converting
the intensity into capacity variables for deliberately selected top soil layers, by the assumption of an average depth without any knowledge on
the type of its distribution, or by employing simple models rendering soil depth as a function of the elevation, slope curvature etc. Currently,
methods for the prediction of soil depth based on soil-landscape regression models are constructed, and methods for non-destructive, geophysical
measurement of soil depth, such as the ground penetration or electric resistivity tomography are being further developed.
The importance and connection between the soil depth and soil transport properties is well illustrated by the fact that variability in correlation
relationships between the soil properties and topographic features at various depths may exist, conditioned by the declining hydraulic conductivity
in the downward direction. Another reason, why even the intensity-capacity approach may not deliver expected reliability and accuracy
in the estimation of forest soil functions, is the enormous spatial variability of the soil hydraulic conductivity and the susceptibility of forest
soils to the preferential flow. Due to non-linear dependence of the water flow velocity on the porous volume properties and the occurrence of
structural heterogeneity of forest soils, the pedotransfer functions do not allow for viable predictions of the soil hydraulic conductivity from static
properties. As an alternative to a time consuming, labour intensive and little representative direct measurement on undisturbed samples,
soil hydraulic conductivity is often predictions based on retention curves. The methods are being constantly improved, for instance by a model
allowing for a bimodal distribution of the soil pores. For these reasons, no systematic data on the transport properties of forest soils are available
either abroad, or in Slovakia.
Literature references (including those used in the methodological section)
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