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M. Kobal, M. Urbančič, N. Potočić, B. De Vos, P. Simončič: PEDOTRANSFER FUNCTIONS FOR BULK DENSITY ... Šumarski list br. 1–2, CXXXV (2011), 19-27


sions. It is also needed when estimating soil water reten-cially recent studies evaluating existing PTFs (e.g. De
tion characteristics and is a required input parameter in Voset al., 2005; Martinet al., 2009) warn against
models of water, sediment and nutrient transport (Bouc-usage of PTFs without first testing their accuracy, and
neau et al., 1998).Additionally, soil bulk density is an in-stress the importance of local calibrations of coefficients
dicator of soil compaction, porosity and site productivity in the models.
(Tamminen andStarr,1994;Salifuetal., 1999).


The aim of our study was to develop a local PTF for


Several studies have investigated variation in forest the estimation of soil bulk density of(forest) mineral
soils properties at very detailed spatial scales (Phillips soils in Slovenia. Based on literature, we hypothesized
and Marion,2005; Scharenbrochand Bock -that (1) the bulk density.b correlated strongly with soil
heim 2007) and revealed that soil variability can be organic carbon concentration (OC) and (2) that our
high even on short distances and in small areas. Espe-local PTF perform better than published PTFs.


2 METHODS – Materijali i metode


2.1 Data sources and laboratory work – Izvori podataka i laboratorijski rad
The information on soil bulk
densities as well as physical and
chemical properties of soil horizons
wastaken from the soil database of
the Slovenian Forestry Institute
(SFI). Only the data on soil profiles
opened in year 2006 on the 16 × 16
km network across Slovenia were finally
selected; in total, 45 soil profiles
with 109 soil horizons (Figure
1). Summary information about soil
profiles is presented inTable 1.
Todescribe locations of the soil
profiles and evaluate morphological
and physical properties of the
soil horizons, FAO methodology
was followed (FAO, 2006).In each


soil horizon, separate soil samples
Figure 1 Locations of soil profiles (n = 45) across Slovenia from which the data for


were taken for bulk density estima


development of a local PTF for bulk density (.) estimation was derived.


tion and for chemical and physical
b


Slika 1. Položaj profila tla (n=45) u Sloveniji na osnovi kojih su dobivene lokalne


soil analysis. Samples for bulk den


pedotransfer funkcije (PTF) za procjenu gustoće tla.


sity estimation (ISO 11272) of a


fine earth fraction (< 2mm) were
obtained in five replicates by using
metal O-rings with volume of
5 cm.In the laboratory, soil samp les
were air dried (105 °C) and
weig hed. Variability of bulk density
estimation using metal O-rings
based on 5 replicates is presented in
Figure 2., where almost 80% of values
have a CVless than 10%. Soil
samples for chemical and physical
soil analysis were also air driedand
passed through a 2 mm sieve.The
fine earth fraction (< 2mm) wasre-
tained(UN/ECE ICP-Forests 2006,


http://www.icp-forests.


Figure 2 Frequency distribution for coefficient of variation (CV) for bulk density measure


org/pdf/FINAL_soil.pdf) for furt


3


ments, obtained using 5 cm metal O-rings.


her chemical and physical analyses.


Slika 2. Distribucija frekvencija za koeficijent varijacije (CV) gustoća tala, izmjerenih ko-


The following methods were used:


rištenjem metalnih O-prstenova zapremine 5 cm3