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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
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Statistical analyses were carried out using the R
2.9.3 software environment (R Development Core
Team, 2009). Package ‘’segmented’’was used to fitre-
gression models with segmented relationships(Mug-
geo,2008).
3 RESULTS AND DISCUSSION – Rezultati i rasprava
3.1 Development of local PTF for predicting soil bulk density of mineral part of soil
Razvoj lokalnih pedotransfer funkcija za predviđanje gustoće mineralnog sloja tla
Soil bulk densityand concentration of organic car-
bon were strongly correlated (r = -0.86, p < 0.001).
Other chemical soil properties, except the concentra-
tion of total nitrogen (N), were less correlated with
bulk density (Figure 3).The correlation between bulk
density and base saturation (BS) and the correlation
between bulk density and clay content were not statisti-
cally significant (p > 0.05).
Figure 3 Relationship between bulk density (.b) and concentration of organic carbon (OC), concentration of total nitrogen (N), cation
exchange capacity (CEC), base saturation (BS) and clay content (Clay) for 106 soil samples.
Slika 3. Odnos gustoće tla i koncentracije organskog ugljika (OC), ukupnog dušika (N), pH, kapaciteta za izmjenu kationa (KIK),
sume baza (BS) i sadržaja gline (glina) za 106 uzoraka.
More than 73 % of the total variability of bulk den-
sity was explained byOC (model SFI 1,Table 2).Ad-
ding other chemical properties as explanatory variables
in the multiple regression models(modelsSFI 2, SFI 3,
Table 2 Regression relationship between soil properties as predictors and bulk density as response for 106 soil horizons
(OC – organic carbon, BS – base saturation, CEC – cation exchange capacity, CLAY- clay content.
Tablica 2.Regresijski odnos karakteristika tla kao prediktora i gustoće tla kao odziva za 106 horizonata tla (OC – organski
ugljik, BS – suma baza, KIK - kapacitet za izmjenu kationa, glina – sadržaj gline).
Model
Response variable
Intercept OC pH* BS*
CEC* CLAY*
SE Adj. R
2
Varijabla odziva KIK glina
SFI 1 .b 1.3983 -0.0734 0.1403 0.7384
SFI 2 .b 1.4509 -0.0720 -0.0115 0.1404 0.7379
SFI 3 .b 1.3752 -0.0749 0.0004 0.1399 0.7398
SFI 4 .b 1.3902 -0.0788 -0.0011 0.1402 0.7385
SFI 5 .b 1.3438 -0.0734 0.0019 0.1390 0.7431
SFI 6
.b for OC < 3.6 % 1.4842 -0.1424
0.1257 0.7958.b for OC . 3.6 % 1.1253 -0.0452
* denotes not statistically significant variable in the model
* označava nesignifikantnost varijable u modelu
Bulk density/gustoća tla [g/m3
]
Bulk density/gustoća tla [g/m3
]
Bulk density/gustoća tla [g/m3
]
Bulk density/gustoća tla [g/m3
]
Bulk density/gustoća tla [g/m3
]
Bulk density/gustoća tla [g/m3
]