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ŠUMARSKI LIST 9-10/2017 str. 23     <-- 23 -->        PDF

Saturated hydraulic conductivity (Ks) of soils is affected by texture, structure, bulk density, soil organic matter, and the compaction problem (Göl and Dengiz, 2007). Results of this study have shown significantly higher values of Ks in soils of forest (18.73 cm3 h-1) compared to grasslands soils (5.59 cm3 h-1), and cultivated area soils (2.26 cm3 h-1), (Table 2, and Fig. 6 b). The values of Ks were significantly greater in the forest soils than in other LUTLC. This indicates a specific significance of natural forest in regards to water transport processes in landscape. Results of the analysis indicate that conversion from natural forest to grassland or cultivated land decreases the value of Ks. The Ks values of the soils in the catchment changed depending on the SOM, BD values and compaction problem in grassland soils. The LUTLC has statistically significant (p < 0.01) effects on the Ks. According to the results of the study, there are statistically significant differences between the land use types of forest-grassland and forest-agricultural land. The differences between the LUTLC of agricultural-grassland were found to be statistically not significant (p > 0.05). In catchment scale thus, forest areas may positively influence from relevant hydrological functions like infiltration and percolation.
When the Ks values in the northern aspect were analyzed, Ks values were measured to be lower in the northern aspect due to higher compaction depending on the higher soil water content. In the wet periods, the animals continuously rambled due to lower grass yield of the pasture and compaction the soil. In forest soils, higher amounts of SOM accumulated in the southern aspect; however, the Ks values were measured to be lower in the southern aspect. Again, hydrophobic properties of soils also affected the Ks values. However, Ks did not change as much as the infiltration rate.
Ks were influenced by LUTLC and aspect, with a significant interaction (Table 2). Ks soils of could be ordered as forests > grassland > cultivated area. Ks correlated significantly with BD and soil texture. Soils under cultivated area and grassland have higher BD than the adjacent soils under forests for two aspects. The natural forest soils has the lowest BD value at the north aspect, whereas, the grassland and cultivated area soils has the highest BD values at the either aspect.
DISCUSSION AND CONCLUSION
RASPRAVA I ZAKLJUÈAK
The cultivation and over grazing affected adversely on soil properties and resulted in significant decreases in the SOM, WSA, BD, Ks, and infiltration rate. The values of BD were affected by the land use type. Kobal et al. (2011) indicated that the BD correlated strongly with SOM and carbon concentration in different land use. The amounts of SOM have changed according to the LUTLC and aspect. In their studies, Göl and Dengiz (2007) and Kobal et al. (2011) indicated that the aspect had an impact on the SOM. The difference between SOM amounts of agricultural soils in both aspects was not significant. SOM enhanced the available water capacity. Each 1 % of SOM adds about 1.5 % to available water capacity (Xiao et al., 2014). BD plays an important role through its control of the pore space that retains available water. High bulk densities for a given soil tend to lower the available water capacity (Chen et al., 2007; Fu et al., 2000; Fu et al., 2003). Many studies had been done to study the seasonal changes in soil moisture and vertical soil moisture distribution across different land uses (Wang et al., 2013; Zhang et al., 2006; Zhang et al., 2013).
The infiltration capacity was measured to be the lowest in grassland soils and the highest in agricultural soils. Although many researchers (Plaster, 2014; Pritchett, 1980) reported that the infiltration capacity was the highest in forest soils and the lowest in agricultural soils, the findings from Gökdere catchment were the exact opposite. The measurement of lower infiltration capacity in forest soils could be related with the quality of the SOM in the topsoil. Indeed, Priha (1999) reported that soils under scotch pine (Pinus sylvestris L) forest formation included high amounts of lignin, polyphenol, and resin; therefore, the litter decomposed difficultly and consequently upper soils became hydrophobic. The forest soils chosen for infiltration testing in the Gökdere catchment are under scotch pine formations. Therefore, depending on the hydrophobic nature of top soils, the infiltration rates of forest soils were measured to be lower than that of agricultural soils. In fact, Jones (1994) and Morgan (2005) indicated that hydrophobic characteristics of forest soils reduced the infiltration capacity and did not allow water to permeate in the soil. Moret and Arrúe (2007) indicated that the loosening of surface soil by tillage operations increases the total soil porosity and improve the hydraulic functioning of structured soils. The infiltration capacity of grassland soils is lower due to the compaction caused by animals compress over the soils. Indeed, Thurow et al. (1988) established the significant impact of the grazing intensity on the infiltration. Thurow et al. (1988) indicated that animals compressed the soil with their hooves and reduced the infiltration capacity. Okatan and Reis (1999) determined that hydro physical characteristics of grazing and non-grazing soils were different. Many studies (Bodhinayake and Cheng Si, 2004; Pirastru et al., 2013) determined that the change in LUTLC affects the hydro physical properties of soil. In agricultural land, the infiltration rate of the surface soil is high. Due to excessive compaction in the plow plan, water cannot be carried further down the soil. Therefore, the water entering the soil through infiltration is accumulated at 0 – 30 cm depth. Due to higher litter accumulation and higher availability of materials such as lignin, polyphenol, and resin that give soils hydrophobic characteristics in the surface of forest. Infiltration was affected adversely by over grazing in the wet period depending on the soil water content. In agricultural soils on the other hand,