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ŠUMARSKI LIST 9-10/2018 str. 81     <-- 81 -->        PDF

organic carbon (SOC) and total nitrogen (TN) of the soil. The other part was refrigerated at 4 oC to test soil organic carbon (DOC), nitrate nitrogen (NO3N), ammonium nitrogen (NH4+–N), dissolved organic nitrogen (DON), and soil enzyme activity.
Laboratory Analyses – Laboratorijske analize
The presence of SOC was tested by the Walkley-Black method (Lu, 1999). Soil TN was measured using the micro-Kjeldahl method (Lu, 1999). Soil DOC, NO3-–N, NH4+–N, and DON were extracted with 2 M KCl for 1 h, and the concentrations were determined by a continuous flow autoanalyzer (Skalar San++ 8505, Netherlands). The sucrase and urease activities in the soil were assayed based on the release and quantitative determination of the products of glucose and NH4+–N. Soil samples were incubated with an 8% sucrose solution and a 10% urea solution in a suitable buffer solution for 24 h at 37 oC, and spectrophotometric measurements were performed (Xu and Zheng, 1986). Catalase activity was measured using the 0.1N KMnO4 titration method (Xu and Zheng, 1986). Chitinase activity was determined by incubating a mixture of toluene-treated soil with 1 % (weight/weight) colloidal chitin suspension for 1 h at 37 oC and then, after dilution, assaying the amount of N-acetyl-glucosamine released (Chen et al., 1994).
Statistical analyses – Statističke analize
Statistical analyses were performed using SPSS 16.0 (SPSS Inc., Chicago, USA). All data were checked for normality of distributions and homogeneity of variances prior to analysis. Two-way analysis of variance was used to determine the effects of vegetation type and tourism disturbance on soil variables. Least significant difference tests were used to compare the means between different tourism disturbance intensities. Pearson correlation coefficients were also utilized to evaluate the relationships among corresponding variables. A p-value < 0.05 was considered significant.
RESULTS AND DISCUSSION
REZULTATI I RASPRAVA
In the three sample plots of the plant community, the heavily disturbed soil had an obviously lower organic carbon content than the mildly disturbed soil (p<0.05), and the