Klaudia Kiss

Comparison of soil microbial communities from two distinct karst areas in Hungary

Karst areas belong to the most exposed terrestrial ecosystems, therefore their study have a priority task in Hungary, as well. The aim of this study was to compare the structure, activity and diversity of soil microbial communities from two distinct Hungarian karst areas (Aggtelek NP and Tapolca-basin). Soil samples were taken three times from 6 distinct sites, from different depths. Soil microbial biomass C (MBC), microbial biomass N (MBN), basal respiration (BRESP) and substrate induced respiration (SIR) were measured. The phylogenetic diversity of bacterial communities was compared by Denaturing Gradient Gel Electrophoresis (DGGE). The highest MBC, MBN, BRESP and SIR values were measured in the rendzina soil from Aggtelek. On the basis of biomass and respiration measurements, microbial communities differentiated mainly according to soil depths whereas DGGE profiles of bacterial communities resulted in groups mainly according to sampling sites.

Characterization of Soil Organic Substances by UV-Vis Spectrophotometry in Some Soils of Hungary

UV-Vis spectrometry methods are widely used to characterize soil organic matter, especially humic substances from different extracts of soils. Our aims were to investigate organic characteristics of soils, as part of a project focusing on relationships between solute mineral components and organic matter quality. The study was performed using UV-Vis spectrophotometry on six Hungarian soils. For the characterization of humic substances we used several visible and UV methods. Humic materials were extracted from soils using a variety of extractants. We found that a decrease in pH and an increase in dissolved electrolyte concentration supported coagulation in preferance to dissolution in almost every case. The highest absorbance values was given by extractants which contained sodium-pyrophosphate. In our experience double extraction methods (ENaF/ENaOH according to Hargitai, A talaj szerves anyaganak meghatarozasa es jellemzese. In: Buzas I (ed) Talaj- es agrokemiai vizsgalati modszerkonyv II. Mezőgazdasagi Kiado, Budapest, 1988, E400NaOH+Na4P2O7/E400PBS) and E4/E6 are suitable for analysing humic substances. Comparing these three visible methods there are only slight differences between them. The results do not show strong correlation between visible and UV methods as these techniques analyse different properties of soil humic substances.

Soil Organic Carbon Redistribution by Erosion on Arable Fields

Colloids are thought to move easily, consequently both mineral and organic colloids are overrepresented in runoff and soil loss, which causes selective erosion. Soil loss compound is a function of scale. The enrichment of soil organic carbon (SOC) and of the clay fraction in soil loss was studied at two sites in Hungary. A rainfall simulator was applied to describe selective erosion at micro (<1 m2) and plot (2 × 6 m) scale. At field scale, soil loss samples were taken from 25 to 50 m intensively tilled runoff plots to assess SOC losses. At plot scale, selective erosion takes place as redistribution within the plot with crust formation. Thin sections demonstrate the horizontal structure of the particles on the surface covered by SOC and clay colloids. The rate of SOC enrichment is inversely proportional to the amount of soil loss. Enrichment is significant in the settled (coarse) part of soil loss, while – in contrast to the plot scale results – there is no SOC surplus in the suspended part. SOC components of high molecular weight seem to be increasingly vulnerable to erosion and they are overrepresented in soil loss. Because of their high stability carbon sequestration occurs in the buried horizons.