Monday, 10 July 2006

Comparison of Methods for the Evaluation of Humus Quality of Forest Soils.

Jiri Kulhavy1, Bohumir Lomsky2, Michal Remes1, Ladislav Mensik1, Tomas Fabianek1, and Ida Drapelova1. (1) Mendel Univ of Agriculture and Forestry Brno, Zemedelska 3, Brno, 613 00, Czech Republic, (2) Forestry and Game Management Research Institute, Jiloviste-Strnady, Prague, 15604, Czech Republic

Humus is one of the most important fractions of forest soils. Humus quality ranks among the basic soil characteristics. There are many various methods for assessing the quality of humus based on different principles. Determination of the total organic carbon and nitrogen using methods of elementary analysis and determination of C/N ratio belong to standard procedures. For assessing the quality of humus the ratio is often used of the absorption of pyro-phosphate soil extract at 465 nm and 665 nm (A400/A600) because there is a significant correla-tion between the ratio of absorbances and the ratio of the content of humic and fulvic acids (HA/FA) (Sparks, 1996). Another commonly used method is the fractionation of humus compounds based on the various solubility of humic acids, fulvic acids and other humus sub-stances at various pH (Guerra, Santos 1999). The method of Diffuse Reflectance Infrared Spectroscopy (DRIFT) is a suitable method for the study of the chemical structure of humus compounds. The advantage of this is an elimination of spectra scattering by bands of sorbed water in the ranges of 3300-3000 cm-1 and 1720-1500 cm-1 (Stevenson, 1994). Determination of Organic Carbon (DOC) is an indirect method for assessing the quality of humus. Its principle consists in a fact that Total Carbon (TC) in a solution oxidizes to carbon dioxide either by ther-mal decomposition under the presence of a catalyst or by photooxidation after UV radiation. Originating carbon dioxide is most often detected by infrared spectrometry. Soil samples for testing were taken in forest stands of an upland region of the Czech Republic –the Drahanska Vrchovina Upland with various species composition, viz (1) beech stands (Fagus sylvatica) with fir (Abies alba), (2) pure beech stands (Fagus sylvatica) and (3) pure spruce stands (Picea abies, Karst) in the 1st and 2nd generations. Research plots are situated at an altitude of 600-660 m. Mean annual air temperature is 6.5°C, mean annual precipitation 717 mm. Acid granodiorite is parent rock of the region. Typical Cambisol - acid variant is its soil type. The aim of the study was to compare particular analytical procedures and to evaluate results with respect to different methods of forest management Keywords: humus quality, management impacts, forest soils, Czech Republic. References: (i) Guerra, J.G.M.; Santos, G. de A.: Métodos físicos. In: Santos, G. de A.; Camargo, F.A.O. (Ed.) (1999) : Fundamentos da matéria orgânica do solo: ecossistemas tropicais e subtropi-cais. Porto Alegre: Genesis, pp.267-292. (ii) Sparks, D.L. Ed. (1996): Methods of Soil Analysis, Part 3, Chemical Method, SSSA Book Series Number 5, Soil Science Society of America, Madison, Wisconsin. (iii) Stevenson, F.J. (1994): Humus Chemistry, Genesis, Composition, Reactions. John Wiley & Sons, Inc., New York.

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