Príspevok k problematike určovania špecifickej hmotnosti subhorizontov opadu lesných pôd

Abstract According to national and international laboratory methods, the density of soil samples is determined by pycnometer in heated samples crushed by ultrasound. In mineral soils, the elementary unit of density is represented by a mineral grain of quartz, granite, andesite, etc. On the other hand, in organic soils, the elementary unit is represented by a leaf (or just a part of it), needles, stems and roots. Heating of the mineral grain causes its release from the soil aggregate. Organic parts of the soil are losing air vacuoles by heat treatment while in the same time, carbohydrates, proteins, oils and resins create new chemicals which are heavier than water. That is a reason why density determination of litter subhorizons in forest soils needs to have different rules in comparison with mineral soil samples. Samples with more than 50 volume per cent of organic matter are not treated by heat and do not decompose. In case of high mineral soil content, mineral parts are removed from the sample and their density is determined. The final density is based on mathematically processed data. Abstract Podľa metodik použivanych na Slovensku aj v zahraniči, sa špecificka (merna) hmotnosť pody stanovuje pyknometricky, v drvenych, ultrazvukom rozbitych a varenych vzorkach. Kym v mineralnych podach je elementarnou jednotkou špecifickej hmotnosti mineralne zrno kremeňa, žuly, andezitu a pod., v organickych podach je to list, ihličie, steblo a koreň (cely alebo časť). Varenim sa mineralne zrno z podneho agregatu uvoľni. V organickych zložkach pody sa varenim stracaju vakuoly plne vzduchu, pričom uhľohydraty, bielkoviny, tuky a smoly sa zražaju na chemicke zlučeniny ťažšie ako voda. Preto by sa stanovenia špecifickej hmotnosti subhorizontov opadu lesnych pod mali riadiť inymi pravidlami a postupom pri priprave vzoriek, ako je to pri vzorkach s prevahou mineralnych elementarnych častic. Pripravene a naležite nastrihane, pripadne aj podrvene vzorky s prevahou organickych latok (>50 % objemovych) sa nevaria a chemicky nerozkladaju. V pripade zreteľneho podielu mineralnej zložky pody, tuto časť zo vzorky odstranime, a jeho špecificku hmotnosť stanovime u nas zauživanym sposobom. Vysledna špecificka hmotnosť spočiva v matematickom spracovani ziskanych udajov.