Metsätyypin määräytyminen maalajin ja maaperän kemiallisten ominaisuuksien perusteella

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This study consists of 1228 profiles taken from forest soils mainly situated in South and Central Finland. Nine per cent of the soils are located in the Oxalis-Myrtillus type (OMT), 56 percent in the Myrtillus type (MT), 28 percent in the Vaccinium type (VT), 5 per cent in the Calluna type (CT), and 2 per cent in the Cladina type (CIT). Four layers of each profile were analyzed. In the podsolized soils (80 per cent of all cases) the layers investigated were the litter layer (A0 horizon), the leaching layer (A2), the enrichment layer (B1—2), and the subsoil (C). In the clay, silt and sand soils, in which the podsolization was weak, the uppermost sample was taken from the litter horizon (A0), the second one down to 20 cm, the third from a depth of 20—40 cm., and the fourth at a depth of 40—60 cm. The types OMT, MT and VT are found in all soil types. There are no clay, silt or finer fines and samples taken from CT and CIT, while 57 per cent of all cases were in OMT. On the other hand, only 3 per cent of the sand samples came from OMT, while 54 per cent of the CT samples and 42 per cent of the CIT samples were sand. In general, the uppermost layers of forest soils are the most acid ones. The average pH-value of the litter layers in each forest type is about one pH-unit lower than that of the subsoil of the same type. The mean values of pH(H2O) in the litter layers decrease from pH 4.7 in OMT to pH 4.0 in CIT. According to this study, the litter layer is the richest layer in nutrients in forest soils. The differences between the mineral soil layers are small in each nutrient in the same forest type. The average exchangeable calcium and potassium contents in the surface soil increase with better forest types. The average Ca contents of the mineral soil layers in OMT vary from 366 to 1 060 mg/l soil while the corresponding numbers of CIT, CT and VT are 36-117mg/l. The litter layer of OMT has the highest potassium mean value (177 mg/l) while the lowest value (7 mg/l) is found in the subsoil of CIT. The content of readily soluble phosphorus in the humus layer is 4-10 times as high as that in the deeper mineral soil layers. This is the only regularity to be found in the P contents between the different forest and soil types. Dividing the samples into soil type groups, we can say that the higher the mean values of calcium, potassium and pH, the richer the forest type they represent. Carbon and nitrogen determinations were made from surface soil samples only. The C/N ratio decreases quite regularly from 42 (CIT) to 24 (OMT).