부산대학교 도서관

The distribution of mull and mor, in an area which is believed to have borne forest for a number of centuries at least, led to investigations into the reasons for their development. Although the term forest-floor type has been substituted for humus type, mull and mor are used in the Müller-Hesselman sense. There appeared to be no obvious relationship between the distribution of the various forest-floor subtypes and the results of chemical analyses and pH determinations on soil samples. Where free CaCO₃ occurred in the A₁-horizon, a mull forest floor had developed even on coarse sand and the associated herb flora differed only slightly from that occurring on very acid mull. As the manner in which lime influences most soil processes is still unknown, the areas in which free CaCO₃ occurs were excluded from the investigations. Assessments of various other soil characteristics were made and the frequency of association of the various categories of these characteristics ascertained. It is concluded that the colour of the upper part of the A₁-horizon and its degree of leaching are related to its texture, and that the forest-floor subtypes are more closely related to soil texture than to soil colour or degree of leaching. Each forest-floor subtype is associated with particular colouring of the upper part of the A₁-horizon and variation in both characteristics seems to be similarly associated with variations in topography. There seems to be little demonstrable difference between the influence of the tree species oak and birch on the development of the forest-floor types. The development of forest-floor types is closely related to the two factors soil texture and topography and it is considered that under the conditions of the Hackfort area the differential development of forest-floor types mull and mor and their subtypes is primarily determined by the soil water regime.