Interrelationships of humus cover (pro humus form) with soil cover and plant cover: Humus form as transitional space between soil and plant

Departing from the pedocentric approach, the Estonian soil classification (ESC) is used as a baseline in studying the adequacy of alternative (treating other ecosystems compartments) classifications (forest site types, natural grasslands types, humus cover types). The interrelationships of different classifications are analysed in relation to normally developed mineral soils (forming 72.4% of Estonian soil cover) by means of these soils' pedo-ecological schema. On this genetic-functional schema the pedo-ecological position of soils is characterized by (1) eight-stage litho-genetic scalar and (2) six-stage moisture and aeration conditions scalar. In evaluation of the coinciding extent the total classification units' number, the coinciding percent of unit borders and variability of mean units' accordance was taken into account. The mean accordance of soils units to forest sites, natural grasslands and humus covers types is accordingly 2.2, 3.3 and 1.5. Very good coincidence with soils is seen in natural grasslands and good, in humus covers. The matching of forest site types' classification with soils is imperfect. The mean accordance of forest site types to soils and humus cover units is accordingly 0.50 and 0.74; of humus covers units to soils and forest site types, accordingly 0.68 and 1.35. The humus form (humus cover), formed in the course of mutual interrelationships of plants and soils, reflects more precisely the existing pedo-ecological conditions and is therefore a good indicator for the characterizing of soils' biological activity and productivity. Plant associations of natural grasslands and forests are in long-time scale more changeable (in connection to anthropogenic and environmental pressure) as compared to soil cover properties. Based on soil properties, an ecosystem approach to management, classification and protection of natural resources is highly recommended. The ecosystems management should be developed in accordance with the dominant soil varieties of the soil cover. As a natural body between plant and soil covers, the humus cover merits much more attention.