Pedogenesis: Humus forms and soils under spruce forest by a morphological approach

Abstract

Our investigation pointed out, with a detailed classification, a vast variability of forest humus and soil under spruce forests on two different sites with North and South exposition, permitting to identify a pedogenetic trend between different sylvogenetic phases of forest evolution and specific humus forms.We identified the soil indicators that have to be checked for measuring soil changes relating to humus changing. First of all we noted a humus change on soil morphological features. Such features are produced by physical and biochemical pedofauna bioturbations. Pedofauna according to the peculiar microclimate of the soil, depends on the forest development. Biochemical litter environment produces specific humus form.During the growth of a forest there is a policyclic soil evolution with physical-chemical changes that we can observe in time on soil and humus forms. The humus forms are related with the air (biospheric fluxes), with the organic-mineral components (as micro and macroelements cycles) and with pedofauna. We observe physical change (as structure, porosity, horizontation, particle-size, pattern, mineralogy) and chemical change (as for pH, C, N) in soil horizons which is due to humus change.The humus forms have been investigated in relation to the development of vegetation growth, with the aim to identify a representative humus form of a specific sylvogenetic phase. Such research suggests an hypothesis that the humus form is a guide of the environment states to which it belongs. During the open canopy stage (that is the phase before the presence of very young plantations) it is possible to observe many different humus forms: from the acid one as Moder (Hemimoder), that is heredity of the previous use of the land, to the new form of Mull (Oligomull) that is the result of the new forest cycle, more suitable for spruce renovation.