The significance of humus forms for management and conservation of Mediterranean landscapes

Abstract

In every terrestrial ecosystem organic litter is accumulated to a certain degree making humus forms. By their different physical and chemical conditions, the latter may be quite diverse habitats for plants and soil organisms. Its intermediate position in space and time between living organisms and dead mineral compounds, makes a humus form the centre of regulation of the soil and, some extent, of the whole ecosystem. It may be interpreted as a product of biological feedback mechanisms in a Gaian sense, making sites suitable for organisms. Opposing trends are nutrient conservation versus nutrient transfer and horizonation versus haploidization. These trends lead to mor-like and mull-like humus forms, respectively, the former developing especially well under nutrient and drought stress as well as under cold stress. Whereas humus received full attention in several fields of ecology and its applications, it is practically a ‘forgotten factor’ in landscape ecology. This accounts especially for (sub) Mediterranean landscapes. The present lecture deals with the role of humus forms in some Tuscan landscapes (Solano Basin, Farma Basin), covering the range from Meditteranean up to montane ecosystems. Plant-controlled mor-like humus forms are thought to be more susceptible to human impact than mull-like humus forms. This is indicated for the Solano Basin where they should be handled with care. The significance of humus forms for conservation of nature and landscape is stressed.