Organic matter cycle and humus form profiles
Vegetation growth is largely determined by the characteristics of the environmental factors such as drainage, acidity, salinity and the availability of nutrients. These environmental factors have also great influence on the organic matter cycle by means of decomposition of organic matter and thereby on the rate in which nutrients, stored in the organic matter, become available again for vegetation growth.Differences in nature and rate of the supply of litter on the one hand and the its decomposition on the other hand result in a number of layers or 'horizons' that can be distinguished in the soil. Possibly more layers are on top of each other. Together they constitute the 'humus form profile'. A description of the humus form profile therefore informs us about the organic matter cycle and indirectly also about the environmental factors that are determinative for the vegetation growth.
Humus form types what are they ?
Studying the humus form profile in relation to the environmental factors and the vegetation gives us further insight in the functioning of the ecosystem. In this context a good description of the humus form profile will do fine. However when we want to compare humus form profiles from different locations or even want to map them, a classification of the humus form profiles based on comparing characteristics is required. For this purpose a humus form classification is drawn up so that humus form profiles can be ascribes to a humus form. The humus form type stands for a unity in the classification in the same way as soil- or vegetation types on soil- or vegetation maps respectively. Classification of the humus form profile is done base on the characteristics of the first 40 cm below surface. A systematic illustration of this classification is given in the picture below. The soil profile describes the first 120 cm below surface, the humus form profile describes all layers that contain organic matter while only the first 40 cm below surface are taken into account for the humus form type classification. More details are given in the power point show ecological soil classification.
What can we do with the humus forms ?
Environmental factors (drainage, acidity, salinity and the availability of nutrients) determine the development of the humus form profile. The humus form profile therefore is a useful indicator for the characteristics of these environmental factors. This means that the humus form profile can be used to gain information about the ecological condition on a certain location. Because of this use the humus form profile is part of the toolkit of the 'ecological soil classification'. (See also the power point show on ecological soil classification, in Dutch). Tools of this toolkit can be used to describe the possibilities and the functioning of the location. Which tools to use depends on the kind of question asked and the physical condition of the location.