Micro-Morphological Characteristics of Humus Forms as Indicators of Increased Environmental Stress in Hamburg’s Forests

Abstract

Micro-morphological investigations of some humus forms, decomposition sequences and traces of soil animals in soils of periurban forests of the city of Hamburg, in combination with field investigations and a number of chemical analyses, allow the interpretation that the conditions for the decomposition of organic matter have become one-sided, i.e. have deteriorated with a decrease of biological activities. Even under consideration of the particular visitor stress to which periurban forests are subjected, it can be concluded that the deterioration can be largely attributed to immissions, i.e. to acid precipitation during the last decades. In addition, the comparison with analytical results obtained from a raw-humus site 30 years ago, indicate that soils have become more acid and that in some stands penetration of the H- and Ah-horizons by roots has strongly decreased.