Structure and Reactivity of a Biological Soil Crust from a Xeric Sandy Soil in Central Europe

Abstract

The investigation was designed to explore the structure, composition, and activity of a biological soil crust on an acidic, sandy soil from a temperate climate. The crust covers several hundreds of square meters on the hilltop of a large terminal moraine. The conjugate alga Zygogonium ericetorum forms the essential matrix for the crust, a dense web of algal filaments with interspersed lichens and mosses. The crust is composed of three layers, with an uppermost layer consisting nearly entirely of a dense algal mat. In lower layers, a parasitic fungus, penetrating the algal cells, is another important component of the crust community. In this soil crust, photosynthetic and respiratory activity is stabilized at low water activities.

Keywords:

• biological soil crust
• desiccation tolerance
• electron microscopy
• Fusarium oxysporum
• Zygogonium ericetorum

We are indebted to W. Manz (TU Berlin) and G. Arp (Univ. Göttingen) for providing in situ hybridization probes and access to an image deconvolution system. We thank C. Grüber for excellent technical assistance at the scanning electron microscope.