Morphology, spatial arrangement and origin of macropores in some hapludalfs, West Germany

Twenty oriented blocks, roughly 10 cm along each edge, were collected from the Bv and C horizons of four Hapludalfs near Hannover (West Germany). At least two blocks were obtained from each horizon of each profile. The macropores (0.1--1 mm) in these blocks were then examined by micromorphological methods. The 3-dimensional arrange- ments of pores were observed by two approaches, viz., (1) preparing photographic sequences of successive polished sections obtained from the sample blocks and then stack- ing photographs to simulate pore geometry; (2) preparing resin casts of tubular pores. Examination of stacked photographs and the resin casts by scanning electron microscopy (SEM) followed by electron-optical image analyses indicate interconnected systems of pores with the most frequently occurring diameters between 150 and 250 urn. Interconnections among pores are very similar in numbers throughout the Bv horizons. Comparisons of the diameters, branching, and tapering of macropores with similar features of plant roots suggest that most pores between 0.1 and 1 mm have been produced by roots. Some may be due to fauna, but all seem to have been of biological origin and are therefore considered biopores.