Micro morphology of some yellow-brown earths and podzols of New Zealand

Abstract

Abstract The morphology of a sequence of soils from yellow-brown earths to podzols was studied with the aid of incident light and thin sections. The observations indicate that the following main changes take place with progressive weathering, leaching, and development in the sequence:— 1. A progression in the humus forms of the A horizons from strongly granular mulls with mull humus micro-fabrics to mors with raw humus fabrics preserved even where a change in the vegetation permits the entry of mull-forming earthworms. 2. As the organic cycle concentrates towards the surface, soil fauna and plant roots tend to be progressively concentrated in humic layers, and the mineral soil coarsens in structure. 3. Clay and organic matter progressively lose their intimate, water-stable association, and organic coatings of increasing thickness are inwashed along structure faces of B horizons. 4. Clay is progressively liberated from A horizons, with the eventual development of an iluvial A2 horizon. It is deposited as o...