Physical properties of the mor layer in a Scots pine stand II. Air permeability

Abstract

Mor is a typical humus form in the boreal coniferous forests, but little is known about its air permeability and pore geometry. Thirty undisturbed core samples were collected from a mor layer under a mature Scots pine (Pinus sylvestris L.) stand. Air permeability (Ka) was measured in each sample at six different air-filled porosities (εA) using a constant-pressure air permeameter. The air permeability and the air-filled porosity were used to determine different indices of pore geometry and continuity. The average Ka increased logarithmically from 7.4 × 10−1 to 1.3 × 103 µm2 when εA increased from 0.1 to 0.8. Both the air permeability and pore continuity were high when compared with most other mineral soils and well-decomposed peats. The variations in air permeability and pore continuity with εA were very large. The studied properties had a very large spatial variation in the mor layer which could be caused by the variation in the quality of the debris and the environmental factors affecting the decomposition process during the development history of the mor layer. Key words: Aeration, humus, pore continuity