Hydraulic Properties of Mor Layers in Finland

Mor, which is the most common humus form in Finnish forests, is an important interface between the mineral soil and the atmosphere through which hydraulic processes, e.g. infiltration and evaporation, take place. Hydraulic properties, i.e. water-retention characteristics and the unsaturated hydraulic conductivity K () in the mor layers of low-fertility (CT) Scots pine (Pinus sylvestris L.) sites and medium-fertility (MT) Norway spruce (Picea abies (L.) Karst.) sites were measured on undisturbed samples. Samples were collected from four clusters, each of which contained 3-5 stands of CT and MT sites. Water retention and K() were slightly higher on MT than on CT sites. With a decrease in matric potential () from -4 to -60 kPa, the mean K decreased from 8.8 × 10^-3 to 1.4 × 10^-6m d^-1 and from 6.9 × 10^-3 to 4.9 × 10^-7m d^-1 at the MT and CT sites, respectively. The main source of variation both in water retention characteristics and ^K(^), was the spatial heterogeneity within a stand. ^K(^) did not differ statistically between stands or between clusters within either of the site types studied.