A Study on the Element Extraction from OrganicMatter of Forest Floor of Norway Spruce

The samples of organic matter on forest floor of a Norway spruce stand in Solling, Germany, were extracted. It shows that the decomposition degree of forest floor materials, water: sample ratio, and the pH value in extracting solution are important factors controlling the element extraction. The extraction of most cations is strongly influenced by the H+ exchange mechanism. Therefore lower pH value leads to more extraction; while higher pH value and its increase due to dilution leads to less extraction. Widening water: sample ratio until a certain value leads to a new balance of element concentration between solution and forest floor materials towards more extraction. In addition, the increase of pH value caused by further widening water: sample ration becomes a limiting factor and leads to less extraction, especially for the di and trivalent cations. Combination of these 2 influencing aspects makes the extraction curves versus water: sample ratio very complex. The influences of total element content ( T, μmol(+)·kg-1 forest floor materials), pH value in extracting solution and water: sample ratio ( W, kg·kg-1)on element amount extracted( Y, μmol(+)·kg-1 forest floor materials) can be described in mathematical models. The model is Y=A+(T-A)· exp (-B·pH)/[1+C· exp (-W)] for Na+, K+,Ca2+,Mg2+,Mn 2+,Al3+ and Fe t; while Y=a+b W c for H+. For the water extraction of strongly acidified forest floor materials no expectant optimal water: sample ratio exists. With lower water:sample ratio the variance of element concentration ratios is greater; with higher water: sample ratio the variance of element amount ratios is greater. However, the water content of saturation can be used as a compromised water: sample ratio for the water extraction of strongly acidified sample of organic matter on forest floor. The water content of saturation is 3.4, 3.2, 2.0 kg·kg-1 for O L, O F and O H, respectively.