Impact of humic substances on Sphagnum denticulatum habitats

In 10 softwater lakes of NW Poland (5 very acid and 5 slightly acid) three kinds of Sphagnum denticulatum Bridel [=S. auriculatum Schimper] habitats have been studied: oligohumic (<2.0 mg CDHS dm-3) and α-mesohumic (2.0-4.0 mg CDHS dm-3) and β-mesohumic (4.1-8.0 mg CDHS dm-3). During habitats humification in very acid lakes some water and sediment characteristics, such as pH, conductivity, TDS, and calcium concentration are low and almost invariable, whereas variable are the colour and clearness of the water. In low-acidity lakes the values of habitat characteristics are higher and also nearly invariable. The optimum habitats for S. denticulatum are oligohumic (