Effects of water chemistry,nutrient supply and interspecific interactions on the replacement of Sphagnum subnitens by S. fallax in fens

Abstract

In Dutch rich fens, mid-successional stages dominated by Sphagnum subnitens are rapidly being replaced by other vegetation, dominated by S. fallax.

In both species growth was strongly reduced in more mineral-rich ground water and simulated river water, compared to growth in rain water.

Both species were positively affected by added phosphorus supply, whereas added supply of nitrogen did not alter growth rates.

Nutrient supply seemed to compensate for the intolerance to high mineral levels in S. fallax: nutrient addition stimulated growth in length in ground water and simulated river water. Such compensation was not found in S. subnitens.

Growth in mixed culture positively affected Sphagnum subnitens and negatively affected its successor S. fallax.

The success of Sphagnum fallax in early stages of succession in more eutrophic fens may to some extent be explained by its tolerance to high mineral levels with increased nutrient supply.