Rapid changes in plant assemblages on mud-bottom hollows in raised bog: a sixteen-year study

Abstract

Mud-bottom hollows with bare peat surface are common features of raised bogs in the boreal zone. Due to retarded peat accumulation, these hollows promote changes in plant cover, microtopography and carbon accumulation. We undertook a 16-year study of eight permanent plots in mud-bottom hollows to assess their durability, regularities and causes of development. Annual changes in the areas of plant assemblage types in the plots averaged around 20 %, and changes during the entire study period approached 90 %. Bare peat surfaces existed for 3–12 years on average before being overgrown by lateral expansion of the bordering Sphagnum carpet (average rate of advance 4.1 ± 1.3 cm yr-1) or by clumps of Rhynchospora alba. The annual changes in representation of plant assemblages fluctuated through time and were related to weather factors. The overgrowth of bare peat by Sphagnum carpet was favoured by wetter conditions, whereas overgrowth by the R. alba dominated plant assemblage was temporally less regular and independent of weather.

Keywords

• bare peat
• permanent plots
• plant assemblages
• Rhynchospora alba
• Sphagnum mosses