Importance of water level dynamics for vegetation patterns in a natural percolation mire (Rospuda fen, NE Poland)

Abstract

Although conservation of percolation mires is very important for the European biodiversity, our understanding of their functioning is still insufficient, as most of the studied sites are to some extent degraded. We present a study on the relationship between vegetation patterns, hydrochemical gradients and water level fluctuations carried out in the Rospuda valley (NE Poland), which was recently discovered for science as a uniquely preserved fully functioning percolation mire. Vegetation composition, mire water chemistry and water level dynamics were studied along five transects perpendicular to the valley. Eight major vegetation types were identified: brown moss-small and slender sedge fens, Sphagnum-small sedge fens, brown moss-tall sedge fens, tall sedge-reed fens, pinebirch fen woodlands and shrublands, spruce fen woodlands, inundated alder woodlands, alder spring fen woodlands. The seasonal dynamics of water table was revealed as the major factor explaining vegetation patterns. The studied chemical parameters were relatively homogeneous in the whole mire-there is a rather uniform type of mineral-rich nutrient-poor subsurface water all across the fen.

Understanding the Long Term Ecosystem Stability of a Fen Mire by Analyzing Subsurface Geology, Eco-Hydrology and Nutrient Stoichiometry – Case Study of the Rospuda Valley (NE Poland)

“…A previous study by Jabłońska et al (2011) showed, that the chemical composition of subsurface water (sampled from shallower, 0.5 m-deep, piezometers) is quite uniform within the whole Rospuda mire and is not especially useful for distinguishing vegetation types. In the present study we analysed water from the bottom peat layer (in order to minimise influence of external factors), revealing that the two basins may be fed by groundwater from two different aquifers (Fig.…”

“…At the beginning, vegetation was dominated by (sparse) tall sedge communities, but also scattered trees (Betula, Alnus) could establish, so the peat was, at least periodically, Fig. 1; slope of a mire is presented schematically, for more detailed mire surface levelling, see Jabłońska et al (2011) sufficiently dry to allow growth of trees. The stable ground with underlying sands may also have supported tree growth.…”

“…4, phases m, n correspond to the zones in Fig. 3; slope of a mire is presented schematically, for more detailed mire surface levelling, see Jabłońska et al (2011) caused a positive feedback: because the peat surface could not oscillate with water level movements, reedbeds (in wetter periods) or trees and shrubs (in drier periods) developed, inducing further peat decomposition due to increased evapotranspiration and oxygen transport to the root zone.…”

“…7), with the highest water levels of 25 cm above peat surface, whereas in the lower basin floods were restricted to a narrow riverine zone, not reaching the brown moss-small sedge communities (cf. Jabłońska et al 2011). This difference can, firstly, be explained by the fact that brown moss-small sedge fens in the lower basin are located further away from the river and elevated above its water level (because of the larger valley width and a steeper inclination of the mire, cf.…”

Preface: Restoration, biogeochemistry and ecological services of wetlands

“…However, our understanding of the functioning of intact or pristine systems is still lacking, with the majority of studied sites being to some extent degraded. Jablonska et al (2011) describe the relationship between vegetation patterns, hydrochemical gradients, and water level fluctuations carried out in the Rospuda valley (North East Poland), which was recently discovered as an uniquely-preserved, fully functioning percolation mire.…”