Effects of pollutants in snowmelt onKiaeria starkei, a characteristic species of late snowbed bryophyte dominated vegetation

Abstract

S U M M .^ K \Areas which experience prolonged snowlie and possess a distinctive bryophyte-dominated vegetation are ternied snowbeds. Snow is a very efficient sca\-enger of atmospheric pollution. Because of the dynamics of snowmelt, much of the pollutant load of a snowpack is released in a highly concentrated episode known as the 'acid flush'. This flush IS received by the underlying vegetation when it is covered by the snow and also when it has beet-i exposed after snow cover. Concentrations of pollutants which are already occurring in the meltwater of Scottish snowbeds are shown to be causing damage to the underlying bryophytes. Damage is greatest when the pollutants are received by the plants when out of snow cov-er. Reco\-ery from the damage is slow and in some cases the plants show no signs of recovery 4 wk after exposure to polluted snow nieltwater. Gi\-en the very short growing season available to the plants, damage persisting for so long could tmpinge on the plants' potential for survival. The long-term threat to these sensitive communities is a serious one.

Effects of Simulated Environmental Changes on Growth and Growth Form in a Late Snowbed Population of Pohlia wahlenbergii (Web. et Mohr) Andr

“…Since these life forms are important food sources for herbivores, such a change will inevitably have a substantial impact on higher trophic levels and the diversity of animal guilds. However, most studies so far have been conducted in areas receiving substantial inputs of airborne pollutant N with snowfall (e.g., Bowman, 1992;Woolgrove and Woodin, 1996a, 1996b, 1996c, and the results must be interpreted with this in mind.…”

“…Bryophytes represent an important growth form in the snowbed vegetation, yet they are especially threatened due to their ectohydric nature in combination with their unistratos leaves and lack of cuticle, which makes them extremely sensitive to high concentrations of pollutants in snow (Woolgrove and Woodin, 1996a, 1996b, 1996c. During the last century, the tissue nitrogen content of the snowbed bryophyte Kiaeria starkei has doubled in the central highlands of Scotland (Woolgrove and Woodin, 1996b).…”

“…Snowmelt water polluted with NO 3 2 and SO 4 22 is damaging, especially to the bryophyte vegetation, and causes reduced chlorophyll a:b ratios, decreased nitrate reductase inducibility, membrane damage, and increased susceptibility to damage resulting from exposure. The damaging effects become more pronounced if the bryophytes are subjected to drought after snowmelt, which is often the case in snowbeds, while subnivean plants are less damaged but face a reduced growing season to gain carbon reserves needed to repair the damage; the recovery rate after snowmelt is therefore slow (Woolgrove and Woodin, 1996c). Studies of litter decomposition have shown that 48% (by dry weight) of the available litter in snowbeds is decomposed after one year in the Alps and that, in the snowbeds, litter decomposition is slower than adjacent meadows and cushion plant communities (Schinner, 1983).…”

Ecophysiology of a snow-bed bryophyte Kiaeria starkei during snowmelt and uptake of nitrate from meltwater

“…This is addressed in another paper (Woolgrove and Woodin 1996a). It is also capable of assimilating nitrate from snowmelt, and as nitrate is known to be damaging to bryophytes in excess, this demonstrates that there is significant risk of pollutant damage to snow-bed bryophytes while still under snow.…”

Additive impacts of nitrogen deposition and grazing on a mountain moss-sedge heath

“…leakage can indicate physiological damage in bryophytes, potentially due to N toxicity (Woolgrove and Woodin 1996;Pearce et al 2003). Composite samples of Racomitrium were collected in June 2004 from each of the 31 plots across the three habitat types, for determination of both tissue N content (as described previously for samples in 2003) and K ?…”