The effects of low pH and palliative liming on beech litter decomposition in acid-sensitive streams
The decomposition of allochthonous leaf litter is retarded by stream acidification, but few studies have evaluated whether this effect can be offset by liming – the palliative addition of calcium carbonate either to streams or their catchments. We assessed the response of litter decomposition to pH and experimental liming in Welsh upland streams. Small-mesh (<335 μm) litter-bags containing common beech (Fagus sylvatica L.) were submerged in main river sites along the River Wye, and in replicate acid, circumneutral and experimentally limed tributaries (all n = 3) for 20 days. Beech decomposition was inhibited in acid tributaries and main river sites compared to circumneutral tributaries. Despite having only moderately increased pH relative to acid streams, limed sites had increased decomposition rates that were indistinguishable from naturally circumneutral streams. Decomposition rates increased highly significantly with pH across all 12 sites studied, and values were near identical to those in more prolonged experiments elsewhere. There were no significant variations in shredder numbers with decomposition rate, and no evidence that sites with faster decomposition had smaller shredder proportions. Although based on short-term observations and leaves from just one tree species, these results are consistent with the well-known retardation at low pH of some aspect microbial decomposition (e.g. by hyphomycete fungi). They are among the first to suggest that stream liming to combat acidification might reverse such impacts of low pH. Further data are required on the microbiological causes and ecological consequences of altered detrital processing in acid-sensitive and limed streams.
Keywordsacidification allochthonous detritus decomposition invertebrates leaf litter
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- Ansell, S., 1989. An examination of decay rates and invertebrate colonisation of deciduous and coniferous litter in an acid and a circumneutral stream. M.Sc. Applied Hydrology thesis, Cardiff UniversityGoogle Scholar
- Bradley D. C. and Ormerod S. J. (2002b). Evaluating the precision of kick-sampling in upland streams: the effects of sampling effort, habitat and rarity. Archiv fűr Hydrobiologie 155: 199–121Google Scholar
- Chauvet E. and Suberkropp K. (1998). Temperature and sporulation of aquatic hyphomycetes. Applied Environmental Microbiology 64: 1522–1525Google Scholar
- Lewis, B. R., I. Jűttner, B. Reynolds & S. J. Ormerod, in press. Comparative assessment of stream acidity using diatoms and macroinvertebrates: implications for river management and conservation. Aquatic Conservation: Marine and Freshwater EcosystemsGoogle Scholar
- Moog, O. (ed.), 1995. Fauna Aquatica Austriaca – a comprehensive species inventory of Austrian aquatic organisms with ecological data, first edition, Wasserwirtschaftskataster, Bundesministerium fűr Land-und Forstwirtschaft, WeinGoogle Scholar
- Mulholland P. J., Driscoll C. T., Elwood J. W., Osgood M. P., Palumbo A. V., Rosemond A. D., Smith M. E. S. and Schofield C. (1992). Relationships between stream acidity and bacteria, macroinvertebrates, and fish: a comparison of north temperate and south temperate mountain streams, USA. Hydrobiologia 239: 7–24CrossRefGoogle Scholar
- Rover T. V. and Minshall G. W. (2003). Controls on leaf processing in streams from spatial-scaling and hierarchical perspectives. Journal of the North American Benthological Society 22: 352–358Google Scholar
- Suberkropp K. and Chauvet E. (1995). Importance of stream microfungi in controlling breakdown rates of leaf litter. Ecology 75: 1807–1817Google Scholar