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- Title
Interactive effects of low pH and high ammonium levels responsible for the decline of Cirsium dissectum (L.) Hill.
- Authors
Lucassen, E.C.H.E.T.; Bobbink, R.; Smolders, A.J.P.; van der Ven, P.J.M.; Lamers, L.P.M.; Roelofs, J.G.M.
- Abstract
The decline of Cirsium dissectum in dessicating wetlands is attributed to acidification and eutrophication. Experimental evidence was obtained for the first time on ammonium toxicity under low pH. In a hydroculture experiment, interactive effects of nitrogen forms (250 μmol NH4 or 250 μmol NO3-) and pH (4, 5 or 6) were studied with regard to the vitality of C. dissectum seedlings. The results show that 250 μmol l-1 ammonium as sole nitrogen source only had negative effects on C. dissectum in combination with a low pH. Ammonium uptake at a rhizosphere pH of 4, resulted in lower nitrogen contents of both roots and shoots, lower internal pH of roots and shoots and increased contents of basic amino-acids, resulting in decreased survival rate and biomass development. At higher pH, or when nitrate was the nitrogen source, these processes do not take place. This phenomenon stresses the importance of periodic influence of base rich groundwater during the winter in wet species-rich heathlands and grasslands, necessary to restore the acid neutralising capacity of the soil. Anthropogenic lowering of the groundwater table will lead to acidification enabling ammonium to become toxic to herbaceous plant species such as C. dissectum.
- Subjects
CIRSIUM; THISTLES; WETLANDS; MOORS (Wetlands); BIOMASS; SOILS
- Publication
Plant Ecology, 2003, Vol 165, Issue 1, p45
- ISSN
1385-0237
- Publication type
Academic Journal
- DOI
10.1023/A:1021467320647