Effects of reduced nitrogen and sulphur deposition on the water chemistry of moorland pools.

To assess changes as a result of reduced acidifying deposition, water chemistry data from 68 Dutch moorland pools were collected during the periods 1983-1984 and 2000-2006. Partial recovery was observed: nitrate- and ammonium-N, sulphur and aluminium concentrations decreased, while pH and alkalinity increased. Calcium and magnesium concentrations decreased. These trends were supported by long term monitoring data (1978-2006) of four pools. Increased pH correlated with increases in orthophosphate and turbidity, the latter due to stronger coloration by organic acids. Increased ortho-phosphate and turbidity are probably the result of stronger decomposition of organic sediments due to decreased acidification and may hamper full recovery of moorland pool communities. In addition to meeting emission targets for NO(x), NH(x) and SO(x), restoration measures are still required to facilitate and accelerate recovery of acidified moorland pools.

Even low to medium nitrogen deposition impacts vegetation of dry, coastal dunes around the Baltic Sea.

Coastal dunes around the Baltic Sea have received small amounts of atmospheric nitrogen and are rather pristine ecosystems in this respect. In 19 investigated dune sites the atmospheric wet nitrogen deposition is 3-8kg Nha(-1)yr(-1). The nitrogen content of Cladonia portentosa appeared to be a suitable biomonitor of these low to medium deposition levels. Comparison with EMEP-deposition data showed that Cladonia reflects the deposition history of the last 3-6 years. With increasing nitrogen load, we observed a shift from lichen-rich short grass vegetation towards species-poor vegetation dominated by the tall graminoid Carex arenaria. Plant species richness per field site, however, does not decrease directly with these low to medium N deposition loads, but with change in vegetation composition. Critical loads for acidic, dry coastal dunes might be lower than previously thought, in the range of 4-6kg Nha(-1)yr(-1) wet deposition.