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Final report of the project input-output relationships for intensive monitoring sites
Erisman, J.W.; Vermeulen, A.T.; Vries, W. de; Salm, C. van der; Reinds, G.J.; Draaijers, G.P.J.; Bleeker, A.; Lakkenborg Kristensen, H.; Gundersen, P.
Gepubliceerd door: Publicatie datum:
ECN SF 1-7-2002
ECN publicatienummer: Publicatie type:
ECN-C--02-066 ECN rapport
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This report describes the work done within the project "Input - outputrelationships for Intensive Monitoring sites", EC contract number SG(99) D/10844. The project results are extensively reported in the Technical Report 2000 (De Vries et al., 2001). Input estimates for selected Level II plots are obtained from throughfall measurements corrected for canopy exchange. Output fluxes were obtained using hydrological model output combined with soil concentrations. Leaching fluxes and input estimates provided the balances. Mean yearly interception evaporation ranged from approximately 160 mm for Pine and Oak to approximately 250 mm for Beech and 300 mm for Spruce, reflecting the increasing interception capacity of those tree species. Median transpiration fluxes were rather constant among the tree species and ranged from 325 mm.yr-1 for Pine to 385 mm.yr-1 for Spruce stands. At most plots, the leaching flux of SO4 is higher than that of NO3, despite the generally lower input of S than of N, indicating that SO4 is still the dominant source of actual soil acidification. The median sulphur budget is close to zero, but at a considerable number of sites, sulphur is released by the soil, indicating that these systems are recovering from previous episodes of high sulphate input. The leaching of N is generally negligible below throughfall inputs of 10 kg.ha-1.yr-1. There is a significant relationship between N leaching and N deposition but no significant relationship was found with the soil C/N ratio. Nitrogen budgets show that at most sites (90%) the N input is higher then the N leaching. Variations in base cations leaching were significantly related to the S input and the pH and base saturation. The median base cation balance is close to zero, implying a net adsorption and a net release of base cations at approximately 50% of the plots. The Al leaching flux was significantly related to the SO4 input reflected by the fact that sites with a high Al leaching coincide with sites with a high input of SO4. The geographic patterns of both elements, however, did not coincide very well since soil base saturation was also significantly related to the Al leaching flux.

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