• Application of three Forest-Soil-Atmosphere models to the Speuld experimental forest

      Tiktak A; Grinsven JJM van; Groenenberg JE; Heerden C van; Janssen PHM; Kros J; Mohren GMJ; Salm C van der; Veen JR van de; Vries W de; LBG; SC-DLO; IBN-DLO (1995-02-28)
      Large efforts have been dedicated to investigate effects of atmospheric deposition of sulphur and nitrogen on trees and soil at the forest stand level. For this purpose intensive monitoring programs and integrated models of the water, carbon and nutrient cycle have been developed. This report describes an application of the nutrient cycling and soil acidification model NuCSAM and the integrated water, carbon and nutrient cycling models SoilVeg and ForGro to the Speuld site, a Douglas fir stand on a Cambic podzol. This site was monitored between 1987 and 1991. The models were parameterized and calibrated for this site. Simulated soil water contents, soil solution chemistry, foliage biomass and nutrient status and stem growth between 1987 and 1991 were comparable with observations. However, the models showed large differences with respect to quantities that could not be measured, such as transpiration, leaching fluxes, root uptake fluxes and mineralization fluxes. The generality of the integrated models was further tested by an approximate simulation of a site irrigation and fertigation experiment at a nearby Douglas fir stand between 1987 and 1991. The direction and magnitude of simulated effects of irrigation and fertigation on stem growth, litter fall and needle nutrient status were generally right, but the observed enhanced nitrogen mineralization could not be simulated. Simulation of site response to three Dutch deposition scenarios between 1994 and 2050 showed large differences between the three models, particularly for nitrogen cycling and foliage nutrient status. Nevertheless, all models indicate a fast response of soil solution chemistry to changing deposition. Both SoilVeg and ForGro indicate that direct effects of elevated ozone and SOx concentrations in the atmosphere, and effects of pH and the Al concentration in the soil solution are subsidiary to effects of drought and nitrogen. Our understanding of effects of acid atmospheric deposition on forests, which is based on laboratory experiments, short monitoring studies and integrated simulation is inadequate to quantitatively predict the long-term impact of forests on a nationwide scale.
    • Application of three Forest-Soil-Atmosphere models to the Speuld experimental forest

      Tiktak A; Grinsven JJM van; Groenenberg JE; Heerden C van; Janssen PHM; Kros J; Mohren GMJ; Salm C van der; Veen JR van de; Vries W de; LBG; SC-DLO; IBN-DLO (Rijksinstituut voor Volksgezondheid en Milieu RIVM, 1995-02-28)
      De invloed op bossen van de depositie van zwavel en stikstof, ozon en van op grote schaal onderzocht. Hiertoe zijn een aantal intensieve monitoring studies opgezet en werden modellen van de kringloop van water, nutrienten en assimilaten ontwikkeld. Dit rapport beschrijft de toepassing van het bodemverzuringsmodel NuCSAM, en de geintegreerde modellen SoilVeg en ForGro op het Speulderbos, een Douglas-opstand op een holtpodzol. In dit bos werd van 1987 t/m 1991 een uitgebreide meetcampagne uitgevoerd. De gesimuleerde bodemwatergehalten, concentraties van stoffen in het bodemwater, naaldmassa's, stam-aanwas en nutrientenstatus kwamen redelijk goed overeen met de metingen. De modellen vertoonden echter aanzienlijke onderlinge verschillen op het gebied van grootheden welke niet gemeten konden worden, zoals bosverdamping, drainage, nutrientenopname en mineralisatie. Het gedrag van de geintegreerde modellen werd geverifieerd door toepassing van deze modellen op een irrigatie- en fertigatie experiment op een nabij gelegen Douglas opstand. De modellen konden in het algemeen de effecten van irrigatie en fertigatie op de stam-aanwas redelijk goed voorspellen, maar er waren grote verschillen wat betreft de voorspelde nutrienten status en de stikstof-mineralisatie. De modellen werden vervolgens gebruikt voor scenario analyses voor de periode 1994-2050. Ook hier werden grote verschillen tussen de modellen gevonden voor met name de stikstofkringloop en de nutrienten status (met name het N-gehalte in bladeren). Alle modellen voorspelden dat de concentraties van sulfaat en aluminium in de bodemoplossing snel omlaag gaan na een afname van de verzurende depositie, en dat de concentratie van nitraat een aantal jaren hoog blijft na een afname in de stikstofdepositie. Dit laatste wordt veroorzaakt door opslag van een overmaat aan stikstof in de biomassa en het strooisel. Uit de resultaten van de geintegreerde modellen blijkt verder dat de directe effecten van verhoogde SOx en ozon concentraties in de atmosfeer, alsmede de indirecte effecten van een lage pH en hoge aluminium concentratie een minder groot probleem opleveren dan de effecten van droogte en de overmaat aan stikstof. Onze kennis van de effecten van luchtverontreining en zure depositie op bossen is in het algemeen gebaseerd op laboratoriumstudies en korte monitoring studies. Tot dusverre is het bijna onmogelijk om effecten die in het laboratorium gevonden werden te vertalen naar de veldsituatie. Zolang dit het geval is, blijft elke voorspelling en extrapolatie die met geintegreerde modellen gedaan wordt onzeker, zeker als het gaat om de voorspelling van effecten op een landelijke schaal.
    • Gedrag van zware metalen en nutrienten bij natuurontwikkeling in het Beerze-Reusel Stroomgebied: een probleemverkenning

      Meulen-Smidt GRB ter; Traas TP; Kros J; Bril J; Baveco H; Siepel H; Faber JH; LBG; ECO; AB-DLO; Haren; SC-DLO; Wageningen; IBN-DLO; Arnhem (1997-07-31)
      This study represents a survey into whether mobilisation of heavy metals and nutrients can be a restrictive factor for the development of natural areas in the Beerze-Reusel basin. General risks of soil contamination for development of natural areas are first described, followed by calculations for determining risks for two specific soil types in the Beerze-Reusel basin, by means of coupling models on hydrology, acidification, heavy-metal behaviour and bioaccumulation. Considering the uncertainties in the methodology, this study has been explicitly restricted to a survey. Calculations on the risks of the combination of soil contamination (cadmium and copper), acidification (business-as-usual and an improved scenario) and (no) seepage for a meadow turned into a grassland ecosystem showed that ongoing acid atmospheric deposition in combination with soil contamination can lead to problems for the development of the grassland ecosystem. This happens both directly through acidification effects on vegetation and indirectly through effects of cadmium and copper on different species, and on biological functions of the soil. Effects on soil fauna can also lead to accumulation of organic matter, which can finally result in low species diversity. Copper generally caused less risks than cadmium, but due to ongoing increasing copper concentrations in litter and hence in soil fauna, long-term effects can occur. A scenario in which acid deposition was improved usually showed decreased risks for future ecosystems, but showed that this could also cause higher risks for a longer period due to slower leaching. A scenario comprising seepage up to 20 cm below surface showed hardly any differences in risks for development of natural areas.
    • Long-term changes of chemistry and biota in moorland pools in relation to changes in atmospheric deposition

      Dam H van; Houweling H; Wortelboer FG; Erisman JW; Smeulders SM; LWD; LLO; IBN-DLO; AquaSense TEC (AquaSense TECWageningenDLO-Instituut voor Bosbouw en NatuuronderzoekWageningen, 1996-04-19)
      Major changes in chemistry and biota of three moorland pools have been registered in the period 1979 - 1994 in view of the acidification and eutrophication by atmospheric deposition. The data have been compared with data from the period 1912-1970. By model calculations the changes in these periods were studied with regard to particularly sulphur and nitrogen compounds. Recommendations for future monitoring are made, tailored to the needs of environmental policy.
    • Natuurverkenning 97

      Maas RJM; MNV; IKC-N; IBN-DLO; SC-DLO (Rijksinstituut voor Volksgezondheid en Milieu RIVMIKC-NIBN-DLOSC-DLO, 1997-07-31)
      Natural areas in the Netherlands are - at least in terms of total acreage - increasing again. However, as far as the quality of the areas is concerned, the biodiversity is still decreasing. The Netherlands landscape charcteristics are becoming increasingly similar; large-scale open areas and regional characteristics are disappearing. The future quality of the Netherlands' natural areas will be highly determined by the feasibility of connecting large units of natural areas, by ensuring their environmental quality and by supplementing conservation measures. The national Ecological Network is expected do its work in increasing the species diversity (biodiversity). In carrying out these plans, the high-level ambitions of attaining a coherent network of large natural area units has not proven fully realisable. However, continuing to strive for more concentrated and larger units can ultimately still raise the quality of natural areas. The regional developments in agriculture (scaling-up and intensification), and the decreasing but still large urbanisation and great environmental pressure remain important risk factors, especially in the south and east of the Netherlands, where environmental quality is not yet high enough to meet nature conservation targets. Meeting these targets will therefore demand reductions, especially in ammonia deposition, attunement of the geographical locations of natural areas to emission areas and compensation of the unavoidable decline in quality in the natural areas by quantitative (increased acreage) or qualitative improvements in other areas.<br>
    • Programmeringsstudie Veranderend Landgebruik ; Gedrag van geaccumuleerde stoffen in verband met veranderingen in landgebruik en herstelbaarheid van ecosystemen

      Meulen-Smidt GRB ter; Vries W de; Bril J; Ma W; LBG; AB-DLO; Haren; SC-DLO; Wageningen; IBN-DLO; Arnhem (Dienst Landbouwkundig Onderzoek (DLO), 1996-12-31)
      The aim of this Programming Study on 'Behaviour of Accumulated Contaminants in relation to Land Use Changes and Recoverability of Ecosystems' was to determine: 1) the available knowledge and 2) the short-, medium- and long-term research, needed to develop a risk assessment for the effects of mobilisation of nutrients and contaminants due to land-use changes from agriculture to nature or forest conservation. The most relevant changes in soil condition, which can take place after afforestation, are concluded to be acidification and increase in dissolved organic carbon. The development of wetlands can lead to decreases in redoxpotential and acidification. These changes in soil condition can result in mobilisation of phosphate and heavy metals. Risks from organic micropollutants are probably lower ; however, as yet not much is known about this. Increased contaminant mobility can lead to a decrease in decomposition, an increase in internal concentrations of toxicants in soil fauna and secondary poisoning of terrestrial fauna. The study also concludes that risk assessment for land-use changes will require integration of existing models. A 'quick-and-dirty' model integration is recommended as a 1 to 2-year research programme, along with research on existing nature-development projects to be used as model systems for medium-term research programmes. For long-term research priority will be given to monitoring, process research and model integration.
    • Research at the Speulder forest: assessment of the effects acidification , eutrophication and ozone

      Erisman JW; Draaijers GPJ; Steingrover E; Dijk H van; Boxman A; Vries W de; LLO; IBN-DLO; KUN; SC-DLO (1995-12-31)
      Within the framework of the Dutch Priority Program on Acidification, 10 years of research was conducted at the Douglas fir Speulder forest. The aim of the combined research was to determine the exposure and loads of acidifying and eutrophying pollutants, as well as their harmful influence on the vitality of Douglas fir trees and the forest ecosystem as a whole. Research was conducted to establish the levels and loads of acidifying pollutants and ozone, to determine forest characteristics and follow growth parameters and nutrient status in time and to determine the effects of reduction of loads and levels by manipulation experiments. In this report the results of 10 years of research are used to assess the causal relation between loads and levels on the one hand and effects on the other. For this, critical levels and critical loads were determined specifically for the Speulder forest, and the evolution of its exceedance was assessed. These exceedances were compared to the observed effects, which are defined as ecosystem changes as a result of environmental impacts.