We evaluated the effect of acidic deposition and nitrogen on Austrian forests soils. Until thirty years ago air pollution had led to soil acidification, and concerns on the future productivity of ...forests were raised. Elevated rates of nitrogen deposition were believed to cause nitrate leaching and imbalanced forest nutrition. We used data from a soil monitoring network to evaluate the trends and current status of the pH and the C : N ratio of Austrian forest soils. Deposition measurements and nitrogen contents of Norway spruce needles and mosses were used to assess the nitrogen supply. The pH values of soils have increased because of decreasing proton depositions caused by reduction of emissions. The C : N ratio of Austrian forest soils is widening. Despite high nitrogen deposition rates the increase in forest stand density and productivity has increased the nitrogen demand. The Austrian Bioindicator Grid shows that forest ecosystems are still deficient in nitrogen. Soils retain nitrogen efficiently, and nitrate leaching into the groundwater is presently not a large-scale problem. The decline of soil acidity and the deposition of nitrogen together with climate change effects will further increase the productivity of the forests until a limiting factor such as water scarcity becomes effective.
To evaluate a new N-monitoring program in the framework of the UN-ECE ICP-Vegetation program using mosses as bioindicators, 490 moss samples were collected at 220 sites in Austria and analyzed for ...total N (N content) and delta(15)N signatures. Within-site variability of N content and delta(15)N signatures was tested for the first time on a large scale and was extremely low compared to between-site variability. N content in moss tissue ranged between 0.76% and 1.99% and delta(15)N signatures between -10.04 and -2.45. Altitude was significantly correlated with N content (P=0.021) and delta(15)N signatures (P<0.001). When comparing moss data to deposition data from 35 measurement sites, significant correlations between N content and N deposition (P=0.014) were found. Increasing delta(15)N signatures provided evidence for a change in N source and its respective isotopic composition with altitude, e.g., due to long-distance transport of reactive N or as a result of changes in the wetdry deposition ratio. Our study underlines that N deposition can generally be estimated by N content in mosses on a large scale, but that this approach has certain limitations, especially in areas with large differences in altitude and precipitation.
We modeled the behavior of an Austrian alpine forest ecosystem on calcareous soils under changing climate and atmospheric nitrogen deposition scenarios. The change of nitrate leaching, emission rates ...of nitrogen compounds, and forest productivity were calculated using four process-oriented models for the periods 1998-2002 and 2048-2052. Each model reflects with high detail a segment of the ecosystem: PnET-N-DNDC (photosynthesis-evapotranspiration-nitrification-denitrification-decomposition; short-term nitrogen cycling), BROOK90 (water balance for small and homogenous forest watersheds), HYDRUS (water flux in complex and heterogenous soils), and PICUS v1.3 (forest productivity). The nitrogen balance model (NBM) combines the individual results into a comprehensive picture and extends the specific values beyond the limits of the individual models. The evaluation of the findings was outlined with TRACE, a model enabling a long-term prognosis of nitrogen cycling in annual time steps. Temperature increase and nitrogen input are influenced by various components and processes of the forest ecosystem. An increase of the temperature of 2.5 degrees C led to an enhancement of the N2O emission rates and affected the mineralization and the nitrification rates with the consequence of increased nitrate leaching into the subsoil. Enhanced nitrogen input also showed notable effects on nitrate leaching.
The present paper describes air pollution status and evaluation of risks related to effects of phytotoxic pollutants in the Austrian mountain forests. The results are based on Austrian networks ...(Forest Inventory, Forest Damage Monitoring System, Austrian Bioindicator Grid), the Austrian sample plots of the European networks of the UN-ECE (ICP Forests, Level I and Level II) and interdisciplinary research approaches. Based on the monitoring data and on modelling and mapping of Critical Thresholds, the evaluation of risk factors was possible. Cause–effect relationships between air pollution and tree responses were shown by tree-physiological measurements. Sulfur impact, proton and lead input, concentrations of nitrogen oxides, nitrogen input and ozone were evaluated. The risk was demonstrated at a regional and large-scale national level. Especially the increasing O
3 level and the accumulation of Pb with altitude present most serious risk for mountain forests.
Despite strong reduction of emissions in Europe, pollutants are still a potential stress factor, especially for sensitive mountain forest ecosystems in Austria.
The intensive investigation site 'Mühleggerkopfl' in the North Tyrolean Limestone Alps can be classified as a clean-air area site. The mean concentrations of NOx are far below the effect-related ...limit value of the WHO (30 microg NOx m(-3)). The gravitational depositions in the open field (bulk deposition) ranged from 10.8 to 14.7 kg N ha(-1) a(-1) (throughfall: 11.3 to 12.3 kg N ha(-1) a(-1)) in the measuring years 1998 to 2000. Compared to these data, depositions in other forested areas of the Austrian Alps amounted to up to 30 kg N ha(-1) a(-1). The gravitational depositions (bulk deposition) alone--without considering dry and occult deposition slightly exceeded the lower limit of Critical Loads for coniferous and deciduous forests (>10 kg N ha(-1) a(-1)), but were below the Critical Loads for calcareous forests (15-20 kg N ha(-1) a(-1)).
The intensive investigation site 'Mühleggerköpfl' in the North Tyrolean Limestone Alps can be classified as a clean-air area site. The mean concentrations of NO^sub x^ are far below the ...effect-related limit value of the WHO (30 μg NO^sub x^ m^sup -3^). The gravitational depositions in the open field (bulk deposition) ranged from 10.8 to 14.7 kg N ha^sup -1^ a^sup -1^ (throughfall: 11.3 to 12.3 kg N ha^sup -1^ a^sup -1^) in the measuring years 1998 to 2000. Compared to these data, depositions in other forested areas of the Austrian Alps amounted to up to 30 kg N ha^sup -1^ a^sup -1^. The gravitational depositions (bulk deposition) alone - without considering dry and occult deposition - slightly exceeded the lower limit of Critical Loads for coniferous and deciduous forests (> 10 kg N ha^sup -1^ a^sup -1^), but were below the Critical Loads for calcareous forests (15-20 kg N ha^sup -1^ a^sup -1^).PUBLICATION ABSTRACT
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