Großräumige Regionalisierung der Kohlenstoffbindung in Wäldern Nordrhein-Westfalens

Background, aim and scope The United Nations Framework Convention on Climate Change understands carbon fixation in forests as an important contribution for the reduction of atmospheric pollution in terms of greenhouse gases. According to the German forest inventory on carbon in biomass an amount of 191?t C/ha was roughly estimated, without any spatial differentiation. Therefore, the aim of this investigation was to statistically identify factors that are significant for the carbon fixation and to map the spatial patterns of C sequestration in the federal state North Rhine-Westphalia. Materials and methods Together with information on climate, elevation, vegetation, and deposition, data from two forest monitoring networks were analysed statistically. Geostatistics and the decision tree algorithms Classification and Regression Trees (CART) and Chi-Square Automatic Interaction Detection (CHAID) were applied to calculate surface maps from punctual data on C in vegetation, in dead wood and in soil. Whereas spatial autocorrelation could be detected for the C loads in the humus layers, no surface maps could be calculated for the C contents of the mineral soils and for the forest trees/dead wood. Here, CART and CHAID were used to derive decision trees that were applied on available surface data to predict C loads for the entire study area. Results About 19?t C/ha could be predicted for the humus layer, 67?t C/ha for forest trees/dead wood and 90.7?t C/ha for the soil. An overall mean of 177?t C/ha was calculated for North Rhine-Westphalia lying 14?t C/ha below the German wide mean. Discussion Compared to the calculated results in another investigation a total of 68?mio. t C for the above ground dendromass was estimated. This is 11?mio. t C/ha higher than the amount calculated in this study and may be due to the fact that this value includes the C-pools in both, the brushwood and herbaceous layer in their estimations. The average C concentration in the humus layer all over Germany was found to amount for 20.7?t C/ha which is slightly above the C storage calculated for North Rhine-Westphalia. In the same study a Germany wide C average of 87.9?t C/ha was calculated which is very close to the 90.7?t C/ha calculated in this study. Conclusions The surface estimations of the C-pools in the above-ground biomass, the humus layer and the mineral soil enable to map the efficiency of the C-bounding capacity regarding the fixation of the greenhouse gas CO₂. The mean values derived in this study are in good accordance with estimations based on other techniques. Recommendations and perspectives The approach presented should be verified by application to Germany wide inventory data and by means of Regression Kriging. Furthermore, the C-fixation under climate change should be calculated by combining statistical methods and the dynamic modelling tool WASMOD.     

Eine Weight-of-Evidence-Studie zur Bewertung der Sedimentbelastung und des Fischrückgangs in der Oberen Donau

Background and aim Despite intensive and continuous stocking and improvement of water quality since the 1970s, fish populations, especially those of the grayling (Thymallus thymallus), have declined over the last two decades in the upper Danube River (Germany). In order to assess 1) possible links between molecular/biochemical responses and ecologically relevant effects, and 2) if ecotoxicological effects might be related to the decline in fish catches in the upper Danube river, sediment samples and fish were collected at different locations and analyzed using a weight-of-evidence (WOE) approach with several lines of evidence. The objective of the presentation is to introduce the conceptual framework and to review results of the ongoing study. As previously addressed by Chapman and Hollert (2006) a variety of lines of evidence can be used in WOE studies. Briefly, 1) a comprehensive battery of acute and mechanism-specific bioassays was used to characterize the ecotoxicological hazard potential. 2) Histopathological investigations and the micronucleus assay with erythrocytes were applied, analyzing in situ parameters. 3) Diversity and abundance of benthic macroinvertebrates and fish as well as 4) persistent organic pollutants, endocrine disrupting substances, limnochemical parameters and the concentration of heavy metals were recorded. To identify organic contaminants a spotential causes of sediment toxicity assays, 5) effect directed analysis was applied.     

Is The Ca + K + Mg/Al Ratio in the Soil Solution a Predictive Tool for Estimating Forest Damage?

The ratio between (Ca +K +Mg) and Al in nutrientsolution has been suggested as a predictive tool forestimating tree growth disturbance. However, the ratiois unspecific in the sense that it is based on severalelements which are all essential for plant growth;each of these may be growth-limiting. Furthermore,aluminium retards growth at higher concentrations. Itis therefore difficult to give causal and objectivebiological explanations for possible growthdisturbances. The importance of the proportion ofbase-cations to N, at a fixed base-cation/Al ratio, isevaluated with regard to growth of Picea abies.The uptake of elements was found to be selective;nutrients were taken up while most Al remained insolution. Biomass partitioning to the roots increasedafter aluminium addition with low proportions of basecations to nitrogen. We conclude that the low growthrates depend on nutrient limitation in thesetreatments. Low growth rates in the high proportionexperiments may be explained by high internal Alconcentrations. The results strongly suggest thatgrowth rate is not correlated with the ratio in therooting medium and question the validity of usingratios as predictive tools for estimating forestdamage. We suggest that growth limitation of Picea abies in the field may depend on lowproportions of base cations to nitrate. It istherefore important to know the nutritional status ofthe plant material in relation to the growth potentialand environmental limitation to be able to predict andestimate forest damage.     

Does Soil Acidification Affect Spruce Needle Chemical Composition and Tree Growth?

In 1994, a large survey of soil chemistry was undertaken in thecounty of Värmland in central Sweden (Lundström et al., 1998).The southern part of the county was affected by soilacidification whereas there were no such indications in thenorthern part. To investigate the influence of soil chemistryon the trees at the specific sites, the survey was continued byan analysis of needle chemistry (Norway spruce) which wasundertaken at 150 of the 180 sites, and of tree growth at 65 ofthe 180 sites. Growth was expressed as a ratio between expectedgrowth, estimated with a national, empirical growth model, andthe growth observed in the field. In statistical analyses,using rank correlation, PCA and PLS, there were only weakindications of an influence of soil chemistry on needlechemistry and on tree growth. A moderate correlation betweennitrogen and sulphur in needles was found, which wasinterpreted as an effect of deposition and of processes in thetree canopy. No obvious regional pattern of the growth ratiowas found, in contrast to the clear pattern of soilacidification. The statistical analysis could not with anycertainty point out any of the soil chemistry variables asespecially important for the tree growth ratio.     

Dry Deposition Monitoring in Europe

Between 1993 and 1999 two EU funded projects wereexecuted aimed at (i) the development of drydeposition monitoring methods for core sites andlarge scale application, (ii) the installation andrunning of three core sites in Europe and (iii) the improvement and validation of models used forregional application. This article provides anoverview of the development of depositionmonitoring stations and the main results of thethree core sites, which were operated between1995 and 1998. Furthermore, the results of thedevelopment of a low cost monitoring system arepresented. Continuous measurements were made ofboth wet and dry deposition of sulphur andnitrogen components and base cations. The 4 yearsof data show a decrease in sulphur loads and notrend for the other components. It is shown thatthe surface affinities for sulphur depositionalso changed during the years, underpinning theneed for dry deposition monitoring. A conditionaltime average gradient system was successfullydeveloped and tested and provides a good meansfor low cost monitoring of dry deposition fluxes.The costs can be reduced by a factor of 3–4 without losing the accuracy of the annual average gas fluxes.     

Intraguild predation by <Emphasis Type="Italic">Harmonia axyridis</Emphasis> on coccinellids revealed by exogenous alkaloid sequestration

Summary.  Under laboratory conditions, the multicolored Asian lady beetle, Harmonia axyridis is well known as an intraguild predator of other ladybirds. However the real impact of this exotic species on native species was poorly investigated in the field. Because many ladybird species produce alkaloids as defensive compounds, we propose here a new method of intraguild predation monitoring in coccinellids based on alkaloid quantification by GC-MS. In laboratory experiments, adaline was unambiguously detected in fourth instar larvae of H. axyridis having ingested one egg or one first instar larva of Adalia bipunctata. Although prey alkaloids in the predator decreased with time, traces were still detected in pupae, exuviae and imagines of H. axyridis having ingested one prey when they were fourth instar larvae. Analysis of H. axyridis larvae collected in two potato fields shows for the first time in Europe the presence of exogenous alkaloids in 9 out of 28 individuals tested. This new method of intraguild predation detection could be used more widely to follow the interactions between predators and potential chemically defended insect preys.