Modelling spatial patterns of correlations between concentrations of heavy metals in mosses and atmospheric deposition in 2010 across Europe

Background

This paper aims to investigate the correlations between the concentrations of nine heavy metals in moss and atmospheric deposition within ecological land classes covering Europe. Additionally, it is examined to what extent the statistical relations are affected by the land use around the moss sampling sites. Based on moss data collected in 2010/2011 throughout Europe and data on total atmospheric deposition modelled by two chemical transport models (EMEP MSC-E, LOTOS-EUROS), correlation coefficients between concentrations of heavy metals in moss and in modelled atmospheric deposition were specified for spatial subsamples defined by ecological land classes of Europe (ELCE) as a spatial reference system. Linear discriminant analysis (LDA) and logistic regression (LR) were then used to separate moss sampling sites regarding their contribution to the strength of correlation considering the areal percentage of urban, agricultural and forestry land use around the sampling location. After verification LDA models by LR, LDA models were used to transform spatial information on the land use to maps of potential correlation levels, applicable for future network planning in the European Moss Survey.

Results

Correlations between concentrations of heavy metals in moss and in modelled atmospheric deposition were found to be specific for elements and ELCE units. Land use around the sampling sites mainly influences the correlation level. Small radiuses around the sampling sites examined (5 km) are more relevant for Cd, Cu, Ni, and Zn, while the areal percentage of urban and agricultural land use within large radiuses (75–100 km) is more relevant for As, Cr, Hg, Pb, and V. Most valid LDA models pattern with error rates of <?40% were found for As, Cr, Cu, Hg, Pb, and V. Land use-dependent predictions of spatial patterns split up Europe into investigation areas revealing potentially high (=?above-average) or low (=?below-average) correlation coefficients.

Conclusions

LDA is an eligible method identifying and ranking boundary conditions of correlations between atmospheric deposition and respective concentrations of heavy metals in moss and related mapping considering the influence of the land use around moss sampling sites.

     

Multivariate Patterns of Antioxidative and Photoprotective Defence Compounds in Spruce Needles at Two Central European Forest Sites of Different Elevation

In this work we measured a set of antioxidative and photoprotective compounds (chlorophylls, carotenoids, tocopherol, ascorbate and glutathione), which were suggested previously as stress markers in conifer needles, at two spruce forest sites at different elevation in Saxony, Germany. Most variables differed significantly between current and 1-year-old needles, but only the content of the xanthophyll cycle per mg total chlorophyll and the oxidation state of glutathione were significantly different between the sites. We applied principal component analysis (PCA) to address the question if underlying accumulated variables are similar to the ones found in spruce needles across Alpine elevation profiles and/or for pines in Mediterranean ecosystems. Four principal components (accumulated variables, PC) representing 68% of the total variance of the dataset were extracted. PC 1 encompassed total chlorophyll, lutein, and β-carotene contents, PC 2 combined the epoxidation state of xanthophylls, ascorbate content and redox state, and glutathione content, PC 3 represented the content of xanthophylls and the redox state of glutathione, and PC 4 encompassed the content of α-carotene and the epoxidation state of xanthophylls. Only PC 3 was significantly different between sites. The PCA structure shows many similarities to corresponding findings in studies on spruce in mountain forests in the Alps and pines in Mediterranean systems. This corroborates the interpretation of PCs as indicative for underlying physiological processes. However, separation of the two investigated sites by PCs was in the present case study not superior to the separation by single input variables.     

Crown condition dynamics of oak in southern Sweden 1988’999

Crown defoliation of oak (Quercus robur and Q. petraea) was analysed in 808 trees during three forest condition surveys (1988, 1993, and 1999) in the southern Sweden. From 1988 to 1999 crown defoliation increased by more than 20%. Changes in crown defoliation were related to the pH in the upper 20–30 cm of the mineral soils, which was closely connected to other measures of soil fertility (cation exchange capacity, CEC and C/N ratio). Trees growing on soils with a high pH (≥4.00, in BaCl₂ filtrate), high CEC and low C/N ratio had significantly lower crown defoliation than trees growing on more acid soils (pH <4.00), indicating that less favourable soil conditions may further enhance oak decline. Age did not differentiate trees with respect to crown defoliation, indicating that decline in crown condition was not due to an age-related increase in crown transparency. Considering only trees younger than 100 years, a significant interaction was observed between changes in crown defoliation and soil pH. Trees younger than 100 years old growing on more acidic soils had a greater increase in crown transparency than trees on more basic soils between 1988 and 1999. Trees ≥100 years old had significantly higher defoliation on more acidic than on more basic soils, however defoliation dynamics of these trees over 1988–99 was not related to soil acidity. Two biotic agents (insect and fungal leaf infections) evaluated in this study did not prove to be important drivers of defoliation dynamics.     

Modelling the spatial population dynamics of the green oak leaf roller (Tortrix viridana) using density dependent competitive interactions: Effects of herbivore mortality and varying host-plant quality

Cyclic population dynamics of forest insects with periods of more than two generations have been discussed in relation to a variety of extrinsic and intrinsic forces. In the present study, we employed the selection pressure of density dependent competitive interactions according to Witting's equations (Witting, 2000) as driver for a discrete spatiotemporal model of the green oak leaf roller (Tortrix viridana). The model was successfully parameterised to rebuild the cyclic population dynamics of an empirical data set of a 30-year leaf roller monitoring in Russia. Our analysis focussed on the role of herbivore mortality and host plant food quality, which have a significant effect on T. viridana population dynamics. An additional egg or larvae mortality lowers population density and can lead to selection pressures that favour individuals with higher growth rate. This increased population growth rate can not only compensate the additional mortality, but also can lead to higher average moth abundances in subsequent generations. Furthermore, we analysed the effect of inter- and intraspecific variation in host plant quality on herbivore population dynamics and the spatial distribution of abundance and defoliation patterns. We found significant effects of the qualitative composition of a trees neighbourhood on the herbivore population of the respective tree. Also, the patchy damage patterns observable in reality have been reproduced by the present model. The applicability of the model approach and the putative genetic processes underlying Witting's model are discussed.     

Soil microbes drive the classic plant diversity-productivity pattern

Ecosystem productivity commonly increases asymptotically with plant species diversity, and determining the mechanisms responsible for this well-known pattern is essential to predict potential changes in ecosystem productivity with ongoing species loss. Previous studies attributed the asymptotic diversity-productivity pattern to plant competition and differential resource use (e.g., niche complementarity). Using an analytical model and a series of experiments, we demonstrate theoretically and empirically that host-specific soil microbes can be major determinants of the diversity-productivity relationship in grasslands. In the presence of soil microbes, plant disease decreased with increasing diversity, and productivity increased nearly 500%, primarily because of the strong effect of density-dependent disease on productivity at low diversity. Correspondingly, disease was higher in plants grown in conspecific-trained soils than heterospecific-trained soils (demonstrating host-specificity), and productivity increased and host-specific disease decreased with increasing community diversity, suggesting that disease was the primary cause of reduced productivity in species-poor treatments. In sterilized, microbe-free soils, the increase in productivity with increasing plant species number was markedly lower than the increase measured in the presence of soil microbes, suggesting that niche complementarity was a weaker determinant of the diversity-productivity relationship. Our results demonstrate that soil microbes play an integral role as determinants of the diversity-productivity relationship.     

Driving anger expression in Germany—Validation of the Driving Anger Expression Inventory for German drivers

Objective: The main objective of this article is to examine whether the Driving Anger Expression Inventory (DAX) applies to German drivers because this scale has previously been given to drivers in many different countries.

Methods: We applied German versions of the DAX, the Driving Anger Scale (DAS), and the State-Trait Anger Expression Inventory (STAXI) to a sample of 501 German drivers. We computed confirmatory factor analysis and principal axis factoring (PAF) analysis to examine the structure of driving anger expression in Germany. Finally, we related the drivers’ anger exp ression scores to their driving anger experiences and their general anger propensities to assess the validity of the DAX for German drivers.

Results: Results indicated that the DAX’s original factor structure does not apply to German drivers because the confirmatory factor analysis did not show a good model fit. An item analysis revealed that many DAX items had no meaningful variability. They were excluded from further analysis. The subsequent PAF analysis indicated that German drivers do not use personal physical aggression to express their driving anger. Instead, they reported unique preventive anger expression management behavior. In addition, their driving anger expressions were significantly related to their driving anger experiences and their general anger propensities indicated the validity of the refined DAX for German drivers.

Conclusions: We conclude that German drivers do not use strong behaviors to express their driving anger. Many statements of Deffenbacher et al.’s (Behav Res Ther. 40:717–737, 2002) original American questionnaire were not applicable for our sample of German drivers. These findings are in line with several other studies showing discrepancies in driving anger expression in various countries. Future investigations should examine the reasons for discrepancies in driving anger expression.