Pierre P. Kastendeuch

Classification of summer wind fields over complex terrain

In order to identify the representative flow patterns occurring in the Fecht Valley (region of Alsace, France) in summer, an automated wind-field classification is applied to wind observations collected during a field experiment. Fourteen meteorological stations placed at various topographic sites provided the necessary data on two scales. On the mesoscale of the Fecht Valley (230 km 2 ), the groups obtained by the classification reflect the diurnal and seasonal cycles of winds. On the microscale of the Ringelbach catchment (0 36 km 2 ), no diurnal cycle is observed in the sequence of the groups. Radiation balance and thermal forcing are the main factors governing the local flows during anticyclonic periods in the Fecht Valley, whereas external factors dominate the flow in the Ringelbach catchment area. A possible explanation for the different behaviour can be found in differences in scale, topography, and exposure between the two hydrological basins. On the basis of the classifications, the principal characteristics of the wind fields are studied and matrices of transition probabilities between wind fields are estimated. For climatic research in complex terrain, with its strong channelling of wind, an automated classification is helpful in the sense that it gives a realistic overview of the representative wind flows occurring in an area, without the need of any a priori knowledge. 1997 by the Royal Meteorological Society. Int. J. Climatol. 17: 521-534, 1997.

Variation in ectomycorrhizal fungal communities associated with Silver linden (Tilia tomentosa) within and across urban areas

Trees in urban areas face harsh environmental conditions. Ectomycorrhizal fungi (EcM) form a symbiosis with many tree species and provide a range of benefits to their host through their extraradical hyphal network. Although our understanding of the environmental drivers and large scale geographical variation of EcM communities in natural ecosystems is growing, our knowledge of EcM communities within and across urban areas is still limited. Here, we characterized EcM communities using Illumina miseq sequencing on 175 root samples of the urban tree Tilia tomentosa from three European cities, namely Leuven (Belgium), Strasbourg (France) and Porto (Portugal). We found strong differences in EcM richness and community composition between cities. Soil acidity, organic matter and moisture content were significantly associated with EcM community composition. In agreement, the explained variability in EcM communities was mostly attributed to general soil characteristics, whereas very little variation was explained by city and heavy metal pollution. Overall, our results suggest that EcM communities in urban areas are significantly associated with soil characteristics, while heavy metal pollution and biogeography had little or no impact. These findings deliver new insights into EcM distribution patterns in urban areas and contribute to specific inoculation strategies to improve urban tree vitality.

Vegetation reflectance spectroscopy for biomonitoring of heavy metal pollution in urban soils

Heavy metals in urban soils may impose a threat to public health and may negatively affect urban tree viability. Vegetation spectroscopy techniques applied to bio-indicators bring new opportunities to characterize heavy metal contamination, without being constrained by laborious soil sampling and lab-based sample processing. Here we used Tilia tomentosa trees, sampled across three European cities, as bio-indicators i) to investigate the impacts of elevated concentrations of cadmium (Cd) and lead (Pb) on leaf mass per area (LMA), total chlorophyll content (Chl), chlorophyll a to b ratio (Chla:Chlb) and the maximal PSII photochemical efficiency (Fv/Fm); and ii) to evaluate the feasibility of detecting Cd and Pb contamination using leaf reflectance spectra. For the latter, we used a partial-least-squares discriminant analysis (PLS-DA) to train spectral-based models for the classification of Cd and/or Pb contamination. We show that elevated soil Pb concentrations induced a significant decrease in the LMA and Chla:Chlb, with no decrease in Chl. We did not observe pronounced reductions of Fv/Fm due to Cd and Pb contamination. Elevated Cd and Pb concentrations induced contrasting spectral changes in the red-edge (690-740 nm) region, which might be associated with the proportional changes in leaf pigments. PLS-DA models allowed for the classifications of Cd and Pb contamination, with a classification accuracy of 86% (Kappa = 0.48) and 83% (Kappa = 0.66), respectively. PLS-DA models also allowed for the detection of a collective elevation of soil Cd and Pb, with an accuracy of 66% (Kappa = 0.49). This study demonstrates the potential of using reflectance spectroscopy for biomonitoring of heavy metal contamination in urban soils.