Description:
Description:
The gases NO and N2O are produced in soils by nitrifying and denitrifying bacteria, and the magnitude of the emissions is controlled by the availability of N as ammonium (NH4) or nitrate (NO3) and also by certain climatic and soil properties which promote nitrification or denitrification, e.g. temperature, rainfall, organic matter content (Skiba & Smith 2000).
Description:
Description:
Where plant growth may be limited by P availability or when enhanced N deposition may lead to reduced availability and/or uptake, measurements of the N:P ratios in selected species may provide a better indication of N saturation. Optimum N:P ratios for plant growth range from 10-14 (van den Driesshe, 1974; Ingestad, 1979). Low ratios (<10) indicate N limited growth and high ratios (>14) indicate P limitation (Koerselma & Meuleman, 1996).
Previous experience:
Description:
Description:
The VDI approach is a standardized German method that was devised to assess changes in lichen communities over wide geographical areas in order to assess the influence of air pollution in Central Europe. The method is based on the frequency of occurrence of selected widespread lichen species within a unit area on selected tree trunks.
Description:
A method developed in Italy to assess deviation from natural lichen diversity on trees in sites within a homogeneous bioclimatic area. LD is calculated using the sum of frequencies on trees of the same species within 10 samples of units 15 cm x 10 cm (30 cm x 50 cm) and the mean calculated from the number of relevees. A 5-scale class of deviation from naturality is based on % deviation from the natural LD values in the area and can be correlated with climatic, land management and pollution data. Loppi et al. (2003)
Description:
