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:
Insect pests: It is generally thought that the increased infestations of insect pests particularly sucking insects, observed following N addition from the atmosphere or as fertiliser, is a response to increased N content of the plants. While the presence of certain pests may indicate an effect of N deposition, their absence does not indicate the lack of an effect and the introduction of pests in order to observe change is not acceptable.
Description:
The ability of plants to minimise the risk of freezing damage is conferred by sychronising their phenology with the growing environment. The indigenous flora generally has a good safety margin between its frost hardened status and minimum temperatures, unless the growth environment changes. A negative link between enhanced N deposition and reduced frost hardiness was widely suspected to be a casual factor in the observed decline of red spruce in the nineteen eighties (Eagar & Adams 1992).
Description:
Description:
