Impact of nitrogen on British forests

New research to accurately map the UK’s nitrogen levels at a detailed level

News from Forest Research: July 2009

Throughfall collectors in a forest monitoring site

Nitrogen is essential to the health of the environment, but while some countries struggle to get enough, the UK as a whole has too much. Excess nitrogen can saturate the soil, leading to higher levels in water than are desirable and posing a risk to the nutrient balance and therefore the health of trees.

New research is being carried out to accurately map the UK’s nitrogen levels at a detailed level. The work also aims to understand the effects of excess nitrogen on forest and soil biochemistry and the impacts of nitrogen variability. Current national mapping indicates that the majority of UK broadleaf and conifer woodlands exceed the ‘critical load’ threshold for nitrogen deposition levels, above which it is thought that there may be undesirable effects on soils, vegetation and water. Despite this, widespread negative effects have not yet been widely seen except at woodland edges. The new smaller-scale research will determine if national critical load maps could be overestimating the proportion of UK woodlands at risk from excess nitrogen. These evaluations will help to estimate nitrogen impacts for different sizes of forest blocks and improve critical load modelling by taking into account woodland size, shape and proximity to nitrogen sources such as agriculture, farming and roads, especially in England where forest land is fragmented.

Nitrogen levels in the UK are predicted to remain high for some time, so this work will provide a valuable assessment of current concentrations and variability of nitrogen deposition, and also the forest and soil’s response. It is hoped that the results from this research will help contribute to future guidance on possible ways to minimise nitrogen impacts, such as different forest management techniques that may increase nitrogen absorption.

For more information contact Elena Vanguelova.

      

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This and other news stories can be found in the July 2009 issue of FR News, our online newsletter.