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Title: The effects of excess nitrogen deposition on Norway spruce : studies of nutrition, metabolism and soil acidification in relation to European forest decline
Author: Wilson, Emma Jane
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 1991
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Forest decline was first identified in Germany in the late 1970's and is now widespread throughout Europe. Recently, anthropogenic sources of nitrogen have been implicated in forest decline. This thesis describes an open-air spray experiment to investigate the effects of inputs of excess nitrogen on soil acidification and the nutrition and metabolism of Norway spruce (Picea abies L. Karst). N was applied as ammonium or nitrate in simulated rain to either the soil or the foliage to assess a) the response to different chemical forms of N, and b) the importance of foliar uptake and soil-mediated processes. Several experiments showed that Norway spruce was unable to utilise NO3 or NH4+ by foliar absorption, and root uptake appeared to be the main assimilation pathway for N. It is unlikely therefore, that wet-deposited N will accumulate in the foliage to toxic concentrations, or disrupt acid-base balance in the shoot. Excess N deposition may have deleterious effects on the nutrition of Norway spruce. NH4+ applied to the canopy and NO3- applied to the soil decreased the foliar concentrations of potassium and phosphorus, respectively. This may be significant for British upland forests where P status is often marginal. Inputs of (NH4)2SO4 to the soil reduced foliar concentrations of magnesium, and could induce a deficiency in Norway spruce on soils of low Mg status. There was no evidence for a role of NO3--N in the "Type 1" decline of Central Europe. The effects on mineral nutrition were supported by analyses of soil leachate which showed that soil acidification, base cation leaching and the mobilisation of acidic cations were greater in NH4+ than NO3- treatments. The implications of the Excess Nitrogen Experiment for canopy interactions, ''nitrogen saturation" and "critical loads" are considered.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available