Nitrogen Deposition :: Maritime Cliff and Slopes

Effects and implications

  • Potential increase in graminoid (grass) biomass, with adverse effects on forbs.
  • Loss of sensitive lichen species

Overview: evidence, processes and main impacts

This habitat represents a range of different systems for which there is no known experimental information on the impacts of nitrogen deposition.

The habitats vary with climate, degree of exposure to salt, geology and soil type, level of grazing and seabird activity. These factors would imply a range of sensitivities to N deposition. Habitats dominated by N sensitive lichens e.g. rocky cliffs would be expected to be the most impacted by N.

Drought is often an issue for vegetation on shallow soils, so N deposition could exacerbate drought problems. Likewise inappropriate grazing management will exacerbate N eutrophication effects and N deposition may well exacerbate consequences of non native and invasive  species.

Many cliff habitats support large bird colonies which will substantially increase N deposition in the locality form of NH3 and P and K (guano) inputs in these environments.

Pollutant type and risk

Type of N deposition

Form of N

Risk areas

Dry deposition

Gaseous

NH3

Cliffs supporting breeding seabird colonies

 

 

NOx

Unlikely to be a problem

Wet deposition

precipitation and occult

(cloud, mist)

Ammonium, (NH4+)

Nitrate, (NO3-)

in varying proportions

High wet N deposition areas

Indicators of N enrichment

  • None available

Example evidence of species specific responses

  • None available

Critical Load/Level: 

Habitat/ Ecosystem Type Eunis Code Critical Load/ Level Status Reliability Indication of exceedance Reference
Low and medium altitude hay meadows E2.2

20-30 kg N ha-1 year-1

UNECE 2010 - Noordwijkerhout workshop expert judgement

Increase in tall grasses, decrease in diversity.

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