Nitrogen deposition :: Hedgerows

Effects and implications

  • Loss of sensitive lichen species

Overview: evidence, processes and main impacts

Hedgerows can support N sensitive epiphytes. Species diversity is often restricted by the absence of a source of appropriate seed, caused by the use of highway management herbicides, and cutting restricting seed and berry production.

Hedgerows containing evergreens will be sensitive to ammonia, especially during the winter when low temperatures compromise assimilation leading to toxicity and exacerbation of winter desiccation.

Pollutant type and risk

Type of N deposition

Form of N

Risk areas

Dry deposition

Gaseous

NH3

Hedgerows in rural areas with elevated background concentration.  Higher dry deposition is found close to point sources e.g. intensive livestock units.

 

NOx

Hedgerows close to combustion plants, and major roads and urban areas.

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
Broadleaved deciduous woodland G1

10-20 kg N ha-1 year-1

 UNECE 2010 - Noordwijkerhout workshop reliable

Changes in soil processes, nutrient imbalance, altered composition mycorrhiza and ground vegetation.

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