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
Nitrogen Deposition :: Broadleaved deciduous woodland
Critical Load/Level Values
10-20 kg N ha-1 year-1
Status
UNECE 2010 - Noordwijkerhout workshop
Habitat/Ecosystem Type
Broadleaved deciduous woodland
Description
Changes in soil processes, nutrient imbalance, altered composition mycorrhiza and ground vegetation.
Reliability
reliable
Eunis
G1