Published on: Mar 4, 2016
Transcripts - Pollutants
POLLUTANTS AND FOREST HEALTH
Air pollutants may impact trees as both wet and dry deposition.
Wet deposition -rain, hail, and snow, and is largely determined by atmospheric
Dry deposition - gases, aerosols, and dust, and is largely influenced by physical and
chemical properties of the receptor surface
air pollutants- sulphur compounds, nitrogen compounds, ozone and heavy metals.
Sulphur dioxide (SO2) was the first air pollutant found to cause damage to trees
damaging trees directly via their foliage
SO2 + H20 sulphurous acid (H2SO3) and sulphuric acid(H2SO4)
formation of acid precipitation
indirect damage of trees
The direct effects of O3, SO2, NO2, and NH3 include visible leaf damage, a decrease in
the number of needle age classes in conifers, and elevated pollutant concentrations in
Indirect effects include soil acidification, which results in leaching of base cations,
thereby releasing toxic species of aluminium (Al).
Air pollution causes water and nutrient imbalances and higher sensitivity to frost,
droughts, insect pest attacks, and fungal diseases.
Elevated levels of N-compounds contribute to eutrophication.
N is usually the growth-limiting nutrient in forest and semi-natural terrestrial
ecosystems, chronic excess of N can lead to saturation manifested by increased
leaching of inorganic N (generally nitrate).
Increased leaching of nitrate enhances acidification of soils and surface waters, and the
risk of eutrophication of coastal marine areas and groundwater quality.
N enrichment has been shown to increase fungal and bacterial diseases of foliage
(Snoeijers et al. 2000).
Nitrogen fertilisation has also been shown to increase root rot of eucalyptus caused by
Phytophthora species (Marks et al. 1973).
O3 can cause significant effects on photosynthesis of broadleaved species (–10%) and
has less to no effect on conifers (Wittig et al. 2007)
O3 gives conifers an advantage in mixed deciduous forests that can lead to changes in
Fast-growing pioneer species, such as birch, aspen, and poplar, have been shown to be
more O3-sensitive than climax species, such as beech and oak (Matyssek et al. in press).
Plants emit isoprene into the air with high NOx concentrations,O3 levels can increase.
the damaging effects of O3 are ameliorated by isoprene (Velikova and Loreto 2005, Loreto
and Fares 2007).
Isoprene -producing taxa may become more abundant because of their greater resistance
O3 decreases global plant productivity (GPP) by more than 20% in 17 of the world’s
priority-conservation ecoregions (G200), covering an area of 1.4 million km2
The combined effects of SO2 and heavy metal pollution and fire result in the
replacement of coniferous forests by birch forests, which have a different albedo and
An increase in the production of O3 is influenced by increased temperature,
increased sunlight, decreased humidity (all components of climate change), and the
increase in long-range transport of pollutants.
NOx and NH3 as well as HNO3 vapor may have direct phytotoxic effects but only at high
concentrations (Bytnerowicz et al., 1999).
O3 has the highest phytotoxic potential and is predicted that by 2100 half of the World’s
forest will be exposed to phytotoxic O3 levels (Fowler et al., 1999).
Climate change parameters that trigger stomata opening (e.g., increasing temperature)
increase the sensitivity of plants to APs like SO2 and O3.
O3 slows the stomatal response to reduced water availability (Paoletti, 2005).
Climate change parameters that lead to a longer growing season (e.g., warming) increase
the exposure of plants to APs like SO2 and O3, whereas parameters that shorten the
growing season (e.g., water stress) reduce the exposure and damage (Guardans, 2002).
multi-effect problem extended towards radiative forcing (EEA, 2004b).
SO2 Nox NH3 VOC CO PM CH4 CO2 þ GHGs
Acidification X X X
Eutrophication X X
Surface ozone X X X X
Direct X X X
Via aerosols X X X X X
Via OH X X X X