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TRANSCRIPT
Effects of Ammonia on Terrestrial Vegetation
Speaker
Dr. Sagar KrupaUniversity of Minnesota
The Nitrogen Cycle
2NH4 + 3O2 → 2NO2 + 2H2O + 4H2NO2 + O2 → 2NO3
Source: Modified from Brady (1990) and Krupa (2003)
–NH2
Soil organic material
NO3–
NO2–
NH4+
(2N)
(1N)
Source: Modified from Fangmeier et al. (1994)
glutamate glutamate
glutamine
amino acidsproteinsmetabolism
glutamatesynthaseGOGAT
glutaminesynthaseGS
2-oxoglutarate
2e–, 2H+ NAD(P)H, Fdred
ATPNHy
ADPH2O, P1
Source: Modified fromGarrett and Grisham (1997)
(3N)(3N)
(4N)
(2N)
Summary Examples of Atmospheric NH3 Concentrations*
Forest fires350 ppb (250)Canada
Close to poultry farm bldg.650 m from bldg.
84 ppb (60)4.2 ppb (3.0)
UK
Winds from cattle feedlots, dairy and poultry farmsWinds from other directions
57 ppb (39.67)
<1–2 ppb (0.70–1.4)
California
2-year background meanAgricultural area: meanMaximum
0.37 ppb (0.26)2.16–2.88 ppb (1.5–2.0)11.62–16.66 ppb (8.3–11.9)
Alberta, Canada
Annual mean (1996–2000)0.085–15.40 ppb (0.06–11)
UK
Background mean<50 ppt (0.035)Remote
CommentConcentration**Location
*Source: Modified from Krupa (2003). **Values in parentheses are in µg m–3.
Summary Examples of Deposition Velocities (Vd) for NH3 and NH4
+ (cm s–1)*
0.50–1.5Tree species
0.44–0.60Herb
0.20BogNH4+
0.50–3.6Tree species
0.30–1.30.03–0.13
Different species (Day) (Night)
1.6Herb
0.10–1.9Bog
0.06–1.0SoilNH3
Range VdReceptorChemical Species
*Source: Modified from Krupa (2003).
Concentration gradientCompensation pointStomatal opening
Shoot uptake (NH3/NH4
+)
Root uptake (NH4
+)
Assimilation capacity
Developmental stage
Root NHy assimilation
Shoot NHy assimilation
NHy accumulation
N organic
NHy pool Toxicity
Primary effects
Secondary effects
Pathways and factors governing the effects of NH3 on plants.
Source: Modified from Fangmeier et al. (1994).
Summary Examples of Experimental NH3Exposures in Chambers or Greenhouse
Conditions in Vegetation Effects Studies*
~12~125–139Mycorrhizae
2021
~69~104
Frost hardiness
~12–3212
~35–70~140
Dry weight
~32–3~7
~21~167
~104–208
Visible foliar injury
323813
~35 ~69
~125–1250
N and nutrient content
Exposure Duration (Weeks)
Mean Exposure Concentration (ppb)
Parameter Measured
*Source: Modified from Krupa (2003).
Source: Krupa (2003)
Source: Krupa (2003)
Summary of Examples of Plant Responses to NH3 Exposures:
General Trends*, **
Visible injury (NH3 –O3)
Frost hardiness (NH3 –SO2)
Survival rate (NH3 –SO2)
Visible injury (NH3 –SO2)
MycorrhizaeFrost hardiness
Survival rateShoot : Root ratio
Height growthDry weight
Flowering0Visible foliar injury
Nutrient content (e.g., P, K)
N content
EffectParameterEffect***Parameter
*Source: Modified from Krupa (2003).**Most results based on chamber or greenhouse studies.*** = Increase, = Decrease, 0 = No change.
Selected Plant Species Very Sensitive to Acute or Visible NH3 – Induced Foliar
Injury*,**
Ambrosia artemisifolia
RagweedRhacomitriumlanuginosum
Moss
Others
Spirea vanhoutteiSpireaPopulus balsamiferaPoplar, balsam
Pinus strobusPine, whiteCrataegus spp.Hawthorn
Trees & Shrubs
Pisum sativumPeaBrassica oleraceaCauliflower
Phaseolus vulgarisBeanHordeum vulgareBarley
Crops
Latin NameCommon Name
Latin NameCommon Name
*Source: Modified from Krupa (2003).**There are a total of more than 150 plant species that contain cultivars, varieties and genotypes that are either sensitive or intermediate in their response.
Summary Examples of the Range of NH4+ –
N Deposition (kg ha–1 yr–1) in Open Fields and Under Different Plant Canopies*
1.7511.219.6Heather
2.0014.028.0Grass
2.5016.842.0Deciduous
2.70–6.809.2–14.130.1–95.6Conifer
Ratio (1): (2)***
Bulk Deposition (2)**
Canopy Deposition (1)**
Plant Species
*Source: Modified from Fangmeier et al. (1994).**Canopy deposition = Through-fall + stem-flow, Bulk deposition = open area.***Range calculated from individual data points.
Some Examples of N Saturated Forests in North America*
7.57.5–8.03000–4000
Alpine tundra, sub-alpine conifer
Front Range, CO
19.210.31800Red spruceGreat SmokyMt. Natl. Park, NC
47**32**1650Red spruceWhitetop Mt., VA
17.9–23.67.0–7.7 (as throughfall)
350–400Sugar maple, yellow birch
Turkey Lakes, ON, Canada
38.94.7 + >100 (N2 fixation)
220Red alderCascade Mts., WA
N Output(kg ha–1 yr–1)
N Input (kg ha–1 yr–1)
Elevation(m MSL)
Forest Type
Location
*Source: Modified from Fenn et al. (1998).**Values appear high. However, according to the specific authors, NO3
– concentrations in the soil solutions were high and there was a lack of tree growth response to N fertilization and therefore, N saturation.
Some Examples of Distribution and fate of NH4
+ - N Applied to Forest Ecosystems*
7.57.5–8.03000–4000Alpine tundra, sub-alpine conifer
Front Range, CO
19.210.31800Red spruceGreat Smoky Mts. Natl. Park, NC
0.04–1023.3580–1080Chaparral, grasslands
San Gabriel Mts., CA
Stage 1 N loss
9.3396–661Northern hardwoods, hardwood/conifer
Adirondack Mts., NY
38.94.7 + >100N2 fixation
220Red alderThompson Forest, Cascade Mts., WA
N output(kg ha–1
yr–1)
N input(kg ha–1
yr–1)
Elevation(m, MSL)
Forest TypeLocation
*Source: Modified from Fenn et al. (1998).
10–20Forests
5–10Heather, bogs
5–10Ombotrophic bogs
20–35Mesotrophic fens
10–15Montane-subalpine grassland
10–15Neutral-acid–species-rich grassland
14–25Calcareous species-rich grassland
5–15Arctic and alpine heaths
<20Species-rich heaths/acidic grasslands
17–22Lowland wet-heathland
15–20Lowland dry-heathland
<15–20Acidic (managed) deciduous forest
15–20Acidic (managed) coniferous forest
3–48Forests on calcareous soil
3–14Forests on silicate soil
Critical Load(kg N ha–1 yr–1)
Ecosystem
Critical Loads for Total N Deposition*
*Source: Modified from Fangmeier et al. (1994).
55Variability not accounted or variability accounted by parameters not measured
45Sub-total
n.s.Bark SO42-, NO3
-, NH4+
10Others (tree diameter, interactions)
2NH3
4Bark pH
9Tree species
5NO2
15SO2
% VarianceVariable
Importance of Environmental Variables with a Significant (p = 0.05) Effect on Lichens*
*Source: Modified from Van Dobben and Ter Braak (1998).
Adverse effect
Changes in inter-species competition due to N availability
Other environmental factors
Increase in bark pH
Soil acidification due to nitrification, mobilization of Al, increased N availability
Ammonia (NH3)
ToxicitySoil acidification, mobilization of Al and mobilization of transition metals within wood
Sulfur dioxide (SO2)
LichensHigher PlantsVariable
Fundamental Differences in the Effects of Atmospheric SO2 and NH3 on Terrestrial Higher Plants and Epiphytic Lichens*
*Source: Modified from Van Dobben and Ter Braak (1998).
“Critical Levels”
The concentrations of pollutants in the atmosphere above which direct adverse effects on receptors, such as plants, ecosystems or materials may occur according to
present knowledge (UN-ECE, 1988).
“Critical Loads”
A quantitative estimate of an exposure to one or more pollutants below which harmful effects on specified sensitive elements of the environment do not occur
according to present knowledge (Nilsson and Grennfelt, 1988).
1 year11.5 (8)
1 month29–72 (20–50)
1 day389–397 (270–276)
1 hour4752 (3300)
DurationNH3 – Concentrationppb (µg m–3)
Critical Levels (Exposures) for NH3*
*Source: Modified from Fangmeier (1994).
10–20 kg ha-1 yr-1 of Total (dry + wet) N
Deposition would protect forests (depending on the soil conditions)
5–10 kg ha-1 yr-1 of Total (dry + wet) N
Deposition would protect heaths, bogs, cryptogams, etc.
Critical Loads for Total N Deposition (Summary)
Atmospheric Ammonia Eco-toxicology: Terrestrial Vegetation
1. Air Concentrations: Expected No Effects Value (ENEV)
NH3 concentration 48 µg m-3 = Load Flux 24–290 kg N ha-1 yr-1
2. ENEV – Mean Compensation Point (ENEVcp)
5.1 µg m-3 = Load Flux 4.8–58 kg N ha-1 yr-1
3. Critical Load Threshold Flux Density
10 kg N ha-1 yr-1
(Sheppard, 2002)
10–20 kg N ha-1 yr-15–10 kg N ha-1 yr-1
2. Forests1. Most Sensitive Ecosystems
Critical Loads