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