consequences of nitrogen deposition to rocky mountain
TRANSCRIPT
Consequences ofNitrogen Deposition to
Rocky Mountain National Park
Jill S. Baron, US Geological Survey
M.Hartman, D.S.Ojima, K. Nydick, H.M. Rueth
B.Moraska Lafrancois, A.P. Wolfe, J. Botte, W.D. Bowman
Life is Short – Have Conclusions First!
• Nitrogen deposition is higher on the EAST side of Rocky Mountain National Park
• On the east side of the Front Range we have observed:– Changes in alpine tundra vegetation– Increased uptake of N by trees– Faster rates of soil nitrogen cycling– High year-round lake and stream N
concentrations – Large changes in algal composition,
beginning ca. 50 years ago
• Context: why care about nitrogen?
• Long-term research in and around Rocky Mountain National Park: how we know what we know
• The cascade of nitrogen deposition effects
• Research results
Why care about nitrogen?
• Nitrogen is necessary for life• Most N on Earth is in a form
unusable by living organisms• The Green Revolution
occurred largely due to synthetic N fertilizers
• Humans depend on fossil fuels for transportation and energy
• Thus, to sustain human life, we convert unusable N to reactive forms.
Nitrogen in the environment• All of the reactive N
created by fossil fuel combustion enters the environment.
• Ammonia from agriculture, especially animal feedlots, enters the environment
• Nitrogen is accumulating in the environment
NO3 NH4 NOx
NO NO2 NH3 NOx
NH3
More nitrogen is now fixed by human activities than by natural processes
Vitousek et al.
Nitrogen accumulation contributes to:
• Acid deposition• Coastal dead zones• Lake and river eutrophication• Unnatural rates of forest
growth• Loss of biodiversity• Smog• Greenhouse effect• Stratospheric ozone depletion
High N waters
Altered plant communities
(plants, lichens,fungi)
In the West, Ecological Effects are Found Adjacent to Urban and Agricultural Areas
Fenn et al. 2003
Increased InvasiveSpecies and Altered Fire
Regime
Colorado population and emissions trendsColorado Population
0500,000
1,000,000
1,500,0002,000,0002,500,0003,000,0003,500,000
4,000,0004,500,0005,000,000
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
US Census Bureau
NOx emissions, CO and West/10
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Thou
sand
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US EPA
CO population vs emissions
y = 1E-04x - 36.305R2 = 0.9081
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0 1,000,000 2,000,000 3,000,000 4,000,000 5,000,000
Nitrogen oxide emissions are very tightly related to population.
The Continental Divide separatesairsheds in Rocky Mountain National Park
Spring/summer upslope winds move
Front Range air to mountains
• Context: why care about nitrogen?
• Long-term research: how we know what we know
• The cascade of nitrogen deposition effects
• Research results
Foundations
• 23+ years of long-term monitoring in Loch Vale Watershed
• Experiments in field and lab to test cause and effect
• Modeling of ecosystem processes and “what-if” scenarios
• Spatial comparisons in Colorado and across western US
Long-term Program Objectives
• To understand and differentiate natural processes from unnatural, human-caused drivers of change
• To understand and quantify the effects of atmospheric deposition on high elevation ecosystems
• To share knowledge with managers so they are better informed
Our equipment is sturdy and Park Service Brown
Rain Gages
NADP Buckets
Stream GageSoil Lysimeter
Loch Vale Research has been widely reviewed and published
• 78 Journal Papers• 26 Graduate Degrees• 1 Loch Vale Book• 1 Special Journal
Section• 9 Methods and QA
Reports• 154 Total Publications
• Context: why care about nitrogen?
• Long-term research: how we know what we know
• The cascade of nitrogen deposition effects
• Research results
Pathways and Effects of Excess Nitrogen Deposition
N Deposition
FertilizationLoss of Soil
Buffering
Changes in Aquatic Species
LakeEutrophication
Loss of Lake ANC(acidification)
N SaturationChanges inPlant Communities
• Context: why care about nitrogen?
• Long-term research: how we know what we know
• The cascade of nitrogen deposition effects
• Research results
In the alpine nitrogen favors sedges and grasses over flowering plants
Niwot Ridge researchshows sedges and
grasses grow better with N than flowering plants in both experiments and surveys(Korb and Ranker 2001; Bowman et al. in review)
East-side forests are closer to N saturation
Six pairs of sites were similar in all
characteristics except for N deposition amount
East side stands differed significantlyfrom west side forests: - higher needle and soil N, - lower C:N ratios, - higher soil N cycling rates
Experimental Fertilization of Small Forest Plots
Effects
- nitrate leached from soils => symptom of saturation
- base cations leached from soils => depletes soil buffering capacity and fertility
Rueth et al. 2001, Geick et al. in prep
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Min
eral
izat
ion
Rat
e (u
g N
/g/d
)
0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6Organic Soil %N
FC-WBR-W
BC-W WR-W
WA-W
LL-E
BP-E
MP-E
ER-E
GF-W
LV-EML-E
R2=0.62
As soils accumulate N, microbial activity increases
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%N Forest Floor
Nitr
ifica
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ugN
/g/dColorado Front Range
Baron et al. 2000Rueth & Baron 2001 Similar patterns in
New England, USAMcNulty et al. 1991
East-side lakes have higher N concentrations
Means (ueq/L)
East 10.5 (5.0) West 6.6 (4.3)
n=44, p = 0.02
Baron et al. 2000
Lake Sediments serve as Proxies for Past Environmental Change
Wolfe et al., 2001, 2003, Baron et al. 1986
Diatoms are good indicators of environmental change
• Diatoms are algae: single-celled aquatic plants
• Species are very sensitive to water chemistry
• Glass (silica) cell walls do not decompose
• Each species has unique cell walls
Diatom Indicators of Disturbance IncreasedAbruptly in east-side lakes ca. 1950-1960
Sky Pond
1950
Asterionella formosa Fragillaria crotonensis Aulacoseira spp.
Lakes Have Changed More Since 1950 than Previous 14,000 Yrs
The rate of change in diatoms post-1950 is an order of magnitude greater than any change since Pleistocene.
The abundance of diatoms is 8-25x greater post-1950.
Caused by dominance of 2 disturbancespecies: Asterionella formosa and Fragilaria crotonensis. >40% of total diatoms since 1950
A. formosa and F. crotonensisare indicators of nutrient-rich waters
Experiments with Bioassays (Bottles), Mesocosms (Hula Hoops),
and Lakes
Lafrancois et al. 2003, 2004, Nydick et al. 2003, 2004a, b
Experiments: Productivity increased with added N and N+P. Communities changed to nutrient-loving algae.
Chrysophytes
Green Algae
N Additions = Eutrophication
increased productivitychanged algal community
Dinobryon sp.
Chlamydomonas sp.
Summary of Research Results
N Deposition
FertilizationLoss of Soil
Buffering
Changes in Aquatic Species
LakeEutrophication
Loss of Lake ANC(acidification)
N SaturationChanges inPlant Communities
Phew! We made it! Conclusions
• Nitrogen deposition is higher on the EAST side of Rocky Mountain National Park
• On the east side of the Front Range we have observed:– Changes in alpine tundra vegetation– Increased uptake of N by trees– Faster rates of soil nitrogen cycling– High year-round lake and stream N
concentrations – Large changes in algal composition,
beginning ca. 50 years ago– Acidification has not yet occurred
http://www.nrel.colostate.edu/projects/lvws/
Human Dominance of Earth System
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Perc
ent c
hang
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LandTransformation
CO2Concentration
WaterUse Nitrogen
Fixation
Plant Invasion
Bird Extinction
MarineFisheries
Vitousek et al. 1997