![Page 1: Eric Bird Purdue University Calumet Flora Richardson Fellowship Recipient](https://reader036.vdocuments.us/reader036/viewer/2022062410/56816359550346895dd4137d/html5/thumbnails/1.jpg)
Investigating the mechanisms by which available nitrogen affects biodiversity of a plant community native to the Indiana Dunes
National Lakeshore
Eric BirdPurdue University Calumet
Flora Richardson Fellowship Recipient
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Concern
• Atmospheric deposition of nitrogen is high in the Midwestern and Eastern United States
• The Indiana Dunes receive approximately 15kg ha-1 y-1 nitrogen as wet deposition
• Research has shown that increases in available nitrogen to low nitrogen ecosystems affects species composition and can have an overall negative affect on biodiversity
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Preliminary research shows that ammonium nitrate treatment
• Reduces the total biomass of some species
• Alters how species allocate biomass (aboveground vs. belowground)
• Reduces the germination success of some species
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Setup
• Use laboratory experiments to determine which species are hindered by nitrogen treatment and…
• Use this information to predict which species will occur less frequently in a constructed native plant community grown in the field against a gradient of available nitrogen
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Species investigated• Schizachyrium scoparium – little bluestem grass• Elymus canadensis – Canada wild rye• Panicum virgatum – switchgrass • Sorghastrum nutans – Indiangrass • Rudbeckia hirta – black eyed susan• Echinacea purpurea – purple cone flower• Dalea purpurea – purple prairie clover• Monarda punctata – dotted mint• Liatris aspera – rough blazing star• Lupinus perennis - lupine
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Experiments
• Biomass allocation – greenhouse
• Germination – laboratory
• Aboveground biomass production – field
• Biodiversity – field
• Competition – field
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Biomass allocationgreenhouse
• Purpose: to determine the relationship between available nitrogen and biomass allocation of ten native species
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Biomass allocationgreenhouse
• Hypothesis: if amount of ammonium nitrate increases then some species will allocate more biomass to aboveground growth while others will not.
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Biomass allocationgreenhouse
• Four treatment groups (n = 5): – control– 30kg ha-1
– 60kg ha-1 – 120kg ha-1
• Biomass will be harvested after approximately 6 months of growth.
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Biomass allocationgreenhouse
• Prediction 1: species that allocate more biomass to aboveground growth will outcompete other species in the field as available nitrogen increases
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Competition and biomass allocationfield
• Purpose: to determine whether aboveground or belowground biomass allocation increases the relative dominance of a species in a high nitrogen environment
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Preliminary researchbiomass allocation
• Table 1 aboveground and belowground percent biomass for E. canadensis and S. scoparium (n = 5)
BiomassPercentage Schizachyrium scoparium Elymus canadensis
ControlMean (g)
NitrogenMean (g) p-value
ControlMean (g)
NitrogenMean (g) p-value
Aboveground 50.3 ± 4.75 63.8 ± 5.45 0.0990 53.9 ± 2.04 43.7 ± 2.59 0.0149
Belowground 49.7 ± 4.75 36.2 ± 5.45 0.0990 46.1 ± 2.63 56.3 ± 2.59 0.0149
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Competition and biomass allocationfield
• Prediction 1: species that allocate more biomass to aboveground growth will outcompete other species in the field as available nitrogen increases
• Hypothesis 1: if biomass allocation determines relative dominance then one of the two species should dominate at increased nitrogen levels
• Hypothesis 2: if preliminary data and prediction 1 are correct then in high treatment groups S. scoparium will allocate more biomass to aboveground growth and will increase in relative dominance over E. canadensis
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Competition and biomass allocationfield
• Two species: E. canadensis, and S. scoparium
• Four treatment groups (n = 5): – Control– 30kg ha-1
– 60kg ha-1
– 120kg ha-1
• Rectangular plastic containers are buried at the field site and half seeded with each of the two species. After one growing season the percent coverage by each species is determined
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Germination laboratory
• Purpose: to determine the relationship between the concentration of ammonium nitrate and the germination success of ten native species.
• Hypothesis: if ammonium nitrate concentration is increased then the germination success of most species will be reduced
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Preliminary research germination
0
1
2
3
4
5
6
MEAN RELATIVE GERMINATION OF EACH SPECIES IN CONTROL GROUP
PG
SN
LP
SS
MP
EP
EC
PV
RH
DP
MEA
N R
ELAT
IVE
PERC
ENT
GERM
INAT
ION
0
0.5
1
1.5
2
2.5
3
3.5
4
MEAN RELATIVE GERMINATION OF EACH SPECIES IN LOW GROUP
PGSNLPSSMPEPECPVRHDP
MEA
N R
ELAT
IVE
PERC
ENT
GERM
INAT
ION
0
1
2
3
4
5
6
7
MEAN RELATIVE GERMINATION OF EACH SPECIES IN HIGH GROUP
PGSNLPSSMPEPECPVRHDP
MEA
N R
ELAT
IVE
PERC
ENT
GERM
I-N
ATIO
N
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Germination laboratory
• Four treatments (n = 7): – Control– 1000ppm– 2000ppm– 4000ppm
• Seeds germinated in petri dishes containing mineral sand at 22°C for 6 weeks
• Number of germinated seeds recorded each week
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Germination laboratory
• Prediction 2: Species that are most successful at germinating at higher end of the spectrum should occur more frequently in the field as ammonium nitrate levels increase
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Biodiversityfield
• Purpose: to determine whether available nitrogen affects biodiversity of a plant community native to the Indiana dunes
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Biodiversityfield
• Prediction 1: species that allocate more biomass to aboveground growth will outcompete other species in the field as available nitrogen increases
• Prediction 2: Species that are most successful at germinating at higher end of the spectrum should occur more frequently in the field as ammonium nitrate levels increase
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Biodiversityfield
• Hypothesis 1: if nitrogen levels increase then biodiversity will decrease
• Hypothesis 2: if biodiversity decreases as a result of nitrogen additions then predictions 1 and 2 will be true
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Biodiversityfield
• Four treatment groups (n = 5): – Control– 30kg ha-1
– 60kg ha-1
– 120kg ha-1
• Species are seeded in 2x2m plots at field site. Percent coverage and aboveground biomass of each species is determined after two seasons.
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Summary
• It is expected that nitrogen additions will– Reduce germination of most species– Cause some species to allocate more biomass
aboveground
• Therefore– As nitrogen levels increase few species with high
germination success and aboveground biomass allocation will begin to dominate and biodiversity will decline as a result