Investigating the mechanisms by which available nitrogen affects biodiversity of a plant community native to the Indiana Dunes National Lakeshore Eric Bird Purdue University Calumet Flora Richardson Fellowship Recipient

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

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

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

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

Experiments Biomass allocation – greenhouse Germination – laboratory Aboveground biomass production – field Biodiversity – field Competition – field

Biomass allocation greenhouse Purpose: to determine the relationship between available nitrogen and biomass allocation of ten native species

Biomass allocation greenhouse Hypothesis: if amount of ammonium nitrate increases then some species will allocate more biomass to aboveground growth while others will not.

Biomass allocation greenhouse 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.

Biomass allocation greenhouse Prediction 1: species that allocate more biomass to aboveground growth will outcompete other species in the field as available nitrogen increases

Competition and biomass allocation field Purpose: to determine whether aboveground or belowground biomass allocation increases the relative dominance of a species in a high nitrogen environment

Preliminary research biomass allocation Table 1 aboveground and belowground percent biomass for E. canadensis and S. scoparium (n = 5) Biomass PercentageSchizachyrium scopariumElymus canadensis Control Mean (g) Nitrogen Mean (g)p-value Control Mean (g) Nitrogen Mean (g)p-value Aboveground50.3 ± ± ± ± Belowground49.7 ± ± ± ±

Competition and biomass allocation field 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

Competition and biomass allocation field 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

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

Preliminary research germination

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

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

Biodiversity field Purpose: to determine whether available nitrogen affects biodiversity of a plant community native to the Indiana dunes

Biodiversity field 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

Biodiversity field 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

Biodiversity field 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.

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