Major

Environmental Science

Anticipated Graduation Year

2021

Access Type

Open Access

Abstract

As the most commonly-limiting nutrient in terrestrial ecosystems,

nitrogen plays a critical role in carbon sequestration and other

ecosystem services. However, it is notoriously difficult to measure

the availability of nitrogen in the forms that plants are able to take

up. We conducted a combined lab and greenhouse experiment to

determine the sampling sizes required to reliably measure plant

nitrogen availability in forest soils collected from two plots at The

Morton Arboretum, one angiosperm-dominated and the second

gymnosperm-dominated. We used two methods to measure plant

nitrogen availability in our forest soil samples: lab incubations and

phytometer growth. Lab incubations measure mineral nitrogen

concentration before and after a two-week incubation period to

determine net nitrogen mineralization. Phytometer growth indexes

nitrogen availability via height and biomass of seedlings grown in

the soil. Using 40 soil cores per plot, we will determine how

many samples are required to have an 80% chance of detecting

significant results between plots with a two-fold increase or

decrease in nitrogen availability. By determining minimum

sample sizes required, this pilot study will aid in the efficient

design of an upcoming larger study comparing soil nitrogen

availability across 18 plots at The Morton Arboretum.

Community Partners

The Morton Arboretum

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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Measuring plant nitrogen availability in forest soils with lab incubations and phytometer growth assays: a power analysis

As the most commonly-limiting nutrient in terrestrial ecosystems,

nitrogen plays a critical role in carbon sequestration and other

ecosystem services. However, it is notoriously difficult to measure

the availability of nitrogen in the forms that plants are able to take

up. We conducted a combined lab and greenhouse experiment to

determine the sampling sizes required to reliably measure plant

nitrogen availability in forest soils collected from two plots at The

Morton Arboretum, one angiosperm-dominated and the second

gymnosperm-dominated. We used two methods to measure plant

nitrogen availability in our forest soil samples: lab incubations and

phytometer growth. Lab incubations measure mineral nitrogen

concentration before and after a two-week incubation period to

determine net nitrogen mineralization. Phytometer growth indexes

nitrogen availability via height and biomass of seedlings grown in

the soil. Using 40 soil cores per plot, we will determine how

many samples are required to have an 80% chance of detecting

significant results between plots with a two-fold increase or

decrease in nitrogen availability. By determining minimum

sample sizes required, this pilot study will aid in the efficient

design of an upcoming larger study comparing soil nitrogen

availability across 18 plots at The Morton Arboretum.