DOI: 10.5061/dryad.g79cnp611
title: Nitrogen deposition weakens soil carbon control of nitrogen dynamics across the contiguous United States

description: Anthropogenic nitrogen (N) deposition is unequally distributed across
 space and time, with inputs to terrestrial ecosystems impacted by industry
 regulations and variation in human activity. Soil carbon (C) content
 normally controls the fraction of mineralized N that is nitrified
 (ƒnitrified), affecting N bioavailability for plants and microbes.
 However, it is unknown whether N deposition has modified the relationships
 between soil C, net N mineralization, and net nitrification. To test
 whether N deposition alters the relationship between soil C and net N
 transformations, we collected soils from coniferous and deciduous forests,
 grasslands, and residential yards in 14 regions across the contiguous U.S.
 that vary in N deposition rates. We quantified rates of net nitrification
 and N mineralization, soil chemistry (soil C, N, and pH), and microbial
 biomass and function (as beta-glucosidase (BG) and N-acetylglucosaminidase
 (NAG) activity) across these regions. Following expectations, soil C was a
 driver of ƒnitrified across regions, whereby increasing soil C resulted in
 a decline in net nitrification and ƒnitrified. The ƒnitrified value
 increased with lower microbial enzymatic investment in N acquisition
 (increasing BG:NAG ratio) and lower active microbial biomass, providing
 some evidence that heterotrophic microbial N demand controls the ammonium
 pool for nitrifiers. However, higher total N deposition increased
 ƒnitrified, including for high soil C sites predicted to have low
 ƒnitrified, which decreased the role of soil C as a predictor of
 ƒnitrified. Notably, the drop in contemporary atmospheric N deposition
 rates during the 2020 COVID-19 pandemic did not weaken the effect of N
 deposition on relationships between soil C and ƒnitrified. Our results
 suggest N deposition can disrupt the relationship between soil C and net N
 transformations, with this change potentially explained by weaker
 microbial competition for N. Therefore, past N inputs and soil C should be
 used together to predict N dynamics across terrestrial ecosystems.
description: # Nitrogen deposition weakens soil carbon control of nitrogen dynamics
 across the contiguous United States
 [https://doi.org/10.5061/dryad.g79cnp611](https://doi.org/10.5061/dryad.g79cnp611) ## Description of the data and file structure Soils were collected across the contiguous United States as an effort to understand the biogeochemical responses to the COVID-19 pandemic. Data associated with sites were used to describe the characteristics of each site's climate and atmospheric nitrogen deposition. NA: Not applicable ### Files and variables #### File: Soil\_data.csv **Description:** Carbon and nitrogen cycling data for the main analysis of the text. ##### Variables * Region: Name of the region the soil was collected. * Site: Name of the site within the region that soil was collected. * Date: Date of soil collection (MM/DD/YY). * Plot: Plot number. * MAT: 30-year mean annual temperature of the closest weather station in the National Weather Service Cooperative Network (degrees Celsius). * MAP: 30-year mean annual precipitation of the closest weather station in the National Weather Service Cooperative Network (millimeters). * GravimetricWaterContent: Gravimetric moisture content of soil sample (grams water grams-1 dry soil). * SoilpH: pH of soil slurry (1:2 volumetric ratio of soil and deionized water) (unitless). * ActiveMicrobialBiomass_SIR: Rate of maximum CO2 production from the addition of labile carbon (micrograms CO2-C grams-1 dry soil hour-1). * Net_NMineralization: Rate of net change of inorganic nitrogen (NH4 + NO3) after 28 days of laboratory incubation (micrograms N grams-1 dry soil day-1). * Net_Nitrification: Rate of net change of nitrate (NO3) after 28 days of laboratory incubation (micrograms N grams-1 dry soil day-1). * BG_activity: Maximum potential betaglucosidase activity (nanomoles substrate grams-1 dry soil hour-1). * NAG_activity: Maximum potential N-acetyl-glucosaminidase activity (nanomoles substrate grams-1 dry soil hour-1). * SoilC: Total soil carbon (%). * SoilN: Total soil nitrogen (%). #### File: NCycling2020\_2021\_data.csv **Description:** Nitrogen cycling data for the main analysis of the text comparing years 2020 and 2021. ##### Variables * Region: Name of the region the soil was collected. * Site: Name of the site within the region that soil was collected. * Date: Date of soil collection (MM/DD/YY). * Plot: Plot number. * Net_NMineralization: Rate of net change of inorganic nitrogen (NH4 + NO3) after 28 days of laboratory incubation (micrograms N grams-1 dry soil day-1). * Net_Nitrification: Rate of net change of nitrate (NO3) after 28 days of laboratory incubation (micrograms N grams-1 dry soil day-1). #### File: NADP\_data.csv **Description:** National Trends Network data from the National Atmospheric Deposition Program. Data were accessed online on November 14, 2023. ##### Variables * Region: Name of the region the soil was collected. * Site: Name of the site within the region that soil was collected. * Year: Year of annual atmospheric deposition. * TotalN_deposition: Yearly rate of atmospheric total N deposition (kilograms N hectare-1 year-1). * NH4Wet_deposition: Yearly rate of atmospheric wet ammonium (NH4) deposition (kilograms N hectare-1 year-1). #### File: CASTNET\_data.csv **Description:** Clean Air Status and Trends Network data from the U.S. Environmental Protection Agency. Data were accessed online on February 14, 2024. ##### Variables * Station: Name of the CASTNET station. * Year: Year of annual dry N atmospheric deposition. * Week: Week of year. * DateOn: Day started for collection week. * DateOff: Day ended for collection week. * NH4: Weekly rate of dry NH4-N deposition (kilograms N hectare-1 week-1). * NO3: Weekly rate of dry NO3-N deposition (kilograms N hectare-1 week-1). #### File: Weather\_data.csv **Description:** Daily weather data from the National Weather Service Cooperative Network. These data were used to calculate monthly precipitation and potential evapotranspiration to identify climate. ##### Variables * Region: Name of the region the soil was collected. * Site: Name of the site within the region that soil was collected. * Name: Name of weather station. * Station: Station identification. * Date: Date of year (MM/DD/YY). * Precip: Daily precipitation (millimeters). * TMax: Maximum temperature (degrees Celsius). * TMin: Minimum temperature (degrees Celsius). * Latitude: Latitude of weather station. ## Code/software Data were analyzed using R (V4.3.3) within the RStudio environment (V2023.12.1+402).