DOI: 10.5061/dryad.bvq83bkjj
title: Gains in soil C storage under anthropogenic N deposition are rapidly lost following its cessation

description: In the northern Hemisphere, anthropogenic nitrogen (N) deposition
 contributed to the enhancement of the global terrestrial carbon (C) sink,
 partially offsetting CO2 emissions. Across several long-term field
 experiments, this ecosystem level response was determined to be driven, in
 part, by the suppression of microbial activity associated with the
 breakdown of soil organic matter. However, since the implementation of
 emission abatement policies in the 1970’s, atmospheric N deposition has
 declined globally, and the consequences of this decline are unknown. Here,
 we assessed the response of soil C storage, and associated microbial
 activities, in a long-term field study that experimentally increased N
 deposition for 24-years. We measured soil C and N, microbial activity, and
 compared effect sizes of soil C in response to, and in recovery from, the
 N deposition treatment across the history of our experiment (1994-2022).
 Our results demonstrate that the accumulated C in the organic horizon has
 been lost and exhibit additional deficits 5-years post-termination of the
 N deposition treatment. These findings, in part, arise from mechanistic
 changes in microbial activity. Soil C in the mineral soil was less
 responsive thus far in recovery. If these organic horizon C dynamics are
 similar in other temperate forests, the northern Hemisphere C sink will be
 reduced and climate warming will be enhanced.
description: # README: Gains in soil carbon storage under anthropogenic nitrogen
 deposition are rapidly lost following its cessation Corresponding author:
 Zachary B. Freedman E-mail:
 [zfreedman@wisc.edu](mailto:zfreedman@wisc.edu) The raw data submitted
 include the following parameters: organic horizon carbon content, organic
 horizon nitrogen content, mineral soil carbon content, organic horizon
 mass, soil respiration, and soil extracellular enzyme activity potential.
 ## Description of the data and file structure All data files contain the
 following information: -"Site": site where sample was collected
 from. There are 4 sites in Michigan, USA that are located: -"A":
 46°52'N, 88°53'W -"B": 45°33'N, 84°51'W
 -"C": 44°23'N, 85°50'W -"D": 43°40'N,
 86°09'W -"Plot": numeric identifier given to each 30 x 30
 meter plot (n = 6 per site) -"Treatment": refers to the amount
 of nitrogen deposition at the plot-level -"Ambient": plots that
 receive ambient atmospheric nitrogen deposition (wet + dry total
 deposition), which varies by site -Site A: 0.68 g N m-2 y-1 -Site B: 0.91
 g N m-2 y-1 -Site C: 1.17 g N m-2 y-1 -Site D: 1.18 g N m-2 y-1
 -"NDep": plots that received experimental nitrogen additions in
 the form of 30kg NO3--N ha-1 yr-1 from 1994-2017 -"Type": refers
 to soil type -"Organic horizon": Oe/Oa horizon -"Mineral
 soil": 0-10cm depth, A horizon of sandy spodosol soil (Kalkaska
 series) 1. Organic horizon carbon content (organic_horizon_C.csv) -Organic
 horizon carbon content of one homogenized sample per plot per site (from
 10 random 10 by 10 cm cut squares of Oe/Oa horizon) for each sampling year
 -For years 1994-2016, values are expressed in g kg-1 -For the year 2022,
 values are expressed twice. Under the "2022 (g/m2)" column the
 values are expressed in g/m2. Under the "2022 (%)" column, the
 values are expressed as % -Both forms are used/presented in the manuscript
 and hence why the data is presented twice in the raw data file 2. Organic
 horizon nitrogen content (organic_horizon_N.csv) -Organic horizon nitrogen
 content of one homogenized sample per plot per site (from 10 random soil
 cores to 10 cm depth) for each sampling year -For years 1994-2016, values
 are expressed in g kg-1 -For the year 2022, values are expressed twice.
 Under the "2022 (g/m2)" column the values are expressed in g/m2.
 Under the "2022 (%)" column, the values are expressed as % -Both
 forms are used/presented in the manuscript and hence why the data is
 presented twice in the raw data file 3. Mineral soil carbon content
 (mineral_soil_C.csv) -Mineral soil carbon content of one homogenized
 sample per plot per site (from 10 random soil cores to 10 cm depth) for
 each sampling year -Values are expressed in g/m2 4. Organic horizon mass
 (organic_horizon_mass.csv) -Mass of the homogenized organic horizon sample
 per plot per site (from 10 random 10 by 10 cm cut squares of Oe/Oa
 horizon) collected between 14-17 September 2022 -Values are expressed in
 g/m2 5. Respiration (respiration.csv) -Soil respiration of one homogenized
 sample per plot per site collected between 14-17 September 2022
 -Respiration values were obtained by performing a laboratory incubation
 experiment -Respiration measurements were taken 24, 48, and 72 hours after
 jar wetting using an EGM-5 Infrared Gas Analyzer (IRGA) -Values obtained
 from the 72-hour sampling period were used to calculate C respired as g C
 g soil-1 s-1 6. Enzymes (enzymes.csv) -Soil extracellular enzyme activity
 potential of one homogenized sample per plot per site collected between
 14-17 September 2022 -"Moisture": % moisture of sample
 (determined in lab) -"PER": Peroxidase -"PPO":
 Polyphenol Oxidase -"BG": Beta-Glucosidase