DOI: 10.5061/dryad.fbg79cp2r
title: Trophic regulation of soil microbial biomass under nitrogen enrichment: A global meta-analysis

description: Eutrophication, including nitrogen (N) enrichment, can affect soil
 microbial communities through changes in trophic interactions. However, a
 knowledge gap still exists about how plant resources (‘bottom-up effects’)
 and microbial predators (‘top-down effects’) regulate the impacts of N
 enrichment on microbial biomass at the global scale. To address this
 knowledge gap, we conducted a global meta-analysis using 2885 paired
 observations from 217 publications to evaluate the regulatory effects of
 plant biomass and soil nematodes on soil microbial biomass under N
 enrichment across terrestrial ecosystems. We found that the effects of N
 enrichment on soil microbial biomass strongly varied across ecosystems. N
 enrichment decreased the soil microbial biomass of natural grasslands and
 forests due to soil acidification and the subsequent losses of predatory
 and microbivorous nematodes stimulating microbial growth. By contrast, N
 enrichment increased the microbial biomass of managed croplands mainly via
 increasing plant biomass production. The short-term of N enrichment
 (experimental duration ≤ 5 years) could reduce microbial biomass via
 decreasing nematode abundance across diverse ecosystems, whereas the
 long-term of N enrichment (experimental duration &gt; 5 years) mainly
 promoted microbial biomass via increasing plant biomass. These findings
 highlight the critical roles of microbial predators and plant input in
 shaping microbial responses to N enrichment, which are highly dependent on
 ecosystem type and the period of N enrichment. Earth system models that
 predict soil microbial biomass and their linkages to soil functioning
 should consider the variations in plant biomass and soil nematodes under
 future scenarios of N deposition.
description: We systematically searched all peer-reviewed studies on the
 effects of N enrichment on plant biomass, microbial biomass, and
 nematodes, using the Web of Science, Google Scholar, and the China
 National Knowledge Infrastructure Database (to 1st January, 2023). We used
 the following search string: (nitrogen addition OR nitrogen application OR
 nitrogen deposition OR nitrogen enrichment OR nitrogen fertilization OR
 nitrogen input OR nitrogen amendment) AND (fungi OR bacteria OR microbial
 biomass OR microbial community) AND (plant OR crop OR plant biomass OR
 above-ground biomass OR below-ground biomass OR root biomass OR yield OR
 nematod* OR fungivor* OR bacterivor* OR omnivor* OR predat* OR carnivor*
 OR nematode community OR nematode feeding groups OR bacterial-feeding
 nematode OR fungal-feeding nematode OR omnivorous nematode OR carnivorous
 nematode). The references listed in relevant previously published reviews
 and meta-analyses were also searched. In total, 207 studies from 217
 publications were included in our database. Data were directly extracted
 from the text and tables of publications or digitized by WebPlotDigitizer
 4.1 (https://autom eris.io/WebPlotDigitizer/) if presented in figures.
 From each study, we extracted data on the experimental duration (years),
 soil microbial biomass carbon, nematode abundance, plant biomass, and soil
 environmental factors.To assess the effect size of N enrichment on all
 response variables, we used the natural log-transformed response ratio
 (lnRR). And we used the sample sizes of response variables for
 weighting.
description: **This README file was generated on 2024-01-12 by Wen Xing.** **GENERAL
 INFORMATION** 1\. Title of Dataset: Trophic regulation of soil microbial
 biomass under nitrogen enrichment: A global meta-analysis. 2\. Author
 Information    A. Principal Investigator Contact Information Name:
 Xiaoming Lu Institution: State Key Laboratory of Vegetation and
 Environmental Change, Institute of Botany, Chinese Academy of Sciences
 Address: Beijing, China Email: B. Associate
 or Co-investigator Contact Information Name: Wen Xing Institution:
 Institute of Environment and Sustainable Development in Agriculture,
 Chinese Academy of Agricultural Sciences Address: Beijing, China Email:
 3\. Date of data collection (single date, range,
 approximate date): 1998-2023. 4\. Geographic location of data collection:
 Global terrestrial ecosystems. 5\. Information about funding sources that
 supported the collection of the data: None. **SHARING/ACCESS INFORMATION**
 1\. Licenses/restrictions placed on the data: CC0 1.0 Universal (CC0 1.0)
 Public Domain 2\. Links to publications that cite or use the data: Xing,
 W., Chen, X.L., Thakur, M.P., Kardol, P., Lu X. M., Bai, Y.F. (2024).
 Trophic regulation of soil microbial biomass under nitrogen enrichment: a
 global meta-analysis. Functional Ecology. 3\. Links to other publicly
 accessible locations of the data: None. 4\. Links/relationships to
 ancillary data sets: None. 5\. Was data derived from another source? No.
        A. If yes, list source(s): NA. 6\. Recommended citation for this
 dataset: Xing, W., Chen, X.L., Thakur, M.P., Kardol, P., Lu X. M., Bai,
 Y.F. (2024). Data from: Trophic regulation of soil microbial biomass under
 nitrogen enrichment: a global meta-analysis. Dryad Digital Repository.
 **DATA & FILE
 OVERVIEW** 1\. File List: FE_Data_used_for_analysis_2024_01_12.xlsx 2\.
 Relationship between files, if important: None 3\. Additional related data
 collected that was not included in the current data package: None. 4\. Are
 there multiple versions of the dataset? No.        A. If yes, name of
 file(s) that was updated: NA.               i. Why was the file updated?
 NA.               ii. When was the file updated? NA **DATA-SPECIFIC
 INFORMATION FOR: FE_Data_used_for_analysis_2024_01_12.xlsx** 1\. Number of
 variables: 29 2\. Number of cases/rows: 595 3\. Variable List: \*
 Reference_ID: the ID of collected references, a total of 217 references in
 our meta-analysis. \* Reference: the name of collected references,
 including the name of the first author and date (year) of publication. \*
 Study: the ID of studies, a total of 207 studies in our meta-analysis.
 Each site of the selected papers was treated as an independent study. If
 more than one independent experiment was conducted at different sites in
 one paper, they were treated as distinct studies. Those studies that were
 conducted at the same site under an identical experimental design but
 presented in separate papers were considered as one study. \* Ecosystem:
 ecosystem types, encompassing grasslands, forests, and croplands,
 respectively. \* Ecosystem_detail: detailed ecosystem types. Grasslands
 covered temperate grassland and meadow, alpine grassland and meadow,
 desert, savanna, and tundra. Forests covered boreal forest, temperate
 forest, and tropical forest, respectively. \* Duration(year): experimental
 duration (year). \* Duration_category: short-term (experimental duration ≤
 5 years) and long-term (&gt; 5 years). \* ln*RR*.Microbial_biomass: the
 natural log-transformed response ratio (ln*RR*) of microbial biomass
 carbon and had no units. In detail, ln*RR* = ln(Xt /Xc), where Xt and Xc
 are the mean values of response variables in the N enrichment and control
 plots, respectively. Because Xt and Xc had the same units, the ln*RR*
 would have no units when calculated from the formula: ln*RR* = ln(Xt /Xc).
 \* wt.Microbial_biomass: the weight of each ln*RR* of microbial biomass
 carbon observation and had no units. In detail, *wt*= (Nc × Nt)/(Nc + Nt),
 where *wt* is the weight of each ln*RR* observation, while Nt and Nc
 represent the number of replications in the N enrichment treatments and
 control, respectively. And thus the wt.Microbial_biomass also had no
 units. \* ln*RR*.Fungal_biomass: the natural log-transformed response
 ratio (ln*RR*) of fungal biomass and had no units. \* wt.Fungal_biomass:
 the weight of each ln*RR* of fungal biomass observation and had no units.
 \* ln*RR*.Bacterial_biomass: the natural log-transformed response ratio
 (ln*RR*) of bacterial biomass and had no units. \* wt.Bacterial_biomass:
 the weight of each ln*RR* of bacterial biomass observation and had no
 units. \* ln*RR*.Total_nematodes: the natural log-transformed response
 ratio (ln*RR*) of total nematode abundance and had no units. \*
 wt.Total_nematodes: the weight of each ln*RR* of total nematode abundance
 observation and had no units. \* ln*RR*.Bacterial_feeders: the natural
 log-transformed response ratio (ln*RR*) of bacterial-feeding nematode
 abundance and had no units. \* wt.Bacterial_feeders: the weight of each
 ln*RR* of bacterial-feeding nematode abundance observation and had no
 units. \* ln*RR*.Fungal_feeders: the natural log-transformed response
 ratio (ln*RR*) of fungal-feeding nematode abundance and had no units. \*
 wt.Fungal_feeders: the weight of each ln*RR* of fungal-feeding nematode
 abundance observation and had no units. \* ln*RR*.Omni_carnivores: the
 natural log-transformed response ratio (ln*RR*) of omnivorous-carnivorous
 nematode abundance and had no units. \* wt.Omni_carnivores: the weight of
 each ln*RR* of omnivorous-carnivorous nematode abundance observation and
 had no units. \* ln*RR*.Plant_biomass: the natural log-transformed
 response ratio (ln*RR*) of plant biomass and had no units. \*
 wt.Plant_biomass: the weight of each ln*RR* of plant biomass observation
 and had no units. \* ln*RR*.NH4+: the natural log-transformed response
 ratio (ln*RR*) of soil ammonium concentration and had no units. \*
 wt.NH4+: the weight of each ln*RR* of soil ammonium concentration
 observation and had no units. \* ln*RR*.NO3-: the natural log-transformed
 response ratio (ln*RR*) of soil nitrate concentration and had no units. \*
 wt.NO3-: the weight of each ln*RR* of soil nitrate concentration
 observation and had no units. \* ln*RR*.pH: the natural log-transformed
 response ratio (ln*RR*) of soil pH and had no units. \* wt.pH: the weight
 of each ln*RR* of soil pH observation and had no units. \* n/a: missing
 values.