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A Global Database of Soil Respiration Data, Version 4.0

Documentation Revision Date: 2018-12-17

Data Set Version: 4.1

Summary

This dataset provides an update to the Soil Respiration Database (SRDB), a near-universal compendium of published soil respiration data. Soil respiration, the flux of autotrophically- and heterotrophically-generated CO2 from the soil to the atmosphere, remains the least well-constrained component of the terrestrial carbon cycle. The database encompasses all published studies that report at least one of the following data measured in the field (not laboratory): annual soil respiration, mean seasonal soil respiration, a seasonal or annual partitioning of soil respiration into its source fluxes, soil respiration temperature response (Q10), or soil respiration at 10 degrees C. The SRDB's orientation is thus to seasonal and annual fluxes, not shorter-term or chamber-specific measurements, and the database is dominated by temperate, well-drained forest measurement locations. Version 4 is the compilation of 1,458 published studies with measurements taken between 1961 and 2016.

The dataset includes a file of soil respiration data and a linked file of study bibliographic data; both files are in comma-separated format.

Figure 1: Locations of SRDB V4 observations, colored by biome. Map produced by the companion SRDBv4.R script.

Citation

Bond-Lamberty, B.P., and A.M. Thomson. 2018. A Global Database of Soil Respiration Data, Version 4.0. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1578

Table of Contents

  1. Data Set Overview
  2. Data Characteristics
  3. Application and Derivation
  4. Quality Assessment
  5. Data Acquisition, Materials, and Methods
  6. Data Access
  7. References
  8. Data Set Revisions

Data Set Overview

The SRDB encompasses published studies that report at least one of the following data measured in the field (not laboratory): annual soil respiration, mean seasonal soil respiration, a seasonal or annual partitioning of soil respiration into its source fluxes, soil respiration temperature response (Q10), or soil respiration at 10 degrees C. The SRDB was designed to capture and make available for analysis the large number of RS studies published since the 1960s. The dataset includes a file of soil respiration data and a linked file of study bibliographic data; both files are in comma-separated format. A script written in R is also included and it contains functions for error-checking and mapping of study locations.

User Note: The compilers of the SRDB database (Bond-Lamberty and Thomson, 2010) make it available to the scientific community both as a traditional static archive (at ORNL DAAC) and as a dynamic community database that will be updated over time by interested users. The dynamic version of the database is hosted on GitHub (at https://github.com/bpbond/srdb as of November 15, 2018). We recommend that citations to this dynamic database always include a version number and download date.

Data Characteristics

Spatial Coverage: Global

Spatial Resolution: Point-based measurements with global extent (see Fig. 1). Coordinates are provided for each sample location.

Temporal Coverage: Compilation of published measurements taken between 1961/01/01 and 2016/06/30. The study date of each record is provided in the dataset.

Temporal Resolution: Annual and seasonal measurements for each study are provided.

Site Boundaries: (All latitude and longitude given in decimal degrees)

Site (Region) Westernmost Longitude Easternmost Longitude Northernmost Latitude Southernmost Latitude Geodetic Datum
Global (point) -162.2 175.77 78.9 -78.20 Unknown

 

Data File Information

The main data file "srdb-data-V4.csv" is a comma-separated file of all the soil respiration and contextual data. Bibliographic information for the studies that appear in the main data file can be found in the "srdb-studies-V4.csv" file. The “Study_number” field is common to both files and indexes the srdb-studies to srdb-data.

Missing values are represented as -9999 for numeric data or NA for text data.

File Description: srdb-data-V4.csv

Column Number Column Name Column Description and Units
1 Record_number Record number
2 Entry_date Entry date (yyyy-mm-dd)
3 Study_number Study number; index into the studies database
4 Author Name of first author
5 Duplicate_record Is record a known duplicate? (Study number)
6 Quality_flag Quality control flags:

Q0 default/none
Q01 estimated from figure
Q02 data from another study
Q03 data estimated--other
Q04 potentially useful future data
Q10 potential problem with data
Q11 suspected problem with data
Q12 known problem with data
Q13 duplicate?
Q14 inconsistency
Further details can generally be found in the notes field (column 105 below)
7 Contributor Data contributor
site and measurement data
8 Country Country
9 Region State/province/region
10 Site_name Name of study site
11 Study_midyear Year study was performed (middle year if multiple years)
12 Years_of_data Years of data; always ≥1
13 Latitude Latitude, decimal; positive=north, negative=south
14 Longitude Longitude, decimal; positive=east, negative=west
15 Elevation Elevation, m
16 Manipulation Manipulation performed (CO2, fertilization, etc.)
17 Manipulation_level Degree of manipulation performed
18 Age_ecosystem Time since ecosystem established, years. This is used when, e.g., the time of conversion of forest to agriculture is known
19 Age_disturbance Time since disturbance, years
20 Species Dominant species
21 Biome Biome (boreal, temperate, etc). Subjective
22 Ecosystem_type Ecosystem type (grassland, forest, etc). Subjective
23 Ecosystem_state Ecosystem state (managed, unmanaged, natural). Subjective. Unmanaged means human management or disturbance in the past, but not currently.
24 Leaf_habit Dominant leaf habit (deciduous, evergreen)
25 Stage Developmental stage (aggrading, mature). Subjective
26 Soil_type Soil description (classification and texture)
27 Soil_drainage Soil drainage (dry, wet). Subjective. Dry means well-drained uplands; wet peatlands, swamps, etc.
28 Soil_BD Soil bulk density, g cm-3
29 Soil_CN Soil C:N ratio
30 Soil_sand Soil percent sand
31 Soil_silt Soil percent silt
32 Soil_clay Soil percent clay
33 MAT Reported mean annual temperature, C
34 MAP Reported mean annual precipitation, mm
35 PET Reported potential evapotranspiration, mm
36 Study_temp Annual temperature in year of study, C
37 Study_precip Annual precipitation in year study of study, mm
38 Meas_method CO2 measurement method
39 Meas_interval Mean interval between soil respiration measurements, days
40 Annual_coverage Annual coverage of soil respiration measurements, fraction (1.0= full year)
41 Partition_method Method used to partition soil respiration source fluxes, following Bond-Lamberty et al. (2004)
annual and seasonal rs fluxes
42 Rs_annual Annual C flux from soil respiration, g C m-2. This can either be reported directly by the study, calculated from reported mean fluxes, or estimated from a figure (in which case a quality control note is made, field 6)
43 Rs_annual_err Error (typically plot-to-plot) for soil respiration annual, g C m-2
44 Rs_interann_err Interannual error reported for soil respiration annual, g C m-2. This is occasionally reported by authors, or defined as the standard deviation between year ‘i’ and year ‘i+1’ (N=2)
45 Rs_max Maximum soil respiration flux, µmol m-2 s-1
46 Rs_maxday Maximum soil respiration flux day of year
47 Rs_min Minimum soil respiration flux, µmol m-2 s-1
48 Rs_minday Minimum soil respiration flux day of year
49 Rlitter_annual Annual soil respiration flux from litter, g C m-2 fraction
50 Ra_annual Annual autotrophic soil respiration flux, g C m-2
51 Rh_annual Annual heterotrophic soil respiration flux, g C m-2
52 RC_annual Root contribution to soil respiration annual fraction
53 Rs_spring Mean spring soil respiration flux, µmol m-2 s-1. Seasons are defined by authors
54 Rs_summer Mean summer soil respiration flux, µmol m-2 s-1
55 Rs_autumn Mean autumn soil respiration flux, µmol m-2 s-1
56 Rs_winter Mean winter soil respiration flux, µmol m-2 s-1
57 Rs_growing Mean growing soil respiration flux, µmol m-2 s-1
58 Rs_wet Mean wet season soil respiration flux, µmol m-2 s-1
59 Rs_dry Mean dry season soil respiration flux, µmol m-2 s-1
60 RC_seasonal Root contribution to seasonal soil respiration, fraction
61 RC_season Season of root contribution
response of rs to temperature and moisture
62 Model_type Type of temperature-response model used
63 Temp_effect Temperature effect on soil respiration (none, positive, negative)
64 Model_output_units Temperature-response model output units
65 Model_temp_min Lower bound of soil temperature range over which model fitted
66 Model_temp_max Upper bound of soil temperature range over which model fitted
67 Model_N Model N
68 Model_R2 Model r-squared
69 T_depth Depth at which soil temperature recorded, cm. A value of -200 (i.e., 2 m above ground) is used for air temperature
70 Model_paramA Model parameter A
71 Model_paramB Model parameter B
72 Model_paramC Model parameter C
73 Model_paramD Model parameter D
74 Model_paramE Model parameter E
75 WC_effect Soil water effect on RS
76 R10 Soil respiration at 10 C, µmol m-2 s-1
77 Q10_0_10 Q10 temperature response, 0-10 C. Q10 values are either reported by authors, calculated from reported soil respiration -temperature regressions, or occasionally estimated from figures (in which case a quality control note is made, field 6)
78 Q10_5_15 Q10 temperature response, 5-15 C
79 Q10_10_20 Q10 temperature response, 10-20 C
80 Q10_0_20 Q10 temperature response, 0-20 C
81 Q10_other1 Q10 temperature response, other temp range
82 Q10_other1_min Lower bound of temperature range of Q10_other1, C
83 Q10_other1_max Upper bound of temperature range of Q10_other1, C
84 Q10_other2 Q10 temperature response, other temp range
85 Q10_other2_min Lower bound of temperature range of Q10_other2, C
86 Q10_other2_max Upper bound of temperature range of Q10_other2, C
ancillary pools and fluxes
87 GPP Annual gross primary production at site, g C m-2
88 ER Annual ecosystem respiration at site, g C m-2
89 NEP Annual net ecosystem production at site, g C m-2
90 NPP Annual net primary production at site, g C m-2
100 ANPP Annual aboveground NPP at site, g C m-2
101 BNPP Annual belowground NPP at site, g C m-2
102 NPP_FR Annual fine root NPP at site, g C m-2
103 TBCA Total belowground carbon allocation at site, g C m-2
104 Litter_flux Annual total litter flux, g C m-2. This should be ghe sum of Litter_flux and Root_litter_flux
105 Rootlitter_flux Annual aboveground litter flux, g C m-2. This is reported very inconsistently (leaf only, leaf and fine woody material, all material, etc). Generally this should not include large woody material
106 TotDet_flux Annual total litter flux, g C m-2. This should be the sum of Litter_flux and Root_litter_flux
107 Ndep Annual nitrogen deposition, g N m-2
108 LAI Leaf area index at site, m2 m-2. Hemispheric (one-sided) if possible
109 BA Basal area at site, m2 ha-1
110 C_veg_total Total carbon in vegetation, g C m-2. This should be the sum of C_AG and C_BG. For this and all "C_" fields, biomass is converted to carbon using a ratio of 0.5 unless study-specific values are available
111 C_AG Total carbon in aboveground vegetation, g C m-2
112 C_BG Total carbon in belowground vegetation, g C m-2
113 C_CR Total carbon in coarse roots, g C m-2
114 C_FR Total carbon in fine roots, g C m-2
115 C_litter Total carbon in standing litter, g C m-2
116 C_soilmineral Total carbon in soil organic matter, g C m-2
117 C_soildepth Depth to which soil C recorded, cm
118 Notes Notes

 

File Description: srdb-studies-V4.csv

Column Number Column Name Column Description
1 study_number Study number; used as a lookup from srdb-data.
2 authors Study authors.
3 title Study title.
4 abstract Abstract.
5 bp Beginning page.
6 citations Citations.
7 copy SRDB Team Member.
8 de Data entry: entered into srdb-data (Y/N)?
9 dld Downloaded: study acquired (Y/N)?
10 doi Digital object identifier.
11 ep Ending page.
12 issue Issue number.
13 nonenglish Is study in a non-English language (Y/N)?
14 notes Notes.
15 pubyear Publication year.
16 rank Rank (1=highly relevant, 4=not relevant). Note this score is not an assessment of the study's scientific merit or validity; it's simply a judgment, based on reading the abstract and title, of how relevant this study is to the database (i.e., is it likely to have appropriate data?)
17 requested Study requested.
18 searchdate Date search performed (yyyy-mm-dd).
19 searchterm Web of Science search term used.
20 sn The ISSN, which is the international standardized code for publication.
21 source Study source (usually journal name).
22 tf Additional publication identifiers to accompany those in column ut.
23 ut Additional publication identifiers.
24 volume Volume number.

 

Companion File Information:

  • An R script, SRDBv4.R, containing functions for error-checking, mapping of study locations, summary statistics, and summary graphics is included. Note that this script requires installation of the following R packages: "ggplot2", "ggExtra", "maps", and "mapdata". The script must be run from the same directory that contains the data files: srdb-data-V4.csv and srdb-studies-V4.csv, as well as the comp file: srdb-data_fields-V4.txt). Error-checking functions include helper functions to check the valid range and data type of each field. Summary statistics include the breakdown of data by Biome, Ecosystem, Rs_annual, R_10, and Q_10. Scripts to create maps are provided: the world map shown in Fig. 1 above, and regional maps. Summary graphics include: Rs summary distributions by Biome, Ecosystem, as well as a plot of Rs_annual vs Rh_annual.
  • The file srdb-data_fields-V4.txt contains a list of all the fields in the main data file.
  • When it was necessary to calculate or estimate annual flux for one of the studies, these calculations and notes were recorded in an Excel spreadsheet. These spreadsheets are provided as a companion file and have been compiled and compressed into a single file, calculations_worksheets_v4.zip.

Application and Derivation

This is a database compiled from published studies about soil surface CO2 flux (soil respiration) measured in the field and intended to serve as a resource for scientific analysis. 

The primary soil respiration units used were gC/m2/yr (for annual fluxes) and umol/m2/s (for mean seasonal fluxes); values were converted as necessary from those provided by study authors. A variety of ancillary data were also entered when reported, including site-related and experimental data, information on ecosystem structure and function, methods used, etc.; we assumed a 12:44 ratio of C to CO2 molecular weights, and that biomass was 50% C (unless specified otherwise in the study).

Quality Assessment

Data were crosschecked against a number of other soil respiration data collections and meta-analyses (Hibbard et al., 2005; Chen and Tian, 2005; Burton et al., 2008; Sotta et al., 2004). Quality flags were assigned based on information provided in a given study and best judgment.

Data Acquisition, Materials, and Methods

For the compilation of SRDB Version 1, investigators collected all available studies in the peer-reviewed scientific literature reporting soil respiration measured in the field; lab incubation studies were not included. The ISI Web of Science constituted the primary source of published studies; search terms used included soil respiration, soil CO2 evolution, etc., and were conducted through the 2008 publication  year. We used each study's title and abstract to decide whether to acquire it; ~40% of the almost 4,700 studies were acquired and examined. 

In Version 2.0, publications from 2009, 2010 and from the first half of 2011 were included and RS data from 164 studies were added. The Google Earth.kmz file of site locations was updated. Additionally, a number of corrections have been made. A number of Age_disturbance fields have been corrected and completed. The Partition_method field has been fixed for many records. Finally, three fields have been deleted: Chamber_method, CH4_flux, N2O_flux. These fields were inconsistent or almost never used.

In Version 3.0, publications from 2012 and RS data from a total of 466 new studies were added. Many corrections were made to older data and a new R script for error-checking and mapping was created. The Google Earth.kmz file was removed and the field CO2_method was renamed to Meas_method. Additionally, two new fields titled Meas_interval and Annual_coverage were added to the data.

In Version 4.0, publications through 2017 were reviewed and more than 1400 observations were added. Many corrections were made to older data.

Short term experiments (i.e., soil respiration measurements made over less than 1-2 weeks) were not entered unless the study authors extrapolated their results to seasonal or annual values; the database is in general not designed to accommodate instantaneous or short-term measurements. In general we did not do additional research to find older publications that might not be listed in the Web of Science. To qualify for inclusion, a study had to report at least one of the following data:

  • Annual soil respiration
  • Mean seasonal soil respiration
  • Annual or seasonal partitioning of soil respiration sources
  • Q10 and associated temperature range
  • R10 (soil respiration at 10 degrees C)

If at least one of these data was reported, or could be calculated with few or no assumptions, e.g., easily estimated from points in a figure, the study was entered into the database. For example, sometimes a study will show monthly soil respiration in a figure but not compute an annual flux, and so estimates were made from the figure. This was noted in a quality flag.

When it was necessary to calculate or estimate annual flux for one of the studies, these calculations and notes were recorded in an Excel spreadsheet (*.xlsx). File names start with the assigned four-digit “Study_number” that indexes the srdb-studies and srdb-data files. For example, "0020 WitkampEcology 1966.xlsx" and "4634 Webster JGR 2008.xlsx". These spreadsheets are provided zipped into a single file, calculations_worksheets_v4.zip.

Data Access

These data are available through the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

A Global Database of Soil Respiration Data, Version 4.0

Contact for Data Center Access Information:

References

Bond-Lamberty, B. and A.M. Thomson. 2010. A global database of soil respiration measurements, Biogeosciences, 7, 1321-1344, https://doi.org/10.5194/bgd-7-1321-2010

Burton, A. J., Melillo, J. M., and Frey, S. D. 2008.: Adjustment of forest ecosystem root respiration as temperature warms, Journal of Integrative Plant Biology, 50, 1467-1483, https://doi.org/10.1111/j.1744-7909.2008.00750.x

Chen, H., and Tian, H.-Q. 2005. Does a general temperature-dependent Q(10) model of soil respiration exist at biome and global scale?, Journal of Integrative Plant Biology, 47, 1288-1302. https://doi.org/10.1111/j.1744-7909.2005.00211.x

Hibbard, K. A., Law, B. E., and Sulzman, J. 2005. An analysis of soil respiration across northern hemisphere temperate ecosystems, Biogeochemistry, 73, 29-70, https://doi.org/10.1007/s10533-004-2946-0

Sotta, E. D., Meir, P., Malhi, Y., Nobre, A. D., Hodnett, M., and Grace, J. 2004. Soil CO2 efflux in a tropical forest in the central Amazon, Global Change Biol., 10, 601-617, https://doi.org/10.1111/j.1529-8817.2003.00761.x

Data Set Revisions

SRDB Version ORNL DAAC Release Date Number of Records Study Date Range

Version 4.0

2018/11/21

6,631

1961-2016

Version 3.0

2014/07/24

5,173

1961-2012

Version 2.0

2012/03/01

4,387

1961-2009

Version 1.0

2010/04/30

3,379

1961-2007

Version 4.0: Data from 1,750 studies have been entered into the database, constituting 6,631 records. The data span the measurement years 1961-2016 and are dominated by temperate, well-drained forests. The source for Version 4.0 is the github site https://github.com/bpbond/srdb as of November 21, 2018.

Version 4.1:  The srdb-studies-V4.csv file was updated with the file from the github site https://github.com/bpbond/srdb as of December 17, 2018.