DOI: 10.5061/dryad.18931zcxk
title: GLOWCAD: A global database of woody tissue carbon concentrations/fractions

description: Woody tissue carbon (C) concentration is a key wood trait necessary for
 accurately estimating forest C stocks and fluxes, which also varies widely
 across species and biomes. However, coarse approximations of woody tissue
 C (e.g., 50%) remain commonplace in forest C estimation and reporting
 protocols, despite leading to substantial errors in forest C estimates.
 Here, we describe the Global Woody Tissue Carbon Concentration Database
 (GLOWCAD): a database containing 3,676 individual records of woody tissue
 C concentrations from 864 tree species. Woody tissue C concentration
 data—i.e., the mass of C per unit dry mass—were obtained from live and
 dead woody tissues from 130 peer-reviewed sources published between
 1980-2020. Auxiliary data for each observation include tissue type, as
 well as decay class and size characteristics for dead wood. In GLOWCAD,
 1,242 data points are associated with geographic coordinates, and are
 therefore presented alongside 46 standardized bioclimatic variables
 extracted from climate databases. GLOWCAD represents the largest available
 woody tissue C concentration database, and informs studies on forest C
 estimation, as well as analyses evaluating the extent, causes, and
 consequences of inter- and intraspecific variation in wood chemical
 traits.
description: <em>Literature
 review</em>             Data compilation expanded earlier versions of
 the GLOWCAD first initiated in 2012<sup>26</sup>, and more recently published in
 2018<sup>20,30</sup> and 2021<sup>31,32</sup>. GLOWCAD is therefore based on a systematic
 search on primary literature of all peer-reviewed papers that cited
 previously published studies on woody tissue C
 concentrations<sup>20,24-26</sup>. We used key terms “carbon”, “tree”, “wood
 carbon”, “coarse woody debris”, “dead wood”, and “wood nutrient”, as well
 as “carbon” aside major tree tissue types (including “wood”, “bark”,
 “root” and “stem”) to search four web-based platforms (Google Scholar, Web
 of Science, Web of Knowledge, and Scopus) identifying additional
 peer-reviewed publications that present species- specific woody tissue C
 concentration data.             In addition to peer-reviewed papers,
 other sources of data included in GLOWCAD include the TRY Plant Trait
 Database (v. 5.0)<sup>33</sup><sup> </sup>and the Global Root
 Traits (GRooT) Database<sup>34</sup>. The TRY datasets included are the Subarctic
 Plant Species Database (dataset ID 105), Plant Traits for Pinus and
 Juniperus Forests in Arizona (dataset ID 193), Plant Physiology Database
 (dataset ID 97), Panama Tree Traits Database (dataset ID 230), FRED
 database (dataset ID 339), and the ECOCRAFT Database (dataset ID 12).
 While most root C values in GRooT were included in the FRED database (v.
 2.0)<sup>35</sup>, data from 10 papers in GRooT were added to
 GLOWCAD (n=197 data points): Isaac et al,  2017; Liu et al, 2019; Wang et
 al, 2018; Minden et al, 2014; Alameda et al, 2012; Aubin et al, 2016;
 Fernández-García et al, 2014; Grechi et al, 2007; Ineson et al, 1996; and
 Pregitzer et al, 1995. <em>Wood C data attributes          </em>
 To be included in GLOWCAD, the
 species-specific binomial nomenclature and tissue-specific information for
 each woody tissue C sample was required. A detailed field and lab
 methodology was also necessary, in order to maximize our sample size while
 permitting reliable species- and tissue-specific analysis. Where a single
 paper contained multiple tissue- and species-specific woody tissue C
 records, all the published values were recorded. In the majority of cases,
 woody tissue C data were extracted directly from published tables or from
 supplementary data of the articles. In instances where woody tissue C data
 were published as figures, the data was extracted using the
 WebPlotDigitizer v4.2 software<sup>36</sup>. If species-by-tissue-specific woody tissue C
 data were not published, the corresponding authors were contacted to
 provide data. Each published woody tissue C record was then
 classified according to the forest biome in which it was sampled. A small
 number of studies (e.g. <sup>37</sup>) presented both boreal and temperate data,
 which were differentiated in our database based on the sampling location
 coupled with a consultation of species distribution maps. Species taxonomy
 was first recorded as presented as in published articles. A final list of
 taxa was then compared with, and resolved according to, the Taxonomic Name
 Resolution Service v. 4.0<em>38</em>. Both original and resolved taxonomy is
 maintained in GLOWCAD. Inclusion of new published data was halted as of
 Dec. 31, 2020. <em>Dead wood C data
 attributes</em> When classifying dead wood data, we considered
 three primary factors associated with woody tissue decomposition and
 related chemical change: A) decay class (DC), B) position, and C) size
 (diameter and length). In the majority of publications, dead woody tissue
 C values were reported along a conventional 1-5 DC scale. These values
 were included in GLOWCAD as published, while noting the DC scale employed.
 In cases where DC was reported as a two-category range (e.g. DC 1-2), the
 higher DC was included in GLOWCAD. In cases where a multiple category DC
 was presented (e.g. DC 3-5), the middle DC value was used in GLOWCAD. In
 the few instances DC was reported along a 0-5 point scale (where DC of 0
 was defined as dead and not live wood), dead wood reported with a DC of 0
 was classified as DC 1. Lastly, in a subset of papers the number of years
 since tree death (instead of DC) was reported. In these cases, years since
 death were converted to DC based on published decay class transition
 metrics (e.g., <sup>39</sup>). When classifying position of dead wood,
 “standing” referred to snags and suspended woody debris, and “downed”
 referred to anything sampled from the forest floor. The default position
 was “downed” for the few publications that did not specify
 position.
description: GLOWCAD is openly available
 for use in any application. It can be accessed via 1) the DRYAD Digital
 Repository (information to be updated upon acceptance), 2) a GitHub
 repository (information to be updated upon acceptance), 3) the TRY Plant
 Trait Database (information to be updated upon acceptance), and 4) upon
 request to the corresponding author. GLOWCAD is licensed under CC-BY
 4.0.