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A Global Database of Litterfall Mass and Litter Pool Carbon and Nutrients
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Revision Date: March  30, 2015

Summary:

Measurement data of aboveground litterfall and littermass and litter carbon, nitrogen, and nutrient concentrations were extracted from 685 original literature sources and compiled into a comprehensive database to support the analysis of global patterns of carbon and nutrients in litterfall and litter pools. Data are included from sources dating from 1827 to 1997.

The reported data include the literature reference, general site information (description, latitude, longitude, and elevation), site climate data (mean annual temperature and precipitation), site vegetation characteristics (management, stand age, ecosystem and vegetation-type codes), annual quantities of litterfall (by class, kg m-2 yr-1), litter pool mass (by class and litter layer, kg m-2), and concentrations of nitrogen (N), phosphorus (P), and base cations for the litterfall (g m-2 yr-1) and litter pool components (g m-2).

The investigators intent was to compile a comprehensive data set of individual direct field measurements as reported by researchers. While the primary emphasis was on acquiring C data, measurements of N, P, and base cations were also obtained, although the database is sparse for elements other than C and N.

Note that litterfall and litter pool masses (as dry matter) were not converted to carbon. This conversion fraction (~0.5 by mass) can vary and so the data compilers did not convert the reported measurements so that others using the database can choose appropriate conversion factors.

Each of the 1,497 records in the database represents a measurement site. Replicate measurements were averaged according to conventions described in Section 5 and recorded for each site in the database. The sites were at 575 different locations.

The database is provided in a single comma delimited (.csv) format file. A Shapefile with litterfall and littermass, and selected nutrient data is also provided. Companion files include the bibliographic sources for the data provided, in both ASCII text (.txt) file and as a .pdf file, and a .pdf file with the definitions for Olson Ecosystem, Holdridge Life Zone, and Matthews vegetation type codes.

global distribution of data in database


Figure 1. Global distribution of the 575 sites in the database.

 

Acknowledgments:

This data collection started with a sabbatical visit in 1987 by W.M. Post to Dr. Paul Zinke’s laboratory at the University of California, Berkeley. Dr. Zinke’s collection of reference materials and those in the UC Berkeley Forestry Library provided a wealth of worldwide data from forestry reports and international literature sources. Additional support for assembling more recently published data was supported by NASA with funding from the ORNL DAAC to Elizabeth Holland, James Sulzman, and Robbie Staufer working at NCAR. A large collection of Russian data was contributed by Olga Krankina. Data published after 1997 are not included in this database.

Data and Documentation Access:

Get Data: http://daac.ornl.gov/cgi-bin/dsviewer.pl?ds_id=1244

Companion Files:

1) The bibliographic sources for the data are provided in ASCII text format, Litterfall_source_bibliography.txt and as Litterfall_source_bibliography.pdf file.

2) The Litterfall_code_companion.pdf file provides the definitions for Olson Ecosystem, Holdridge Life Zone, and Matthews vegetation type codes.

Data Citation:

Cite this data set as follows:

Holland, E. A., W. M. Post, E. Matthews, J. Sulzman, R. Staufer, and O. Krankina. 2015. A Global Database of Litterfall Mass and Litter Pool Carbon and Nutrients. Data set. Available on-line [http://daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, USA. http://dx.doi.org/10.3334/ORNLDAAC/1244

Previous Version Note: The metadata and documentation for this product were previously available from the ORNL DAAC as:

Holland, E. A., W. M. Post, E. Matthews, J. Sulzman, R. Staufer, and O. Krankina. 2005. Global Patterns of Litterfall and Litter Pool Carbon and Nutrients. Data set. Available on-line [http://daac.ornl.gov/] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A.

Previously, the data were only available upon request from W.M. Post. The ORNL DAAC reviewed the site and location data before posting the files on-line. One duplicate site and four locations were corrected (e.g., positive longitudes changed to negative). Documentation was updated to reflect the latest description of SITE_ID (formerly ID) and row uniqueness.

Table of Contents:

1. Data Set Overview:

Measurement data of aboveground litterfall and littermass and litter carbon, nitrogen, and nutrient concentrations were extracted from 685 original literature sources and compiled into a comprehensive database to support the analysis of global patterns of carbon and nutrients in litterfall and litter pools. Data are included from sources dating from 1827 to 1997.

The reported data include the literature reference, general site information (description, latitude, longitude, and elevation), site climate data (mean annual temperature and precipitation), site vegetation characteristics (management, stand age, ecosystem and vegetation-type codes), annual quantities of litterfall (by class, kg m-2 yr-1), litter pool mass (by class and litter layer, kg m-2), and concentrations of nitrogen (N), phosphorus (P), and base cations for the litterfall (g m-2 yr-1) and litter pool components (g m-2).

Note that litterfall and litter pool masses (as dry matter) were not converted to carbon. This conversion fraction (~0.5 by mass) can vary and so the data compilers did not convert the reported measurements so that others using the data base can choose appropriate conversion factors.

The investigators intent was to compile a comprehensive data set of individual direct field measurements as reported by researchers. While the primary emphasis was on acquiring C data, measurements of N, P, and base cations were also obtained, although the database is sparse for elements other than C and N.

Each of the 1,497 records in the database represents a measurement site. Replicate measurements were averaged according to conventions described in Section 5 and recorded for each site in the database. The sites were at 575 different locations.

 

2. Data Characteristics:

Spatial Coverage

There is a generally global distribution of the 575 sites included in the database.

Temporal Coverage

The data are from published studies between 1827-01-01 and 1997-12-31

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

Site (Region) Westernmost Longitude Easternmost Longitude Northernmost Latitude Southernmost Latitude
Global-156.7 176.2 72.5 -54.5

Data File Information

There is one comma separated (.csv) data file and one Shapefile provided with this data set. Missing numeric and text values are represented by -99.

File: Global_Litterfall.csv

What columns uniquely define a row?

The provided file is sorted by SITE_ID and REFERENCE1.

Why do some columns contain only missing values?

The investigators intent was to compile a comprehensive data set of individual direct field measurements as reported by researchers. While the primary emphasis was on acquiring C data, measurements of N, P, and other base cations were also sought, but not always obtained. The blank cells and columns indicate that the reference sources were reviewed for these measurements but no measurements were reported. Therefore, the database is sparse for elements other than C and N. The table below includes two columns that show the completeness of each reported data column.

File: Global_Litterfall.zip

When unzipped, this shapefile contains six files (*.shx, *.dbf, *.prj, *.sbn, *.sbx, and *.shp). Due to shape file volume constraints, the columns Reference and Reference2 were omitted and the sets of columns for Mn, Na, and K concentration were also omitted.

Parameters of the shapefile:

Geometry Type: Point
Geographic Coordinate System: GCS_WGS_1984
Datum: D_WGS_1984
Prime Meridian: Greenwich
Angular Unit: Degree

Extent-
North: 72
South: -54
East: 176
West: -157

Attributes are defined in the following description table.

Table 1. Data file description

Column Number Column Heading Column Name Units Notes Number of non-missing values. 1,497 records. Percent completeness
Site Information Fields ( 0 – 15 ) Missing data code: -99    
       
0 SITE_ID SITE_ID 5-7 digit code Digits 1-3 identify the source publication and digits 4-7 represent different sites for which measurements are reported. Sites defined as “0000” indicate that data are reported for only one site. SITE_ID values are not unique. 1,497 100
1 PLOTNAME PLOTNAME General description of the measurement location, such as country, state, and/or region. 1,497 100
2 LATITUDE LATITUDE Decimal degrees If exact longitude and latitude are not given in the data source, we used descriptions of the site, together with detailed maps, to estimate the longitude and latitude of the site. 1,497 100
3 LONGITUDE LONGITUDE Decimal degrees If exact longitude and latitude are not given in the data source, we used descriptions of the site, together with detailed maps, to estimate the longitude and latitude of the site. 1,497 100
4 ELEVATION ELEVATION m Elevation in meters as reported in the data source. 1,497 100
5 MEANTEMP MEANTEMP degrees C Mean annual temperature was recorded if reported. Otherwise, we used nearest weather station data to estimate MAT for the site. 1,497 100
6 BIOTEMP BIOTEMPERATURE degrees C Biotemperature is the annual mean unit-period temperature with substitution of zero for all temperature values below 0 degrees C and above 30 degrees C. 55 3.7
7 PRECIP PRECIPITATION mm If precipitation was not reported, we used a climate atlas to estimate precipitation. 1,497 100
8 OLSON OLSON CODE Olson Olson Ecosystem codes, 0-99. See code companion file for definitions. 810 54.2
9 LIFEZONE LIFEZONE numeric Holdridge Life Zone Codes, 0-37. See code companion file for definitions. 1,497 100
10 MATTHEWS MATTHEWS CODE numeric Matthews vegetation type code, 1-32. See code companion file for definitions. 1,497 100
11 VEGETATION VEGETATION text Based on the source document, we recorded dominant species, lifeforms, physiognomic descriptions, environmental conditions. 1494 99.8
12 MANAGED MANAGED CODE text Code: Yes (Y); No (N). A site was considered unmanaged if relatively undisturbed at the time measurements were made and managed if strongly influenced by humans. 789 52.8
13 AGE PLOT AGE years If stand is not known to be disturbed then “mature” was assigned. 925 61.8
14 REFERENCE1 REFERENCE1 text Short citation (Author, year, publication, volume, pages) of source publications. See Litterfall_source_bibliography companion file (In combination with SITE_ID, uniquely identifies a data row) 1,497 100
15 REFERENCE2 REFERENCE2 text Short citation (Author, year, publication, volume, pages) of source publications. See Litterfall_source_bibliography companion file. 188 12.6

Column Number Column Heading Column Name Number of non-missing values. 1,497 records Percent completeness
Litter Data Fields ( 16 – 191 )               Missing data code: -99
 
Litterfall: Units are in kg m-2 yr-1
 
16 LFLLW LEAF_FALL 670 44.8
17 SWFLLW SMALL_WOOD_FALL 401 26.8
18 FINFLLW LEAF_AND_SMALL_WOOD_FALL 134  
19 RPRFLLW REPRODUCTIVE_FALL 302 20.2
20 LTRFLLW TOTAL_FINE_LITTER_FALL 650 43.5
21 LWFLLW LARGE_WOOD_FALL 72 4.9
 
Litter Pool Masses: Units are in kg m-2
22 LLEAFW L_LEAF_WEIGHT 83 5.6
2.7 LSWW L_SMALL_WOOD_WEIGHT 39 2.7
24 LFINW L_FINE_WEIGHT 1 0.1
25 LRPRW L_REPRODUCTIVE_WEIGHT 38 2.6
26 LLTRW L_LITTER_WEIGHT 66 4.5
27 FLEAFW F_AND_H_LEAF_WEIGHT 51 3.5
28 FSWW F_AND_H_SMALL_WOOD_WEIGHT 8 0.6
29 FFINW F_AND_H_FINE_WEIGHT 26 1.8
30 FRPRW F_AND_H_REPRODUCTIVE_WEIGHT 8 0.6
31 FLTRW F_AND_H_LITTER_WEIGHT 94 6.3
32 TLEAFW TOTAL_LEAF_WEIGHT 142 9.5
33 TSWW TOTAL_SMALL_WOOD_WEIGHT 151 10.1
34 TFINW TOTAL_FINE_WEIGHT 121 8.1
35 TRPRW TOTAL_REPRODUCTIVE_WEIGHT 27 1.9
36 TLTRW TOTAL_LITTER_WEIGHT 467 31.2
37 LWW LARGE_WOOD_WEIGHT 164 11
 
Litterfall N: Units are in g m-2 yr-1
38 LFLLN LEAF_FALL_N 222 14.9
39 SWFLLN SMALL_WOOD_FALL_N 122 8.2
40 FINFLLN FINE_FALL_N 36 2.5
41 RPRFLLN REPRODUCTIVE_FALL_N 68 4.6
42 LTRFLLN LITTER_FALL_N 335 22.4
43 LWFLLN LARGE_WOOD_FALL_N 39 2.7
 
Litter Pool N: Units are in g m-2
44 LLEAFN L_LEAF_N 4 0.3
45 LSWN L_SMALL_WOOD_N 1 0.1
46 LFINN L_FINE_N 2 0.2
47 LRPRN L_REPRODUCTIVE_N 2 0.2
48 LLTRN L_LITTER_N 43 2.9
49 FLEAFN F_AND_H_LEAF_N 2 0.2
50 FSWN F_AND_H_SMALL_WOOD_N 1 0.1
51 FFINN F_AND_H_FINE_N 1 0.1
52 FRPRNF_AND_H_REPRODUCTIVE_N 1 0.1
53 FLTRN F_AND_H_LITTER_N 49 3.3
54 TLEAFN TOTAL_LEAF_N 36 2.5
55 TSWN TOTAL_SMALL_WOOD_N 28 1.9
56 TFINN TOTAL_FINE_N 5 0.4
57 TRPRN TOTAL_REPRODUCTIVE_N 21 1.5
58 TLTRN TOTAL_LITTER_N 220 14.7
59 LWN LARGE_WOOD_N 30 2.1
 
Litterfall P: Units are in g m-2 yr-1
60 LFLLP LEAF_FALL_P 180 12.1
61 SWFLLP SMALL_WOOD_FALL_P 98 6.6
62 FINFLLP FINE_FALL_P 40 2.7
63 RPRFLLP REPRODUCTIVE_FALL_P 59 4
64 LTRFLLP LITTER_FALL_P 308 20.6
65 LWFLLP LARGE_WOOD_FALL_P 21 1.5
 
Litter Pool P: Units are in g m-2
66 LLEAFP L_LEAF_P 3 0.3
67 LSWP L_SMALL_WOOD_P 1 0.1
68 LFINP L_FINE_P 2 0.2
69 LRPRP L_REPRODUCTIVE_P 2 0.2
70 LLTRP L_LITTER_P 32 2.2
71 FLEAFP F_AND_H_LEAF_P 2 0.2
72 FSWP F_AND_H_SMALL_WOOD_P 1 0.1
73 FFINP F_AND_H_FINE_P 1 0.1
74 FRPRP F_AND_H_REPRODUCTIVE_P 1 0.1
75 FLTRP F_AND_H_LITTER_P 39 2.7
76 TLEAFP TOTAL_LEAF_P 72 4.9
77 TSWP TOTAL_SMALL_WOOD_P 27 1.9
78 TFINP TOTAL_FINE_P 4 0.3
79 TRPRP TOTAL_REPRODUCTIVE_P 19 1.3
80 TLTRP TOTAL_LITTER_P 175 11.7
81 LWP LARGE_WOOD_P 31 2.1
 
Litterfall Ca: Units are in g m-2 yr-1
82 LFLLCA LEAF_FALL_CA 153 10.3
83 SWFLLCA SMALL_WOOD_FALL_CA 80 5.4
84 FINFLLCA FINE_FALL_CA 36 2.5
85 RPRFLLCA REPRODUCTIVE_FALL_CA 51 3.5
86 LTRFLLCA LITTER_FALL_CA 282 18.9
87 LWFLLCA LARGE_WOOD_FALL_CA 21 1.5
 
Litter Pool Ca: Units are in g m-2
88 LLEAFCA L_LEAF_CA 2 0.2
89 LSWCA L_SMALL_WOOD_CA 1 0.1
90 LFINCA L_FINE_CA 2 0.2
91 LRPRCA L_REPRODUCTIVE_CA 2 0.2
92 LLTRCA L_LITTER_CA 37 2.5
93 FLEAFCA F_AND_H_LEAF_CA 2 0.2
94 FSWCA F_AND_H_SMALL_WOOD_CA 1 0.1
95 FFINCA F_AND_H_FINE_CA 1 0.1
96 FRPRCA F_AND_H_REPRODUCTIVE_CA 1 0.1
97 FLTRCA F_AND_H_LITTER_CA 43 2.9
98 TLEAFCA TOTAL_LEAF_CA 64 4.3
99 TSWCA TOTAL_SMALL_WOOD_CA 20 1.4
100 TFINCA TOTAL_FINE_CA 8 0.6
101 TRPRCA TOTAL_REPRODUCTIVE_CA 19 1.3
102 TLTRCA TOTAL_LITTER_CA 171 11.5
103 LWCA LARGE_WOOD_CA 21 1.5
 
Litterfall Mg: Units are in g m-2 yr-1
104 LFLLMG LEAF_FALL_MG 131 8.8
105 SWFLLMG SMALL_WOOD_FALL_MG 66 4.5
106 FINFLLMG FINE_FALL_MG 29 2
107 RPRFLLMG REPRODUCTIVE_FALL_MG 45 3.1
108 LTRFLLMG LITTER_FALL_MG 258 17.3
109 LWFLLMG LARGE_WOOD_FALL_MG 21 1.5
 
Litter Pool Mg: Units are in g m-2
110 LLEAFMG L_LEAF_MG 2 0.2
111 LSWMG L_SMALL_WOOD_MG 1 0.1
112 LFINMG L_FINE_MG 2 0.2
113 LRPRMG L_REPRODUCTIVE_MG 2 0.2
114 LLTRMG L_LITTER_MG 31 2.1
115 FLEAFMG F_AND_H_LEAF_MG 2 0.2
116 FSWMG F_AND_H_SMALL_WOOD_MG 1 0.1
117 FFINMG F_AND_H_FINE_MG 1 0.1
118 FRPRMG F_AND_H_REPRODUCTIVE_MG 1 0.1
119 FLTRMG F_AND_H_LITTER_MG 38 2.6
120 TLEAFMG TOTAL_LEAF_MG 63 4.3
121 TSWMG TOTAL_SMALL_WOOD_MG 20 1.4
122 TFINMG TOTAL_FINE_MG 8 0.6
123 TRPRMG TOTAL_REPRODUCTIVE_MG 19 1.3
124 TLTRMG TOTAL_LITTER_MG 141 9.5
125 LWMG LARGE_WOOD_MG 20 1.4
 
Litterfall K: Units are in g m-2 yr-1
126 LFLLK LEAF_FALL_K 145 9.7
127 SWFLLK SMALL_WOOD_FALL_K 84 5.7
128 FINFLLK FINE_FALL_K 37 2.5
129 RPRFLLK REPRODUCTIVE_FALL_K 54 3.7
130 LTRFLLK LITTER_FALL_K 283 19
131 LWFLLK LARGE_WOOD_FALL_K 21 1.5
 
Litter Pool K: Units are in g m-2
132 LLEAFK L_LEAF_K 4 0.3
133 LSWK L_SMALL_WOOD_K 1 0.1
134 LFINK L_FINE_K 2 0.2
135 LRPRK L_REPRODUCTIVE_K 2 0.2
136 LLTRK L_LITTER_K 28 1.9
137 FLEAFK F_AND_H_LEAF_K 2 0.2
138 FSWK F_AND_H_SMALL_WOOD_K 1 0.1
139 FFINK F_AND_H_FINE_K 1 0.1
140 FRPRK F_AND_H_REPRODUCTIVE_K 1 0.1
141 FLTRK F_AND_H_LITTER_K 35 2.4
142 TLEAFK TOTAL_LEAF_K 63 4.3
143 TSWK TOTAL_SMALL_WOOD_K 20 1.4
144 TFINK TOTAL_FINE_K 8 0.6
145 TRPRK TOTAL_REPRODUCTIVE_K 19 1.3
146 TLTRK TOTAL_LITTER_K 160 10.7
147 LWK LARGE_WOOD_K 24 1.7
 
Litterfall Na: Units are in g m-2 yr-1
148 LFLLNA LEAF_FALL_NA 42 2.9
149 SWFLLNA SMALL_WOOD_FALL_NA 22 1.5
150 FINFLLNA FINE_FALL_NA 11 0.8
151 RPRFLLNA REPRODUCTIVE_FALL_NA 12 0.9
152 LTRFLLNA LITTER_FALL_NA 75 5.1
153 LWFLLNA LARGE_WOOD_FALL_NA 9 0.7
 
Litter Pool Na: Units are in g m-2
154 LLEAFNA L_LEAF_NA 1 0.1
155 LSWNA L_SMALL_WOOD_NA 1 0.1
156 LFINNA L_FINE_NA 2 0.2
157 LRPRNA L_REPRODUCTIVE_NA 2 0.2
158 LLTRNA L_LITTER_NA 12 0.9
159 FLEAFNA F_AND_H_LEAF_NA 1 0.1
160 FSWNA F_AND_H_SMALL_WOOD_NA 1 0.1
161 FFINNA F_AND_H_FINE_NA 1 0.1
162 FRPRNA F_AND_H_REPRODUCTIVE_NA 1 0.1
163 FLTRNA F_AND_H_LITTER_NA 11 0.8
164 TLEAFNA TOTAL_LEAF_NA 38 2.6
165 TSWNA TOTAL_SMALL_WOOD_NA 2 0.2
166 TFINNA TOTAL_FINE_NA 5 0.4
167 TRPRNA TOTAL_REPRODUCTIVE_NA 1 0.1
168 TLTRNA TOTAL_LITTER_NA 19 1.3
169 LWNA LARGE_WOOD_NA 2 0.2
 
Litterfall Mn: Units are in g m-2 yr-1
170 LFLLMN LEAF_FALL_MN 2 0.2
171 SWFLLMN SMALL_WOOD_FALL_MN 2 0.2
172 FINFLLMN FINE_FALL_MN 2 0.2
173 RPRFLLMN REPRODUCTIVE_FALL_MN 0 0
174 LTRFLLMN LITTER_FALL_MN 19 1.3
175 LWFLLMN LARGE_WOOD_FALL_MN 0 0
 
Litter Pool Mn: Units are in g m-2
176 LLEAFMN L_LEAF_MN 0 0
177 LSWMN L_SMALL_WOOD_MN 0 0
178 LFINMN L_FINE_MN 0 0
179 LRPRMN L_REPRODUCTIVE_MN 0 0
180 LLTRMN L_LITTER_MN 0 0
181 FLEAFMN F_AND_H_LEAF_MN 0 0
182 FSWMN F_AND_H_SMALL_WOOD_MN 0 0
183 FFINMN F_AND_H_FINE_MN 0 0
184 FRPRMN F_AND_H_REPRODUCTIVE_MN 0 0
185 FLTRMN F_AND_H_LITTER_MN 0 0
186 TLEAFMN TOTAL_LEAF_MN 1 0.1
187 TSWMN TOTAL_SMALL_WOOD_MN 0 0
188 TFINMN TOTAL_FINE_MN 0 0
189 TRPRMN TOTAL_REPRODUCTIVE_MN 0 0
190 TLTRMN TOTAL_LITTER_MN 0 0
191 LWMN LARGE_WOOD_MN 0 0

3. Data Application and Derivation:

These data can be used to support the analysis of global patterns of carbon and nutrients in litterfall and litter pools of carbon and nutrients.

 

4. Quality Assessment:

Data sources did not always divide litterfall into the same categories. To accommodate various reporting practices a hierarchy of six categories was developed. Leaf, small wood, reproductive, and large wood were chosen as nominal categories. In addition, “leaf+small wood” and “total fine”  are provided for those studies that did not subdivide the component fractions (Table 2, below).

Different investigators applied different definitions of small wood. The cutoff between small and large wood ranges from 2 mm to 5 cm in diameter. Small wood is defined as  <5 mm when possible. Otherwise the investigators’ definition (sometimes unstated) was used. As a result, the size of material considered to be small wood varies among the data sources.

5. Data Acquisition Materials and Methods:

Literature Review:

Investigators exclusively used literature sources reporting primary measurements of litterfall and littermass. The litter database was developed from about 685 original documents. Data was extracted from published and unpublished documents in the categories of journal articles, books, edited books, technical reports, and theses with publication dates ranging from 1867 to 1997. A complementary bibliographic data set comprising every document used in the compilation was created.

These collections were greatly aided by the reviews of Bray and Gorham (1964), Hutson and Veitch (1985), O’Neill and DeAngelis (1981), Proctor (1983), Vitousek (1984), and Vogt et al. (1986), A first assessment of the utility and thoroughness of our collection took place at a working group meeting hosted by the Max Planck Institute for Biogeochemistry.

Attention was paid to getting relatively complete representation of sites across ecosystem type, climatic regime, and global spatial distribution. Carbon data was of primary concern but measurements for other nutrients were also obtained and include N, P, magnesium (Mg), calcium (Ca), potassium (K), sodium (Na), and manganese (Mn). The data set remains sparse for elements other than C and N. When possible, compositional information (leaf, small wood, reproductive, coarse wood) was retained. Turnover times and decay rates were able to be estimated using this information.

Guidelines for Extracting and Reporting Data:

With such a wide-ranging collection of source literature, deriving a consistent set of guidelines for extracting the data proved difficult. Our approach was to develop guidelines and to include notes with the measurements to increase the probability that the details would be clear about how the primary data was handled. In summary, the reference, site information, and measurements of carbon and nutrients or litter fall and litter pool components were recorded. The measurements were reported in many different units and converted into kg m-2 for dry mass, and into g m-2 for N, P, and nutrients.

Note that dry matter was not converted to carbon. This conversion fraction (~0.5 by mass) can vary and so the reported measurements were not converted so that others using the database could choose appropriate conversion factors.

Each record in the database represents a site. The intention was to compile a comprehensive data set of individual direct field measurements reported by researchers. Most often site averages from replicate research plots were reported in the literature source. However, reported measurements were averaged under the following two circumstances. (1) replicate measurements obtained from a series of plots or litterfall traps at a single site were averaged when the plots were established to characterize spatial variability within a relatively uniform cover type. (2) measurements obtained in consecutive years at a single site were averaged when these measurements were designed to capture interannual variability of a relatively uniform cover type. The averages were recorded in the database. If several measurements were reported, even if for the same litter feature (like leaf litter pool or coarse wood pool), but otherwise distinguished as different by the author (e.g., along an elevational gradient, chronosequence, or completely unrelated in space), these measurements were treated as representing different sites. If several measurements were made during the year to account for seasonal variation then we summed litterfall measurements and reported an annual total and average litter pool measures and reported an annual average. In most cases only a single measurement period is reported. In the case of litterfall this is most often at the beginning of the dormant period when most, but not all, the litterfall occurs. For littermass, one-time measurements are problematic in ecosystems with large seasonal variation in the amount of littermass. If measurements are not taken in the same season then unintended variation is introduced. Often, littermass is measured when it is maximal, at the beginning of the dormant season. Seasonal variation was not adjusted when one time measurements were reported.

Exclusions and Exceptions:

For every source document, the site description, method, and results were carefully reviewed. If a study site was not described well enough to locate within 0.5 degree latitude or longitude, measurements from the source were not used. Data were also omitted if litter fall or litter pools were not reported as oven-dry weight or if units were indecipherable. The only exception made to this dry-weight standard was for standing dead mass since this material is extremely difficult to harvest and dry. Often the weight of standing dead material is estimated using a volume estimate which is already converted to dry weight. The presence or absence of ash, an estimate of non-organic matter in litter and frequently reported with dry mass measurements, was not a criterion used to include or exclude measurements. However, if ash was reported separately from dry mass, the ash weight was subtracted and ash free dry weight was reported.

General Description of Litterfall and Littermass Data Categories

Litterfall:

In nearly every data source only aboveground litterfall production was reported. This database is therefore limited to aboveground litterfall. All reported measurements were converted to weight per unit area and totaled, when appropriate, to year values. For litterfall dry weight we report kg m-2 yr-1. For nutrients we use g m-2 yr-1.

Litterfall may be divided into many categories. Data sources did not always divide litterfall into the same categories. To accommodate various reporting practices we developed a hierarchy of 6 categories. We chose leaf, small wood, reproductive, and large wood as nominal categories. We also provide “leaf+small wood” and “total fine” for those studies that did not subdivide the component fractions (Table 2).

Table 2. Hierarchy of litterfall and littermass categories for plant tissue category used in the database.

Lumped Categories Nominal Categories Split Categories
Total fine Leaf + Small wood Leaf Blade
Petiole
Bud scales
Small wood Twig
Small branch
Bark
Reproductive Reproductive Flower
Pollen
Fruit (seed, fleshy part, husk, cone, etc.)
Large wood Large wood Large branch (fallen)
Bole (fallen)
Standing dead
Not included Not included Roots (fine, small, large)

When possible reported measurements were either lumped or split to fit our nominal categories. If this was not possible the information was recorded in the appropriate lumped categories. In many cases, particularly for reproductive and large wood, not all categories of litterfall were reported. In these cases the corresponding nominal category and any lumped categories that contain this nominal category were marked missing. Different investigators applied different definitions of small wood. The cutoff between small and large wood ranges from 2 mm to 5 cm in diameter. Small wood was defined as  <5 mm when possible. Otherwise the investigators’ (sometimes unstated) definition was used. As a result, the size of material considered to be small wood varies among the data sources.

Littermass:

Littermass measurements reported were converted to weight per unit area. Littermass dry weight is reported as kg m-2. Littermass nutrients is reported as g m-2.

Littermass measurements were divided into categories based on types of plant tissues in the same fashion as litterfall described above.

Littermass pools are often divided into temporal categories based on the degree of decomposition of the constituent materials. These are frequently reported separately because of their differences in nutrient content and importance in nutrient cycling (Aber et al. 1978). These different littermass pools form vertical layers with the most decomposed layer next to the soil surface and the freshest material on the top. The surface or L-layer consists of freshly fallen material that is intact and relatively undecomposed. The next layer down is called the fermentation or F-layer and is largely fragmented, colonized by microbial and fungal decomposers, but still recognizable as to the category of plant tissue. The third layer, in contact with the mineral soil surface is considerably transformed, physically and chemically. This layer is referred to as the humification or H-layer and may or may not be easily distinguished from the surface mineral soil layer. The L, F and H layers are alternatively referred to as the Oa, Oe and Oi layers respectively. In practice it is difficult to objectively distinguish the F and H layers so they are often combined into a F+H layer. If the investigator distinguished separate littermass layers the data were recorded separately into L and F+H categories. If these layers were not distinguished the littermass data were entered as Total category for each plant tissue category (see Table 3).

Table 3. Hierarchy of littermass categories for decomposition category used in the database.

Lumped Categories Nominal Categories Split Categories
Total litter

L layer L layer Oa layer
F+H layer F layer Oe layer
H layer Oi layer

6. Data Access:

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

Data Archive Center:

Contact for Data Center Access Information:

E-mail: uso@daac.ornl.gov
Telephone: +1 (865) 241-3952

7. References:

Aber, J.D., D.B. Botkin, and J.M. Melillo 1978. Predicting the effects of different harvesting regimes on forest floor dynamics in northern hardwoods. Can. J. For. Res. 8:306-315.

Bray, J.R. and E. Gorham 1964. Litter production in forests of the world. Advances in Ecological Research 2:101-157.

Hutson, B.R., and L. G. Veitch. 1985. Relationships between litterfall rate, litter mass and decomposition rate in Eucalyptus forests in southeastern Australia. Australian Journal of Ecology 10.4: 443-450.

O’Neill, R.V. and D.L. DeAngelis 1981. Comparative productivity and biomass relations of forest ecosystems. Dynamic Properties of Forest Ecosystems, 411-449.

Proctor, J. 1983. Tropical forest litterfall. I. Problems of data comparison. Special publications series of the British Ecological Society. Vitousek PM. 1984. Litterfall, nutrient cycling and nutrient limitation n tropical forests. Ecology 65:285-298.

Vitousek PM. 1984. Litterfall, nutrient cycling and nutrient limitation n tropical forests. Ecology 65:285-298.

Vogt, K.A., C.C. Grier, and D.J. Vogt 1986. Production, Turnover, and Nutrient Dynamics of Above- and Belowground Detritus of World Forests. Advances in Ecological Research 15:303-377.

The bibliographic sources for the data are provided as a companion file in ASCII text format, Litterfall_source_bibliography.txt.