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NPP Grassland: NPP Estimates from Biomass Dynamics for 31 Sites, 1948-1994, R1
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Revision date: May 29, 2015

Summary:

This data set includes monthly grassland biomass data, net primary productivity (NPP) estimates, and climate (rainfall amounts and temperature) data for multiple study sites in major grassland types worldwide.  Field measurements of biomass and associated environmental data were compiled for the multiple grassland study sites. When sufficient biomass data were available, NPP was estimated by six different algorithms for 31 grassland sites to examine potential bias associated with the algorithms (Scurlock et al., 2002).

The data consisted of monthly measurements of biomass components including aboveground live material, standing dead, litter, belowground biomass, and belowground dead material. However, many of the sites did not collect all of the components. There are 1,477 field measurements of some component of NPP, all sites having at least aboveground biomass measurements. Of the 31 sites, 20 also measured standing dead and litter or total live plus dead material. In addition, 17 sites measured total belowground biomass, and six of these sites provided separate measurements of live and dead root components. The study sites had from 1 to 29 years of biomass data with an average of three years per site. Five ecoregions were represented, including cold desert steppe, temperate dry steppe, humid savanna, humid temperate, and savanna.

Climatological data for each study site (precipitation, mean monthly maximum temperature, mean monthly minimum temperature) were obtained from the original literature or the original authors, if available. Alternatively, we obtained the climate data from the nearest weather station (<10-km distant, and at similar elevation) if available from existing collections such as the National Climatic Data Center (Asheville, NC, USA.) or the Carbon Dioxide Information and Analysis Center (CDIAC, Oak Ridge National Laboratory, Oak Ridge, TN, USA).

The selection of study sites was based on the availability of complete and consistent information on NPP or at least partial NPP, together with the dynamics of live biomass and dead matter for at least the growing season (Scurlock et al. 2002). Site-description metadata, such as latitude, longitude, elevation, and information on vegetation type (biome), soil type, and land-use history were also desirable for inclusion for study sites in the compilation. Study sites were included that had at least one reference from the peer-reviewed literature.

There are two data files in comma-separated (.csv) format with this data set.

Revision Notes: Only the documentation for this data set has been modified from the original data set publication.

Data Citation:

Cite this data set as follows:

Scurlock, J.M.O., K R. Johnson, and R.J. Olson. 2015. NPP Grassland: NPP Estimates from Biomass Dynamics for 31 Sites, 1948-1994, R1. 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/654

This data set was originally published as:

Scurlock, J. M. O., K. R. Johnson, and R. J. Olson. 2003. NPP Grassland: NPP Estimates from Biomass Dynamics for 31 Sites, 1948-1994. Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A.

Table of Contents:

1. Data Set Overview:

Project: Net Primary Productivity (NPP)

This data set includes monthly grassland biomass data and net primary productivity (NPP) estimates.  Field measurements of biomass and associated environmental data were compiled for multiple study sites in major grassland types worldwide. The selection of study sites was based on the availability of complete and consistent information on NPP or at least partial NPP, together with the dynamics of live biomass and dead matter for at least the growing season (Scurlock et al., 2002). Site description metadata, such as latitude, longitude, elevation, and information on vegetation type (biome), soil type, and land-use history were also desirable for inclusion for study sites in the compilation.

2. Data Description:

Spatial Coverage

Site: Global grassland sites

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

Site (Region) Westernmost Longitude Easternmost Longitude Northernmost Latitude Southernmost Latitude
Global grassland sites -110.78 146.27 60.83 -45.6

Spatial Resolution

Information not available

Temporal Coverage

1948-01-15 - 1994-12-15

Temporal Resolution

Annual estimates derived from monthly measurements.

Data File Information

There are two data files in comma-separated format (.csv) with this data set: Grassland NPP_biomass_months.csv and Grassland NPP_site_summary.csv.

Biomass units (mainly reported in g/m2) are documented in individual NPP data sets available from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Missing or unavailable values are represented by -9999.

File: Grassland NPP_biomass_months (contains 1,477 biomass field measurements)

Variable Description
SITE Unique 3-character site code
TREATMNT Treatment designation
YEAR Year of measurement
MONTH Month of measurement
DAY Day of measurement
JDATE Julian day of year
AGBMASS Above-ground biomass
AGTOTCLP Aboveground total, live + dead
CROWN Crown (IBP sites), added to agbmass
BGTOTMAT Below-ground total, live + dead
STDEAD Standing dead material
LITTER Dead material on ground
BGBMASS Below-ground live root material
BGDEAD Below-ground dead root material
AGTOTMAT Above-ground total, live + dead

Example data records from the Grassland NPP_biomass_months data file:

SITE,TREATMNT,YEAR,MONTH,DAY,JDATE,AGBMASS,AGTOTCLP,CROWN,BGTOTMAT,
STDEAD,LITTER,BGBMASS,BGDEAD,AGTOTMAT
bcn,lngtrm,1972,3,30,90,67.7,-9999,-9999,-9999,-9999,-9999,-9999,-9999,574.4
bcn,lngtrm,1972,6,2,154,198.4,-9999,-9999,-9999,-9999,-9999,-9999,-9999,570.7

File: Grassland NPP_site_summary (contains location, climate, and vegetation characteristics for 31 sites, along with NPP estimates by five methods). For a list of associated references, please refer to the companion file Grassland_NPP_31_References.pdf.

Variable Description
Site Unique 3-character site code
Name Site name
Country Country
Rainfall Mean annual precipitation (mm)
Temperature Mean annual temperature (degrees C)
Elevation Elevation (m)
Latitude Latitude provided in decimal degrees
Longitude Longitude provided in decimal degrees
C3_C4 Type of dominant vegetation C3 or C4
Vegetation Vegetation description
Ecoregion General ecoregion or biome
ECORGN_Bailey Specific ecoregion according to Bailey
Reference Literature citation for site
Start First year of NPP measurements
End Last year of NPP measurements
N_years Number of years
N_trtmt Number of treatments
Ny_x_Nt Total number of years and treatments
AGbiomass/litter Type of aboveground biomass or litter data: Single, Monthly, NA
Bgbiomass Type of below-ground biomass data- Single, Monthly, NA
ANPP_lit ANPP from literature (g/m2/year)
BNPP_lit BNPP from literature (g/m2/year)
TNPP_lit TNPP from literature (g/m2/year)
NYR Number of years used in analysis
MAX_MON Month with maximum ANPP
ANPP1 ANPP Calculated using Method 1
ANPP2 ANPP Calculated using Method 2
ANPP3 ANPP Calculated using Method 3
ANPP4 ANPP Calculated using Method 4
ANPP5 ANPP Calculated using Method 5
ANPP6 ANPP Calculated using Method 6
BNPP1 BNPP Calculated using Method 1
BNPP2 BNPP Calculated using Method 2
BNPP3 BNPP Calculated using Method 3
BNPP4 BNPP Calculated using Method 4
BNPP5 BNPP Calculated using Method 5
NPP1 NPP Calculated using Method 1
NPP2 NPP Calculated using Method 2
NPP3 NPP Calculated using Method 3
NPP4 NPP Calculated using Method 4
NPP5 NPP Calculated using Method 5

Methods referenced in the Grassland NPP_site_summary. See Table 1 of Scurlock et al. 2002 for specific details.

Method Description
1 Peak live biomass
2 Peak standing crop (live plus standing dead matter)
3 Maximum minus minimum live biomass
4 Sum of positive increments in live biomass
5 Sum of positive increments in live and dead plus litter

Example data records from the Grassland NPP_site_summary data file:

Site,Name,Country,Rainfall,Temperature,Elevation,Latitude, Longitude,C3_C4,Vegetation,Ecoregion,ECORGN_Bailey,
Reference,Start,End,N_years,N_trtmt,Ny_x_Nt,AGbiomass/litter, Bgbiomass,ANPP_lit,BNPP_lit,TNPP_lit,NYR,
MAX_MON,ANPP1, ANPP2,ANPP3,ANPP4,ANPP5,ANPP6,BNPP1,BNPP2,BNPP3,BNPP4,BNPP5,NPP1,
NPP2,NPP3,NPP4,NPP5
bcn,Beacon Hill,U.K.,858,11,205,50.92, -0.85,C3,chalk grassland,Humid temperate,Humid temperate broadleaf
forest(243),Williamson(1976),1972,1973,1,1,1, monthly,N/A,691, -9999,-9999,1,8,355,574,287,287,333,287,
-9999,-9999,-9999,-9999,-9999,-9999,-9999,-9999,-9999,-9999
bdk,Badkhyz,Turkmenistan,310,12.6,700,35.68,62,C3,desert steppe, Temperate dry steppe,Temperate dry steppe (343),
Gilmanov et al. (1997),1948,1982,34,1,34,monthly,N/A,100, -9999,-9999,17,5,54,-9999,50,50,-9999,-9999,-9999,
-9999,-9999,-9999,-9999,-9999,-9999,-9999,-9999,-9999

3. Data Application and Derivation:

These grasslands represent a wide environmental gradient. The field data from these study sites were used Gilmanov et al. (1997) to assess grassland differences and CENTURY model robustness.

Grassland biomass dynamics data are provided for comparison with models and estimation of NPP. Climate data are provided for use in driving ecosystem/NPP models.

4. Quality Assessment:

Study sites were included that had at least one reference from the peer-reviewed literature. Quality assurance included mapping the points in geographical space to confirm that they coincided with landforms and checking data ranges for outlying values. For consistency, only measurements from long-term natural or ungrazed treatments were used in the analysis of Scurlock et al. (2002), although measurements are available for manipulated study sites from the ORNL DAAC's NPP data set collection. One of the 31 sites (i.e., Kurukshetra, India) appeared to be an outlier because it has an ANPP that is three to seven times that of the other grassland sites. The high NPP may be a consequence of some undocumented factor such as a previous history of fertilization at the study site. Kurukshetra was included because it met all other criteria for inclusion.

5. Data Acquisition Materials and Methods:

The selection of study sites was based on the availability of complete and consistent information on NPP or at least partial NPP, together with the dynamics of live biomass and dead matter for at least the growing season (Scurlock et al., 2002). Site description metadata, such as latitude, longitude, elevation, and information on vegetation type (biome), soil type, and land-use history were also desirable for inclusion for study sites in the compilation.

The original grassland biomass observations were processed for each site to generate data sets that had common variable names, units of measure, and organization. For example, it was assumed that the variables described in the original literature as outstanding dead, recent dead, and dead were equivalent, representing plant matter which was produced and had died within the current year, and that the variables old dead and litter usually represent the accumulation of previous years' production. Some sites lacked desired information, such as the day of the month that measurements were recorded, or required decisions to assemble the data, such as combining above-ground and below-ground measurements when the components were measured on different days. When possible in these cases, the original literature was examined or authors were contacted to confirm our data processing decisions.

Above-ground and below-ground components were processed separately, and, if measurements for both components were available, above-ground NPP (ANPP) and below-ground NPP (BNPP) were summed to provide total NPP for the site. In the summary of annual NPP, sites with fewer than five biomass measurements for a year were dropped to ensure that the entire growing season was represented (assuming most sites measured biomass on an approximately monthly schedule).

Climatological data for each study site (precipitation, mean monthly maximum temperature, mean monthly minimum temperature) were obtained from the original literature or the original authors, if available. Alternatively, we obtained the climate data from the nearest weather station (<10-km distant, and at similar elevation) if available from existing collections such as the National Climatic Data Center or from CDIAC.

In addition to grasslands, the ORNL DAAC's NPP data set collections includes forest sites based upon field observations (Scurlock and Olson, 2002) to address the need for a high quality data to parameterize, calibrate, and validate terrestrial biosphere models (Olson et al., 2001). NPP estimates in the database draw primarily on the published estimates of NPP. While this analysis of grassland methods demonstrated a potential bias of estimated NPP depending biome type and on which method was used, users are encouraged to review site information to decide which NPP estimates are appropriate for a particular application.

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:

Gilmanov, T.G., W.J. Parton and D.S. Ojima. 1997. Testing the CENTURY ecosystem level model on data sets from eight grassland sites in the former USSR representing a wide climatic/soil gradient. Ecological Modelling 96: 191-210. doi: 10.1016/S0304-3800(96)00067-1

Scurlock, J. M. O., K. Johnson, and R. J. Olson. 2002. Estimating net primary production from worldwide extant grassland biomass dynamics measurements. Global Change Biology 8:736-748.

Scurlock, J. M. O., and R. J. Olson. 2002. Terrestrial Net Primary Productivity--A brief history and a new worldwide database. Environmental Reviews 10:91-109.

Olson, R. J ., K. Johnson, D. Zheng, and J. M. O. Scurlock. 2001. Global and Regional Ecosystem Modeling: Databases of Model Drivers and Validation Measurements. ORNL/TM-2001/196. Oak Ridge National Laboratory, Oak Ridge, Tennessee.