Revision Date: October 05, 2005

NPP Grassland: Central Plains Experimental Range (SGS), U.S.A., 1970-1975

Summary:

Productivity of a shortgrass prairie steppe was monitored at the Central Plains Experimental Reserve (CPER), also known as the Pawnee Grassland study site, from 1939 to the present. Measurement of monthly dynamics of above-ground plant biomass were made from 1970 to 1975, for untreated and treated plots with irrigation, fertilisation, and both irrigation and fertilisation together. Annual above-ground net primary production (NPP) was estimated by summing peak total biomass for different functional groups of vegetation between 1970 and 1975, and long-term annual above-ground NPP between 1939 and 1990 was estimated by correlation with records of forage production. Above and below ground NPP estimates, using (i) biomass increment methods and (ii) 14-C turnover methods, are available for 1985-88. Work was originally carried out by the US Agricultural Research Service, and later under the US Long-Term Ecological Research (LTER) programme. Data on soil dynamics at CPER were used in the development of the CENTURY plant/soil organic matter model.

Climate data for this site are also available: see Any Other Relevant Information in section 11 of this document.

More information on the entire Net Primary Production Project can be found at the NPP homepage.

Table of Contents

  1. Data Set Overview
  2. Investigator(s)
  3. Theory of Measurements
  4. Equipment
  5. Data Acquisition Methods
  6. Observations
  7. Data Description
  8. Data Organization
  9. Data Manipulations
  10. Errors
  11. Notes
  12. Application of the Data Set
  13. Future Modifications and Plans
  14. Software
  15. Data Access
  16. Output Products and Availability
  17. References
  18. Glossary of Terms
  19. List of Acronyms
  20. Document Information

1. Data Set Overview:

Data Set Identification:

NPP Grassland: Central Plains Experimental Range (SGS), U.S.A., 1970-1975

Data Set Introduction:

The CPER study site (40.82 N 104.77 W) is situated near the town of Nunn in northern Colorado, U.S.A., about 110 km north of Denver. The shortgrass prairie is typically grazed annually by domestic animals, and would have been grazed by wild buffalo prior to the mid 19th century. Some of the region has been converted to arable crops, and some has subsequently been restored to grassland under the US Conservation Reserve Programme (Dodd and Lauenroth, 1979; Lauenroth and Sala, 1992).

Objective/Purpose:

Net primary productivity was determined, initially under the auspices of the US Agricultural Research Service, since there was a lack of information on the grazing capacity of the Great Plains.

Summary of Parameters:

There are nineteen (19) parameters for this dataset. Items 1 and 2 refer to the site and the treatment of the site. Items 3, 4, 5, and 6 indicate the date of data collection.
1. Site
2. Treatment
3. Year
4. Month
5. Day
6. Julian date
7. Date in decimal year
8. Above ground live biomass of herbaceous layer
9. Above ground live biomass of forbs
10. Above ground live biomass of grasses
11. Dead herbaceous matter
12. Dead forb matter
13. Dead grass matter
14. Total clipped matter for herbaceous layer
15. Above ground live biomass of shrubs and succulents
16. Dead shrubs and succulents
17. Above ground biomass
18. Standing dead
19. Total above-ground clipped matter

Discussion:

Annual peak biomass data are available 1939-1990, with more detailed data on monthly above-ground biomass dynamics for several treatments 1970-1975.

Related Data Sets

NPP data from other grassland sites are available elsewhere in this archive. Summary tables containing site characteristics and meta-data for all the grassland sites are also available.

2. Investigator(s):

Investigator(s) Name and Title:

Dr. W.K. Lauenroth

Title of Investigation:

Determination of net primary productivity of a short-grass prairie steppe in Colorado.

Contact Information:

Contact 1:

Dr. W.K. Lauenroth
Natural Resource Ecology Laboratory
Colorado State University
Fort Collins, Colorado 80523
U.S.A.
Telephone: +1 (970) 491-7581
Fax: +1 (970) 491-1965
Email Address: billl@bouteloua.cfnr.colostate.edu

Contact 2:

Dr. W.J. Parton
Natural Resource Ecology Laboratory
Colorado State University
Fort Collins, Colorado 80523
U.S.A.
Telephone: +1 (970) 491-1987
Fax: +1 (970) 491-1965
Email Address: billp@poa.nrel.colostate.edu

3. Theory of Measurements:

Net primary production (NPP), sensu stricto, is the total photosynthetic gain (less respiratory losses) of vegetation per unit ground area. For a given period, this is equal to the change in plant mass plus any losses due to death and deomposition, measured for both above ground and below ground plant parts. Earlier estimates of grassland NPP were based on peak standing dry matter only, and the studies of the International Biological Programme (IBP) in the late 1960s and early 1970s were based mainly on above-ground biomass changes, with few estimates of below-ground production.

Peak above-ground live biomass (or in some cases, the difference between maximum and minimum biomass) has been used as an estimate of net primary production - usually where only one or two measurements per year are available. Sometimes a conversion factor has been applied to take account of estimated turnover and the estimated ratio of above-ground to below-ground dry matter.

The "IBP Standard Method" of Milner and Hughes (1968) assumes that where live biomass increases between successive samples, production equals this increase; where biomass decreases or remains the same, production is assumed to be zero. Annual production is then obtained by summing the estimates for each sample interval.

Essentially, this method was used for the IBP synthesis by Singh and Joshi (1979), in particular for their estimates of below-ground production. A modified method was used for above-ground production, determined by a decision matrix (Singh et al., 1975); where increments in live biomass coincided with increases in standing dead matter, the latter were added to the monthly production.

The limitations of the above methods are discussed in detail by Long et al. (1989). In particular, the peak biomass method and variations on the IBP method underestimate production by not accounting for simultaneous growth and death. This may be significant in temperate grasslands with a long growing season, and is particularly a problem in tropical grasslands where the growing season may extend over much of the year. Some limited overestimation may occur by not accounting for periods of negative NPP (due to stress, or translocation between above and below ground plant parts) but underestimation of root turnover is probably the largest source of error. Long et al. (1989) estimated NPP for three terrestrial tropical grassland sites by summing monthly changes in live biomass plus losses due to death and decomposition for above and below ground vegetation. Monthly losses were determined as the change in dead matter plus the estimated disappearance of dead matter through decomposition. Dead matter disapperance was calculated each month as the product of relative decomposition rate and mean amount of dead matter.

Although some correlation between estimates obtained using different methods has been reported (Singh et al., 1975), the degree of underestimation may be strongly site-specific (Linthurst and Reimold, 1978; Long and Mason, 1983). Where sufficient data are available for a given grassland site, it may be possible to estimate NPP according to the different methods for the purposes of comparison. This may involve entry of data into algorithms or a spreadsheet containing these algorithms.

4. Equipment:

Sensor/Instrument Description:

Collection Environment:

Ground level

Platform/Source:

Field investigation

Platform/Source Mission Objectives:

Determination of net primary productivity

Key Variables:

Above-ground live/dead biomass of herbaceous layer, forbs, grasses, shrubs and succulents;
Total clipped matter for herbaceous layer, above ground biomass;
Above ground biomass; Standing dead

Principles of Operation:

SEE "3. Theory" Above

Sensor/Instrument Measurement Geometry:

Not Applicable

Manufacturer of Sensor/Instrument:

Information Not Available

Calibration:

Not Applicable

5. Data Acquisition Methods:

Between 1970 and 1975, seasonal biomass dynamics were determined by harvesting at approximately monthly intervals (Dodd and Lauenroth, 1979). From 1970 to 1972, total standing crop was determined by species, and from 1973 to 1975, the harvested plant matter was separated into live biomass, standing dead matter, dead matter from the previous year, and perennial vegetation.

Dry weight of each above ground category was determined each month by clipping to ground level within 10-12 circular quadrats of 0.5 m2. Below-ground plant matter was sampled in late summer from 1972 to 1974.

6. Observations:

Data/Field Notes:

Refer to Principal Investigator (see 2. above) for details of any peculiar conditions at the time of data collection

site elevation (m): 1625

mean annual precipitation (mm): 310

mean monthly min temperature (C): -10.9 (Jan)

mean monthly maximum temperature (C): 30.6 (July)

vegetation type: shortgrass prairie

dominant species: Bouteloua gracilis (C4 photosynthetic type)

Historical long-term management regime (estimated): annual grazing

Maximum aboveground live biomass (typical month): 75 g m-2 (July)

soil type: sandy loam

soil pH: 6.2

soil texture (sand/silt/clay): 0.70/ 0.15/ 0.15

soil carbon content: 0.8-1.0% OM (0-20 cm)

soil nitrogen content: 0.07-0.08% (0-20 cm)

7. Data Description:

Spatial Characteristics:

Spatial Coverage:

Study site located at 40.82 N, 104.77 W

Spatial Coverage Map:

Not Available

Spatial Resolution:

Not Applicable

Projection:

Not Applicable

Grid Description:

Not Applicable

Temporal Characteristics:

Temporal Coverage:

1939 to 1990. Preview data set to check for data gaps.

Temporal Coverage Map:

Not Applicable

Temporal Resolution:

one year/ one month

Data Characteristics:

There are nineteen (19) parameters for 4 of the 5 datasets. There are 4 treatments at this site, but the same types of data were collected for each treatment and all data files are presented in exactly the same format. Items 1-2 refer to the site and the treatments, respectively. Minimum and maximum values for the remaining parameters are for the combined treatments.

1.
variable=Site
definition=site where data were gathered
code=cpr: CPER Pawnee

2.
variable=Treatmt
definition=long term management of site
code=esa_c: annual grazing, CONTROL (NONE)
code=esa_i: annual grazing, IRRIGATED (treatment E)
code=esa_f: annual grazing, FERTILISED (treatment F)
code=esa_if: annual grazing, IRRIGATED + FERTILISED (treatment G)
code=longterm: annual grazing

3.
variable=Year
definition=year in which data were collected
units=year
minimum=1970
maximum=1975

4.
variable=Mn
definition=month in which data were collected
units=month
minimum=02
maximum=12

5.
variable=Dy
definition=day in which data were collected
units=day
minimum=01
maximum=31

6.
variable=Jdate
definition=Julian date
units=number of the day in the year
minimum=41
maximum=352

7.
variable=Tyear
definition=Date in decimal year
units=year plus the Julian date divided by 365
minimum=1970.92
maximum=1975.63

8.
variable=AGbioherb
definition=Above ground live biomass of herbaceous layer
units=[g][m^-2]
minimum=0.05
maximum=543.14

9.
variable=forbs
definition=Above ground live biomass of forbs
units=[g][m^-2]
minimum=0
maximum=242.18

10.
variable=grass
definition=Above ground live biomass of grasses
units=[g][m^-2]
minimum=0.02
maximum=489.58

11.
variable=Deadherb
definition=Dead herbaceous matter
units=[g][m^-2]
minimum=0
maximum=354.35

12.
variable=Deadforb
definition=Dead forb matter
units=[g][m^-2]
minimum=0
maximum=60.52

13.
variable=Deadgras
definition=Dead grass matter
units=[g][m^-2]
minimum=0
maximum=340.85

14.
variable=AGherbclip
definition=Total clipped matter for herbaceous layer
units=[g][m^-2]
minimum=32.54
maximum=618.07

15.
variable=ShrSuc
definition=Above ground live biomass of shrubs and succulents
units=[g][m^-2]
minimum=20.73
maximum=559.06

16.
variable=Deadshrsuc
definition=Dead shrubs and succulents
units=[g][m^-2]
minimum=0
maximum=393.10

17.
variable=AGbiomass
definition=Above ground biomass
units=[g][m^-2]
minimum=21.30
maximum=1102.20

18.
variable=Stdead
definition=Standing dead
units=[g][m^-2]
minimum=0
maximum=677.52

19.
variable=AGTotclip
definition=Total above-ground clipped matter
units=[g][m^-2]
minimum=87.00
maximum=1102.35

There are 4 (four) parameters for the fifth dataset. Items 1-2 refer to the site and the treatments, respectively. Minimum and maximum values for the remaining parameters are for the combined treatments.

1.
variable=Site
definition=site where data were gathered
code=cpr: CPER Pawnee

2.
variable=Treatmt
definition=long term management of site
code=longterm: annual grazing

3.
variable=Year
definition=year in which data were collected
units=year
minimum=1939
maximum=1990

4.
variable=ANPP
definition=Above ground net primary production
units=[g][m^-2]
minimum=62
maximum=143

Sample Data Record

                                                                           
Site   Treatmt   Year   Mn   Dy   Jdate   Tyear        AGbioherb   forbs     grass    Deadherb    
--------------------------------------------------------------------------------------------------
cpr    esa_c     1970   04   26    116     1970.318     32.96      0.20        32.76    9.62

Deadforb  Deadgras   AGherbclip   ShrSuc   Deadshrsuc   AGbiomass   Stdead   AGTotclip
----------------------------------------------------------------------------------------
0.00      9.62       42.58        49.60    0.00         82.56       9.62     92.18

8. Data Organization:

Data Granularity:

The data files associated with the CPER Pawnee Grassland are listed below.

1. Data File cpr1_npp.txt 3.3 KBytes
Period: 26 Apr 1970 through 18 Aug 1975
Latitude: 40.82N, Longitude: 104.77W

2. Data File cpr2_npp.txt 3.3 KBytes
Period: 26 Apr 1970 through 18 Aug 1975
Latitude: 40.82N, Longitude: 104.77W

3. Data File cpr3_npp.txt 3.3 KBytes
Period: 26 Apr 1970 through 18 Aug 1975
Latitude: 40.82N, Longitude: 104.77W

4. Data File cpr4_npp.txt 3.3 KBytes
Period: 26 Apr 1970 through 18 Aug 1975
Latitude: 40.82N, Longitude: 104.77

5. Data file cpr5_npp.txt
Period: 1939 through 1990
Latitude: 40.82N, Longitude: 104.77

A general description of data granularity as it applies to the IMS appears in the EOSDIS Glossary.

Data Format:

The datasets are ASCII files. The first 18 lines are metadata; data records begin on line 19. The variable values are delimited by semi-colons. The value -999.9 is used to denote missing values.

Below is an example from the cpr1_npp.txt, cpr2_npp.txt, cpr3_npp.txt, and cpr4_npp.txt files. 

Site;Treatmt;Year;Mn;Dy;Jdate;Tyear; AGbioherb; forbs; grass;Deadherb;Deadforb;Deadgras;AGherbclip;ShrSuc;Deadshrsuc;AGbiomass;Stdead;AGTotclip [units g/m2]  

cpr; esa_c  ;1970;04;26; 116; 1970.318;  32.96;  0.20; 32.76;  9.62; 0.00;  9.62;  42.58;  49.60;   0.00;  82.56;   9.62;  92.18
cpr; esa_c  ;1970;05;12; 132; 1970.362;  53.87;  1.22; 52.65;  0.00; 0.00;  0.00;  53.87;  38.46;   0.00;  92.33;   0.00;  92.33
Below is an example from the cpr5_npp.txt file. 
Site;Treatmt;Year; ANPP (estimated by correlation with forage production)  [units g/m2/year]     

cpr ;longterm;1939;     84
cpr ;longterm;1940; -999.9

9. Data Manipulations:

Formulae:

Derivation Techniques and Algorithms:

It is planned to make algorithms and/or software available for calculating NPP from data sets using different methods.

Data Processing Sequence:

Information Not Available

Calculations:

Information Not Available

Graphs and Plots:

Information Not Available

10. Errors:

Information Not Available

11. Notes:

Limitations of the Data:

Net primary production of grasslands is subject to a number of different methods of estimation from biomass data, some of which may be inappropriate for particular biome types. Methodology of estimation/calculation needs to be taken into account, as well as methodology of measurement, when making comparisons between different regions. Errors in biomass measurement may also occur between different study sites. For short time series of data it may be assumed that measurement methodology remains consistent; however, over very long time series changes in staff, tools, etc. may lead to "calibration" errors.

Known Problems with the Data:

Information Not Available

Usage Guidance:

See "Limitations of the Data" above

Any Other Relevant Information About the Study:

Monthly climate data from 1912 to 1990 (monthly maximum and minimum temperature and monthly rainfall) are available for this study site in the file cpr_cli.txt.

12. Application of the Data Set:

Data on net primary production of particular ecosystem types worldwide is in demand from modellers working at a variety of scales from Global Climate Models (GCMs) to regional or national estimates of carbon fluxes between atmopsphere, biosphere and soils.

The very long-term peak biomass data for the CPER site, and the response to nitrogen fertiliser and irrigation, are particularly suitable for model validation.

13. Future Modifications and Plans:

Refer to Principal Investigator for details of continuing data collection.

14. Software:

Software Description:

Utility software is planned to available for (i) generating quasi-real daily/hourly climate data from the monthly data; (ii) calculating NPP from data sets using different algorithms, crude root/shoot ratios, etc.

Software Access:

Not Yet Available

15. Data Access:

Contact Information:

ORNL DAAC User Services Office
Oak Ridge National Laboratory
Oak Ridge, TN
U.S.A.

Telephone: 865-241-3952
Email Address: ornldaac@ornl.gov

Data Center Identification:

ORNL Distributed Active Archive Center
Oak Ridge National Laboratory
Oak Ridge, TN
U.S.A.

Telephone: 865-241-3952
Email Address: ornldaac@ornl.gov

Procedures for Obtaining Data:

Users may place requests by telephone, electronic mail, or FAX. Data are also available via the World Wide Web at http://daac.ornl.gov.

Data Center Status/Plans:

NPP data are available from the ORNL DAAC. Please contact the ORNL DAAC User Services Office for the most current information about these data.

16. Output Products and Availability:

Available on-line, as computer FTP file (zipped or unzipped), on CDs, or on IBM-formatted diskettes.

17. References:

Dodd, J.L. and W.K. Lauenroth (1979) Analysis of the reponse of a grassland ecosystem to stress. IN: Perspectives in Grassland Ecology (N.R. French, ed.). Ecological Studies 32. Springer-Verlag, New York. pp. 43-58.

Lauenroth, W. K. 1992. Net Primary Production for CPER Pawnee Grassland Site Dataset, In Lauenroth, W.K. and O.E. Sala (1992) Long-term forage production of North American shortgrass steppe. In: Ecological Applications 2, 397-403.

Lauenroth, W.K. and O.E. Sala (1992) Long-term forage production of North American shortgrass steppe. Ecological Applications 2, 397-403.

Linthurst, R. and R.J. Reimold (1978) An evaluation of methods for estimating the net primary production of estuarine angiosperms. J. Applied Ecology 15, 919-932.

Long, S.P. and Mason, C.F. (1983) Saltmarsh Ecology. Blackie, Glasgow.

Long, S.P., E. Garcia Moya, S.K. Imbamba, A. Kamnalrut, M.T.F. Piedade, J.M.O. Scurlock, Y.K. Shen and D.O. Hall (1989) Primary productivity of natural grass ecosystems of the tropics: a reappraisal. Plant and Soil 115, 155-166.

Milner, C. and R.E. Hughes (1968) Methods for the Measurement of the Primary Production of Grassland. IBP Handbook No.6. Blackwell, Oxford.

Singh, J.S. and M.C. Joshi (1979) Tropical grasslands primary production. IN: Grassland Ecosystems of the World (R.T. Coupland, ed.) Cambridge University Press. pp. 197-218.

Singh, J.S., W.K. Lauenroth and R.K. Sernhorst (1975) Review and assessment of various techniques for estimating net aerial primary production in grasslands from harvest data. Botanical Review 41, 181-232.

18. Glossary of Terms:

A general glossary for the DAAC is located at http://cdiac.esd.ornl.gov/cdiac/glossary.html.

A glossary of EOSDIS terms is available at http://www-v0ims.gsfc.nasa.gov/v0ims/glossary.of.terms.html.

19. List of Acronyms:

A general list of acronyms for the DAAC is available at http://cdiac.esd.ornl.gov/cdiac/pns/acronyms.html.

The EOSDIS Acronym and Abbreviation List is located at http://www-v0ims.gsfc.nasa.gov/v0ims/acronyms.html

20. Document Information:

Document Revision Date:

February 10, 1998 (data citation revised on September 23, 2002)

Document Review Date:

February 10, 1998.

Document ID:

ORNL-NPP_CPR

Citation:

Uresk, D., P. L. Sims, and J. L. Dodd. 1996. NPP Grassland: Central Plains Experimental Range (SGS), U.S.A., 1970-1975. 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.

Document Curator:

webmaster@www.daac.ornl.gov

Document Author:

Dr. J. M. O. Scurlock

Document URL:

http://daac.ornl.gov/NPP/guides/cpr_guide.html

CPER Site | NPP Page | ORNL Home Page
Revision Date: October 05, 2005
URL: http://daac.ornl.gov/NPP/guides/cpr_guide.html