Revision Date: October 05, 2005

NPP Grassland: Nairobi, Kenya, 1984-1994

Summary:

Net primary production of a savanna grassland in Nairobi National Park, Kenya, was determined from 1984 to 1994 by monitoring monthly dynamics of live biomass and dead matter, above and below ground, together with monthly litter bag estimates of decomposition rates above and below ground. The method for calculating net primary production accounted for simultaneous growth and death, and carbon flows to all trophic levels. Work was carried out under the United Nations Environment Programme (UNEP) Project on "Primary productivity of grass ecosystems of the tropics" and continued under subsequent UNEP and UK-ODA sponsored international projects.

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: Nairobi, Kenya, 1984-1994

Introduction:

The Nairobi study site (1.33 S 36.83 E) is situated at the southern end of Nairobi National Park, about 30 km south-east of Nairobi. The area is a typical East African grass savanna, which was used as grazing or holding ground for cattle for many years prior to the establishment of Nairobi National Park in 1946, when cattle grazing ceased and the area became a refuge for large herbivores (Kinyamario and Imbamba, 1992; Long et al., 1989).

Objective/Purpose:

Net primary productivity was determined, initially under the auspices of a collaborative UNEP Project, since there was a lack of information on the productive capacity and carbon cycling of East African grasslands.

Summary of Parameters:

There are fifteen (15) 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. Date in decimal year
7. Above ground biomass
8. Standing dead
9. Litter
10. Above ground total matter
11. Below ground biomass
12. Below ground dead
13. Below ground total matter
14. Above ground net primary production (calculated)
15. Below ground net primary production (calculated)

Discussion:

Complete data are available from 1984 through 1986, including a very dry year (1984) and a wet year (1985). Data collection ceased in 1987. In 1988 data collection started again, this time with two seperate but adjacent plots. One was clipped in September 1989; subsequently both plots were given the same treatment.

Related Datasets:

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

2. Investigator(s):

Investigator(s) Name and Title:

Prof. J.I. Kinyamario

Title of Investigation:

Determination of net primary productivity of a savanna grassland in Nairobi National Park

Contact Information:

Prof. J.I. Kinyamario
Department of Botany
University of Nairobi
P.O. Box 30197
Nairobi
KENYA
Telephone Number: +254 (2) 447665 or 447865
Mobile phone: (0733) 623318
Fax: +254 (2) 449845
Email Address: jenesiok@uonbi.ac.ke

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 decomposition, 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 disappearance 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 biomass/ standing dead matter/ litter;

below-ground live/dead root biomass;

Principles of Operation:

See "3. Theory" Above

Sensor/Instrument Measurement Geometry:

Not Applicable

Manufacturer of Sensor/Instrument:

Information Not Available

Calibration:

Not Applicable

Specifications:

Not Applicable

Tolerance:

The number of replicate quadrats was sufficient to ensure a Standard Error of less than 20% of the mean.

Frequency of Calibration:

Not Applicable

Other Calibration Information:

Not Applicable

5. Data Acquisition Methods:

Changes in live biomass and dead matter, above and below ground, were measured at monthly intervals (Kinyamario and Imbamba, 1992; Long et al., 1989).

Dry weight of each above ground category was determined each month by clipping to ground level within 20 quadrats, 1.0 m x 0.25 m, located by a randomized block design. Clipped material from each quadrat was sub-sampled to approx. 100 g fresh weight before sorting. Litter (fallen dead matter) was carefully swept and collected from the area of each quadrat. Live leaves were separated from dead on the basis of tissue necrosis, dead portions being removed from otherwise green leaves. Similar sorting methods were used for stems, paying attention to removal of dead sheaths from live stems.

Below-ground plant matter was sampled by removing soil cores from the center of each quadrat. For the first two years of data collection, 5-10 soil cores were taken each month. Later measurements comprised 40 soil cores combined in groups of four to make 10 samples (in order to reduce sample variance). Soil cores were taken to a 15 cm depth, since initial studies showed that this accounted for more than 90% of the root system. Soil cores were washed over a 2 mm sieve, since ability to pass through a 2 mm mesh was taken as the arbitrary division between recognizable dead matter and particulate organic matter (for both above and below-ground matter). Large roots were removed and weighed separately from fine roots (less than about 1 mm diameter). Fine roots were sub-sampled to about 1.0 g fresh weight. Live and dead roots were separated on the basis of tissue necrosis, using vital staining with tetrazolium salts where visual discrimination was not otherwise possible.

All sorted plant matter was thoroughly washed and dried to constant weight at 90 C.

Monthly decomposition rates were determined using litter bags. Dead above-ground matter was placed at the ground surface, and dead below-ground matter was inserted at 5 cm depth with the soil carefully replaced above the litter bag. Litter bags were of 2 mm nylon mesh, 8 cm x 6 cm, containing approx. 2.0 g dead matter obtained at random from the previous monthly sample. They were recovered from the field after one month, their contents washed over a 2 mm mesh sieve and dried to constant weight. Loss of material was taken to be the rate at which a random sample of dead matter would decompose over that month, and was expressed as a relative rate of decomposition.

6. Observations:

Data/Field Notes:

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

site elevation (m): 1600

mean annual precipitation (mm): 680

mean monthly min temperature (C): 10.8 (July)

mean monthly maximum temperature (C): 28.5 (Mar)

vegetation type: grass savanna

dominant species: Themeda triandra (C4 photosynthetic type)

historical long-term management regime: grazing with fire every 5 years

maximum aboveground live biomass (typical month): 337 g m-2 (July)

soil type: black clay grumsolic vertisol

soil pH: 7.5

soil texture (sand/silt/clay): 0.13/ 0.17/ 0.70

soil carbon content: 3500 g/m2 (0-20 cm)

soil nitrogen content: 367 g/m2 (0-20 cm)

7. Data Description:

Spatial Characteristics:

Spatial Coverage:

100 m x 150 m study site located at 1.33 S, 36.83 E

Spatial Coverage Map:

Not Available

Spatial Resolution:

Not Applicable

Projection:

Not Applicable

Grid Description:

Not Applicable

Temporal Characteristics:

Temporal Coverage:

July 1984 to November 1994. Preview data set to check for data gaps.

Temporal Coverage Map:

Not Applicable

Temporal Resolution:

One month

Data Description:

Parameter/Variable:

There are fifteen (15) parameters for each of these 2 datasets. There are 2 treatments at this site, but the same types of data were collected for each treatment and both 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=nrb: Nairobi

2.
variable=Treatmt
definition=long term management of site
code=1_lngtrm: grazing with burning every 5 years
code=2_clip89: grazing with burning every 5 years; clipped September 1989

3.
variable=Year
definition=year in which data were collected
units=year
minimum=1984
maximum=1994

4.
variable=Mn
definition=month in which data were collected
units=month
minimum=01
maximum=12

5.
variable=Dy
definition=day in which data were collected
units=day
minimum=15
maximum=15

6.
variable=Tyear
definition=Date in decimal year
units=year plus the Julian date divided by 365
minimum=1984.540
maximum=1994.870

7.
variable=AGbiomass
definition=Above ground live biomass
units=[g][m^-2]
minimum=0
maximum=341.9

8.
variable=Stdead
definition=Standing dead
units=[g][m^-2]
minimum=0
maximum=690.8

9.
variable=litter
definition=dead biomass found above ground
units=[g][m^-2]
minimum=0
maximum=323.6

10.
variable=AGtotmatter
definition=above ground total matter
units=[g][m^-2]
minimum=0
maximum=989

11.
variable=BGbiomass
definition=Below ground biomass
units=[g][m^-2]
minimum=17.7
maximum=563.8

12.
variable=BGdead
definition=Below ground dead
units=[g][m^-2]
minimum=35.66
maximum=425.98

13.
variable=BGtotmatter
definition=below ground total matter
units=[g][m^-2]
minimum=66.3
maximum=730.5

14.
variable=ANPP
definition=Above ground net primary production
units=[g][m^-2]
minimum=-208.61 (negative value)
maximum=322.11

15.
variable=BNPP
definition=below ground net primary production
units=[g][m^-2]
minimum=-224.35 (negative value)
maximum=356.67

Sample Data Record:

Site   Treatmt   Year   Mn  Dy   Tyear    AGbiomass   Stdead   litter
----------------------------------------------------------------------
nrb    1_lngtrm  1984   07  15   1984.540 156.3       144.3     311.1

AGtotmatter   BGbiomass   BGdead   BGtotmatter   ANPP    BNPP
-------------------------------------------------------------
611.8          295.5      305.6     601.1        -999.9  -999.9

8. Data Organization:

Data Granularity:

The data files associated with the Nairobi Grassland are listed below.

1. Data File nrb1_npp.txt 12.8 KBytes
Period: 15 Jul 1984 through 15 Nov 1994
Latitude: 1.33S, Longitude: 36.83E

2. Data File nrb2_npp.txt 2.9 KBytes
Period: 15 Jul 1984 through 15 Nov 1994
Latitude: 1.30S, Longitude: 36.80E

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

Data Format:

The dataset is an ASCII file. 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. 
Site;Treatmt;Year;Mn;Dy;Tyear;AGbiomass;Stdead;litter;AGtotmatter;BGbiomass;BGdead;BGtotmatter;ANPP;BNPP [units g/m2]  

nrb;1_lngtrm;1984;07;15;1984.540; 156.3; 144.3; 311.1; 611.8; 295.5; 305.6; 601.1;-999.9;-999.9
nrb;1_lngtrm;1984;08;15;1984.620; 120.9; 141.1; 323.6; 585.6;  89.7;  99.8; 189.5;-999.9;-999.9

Site;Treatmt;Year;Mn;Dy;Tyear;AGbiomass;Stdead;litter;AGtotmatter;BGbiomass;BGdead;BGtotmatter;ANPP;BNPP [units g/m2]  

nrb;2_clip89;1989;10;15;1989.790;   0.0;   0.0;   0.0;   0.0; 106.8;  97.7; 204.5;-999.9;-999.9
nrb;2_clip89;1989;11;15;1989.870;  38.1;   0.0;   0.0;  38.1;  17.7;  48.6;  66.3;-999.9;-999.9

9. Data Manipulations:

Formulae:

Derivation Techniques and Algorithms:

Algorithms and/or software available for calculating NPP from data sets using different methods are not currently available.

Data Processing Sequence

Information Not Available

Calculations

NPP Data Dictionary

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 1969 to 1989 (monthly maximum and minimum temperature and monthly rainfall) are available for this study site in the file nrb_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 atmosphere, biosphere and soils.

The detailed monthly above and below ground biomass data obtained by the UNEP tropical grasslands project are particularly suitable for validation of models running on a monthly time step.

13. Future Modifications and Plans:

Refer to Principal Investigator for details of continuing data collection and additional data from secondary study sites at Baringo, Kenya (1991-present)

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 IBM-formatted diskettes.

17. References:

Kinyamario, J. I. 1992. Net Primary Production for Nairobi (Kenya) Grassland Site Dataset, In Kinyamario, J.I. and S.K. Imbamba (1992) Savanna at Nairobi National Park, Nairobi. In: Primary Productivity of Grass Ecosystems of the Tropics and Sub-tropics. (Long, S.P., M.B. Jones and M.J. Roberts, eds.). Chapman and Hall, London. pp. 25-69.

Kinyamario, J.I. and S.K. Imbamba (1992) Savanna at Nairobi National Park, Nairobi. In: Primary Productivity of Grass Ecosystems of the Tropics and Sub-tropics. (Long, S.P., M.B. Jones and M.J. Roberts, eds.). Chapman and Hall, London. pp. 25-69.

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 DAAC Glossary.

A glossary of EOSDIS terms is available at EOSDIS Glossary.

19. List of Acronyms:

A general list of acronyms for the DAAC is available at DAAC Acronyms.

The EOSDIS Acronym and Abbreviation List is located at EOSDIS Acronyms

20. Document Information:

Document Revision Date:

December 11, 1997 (data citation revised on September 23, 2002)

Review Date

January 15, 1998

Document ID:

ORNL-NPP_NRB

Citation:

Kinyamario, J. I. 1996. NPP Grassland: Nairobi, Kenya, 1984-1994. 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.

Document Curator:

webmaster@daac.ornl.gov

Document Author:

Dr. J. M. O. Scurlock

Document URL:

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

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