NPP Grassland: Montecillo, Mexico, 1984-1994

Summary:

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:

Introduction:

Objective/Purpose:

Summary of Parameters:

1. Site

2. Treatment

3. Year

4. Month

5. Day

6. Date in decimal year

7. Above ground biomass

8. Above ground total dead

9. Above ground total matter

10. Below ground biomass

11. Below ground dead

12. Below ground total matter

13. Above ground Net Primary Production (calculated)

14. Below ground Net Primary Production (calculated)

15. Relative rate of decomposition for above ground dead matter (calculated)

16. Relative rate of decomposition for below-ground dead matter (calculated)

Discussion:

Related Datasets:

2. Investigator(s):

Investigator(s) Name and Title:

Title of Investigation:

Contact Information:

3. Theory of Measurements:

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:

• soil corer
• quadrat sampling frame
• laboratory balance

Collection Environment:

Platform/Source:

Platform/Source Mission Objectives:

Key Variables:

Below-ground live/dead root biomass;

Decomposition rate, above/below ground

Principles of Operation:

Sensor/Instrument Measurement Geometry:

Manufacturer of Sensor/Instrument:

Calibration:

Specifications:

Tolerance:

Frequency of Calibration:

Other Calibration Information:

5. Data Acquisition Methods:

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:

site elevation (m): 2240

mean annual precipitation (mm): 580

mean monthly min temperature (C): 1.3 (Jan)

mean monthly maximum temperature (C): 26.9 (May)

vegetation type: saline grassland

dominant species: Distichlis spicata (C4 photosynthetic type)

historical long-term management regime (estimated): alluvial plain drained 1911; fire every 6 years

maximum aboveground live biomass (typical month): 430 g m^-2 (Aug)

soil type: solonet/ entisol

soil pH: 9.0 (0-20 cm)

soil texture (sand/silt/clay): 0.47/ 0.35/ 0.18

soil carbon content: Data Not Available

soil nitrogen content: Data Not Available

7. Data Description:

Spatial Characteristics:

Spatial Coverage:

Spatial Coverage Map:

Spatial Resolution:

Projection:

Grid Description:

Temporal Characteristics:

Temporal Coverage:

Temporal Coverage Map:

Temporal Resolution:

Data Description:

Parameter/Variable:

1.
variable=Site
definition=site where data were gathered
code=mnt: Montecillo

2.
variable=Treatmt
definition=long term management of site
code=lngtrm: alluvial plain drained 1911, fire every 6 years; burned February 1986
code=2_burn89: alluvial plain drained 1911, fire every 6 years; burned May 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=1984.460
maximum=1994.960

7.
variable=AGbiomass
definition=above ground biomass
units=[g][m^-2]
minimum=0
maximum=439.1

8.
variable=AGtotdead
definition=above ground total dead
units=[g][m^-2]
minimum=0
maximum=1082.1

9.
variable=AGtotmatter
definition=above ground total matter
units=[g][m^-2]
minimum=0
maximum=1176.1

10.
variable=BGbiomass
definition=below ground biomass
units=[g][m^-2]
minimum=100.1
maximum=736.3

11.
variable=BGdead
definition=below ground dead
units=[g][m^-2]
minimum=302.16
maximum=1318.91

12.
variable=BGtotmatter
definition=total matter found below ground
units=[g][m^-2]
minimum=423.1
maximum=1641.2

13.
variable=ANPP
definition=below ground total matter
units=[g][m^-2]
minimum=-1089.28
maximum=581.62

14.
variable=BNPP
definition=below ground net primary production
units=[g][m^-2]
minimum=-1308.81 (negative value)
maximum=1218

15.
variable=AGr
definition=Relative rate of decomposition for above ground dead matter
units=[g][g][month]
minimum=0.0265
maximum=0.120

16.
variable=BGr
definition=Relative rate of decomposition for below-ground dead matter
units=[g][g][month]
minimum=0.0436
maximum=0.174

Sample Data Record:

Site   Treatmt   Year   Mn   Dy   Tyear     AGbiomass   AGtotdead    
------------------------------------------------------------------
mnt    1_lngtrm  1984   06   15   1984.460   130.9        338.1

AGtotmatter   BGbiomass   BGdead   BGtotmatter    ANPP   
-------------------------------------------------------
469.0         427.2        505.3    932.5        -999.9 

BNPP    AGr       BGr 
----------------------
-999.9 -999.999  -999.999

8. Data Organization:

Data Granularity:

1. Data File mnt1_npp.txt 13.6 KBytes
Period: 15 Jun 1984 through 15 Dec 1994
Latitude: 19.46N, Longitude: 98.91W

2. Data File mnt2_npp.txt 7.9 KBytes
Period: 15 Jun 1989 through 15 Dec 1994
Latitude: 19.46N, Longitude: 98.91W

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

Data Format:

Site;Treatmt;Year;Mn;Dy;Tyear;AGbiomass;AGtotdead;AGtotmatter;BGbiomass;BGdead;BGtotmatter;ANPP;BNPP; [units g/m2] AGr;BGr [units g/g/month]  

mnt;1_lngtrm;1984;06;15;1984.460; 130.9; 338.1; 469.0; 427.2; 505.3; 932.5;-999.9;-999.9;-999.999;-999.999
mnt;1_lngtrm;1984;07;15;1984.540; 265.7; 428.9; 694.6; 292.2; 813.9;1106.2; 415.9; 576.6;-999.999;-999.999

9. Data Manipulations:

Formulae:

Derivation Techniques and Algorithms:

Data Processing Sequence:

Calculations:

Graphs and Plots

10. Errors:

11. Notes:

Limitations of the Data:

Known Problems with the Data:

Usage Guidance:

12. Application of the Data Set:

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:

14. Software:

Software Description:

Software Access

15. Data Access:

Contact Information:

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

Data Center Identification:

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

Procedures for Obtaining Data:

Data Center Status/Plans:

16. Output Products and Availability:

17. References:

Garcia-Moya, E. and P. Montanez C. (1992) Saline grassland near Mexico City. 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. 70-99.

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

19. List of Acronyms:

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

20. Document Information:

Document Revision Date:

Review Date

Document ID:

Citation:

Document Curator:

Document Author:

Document URL: