NOTICE -- The LBA-ECO Project website is no longer being supported.  This archive is a snapshot, as it existed in 2013, of the LBA-ECO website, maintained by NASA Goddard Space Flight Center, and now archived at the ORNL DAAC.  Links to external websites may be inactive. Final data products from the LBA project can be found at the ORNL DAAC.
banner
banner banner banner banner banner banner
banner banner banner banner banner banner banner
home aboutlibrarynews archivecontacts banner

spacer
banner
Investigations
Overview
Abstracts & Profiles
Publications
Research Sites
Meetings
Synthesis Groups
LBA-HYDROMET
LBA-Air-ECO
Logistics
Overview
Field Support
Travel
Visa
Shipping
Data
  Overview
Find LBA Data
Investigator Checklist
Process & Policy
Documentation & Archive
Training & Education
  Overview
Activities Summary
T&E Goals
Student Opportunities
  Folha Amazônica
 
spacer

Investigation:

CD-04 (Goulden / Rocha)

LBA Dataset ID:

CD04_LAI_ESTIMATES

Originator(s):

1. JUAREZ, R.N.
2. DA ROCHA, H.R.
3. FIGUEIRA, A.M.S.
      4. GOULDEN, M.L.
5. MILLER, S.D.

Point(s) of Contact:

ORNL DAAC User Services Office Oak Ridge National Laboratory Oak Ridge, Tennessee 37 (ornldaac@ornl.gov)

Dataset Abstract:

Leaf Area Index (LAI) is a key parameter that affects the surface fluxes of energy, mass, and momentum over vegetated lands, but observational measurements are scarce, especially in remote areas with complex canopy structure. We present an indirect method to calculate the LAI based on the analyses of histograms of hemispherical photographs. The optimal threshold value (OTV), the gray-level required to separate the background (sky) and the foreground (leaves), was analytically calculated using the Entropy Cross Over method (Sahoo et al. 1997). The OTV was used to calculate the LAI using the well-known gap fraction method. This methodology was tested in a managed Amazon forest in the state of Para, Brazil. In general, the error between observed and calculated LAI was ~6%. The methodology presented is suitable for the calculation of LAI since it is responsive to sky conditions, automatic, easy to implement, faster than commercially available software, and requires less data storage.

Beginning Date:

2000-06-01

Ending Date:

2003-05-30

Metadata Last Updated on:

2012-07-18

Data Status:

Archived

Access Constraints:

PUBLIC

Data Center URL:

http://daac.ornl.gov/

Distribution Contact(s):

ORNL DAAC User Services Office Oak Ridge National Laboratory Oak Ridge, Tennessee 37 (ornldaac@ornl.gov)

Access Instructions:

PUBLIC

Data Access:

IMPORTANT: The LBA-ECO Project website is no longer being supported. Links to external websites may be inactive. Final data products from the LBA project can be found at the ORNL DAAC. Please follow the fair use guidelines found in the dataset documentation when using or citing LBA data.
Datafile(s):

LBA-ECO CD-04 LAI Estimated from Photos, km 83 Tower Site, Tapajos National Forest:  http://daac.ornl.gov/cgi-bin/dsviewer.pl?ds_id=1103

Documentation/Other Supporting Documents:

LBA-ECO CD-04 LAI Estimated from Photos, km 83 Tower Site, Tapajos National Forest:  http://daac.ornl.gov/LBA/guides/CD04_LAI_Estimates.html

Citation Information - Other Details:

Juarez, R.N., H.R. da Rocha, A.M. Figueira, M.L. Goulden, and S.D. Miller. 2010. LBA-ECO CD-04 LAI Estimated from Photos, km 83 Tower Site, Tapajos National Forest. Data set. Available on-line [http://daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. http://dx.doi.org/10.3334/ORNLDAAC/1103

Keywords - Theme:

Parameter Topic Term Source Sensor
LEAF CHARACTERISTICS BIOSPHERE VEGETATION FIELD SURVEY CAMERAS
LEAF CHARACTERISTICS BIOSPHERE VEGETATION ANALYSIS CAMERAS

Uncontrolled Theme Keyword(s):  ESTIMATED LEAF AREA INDEX, HEMISPHERICAL PHOTOGRAPHS, LAI, LEAF AREA INDEX

Keywords - Place (with associated coordinates):

Region
(click to view profile)
Site
(click to view profile)
North South East West
Pará Western (Santarém) km 83 Logged Forest Tower Site -3.01700 -3.01700 -54.97070 -54.97070

Related Publication(s):

Juarez, Robinson Negron, H.R. da Rocha, A.M.S. Figueira, M.L. Goulden, and S.D. Miller. 2009. An improved estimate of leaf area index based on the histogram analysis of hemispherical photographs. Agric. Forest Meteorol. 149: 920-928.

Data Characteristics (Entity and Attribute Overview):

Data Characteristics:

There are four files associated with this data set.

- Summary data for the calculations of LAI and PAI between 2000 and 2003 as a comma-delimited ASCII file (CD04_LAI_PAI_photos.csv)

- The program code developed for LAI analysis is provided as an ASCII text file (LAI_otv_gf_program.txt) and

- two hemispherical photos from the study sites are provided as Bitmap images:

- E03April2002.bmp

- E06April2002.bmp



Data in the file CD04_LAI_PAI_photos.csv is organized as follows:



File name: CD04_LAI_PAI_photos.csv,,,,,

File date: 17-Jun-2010,,,,,

Associated LBA Dataset ID: CD04_LAI_Estimates,,,,,



Column,Heading,Units/format,Variable description,,,

----1,Year,yyyy,Year in which the hemispherical photos were taken (yyyy): 2000-2003,,,

----2,Month,mm,Month in which the hemispherical photos were taken: 1= January and 12= December,,,

----3,Row,,Location of photographs within the sampling grid: A-M (see data set documentation ),,,

----4,Status,,Status of the site with respect to logging operations: Pre-logging or Logged. Selective logging began in September 2001.,,,

----5,No_photos,,Number of hemispherical photos included in the calculation of PAI and LAI,,,

----6,PAI,m2 per m2,Mean plant area index for the samping row in meters squared per meter squared (m2 per m2) calculated using the Beer-Lambert equation,,,

----7,LAI,m2 per m2,Mean leaf area index for the row in meters squared per meter squared (m2 per m2) calculated from hemispherical photos,,,



Example data records:

Year,Month,Row,Status,No_photos,PAI,LAI

2000,6,A,Pre-logging,5,4.9,6.36

2000,6,B,Pre-logging,16,4.03,5.23

2000,6,C,Pre-logging,29,4.6,5.97

2000,6,D,Pre-logging,34,4.36,5.66

2000,6,E,Pre-logging,31,4.4,5.71

2000,6,F,Pre-logging,35,4.26,5.53

2000,6,G,Pre-logging,33,4.25,5.52

Data Application and Derivation:

The optimal threshold value (OTV), the gray-level required to separate the background (sky) and the foreground (leaves), was analytically calculated using the Entropy Cross Over method (Sahoo et al. 1997). The OTV was used to calculate the LAI using the well-known gap fraction method. This methodology was tested in a managed Amazon forest in the state of Para, Brazil. In general, the error between observed and calculated LAI was ~6%. The methodology presented is suitable for the calculation of LAI since it is responsive to sky conditions, automatic, easy to implement, faster than commercially available software, and requires less data storage.

Quality Assessment (Data Quality Attribute Accuracy Report):

Quality Assessment:

During image capture, the brightness (luminosity) and contrast (between background and foreground) were tuned to provide visual quality. In general it was observed that high and low brightness values often led to low and high estimates of LAI, respectively. Although contrast and brightness should combine to give better estimates of LAI, their tuning also depended on sky luminosity and canopy architecture.

Process Description:

Data Acquisition Materials and Methods:

Hemispherical photographs and observed data were collected in the Tapajos National Forest, near the micrometeorological tower installed near the km 83 post of BR-163 (Cuiaba-Santarem highway), approximately 70 km south of Santarem, Para, Brazil, and at 153 m above sea level (Goulden et al. 2004). The vegetation is dense tropical humid forest with a canopy height of ~35-40 m, with yellow distrophic latosol (clay oxisol) soil. The annual mean precipitation and temperature are 1911 mm and 25 degrees C, respectively, with the dry season defined from July to November. Evapotranspiration ranges between ~4 mm day-1 in the dry season to ~3 mm day-1 in the wet season (da Rocha et al. 2004). The site was selectively logged in September 2001, removing 12% of the canopy at our measurement site (Miller et al. 2007).



Hemispherical photographs (hereafter simply referred to as images) were collected using the CI-110 Digital Plant Canopy Imager (CID Inc., Camas, Washington, USA) mounted on a tripod, aligned to magnetic north, leveled to 90 cm height aboveground (to the soil surface in the pastureland), and connected to a notebook computer. The device deploys a 150 degree fish-eye lens image, recorded as 180912 pixels, 24-bits gray-level files (BMP format) with 3-by-m-by-n arrays. The set of images were captured using an azimuth angle range from 0 degrees to 360 degrees , and its zenith angle from 0 degrees to 75 degrees. The image files were converted into 8-bit (2D) images by extracting one channel, which reduced to one-third the storage size. This procedure is justifiable since at the gray-level the three channels (blue, red, yellow) have the same values. The histogram analysis was performed using the converted set of images. For the analysis, each image was divided into seven 10 degree-strips from 5 to 75 degrees and the gap fraction and LAI were calculated for each annulus in a pixel-per-pixel basis (using the Interactive Data Language IDL 6.0 running on a 1GHz pentium III PC). LAI was also calculated using the device software (CI-110, Production 1.0, CID Inc. 1997, 1998, hereafter referred to as CI-LAI).



Images were collected at nodes of a 300 m x 600 m regular grid that extended 500 m east, 100 m west, 150 m south, and 150 m north of the flux tower (see supporting documentation).

References:

da Rocha, H.R., M.L. Goulden, S.D. Miller, M.C. Menton, L.D.V.O. Pinto, H.C. Freitas and A.M.S. Figuiera. 2004. Seasonality of water and heat fluxes over a tropical forest in eastern Amazonia. Ecological Applications 14(4): S22-S32.



Goulden, M.L., S.D. Miller, H.R. da Rocha, M.C. Menton, H.C. Freitas, A.M.S. Figuiera and C.A.D. Sousa. 2004. Diel and seasonal patterns of tropical rainforest CO2 exchange. Ecological Applications 14(4) S42-S54.



Miller,S.D., M.L. Goulden, H. da Rocha. 2007. The effect of canopy gaps on subcanopy ventilation and scalar fluxes in a tropical forest. Agricultural and Forest Meteorology 142: 25-34.



Sahoo, P.K., Slaaf, D.W. and Albert, T.A., 1997. Threshold selection using a minimal histogram entropy difference. Optical Engineering, 36(7): 1976-1981.



Sakai RK, Fitzjarrald DR, Moraes OLL, Staebler RM, Acevedo OC, Czikowsky MJ, Da Silva R, Brait E, Miranda V. (2004) Land-use change effects on local energy, water, and carbon balances in an Amazonian agricultural field. Global Change Biology, 10, 895-907.

Skip navigation linksHOME | ABOUT | LIBRARY | NEWS ARCHIVE | CONTACTS | INVESTIGATIONS | LOGISTICS | DATA |TRAINING & EDUCATION

NASA logo
ORNL DAAC
Get Acrobat Reader