Agroforestry Systems

, Volume 79, Issue 2, pp 223–236 | Cite as

Comparative efficiency and accuracy of variable area transects versus square plots for sampling tree diversity and density

  • Cheryl D. NathEmail author
  • Raphaël Pélissier
  • Claude Garcia


Agroforestry systems have been recognized as areas with high conservation potential, and there is a need to quickly assess the biodiversity and tree stocking density available in these systems. However, it is not clear if the commonly used fixed area plot is most efficient for sampling such landscapes, or if a different method could provide equivalent data with less effort. Thus, a field and simulation-based study was carried out to compare the efficiency and accuracy of a variable area transect versus the fixed area square plot. Field efficiency tests were carried out in three habitat types, robusta coffee plantations, arabica coffee plantations and a privately owned forest fragment, in Kodagu, southern India. A simulation study of bias, precision and accuracy of the two methods for tree density estimation also was carried out using various spatial distribution patterns and densities. The variable area transect was significantly more efficient per unit effort in the field than the fixed area square plot. In the simulation tests both methods performed equally well under random spatial distribution. However, under simulated aggregated distribution both methods were positively biased (square plot up to 12% at low density, variable area transect 9–12% at all densities), and under simulated regular distribution the variable area transect was slightly negatively biased (−5 to −7% at medium to high density). The variable area transect thus can be recommended over the square plot for rapid assessment of tree diversity and density, when the vegetation is expected to be randomly dispersed.


Man-hours Bias Precision Spatial dispersion Coffee agroforestry India 



Funding was provided by the CAFNET project of the EuropAid program of the European Union (Connecting, enhancing and sustaining environmental services and market values of coffee agroforestry in Central America, East Africa and India, CAFNET—Europaid/ENV/2006/114-382/TPS). We are grateful to the farmers and estate managers who permitted us to use their properties for data collection. We thank N. Barathan for his assistance with species identification and specimen collection, S. Aravajy for species confirmation, and the technicians, students and field assistants of the French Institute of Pondicherry and Forestry College, Ponnampet, Kodagu, for assistance in the field. We also thank Douglas Sheil for helpful discussions during fieldwork and critical comments on the manuscript, and two anonymous reviewers for their valuable comments.


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Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  • Cheryl D. Nath
    • 1
    Email author
  • Raphaël Pélissier
    • 1
    • 2
  • Claude Garcia
    • 1
    • 3
  1. 1.French Institute of PondicherryPondicherryIndia
  2. 2.UMR AMAP, TA-A51/PS2Montpellier Cedex 5France
  3. 3.CIRAD—UPR 36, TA 10/DMontpellier Cedex 5France

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