Using double-sampling techniques to reduce the number of measurement trees during forest inventories

Authors

  • Curtis L. VanderSchaaf School of Agricultural Science and Forestry, Louisiana Tech University, Ruston, LA 71272
  • Gordon Holley Louisiana Tech University, Ruston, LA 71272
  • Joshua Adams Louisiana Tech University, Ruston, LA 71272

DOI:

https://doi.org/10.21750/REFOR.3.04.28

Keywords:

Basal Area, Loblolly pine, Pinus taeda, VBAR, WBAR

Abstract

Variable-radius sampling techniques are commonly used during forest inventories. For each sample tree at a particular sampling point, diameter and height(s) are measured and then weight is estimated using established equations.  Heights can require a fair amount of time to measure in the field.  Separating the weight per acre estimate into two components; average basal area per acre and WBAR (individual tree weight-basal area ratio) across all points, can often lead to more efficient sampling schemes. Variable-radius sampling allows for a quick estimate of basal area per acre at a point since no individual tree measurements are needed.  If there is a strong relationship between weight and basal area, then by knowing basal area you essentially know weight.  Separation into two components is advantageous because in most cases there is more variability among basal area estimates per point then there is in WBAR. Hence, you can spend more resources establishing many points that only estimate basal area – often called “Count” points. “Full” points are those where individual tree measurements are also conducted. There is little published information quantifying the impacts on basal area, weight, etc., estimates among different “Full/Count” sample size ratios at the same site. Inventories were examined to determine this method’s applicability to loblolly pine plantations in southern Arkansas and northern Louisiana. Results show there is more variability among basal area estimates than WBAR and that the amount of trees being “intensively” measured is excessive.  Based on these four plantations, a “Full” point could be installed ranging from every other point to every fifth point depending on site conditions and the desired variable.

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Author Biographies

  • Curtis L. VanderSchaaf, School of Agricultural Science and Forestry, Louisiana Tech University, Ruston, LA 71272
    Assistant Professor
  • Gordon Holley, Louisiana Tech University, Ruston, LA 71272
    Associate Professor
  • Joshua Adams, Louisiana Tech University, Ruston, LA 71272
    Assistant Professor

References

Avery TE, Burkhart HE (2002) Forest measurements. McGraw Hill. New York. 456 pp.

Bell JF, Alexander LB (1957) Application of the variable plot method of sampling forest stands. Oregon Board of Forestry, Salem, Ore. Res. Note 30. 26 pp.

Coble DW, Grogan J (2007) Comparison of systematic line-point and double sampling designs for pine and hardwood forests in the Western Gulf. South. J. Appl. For. 31:199–206. DOI: https://doi.org/10.1093/sjaf/31.4.199

Cochran WG (1960) Sampling Techniques. John Wiley & Sons, Inc. New York. 330 pp.

Oderwald RG, Jones E (1992) Sample sizes for point, double sampling. Can. J. For. Res. 22:980-983. https://doi.org/10.1139/x92-131 DOI: https://doi.org/10.1139/x92-131

Shiver BD, Borders BE (1996) Sampling techniques for forest resource inventory. John Wiley & Sons, Inc. New York. 356 pp.

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Published

2017-07-01

Issue

Section

Articles

How to Cite

“Using Double-Sampling Techniques to Reduce the Number of Measurement Trees During Forest Inventories”. REFORESTA, no. 3 (July 1, 2017): 31–40. Accessed November 26, 2024. https://journal.reforestationchallenges.org/index.php/REFOR/article/view/53.

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