PREDICTION OF THE ERROR GENERATED BY SMALIAN'S AND HUBER'S FORMULAE IN VOLUME MEASUREMENTS OF Pinus caribaea (MORELET).

Abstract

One of the common methods of volume estimation is the use of mathematical equations.Among such equations, Huber's, Smalian's and Newton's formulae are commonly usedand it is believed that Newton's formula which uses bottom, mid and top diameter of thelog and log length gives most precise volume estimations than Smalian's or Huber'sformulae. The latter two equations use only log length and end diameters and middiameter respectively. Usually for volume calculations Huber's formula is used due to theinvolvement of less measurements (mid diameter and log length)

Present study was conducted in the 26 year old Pinus caribaea plantation in YagiralaForest Reserve situated in the low country wet zone of Sri Lanka. In order to representthe whole area of the forest, stratified random sampling method was used and one O.OShasample plot was laid in each stratum. Altogether 3 plots were selected.

Each tree was divided into twelve one meter long sections using a ranging staff. Threediameters i.e., bottom, mid and top diameters of each section were measured using theSpiegel relascope. Other than section diameters, diameter at breast height (dbh) of thetree was measured using the diameter tape.

Cumulative section volumes per each tree were calculated separately from Im to 12musing Huber's, Smalian's and Newton's formulae. other than the above method volumewas calculated using section lengths separately up to twelve meter long sections usingNewton's formula to test whether log length affect the Newton's volume. When testedthere was no significant difference between two volume types. However, for furtheranalysis Newton's volume calculated using the sectio•. length separately was used.

For each cumulative volume (i.e., lm to 12m) calculated using different formulae werestatistically tested using one way ANOVA. According to the results 6m is the maximumlength for Huber's formula to predict the volume accurately. However it does not show asignificant difference between Smalian's and Newton's formulae up to twelve metersection length.

Generally Huber's formula underestimates and Smalian's formula overestimates thevolume. Therefore it is recommended to use Huber's formula for volume calculations dueto it's ease of use, keeping the log length shorter than 6m.