Estimating optimum sampling size to determine weighted core specific gravity of planted loblolly pine

Abstract

Data from a variability study of loblolly pine ( Pinus taeda L.) based on weighted core specific gravity (WCSG) were examined to show how costs and variance estimates are used in designing efficient sampling strategies. Increment cores for the determination of WCSG were taken from 3957 trees across six distinct physiographic regions in the southeastern United States. More variability was found to exist among stands than within stands. This indicates that reducing the variation of the mean of WCSG can be accomplished by sampling more stands and fewer trees in the region of interest. The number of stands and trees to sample is dictated by the maximum allowable cost and the precision required of the sample mean, and formulas are given for such calculations. The estimate of among-stand variability was found to be similar among the regions of interest, whereas larger within-stand variation was found to exist in the South Atlantic and Hilly regions. The standard error of the mean was found to increase with an increase in the age at which the stand was sampled. When sampling across multiple stands (at any age), little if any gain in the precision of the standard error of the mean is gained by sampling more than 15 trees. In the general case where one is interested only in the value of WCSG in one stand and precision or cost–time factors are not of consideration, it would suffice to sample between 45 and 55 trees at any age.

Effects of Vegetation Management on Wood Properties and Plant Water Relations of Four Conifer Species in the Pacific Northwest of the USA

“…To study the effect of treatment on the whole-tree, a weighted whole-tree value was determined for each individual tree, which was then used to calculate an average whole tree value for each species. Weighted whole-core SG R , SG E , SG L and LW% were computed as the sum of the product of each wood property trait on each ring (earlywood and latewood) by corresponding ring area and divided by total tree cross section area [27].…”

Identification of representative sampling heights for specific gravity and moisture content in plantation-grown loblolly pine (Pinus taeda)

“…It is evident from Figs. 4a and 5a that the number of primary units (stands) sampled plays a key role in decreasing the standard error of whole-tree SG and MC, and sampling more stands reduces the estimated standard error significantly (Jordan et al 2007). However, the decrease in the error of estimate with an increase in the secondary unit sampled (trees within stands) is marginal for both SG and MC ( Fig.…”

Water availability and genetic effects on wood properties of loblolly pine (Pinus taeda)

“…SG of earlywood and latewood from each annual ring for each radial strip was determined at 60 mm intervals. An SG value of 0.48 was used to distinguish earlywood from latewood (Clark et al 2006b;Jordan et al 2007). LW% was calculated for each ring as the percentage of latewood area to total growth ring area (Jayawickrama et al 1997).…”

“…Whole-ring SG, V 2 , and MOE (i.e., SG R , V R 2 , and MOE R ) were determined for each ring as the sum of the product of each wood property trait (early and latewood) by the corresponding early or latewood ring area and divided by total whole-ring area. Weighted whole-core SG, LW%, V 2 , and MOE were calculated as the sum of the product of each wood property trait on each ring (early and latewood) by the corresponding ring BA and divided by total tree BA (Jordan et al 2007).…”

“…The southeastern United States has more than 13 million ha of southern pine plantations (Fox et al 2007) from which about 58% of total US timber is harvested (Jordan et al 2007), constituting the largest timber production zone in the world (McKeand et al 2003;Allen et al 2005). In this region, loblolly pine (Pinus taeda L.) thrives on various sites from east Texas to southern Missouri to north Florida to south New Jersey and is one of the fastest growing pine species, accounting for more than 84% of planted seedlings in the United States (McKeand et al 2003).…”