Pacific Northwest Research Station

Title: Sampling strategies for efficient estimation of tree foliage biomass

Author: Temesgen, Hailemariam; Monleon, Vicente; Weiskittel, Aaron; Wilson, Duncan

Date: 2011

Source: Forest Science. 57(2): 153-163

Description: Conifer crowns can be highly variable both within and between trees, particularly with respect to foliage biomass and leaf area. A variety of sampling schemes have been used to estimate biomass and leaf area at the individual tree and stand scales. Rarely has the effectiveness of these sampling schemes been compared across stands or even across species. In addition, sample size estimates for achieving a certain level of precision have rarely been given. This simulation study used extensive branch and tree foliage biomass data sets for Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) and ponderosa pine (Pinus ponderosa Dougl ex. Laws.) to compare alternative sampling schemes and sample sizes. The use of auxiliary information at the estimation phase resulted in a more cost-efficient sampling scheme than when auxiliary information was used at the design phase. However, using auxillary information at the design phase resulted in more precise estimates than using the same at the estimation phase for the same sample size. For both species, systematic sampling with ratio estimation provided the most efficient estimate of individual tree foliage biomass. In Douglas-fir, stratifying by branch type (i.e., whorl versus interwhorl) resulted in a marginal gain in precision. For Douglas-fir, on average, root mean square error decreased by 43.1% when sample size increased from 6 to 12 branches per tree, with a further decrease of 24.3% when sample size increased from 12 to 18 branches per tree. For ponderosa pine, on average, the root mean square error decreased by 44.4 and 23.9% when the sample size was increased from 6 to 12 and from 12 to 18 branches per tree, respectively. Additional work is needed to understand the appropriate sampling techniques for older conifer tree crowns and sampling multileader deciduous crowns.

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Citation

Temesgen, Hailemariam; Monleon, Vicente; Weiskittel, Aaron; Wilson, Duncan  2011.  Sampling strategies for efficient estimation of tree foliage biomass.   Forest Science. 57(2): 153-163.