Single tree aboveground biomass models for native birch in Iceland

Abstract

In Iceland, mountain birch dominates indigenous woodlands and scrub communities. For use in inventories of the natural birch population, we derived single parameter aboveground biomass functions from a stratified random sample encompassing the entire native birch population. We evaluated the accuracy of these models on independent data from the same population and used regressions of log-transformed predicted versus observed values and compared slope and intercept parameters against the 1:1 line. We propose that the level of accuracy of allometric models might be quantified by the size of Theil's random error component (U e) and the normality of residual variances might be a decisive test of acceptable functions. The commonly used allometric power function without intercept proved highly accurate for diameters at ground level but was biased for diameters measured at 0.5 m up the stem. We compared both non-linear regressions and log-transformed linear regression techniques. The latter produced more accurate models especially for applications to small diameter trees. Power functions with intercept and diameters measured 0.5 m above ground produced accurate estimates, except for trees with diameters less than 50 mm. We suggest allometric models for general use in Iceland for inventories of native birch woodlands and scrub.

Aboveground woody biomass of natural birch woodland in Iceland – Comparison of two inventories 1987-1988 and 2005-2011

“…The stem with greatest diameter was felled and weighed in the field. Subsamples from the stem and branches were taken for dry mass estimations (Jónsson 2004, Jónsson & Snorrason 2018.…”

“…where N is the number of trees per hectare and k the distance from the measured tree to the third nearest tree. Aboveground biomass was calculated for each stem using biomass functions described in Jónsson & Snorrason (2018). Aboveground biomass for each tree was the sum of the biomass estimates for all stems arising from a single root system plus dry mass of stump sprouts weighed in the field.…”

“…We used single tree biomass functions derived for the entire Icelandic birch population (Jónsson & Snorrason 2018) to estimate tree biomass aboveground from diameters measured We used measurements of current mean tree he (Eq. 3)…”

“…5) denoted M11 in Jónsson & Snorrason (2018), where wm is the wet in-field biomass in g, d g is the diameter in mm of the circle of the true basal area at 0.5 m, and a, b and c are constants, 92.4779, 0.3932 and 2.4771, respectively. When using d 0.5 measured with a diameter calliper a factor of 0.9346 given by Jónsson & Snorrason (2018) was used to convert the calliper measurement to d g . To convert wet biomass into dry biomass we used the factor of 0.5372 given by Jónsson & Snorrason (2018).…”

Comparing Non-Destructive Methods to Estimate Volume of Three Tree Taxa in Beijing, China

“…In each diameter group, three subgroups were formed according to the corresponding large, medium, and small tree height-DBH ratio. A minimum of 30 sample trees were selected for individual subgroup, and more than 150 sample trees data in each diameter group was used in the modeling [30,31].…”