Above-ground Stem Volume Research Articles

Stem volume and tree biomass harvested by different thinning intensities from dense and sparse karee stands in Central Bushveld, South Africa

The aim of this study was to determine the aboveground stem volume and tree biomass of the multi-stemmed karee tree (Searsia lancea) for its potential use for producing wood chips and/or pellets. A stratified random sampling was done, by selecting two blocks with both sparse and dense Karee stands. In each block, three sparse and three dense karee stands were identified. Within each block, three thinning treatments of only karee stems (no cutting, 50% cutting and 100% cutting by number of stems) were randomly allocated to the selected stands. The average moisture content of karee wood was 35.43%. A 50% cutting in sparse stands produced a total dry biomass of 8.51 ± 3.63 t ha−1 and stem volume of 11.92 ± 6.28 m3 ha−1, and in dense stands it produced a total dry biomass of 16.05 ± 2.42 t ha−1 and stem volume of 22.97 ± 4.38 m3 ha−1. The 100% cutting (clear-felling) in sparse stands produced a total dry biomass of 10.02 ± 4.48 t ha−1 and stem volume of 14.10 ± 4.01 m3 ha−1, and in dense stands it produced 33.80 ± 2.25 t ha−1 and 60.64 ± 22.97 m3 ha−1. Thus, the clear-felling biomass was significantly higher than that of 50% cutting, which was supported by ANOVA results for tree biomass (p = 0.0078). In contrast, in terms of stem volume, the p-value was 0.08, indicating that 100% cutting was not significantly higher than the 50% cutting treatment. Dense stands were significantly higher than sparse stands in both tree biomass and stem volume comparisons. Generally, this study showed that there is a great potential to utilise stems of karee for biomass.

Predicting branch to bole volume scaling relationships from varying centroids of tree bole volume

A novel “varying-centroid” method is presented for predicting whole-tree, aboveground stem volume (i.e., bole plus branch volume) to bole volume ratios from changes in the centroid of tree bole volume associated with branching of the bole. The method was derived from a simple fractal-like tree model based on a conceptualization of tree branching architecture by Leonardo da Vinci. The method recognizes that the centroid of bole volume (the point at which one half of bole volume is above and one half is below) is always lower than the centroid of whole-tree volume and that shifts in the centroid of bole volume should be predictably related to the size of a tree’s crown. The method assumes that branch-displaced bole volume profiles can be compared with reference bole profiles that are not significantly influenced by branching, at the centroid of bole volume, and that the magnitude of bole centroid displacement predicts the branch volume necessary to cause it. When the method was applied to hardwood trees representing diverse species, sizes, and stand conditions across Michigan, the centroid of bole volume was found to vary predictably with measurable tree crown attributes and bole plus branch wood to bole wood volume ratios were generally predicted within 10% of the true value using the new method.