Tree Form and Stem Taper

Burkhart, Harold E.; Tomé, Margarida

doi:10.1007/978-90-481-3170-9_2

Cited by 9 publications

(7 citation statements)

References 55 publications

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“…Considering the characterization of changes in the stem form or allocation of stem volume growth of a tree, the conventional ways have included either retrospective measurements from trees that were cut down, or modeling of the attributes of interest (e.g., Weiskittel et al 2011;Burkhart and Tomé et al 2012;Kershaw et al 2016). If a tree needs to be cut down for analysis, it will immediately mean the end of the monitoring period, which does not allow continuous time-series studies with several monitoring points.…”

Section: Methods For Detecting and Measuring Changes In Tree And Fore...mentioning

confidence: 99%

Measuring tree growth using terrestrial laser scanning

Luoma¹

2022

Diss. For.

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Forests are dynamic ecosystems that are constantly changing. The most common natural reasons for change in forests are the growth and death of trees, as well as the damage occurring to them. Tree growth appears as an increment of its structural dimensions, such as stem diameter, height, and crown volume, which all affect the structure of a tree. Repeated measurements of tree characteristics enable observations of the respective increments indicating tree growth. According to current knowledge, the tree growth process follows the priority theory, where trees aim to achieve sufficient lightning conditions for the tree crown through primary growth, whereas increment in diameter results from the secondary growth. Tree growth is known to have an effect on the carbon sequestration potential of trees as well as on the quality of timber. To improve the understanding of the underlying cause–effect relations driving tree growth, methods to quantify structural changes in trees and forests are needed. The use of terrestrial laser scanning (TLS) has emerged during the recent decade as an effective tool to determine attributes of individual trees. However, the capacity of TLS point cloud-based methods to measure tree growth remains unexplored. This thesis aimed at developing new methods to measure tree growth in boreal forest conditions by utilizing two-date TLS point clouds. The point clouds were also used to investigate how trees allocate their growth and how the stem form of trees develops, to deepen the understanding of tree growth processes under different conditions and over the life cycle of a tree. The capability of the developed methods was examined during a five- to nine-year monitoring period with two separate datasets consisting of 1315 trees in total. Study I demonstrated the feasibility of TLS point clouds for measuring tree growth in boreal forests. In studies II and III, an automated point cloud-based method was further developed and tested for measuring tree growth. The used method could detect trees from two-date point clouds, with the detected trees representing 84.5% of total basal area. In general, statistically significant changes in the examined attributes, such as diameter at breast height, tree height, stem volume, and logwood volume, were detected during the monitoring periods. Tree growth and stem volume allocation seemed to be more similar for trees growing in similar structural conditions. The findings obtained in this thesis demonstrate the capabilities of repeatedly acquired TLS point clouds to be used for measuring the growth of trees and for characterizing the structural changes in forests. This thesis showed that TLS point cloud-based methods can be used for enhancing the knowledge of how trees allocate their growth, and thus help discover the underlying reasons for processes driving changes in forests, which could generate benefits for ecological or silvicultural applications where information on tree growth and forest structural changes is needed.

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Section: Methods For Detecting and Measuring Changes In Tree And Fore...mentioning

confidence: 99%

Measuring tree growth using terrestrial laser scanning

Luoma¹

2022

Diss. For.

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“…1984). Mixed‐effects models allow autocorrelation to be at least partly accounted for by including random effects (Burkhart and Tomé 2012). The random effects are assumed to follow a multivariate normal distribution with a mean of zero and a positive‐definite variance‐covariance matrix.…”

Section: Methodsmentioning

confidence: 99%

“…This violates the assumption of independence required to apply the nonlinear least squares method, resulting in unbiased parameter estimates but biased and inconsistent estimates of their variance (West et al 1984). Mixed-effects models allow autocorrelation to be at least partly accounted for by including random effects (Burkhart and Tomé 2012). The random effects are assumed to follow a multivariate normal distribution with a mean of zero and a positive-definite variancecovariance matrix.…”

Section: Prediction Of the Taper Parametermentioning

confidence: 99%

A 3D approach to model the taper of irregular tree stems: making plots biomass estimates comparable in tropical forests

Bauwens

Ploton

Ligot

et al. 2021

Ecological Applications

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In tropical forests, the high proportion of trees showing irregularities at the stem base complicates forest monitoring. For example, in the presence of buttresses, the height of the point of measurement (H POM ) of the stem diameter (D POM ) is raised from 1.3 m, the standard breast height, up to a regular part of the stem. While D POM is the most important predictor for tree aboveground biomass (AGB) estimates, the lack of harmonized H POM for irregular trees in forest inventory increases the uncertainty in plot-level AGB stock and stock change estimates. In this study, we gathered an original non-destructive 3D dataset collected with terrestrial laser scanning and close range terrestrial photogrammetry tools in three sites in central Africa. For the 228 irregularly shaped stems sampled, we developed a set of taper models to harmonize H POM by predicting the equivalent diameter at breast height (DBH') from a D POM measured at any height. We analyzed the effect of using DBH' on tree-level and plot-level AGB estimates. To do so, we used destructive AGB data for 140 trees and forest inventory data from eight 1-ha-plots in the Republic of Congo.Our results showed that our best simple taper model predicts DBH' with a relative mean absolute error of 3.7% (R²=0.98) over a wide D POM range of 17 to 249 cm. Based on destructive AGB data, we found that the AGB allometric model calibrated with harmonized H POM data was more accurate than the conventional local and pantropical models. At the plot level, the comparison of AGB stock estimates with and without H POM harmonization showed an increasing divergence with the increasing share of irregular stems (up to -15%). The harmonization procedure developed in this study could be implemented as a standard practice for AGB monitoring in tropical forests as no additional forest inventory measurements is required. This would probably lead to important revisions of the AGB stock estimates in regions having a large number of irregular tree stems and increase their carbon sink estimates. The growing use of 3D data offers new opportunities to extend our approach and further develop general taper models in other tropical regions.Key-words: 1) Allometric above-ground biomass model, 2) biomass changes, 3) buttresses, 4) close-range terrestrial photogrammetry, 5) point of measurement of stem diameter, 6) stem profile 7) taper, 8) terrestrial laser scanning, 9) structure from motion

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“…Tree merchantable stem volume was defined as the sum of the volume of all 1 m log segments up to the 9.1 cm stem top diameter. Stem taper was defined as the rate of decrease in stem diameter with increasing height from ground level to the tree tip (Burkhart and Tomé 2012).…”

Section: Tree Selection For Lumber Quality Evaluationmentioning

confidence: 99%

Translocating seed sources to new geoclimatic environments has limited effect on lumber quality of eastern Canadian white spruce

et al. 2022

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Assisted gene flow according to expected climate gradients is considered as a forest management strategy to mitigate impacts of environmental change on forest growth. However, the effects of seed translocation on wood and lumber quality remain unknown. This study evaluated the effect of provenance origin on lumber production and quality at rotation age in two white spruce provenance trials established in contrasting environments in eastern Canada. Based on 108 sample trees that resulted in 943 pieces of lumber, average volume production at the southernmost site was twice of the production at the northern site. Provenance had a significant influence on growth and lumber strength in the first log but had no effect on lumber stiffness and wood density. Although visual grade yields of No. 2 and better were high in both trials (over 86%), the machine stress rated (MSR) grade potential and percentage of lumber that met the bending stiffness design values of the visual grades were generally low (12% to 26%). Hence, plantation-grown lumber should preferably be machine stress-rated to ensure its fitness for structural end-uses. Management strategies aiming to efficiently sequester carbon should primarily maximize volume productivity in northern sites, as moving seed sources north still reduces provenance productivity, while breeding programs should aim to prevent decrease in lumber stiffness due to augmented productivity and shortened rotation cycles.

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Tree Form and Stem Taper

Cited by 9 publications

References 55 publications

Measuring tree growth using terrestrial laser scanning

Measuring tree growth using terrestrial laser scanning

A 3D approach to model the taper of irregular tree stems: making plots biomass estimates comparable in tropical forests

Translocating seed sources to new geoclimatic environments has limited effect on lumber quality of eastern Canadian white spruce

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