Trunk Taper Research Articles

The Impact of Visual Defects and Neighboring Trees on Wind-Related Tree Failures

Urban trees are often more sun- and wind-exposed than their forest-grown counterparts. These environmental differences can impact how many species grow–impacting trunk taper, crown spread, branch architecture, and other aspects of tree form. Given these differences, windthrow models derived from traditional forest production data sources may not be appropriate for urban forest management. Additionally, visual abnormalities historically labeled as “defects” in timber production, may not have a significant impact on tree failure potential. In this study, we look at urban tree failures associated with Hurricane Irma in Tampa, Florida, USA. We used spatial analysis to determine if patterns of failure existed among our inventoried trees. We also looked at risk assessment data to determine which visual defects were the most common and the most likely to be associated with branch or whole-tree failure. Results indicate that there was no spatial pattern associated with the observed tree failures–trees failed or withstood the storm as individuals. While some defects like decay and dead wood were associated with increased tree failure, other defects such as weak branch unions and poor branch architecture were less problematic.

Variation in trunk taper of buttressed trees within and among five lowland tropical forests

AbstractAccurately projecting global carbon dynamics requires understanding controls over temporal and spatial tropical forest biomass variation. Changes in tropical forest aboveground biomass per area are most commonly estimated using repeat forest plot censuses, but errors in these estimates can be relatively large, limiting our ability to detect real changes in forest carbon. One source of error is nonstandard heights of diameter measurement, which are common in tropical forests because buttressed trees are usually measured above buttresses. Nonstandard and temporally variable measurement heights affect biomass change estimates because tree trunks taper—higher measurements result in smaller diameters and, thus, smaller estimated biomass. Modeling trunk taper is a potential way to correct for biases associated with nonstandard and changing measurement heights. We measured trunk taper for 260 buttressed trees in five lowland tropical forests to assess variation in taper within and among sites. Trunks taper more slowly in trees with larger diameters above buttress, taller buttresses, and higher wood density; these variables together explain 29% of taper variation. We also used plot data to quantify the distribution of measurement heights—and potential for bias in biomass estimates. We found significant variation in measurement heights among plots, and over time within plots. At the site level, our general taper model (taper predicted from diameter above buttress, buttress height, and wood density) produced site‐level biomass estimates within 3.4%, on average, of estimates from measured taper. We recommend using this model to reduce bias from nonstandard measurement heights in studies of tropical forest biomass variation.Abstract in Spanish is available with online material.

Wind and gravity in shaping Picea trunks

Key messageSpruce trunk tapering corresponds closely to tapering required to resist bending forces caused by wind and gravity.Understanding why trunks (tree stems) are the size that they are is important. However, this understanding is fragmented into isolated schools of thought and has been far from complete. Realistic calculations on minimum trunk diameters needed to resist bending moments caused by wind and gravity would be a significant step forward. However, advancements using this biomechanical approach have been delayed by difficulties in modelling bending of trunks and wind gusts. We felled and measured five Norway spruces (Picea abies) in an unthinned monoculture in southeastern Finland planted 67 years earlier. We then focused on forces working on storm-bent (maximally bent) trees caused by gravity and the strongest gust in a 1-h simulation with a large-eddy simulation model. The weakest points along the trunks of the three largest trees resisted mean above-canopy wind speeds ranging from 10.2 to 12.7 m s−1 (3.3-fold in the strongest gust), but the two smallest were well protected by a dense layer of leaves from the bending tops of larger trees, and could have resisted stronger winds. Gravity caused approximately one quarter of the critical bending moments. The wind that breaks the trunks in their weakest points is close to breaking them in other points, supporting the importance of bending moments caused by wind and gravity in the evolution of trunk taper.

Bivariate and generalized models for taper stem representation and assortments production of loblolly pine (Pinus taeda L.)

Modeling is an important statistical tool to Forest Science, especially to forest planning by predicting the forest's yield and assortments, for instance. This paper evaluated the accuracy of bivariate and generalized linear mixed modeling in the representation of the Pinus taeda L. trunk taper and the estimation of its assortments. To compose the fitting data, 558 trees from plantations located in the Southern region of Santa Catarina, Brazil, were scaled. Initially, the data's bivariate normality was evaluated, and the bivariate standard normal distribution was fitted. Six generalized linear mixed models were fitted for the bivariate representation of diameter and height in the trunk. Afterwards, some statistical indices were obtained to verify the quality of the fitted models and, in a complementary way, of the bivariate graphs of the residuals. Even with the application of Box-Cox transformation, the results indicate the non-normality of the variables, but the transformation contributed to improve the model fitting in 50%. The ordinal and exponential models obtained the best statistics for height representation, with the Akaike Information Criterion (AIC) value being reduced from 16,430.13 to 5,686.78 when considering normal distribution. When evaluating the assortments prediction, there were high discrepancies in the estimated values (246 logs for sawmill and 120 logs for veneers) versus the observed ones (881 logs for sawmill and 628 logs for veneers), which corresponds to a 75% underestimation of total logs per hectare. Thus, the generalized linear mixed modeling improved the trunk taper representation, and the bivariate modeling was not efficient to predict assortments production.

Efeito do sistema de plantio e da exposição solar sobre a alocação da biomassa no desenvolvimento inicial do eucalipto

Este trabalho foi desenvolvido com o objetivo de comparar a alocação da biomassa arbórea, a conicidade do tronco e a relação altura e diâmetro ao longo do fuste de árvores de eucalipto implantadas em sistema silvipastoril, em diferente exposição solar, e em monocultivo. Os dados foram coletados em 13 árvores amostras aos 27 meses de idade, selecionadas em função do intervalo de confiança da média dos diâmetros a altura do peito (DAP) e da posição das árvores na faixa de plantio, com face de exposição sul, norte e central. Concluiu-se que na comparação com o monocultivo, as árvores plantadas em sistema silvipastoril apresentaram menor altura total, maior conicidade e maior biomassa na copa. No sistema silvipastoril, não houve efeito da posição da árvore na faixa de plantio sobre a produção total de biomassa na parte aérea, porém, árvores com face de exposição norte foram mais baixas, cônicas e produziram maior biomassa de galhos e folhas nas partes inferiores da copa.

Improving estimates of biomass change in buttressed trees using tree taper models

SummaryRepeat censuses of tree plots are key tools for investigating forest carbon fluxes. Current measurement procedures for trees with buttresses or trunk irregularities – trees that account for a large fraction of tropical forest biomass –introduce substantial systematic error in plot‐level estimates of biomass change. The diameters of buttressed trees are measured above the standard height of 1·3 m, and the measurement heights on individual trees are often moved upwards as buttresses grow. Because tree trunks taper (diameter decreases with height), biomass growth in buttressed individuals tends to be underestimated. Methods have been introduced to correct biomass growth estimates in individual trees for increases in measurement height; however, these methods change the distribution of effective measurement heights over time, introducing biases in plot‐level estimates of biomass change.In this study, we developed and applied new methods to measure and model trunk taper, and to use taper models to correct estimates ofAGBchange for changing measurement heights. We measured trunk taper above buttresses in 190 stems on Barro Colorado Island, Panama (BCI), a site where more than half of forest biomass is in trees measured above standard height. We compared proposed taper models to see which best described our measured taper data, then used the best taper model to correct for changing measurement heights in the historical plot data. Specifically, for all diameter measurements taken above 1·3 m, we calculated equivalent diameters at 1·3 m and substituted these into allometric equations to examine biomass change over time.We found that measured taper was best fit by an exponential model with a rate parameter that varied with measured diameter (tree size), height of measurement (buttress height) and species. Whereas uncorrected data show a decrease in biomass of 0·21% year−1between 1985 and 2010 onBCI, taper‐corrected data show an increase of 0·18% year−1.The novel correction method presented here converts all measured diameters to one standard effective measurement height. This corrects for biases at the plot level and provides a stronger foundation for measuring biomass change in tropical forests.

The use of forest-derived specific gravity for the conversion of volume to biomass for open-grown trees on agricultural land

Accounting for agroforestry contributions to carbon sequestration and cellulosic feedstock production requires biomass equations that accurately estimate biomass in open-grown trees. Since equations for open-grown trees are rare and developing these is expensive, existing forest-based equations are an attractive alternative for open-grown trees in carbon accounting and biomass modeling. How accurate this alternative is depends on how similar the key attributes, such as specific gravity, trunk shape, and crown architecture, are between open- and forest-grown trees. We evaluated the use of forest-derived specific gravity for conversion of volume to biomass for morphologically distinct open-grown species: green ash, ponderosa pine, and eastern redcedar. Trunk biomass was consistently and significantly underestimated from 6.3% to 16.6% depending on species, indicating open-grown trees have greater trunk specific gravity than forest-grown counterparts within the same geographic region; however a conclusive difference in branch specific gravity was not found between open- and forest-grown trees. Open-grown trees have greater trunk specific gravity, sharper trunk taper, and larger crown. When forest-based equations are used for trunk biomass of open-grown trees, the greater trunk specific gravity results in underestimation; however, the sharper trunk taper results in overestimation. Studies are needed to examine whether the underestimation could be offset by the overestimation and how the larger crown affects biomass estimation when forest-based equations are used for open-grown trees. Our results provide an essential understanding to interpret the biometric relationship of open- to forest-grown trees and to develop an efficient means how forest-based equations might be best modified for open-grown trees.

Growth, survival, and root system morphology of deeply planted Corylus colurna 7 years after transplanting and the effects of root collar excavation

Urban trees are frequently planted with their root collars and structural roots buried well below soil grade, either because of planting practices, nursery production practices, or both. These deeply planted structural roots can impair tree establishment and are thought to reduce tree growth, lifespan, and stability, although research has provided few and contradictory results on these questions to date. This study examines container-grown (55 L) Turkish hazel trees ( Corylus colurna L.), planted either at grade, 15 cm below grade, or 30 cm below grade into a well-drained silt loam soil, over nearly 8 years. Five years after planting, in 2004, remediation treatments (root collar excavations) were performed on two replicates of each below-ground treatment. Subsequently, all trees were subjected to flooding stress by being irrigated to soil saturation for approximately 6 weeks. In 2006, flooding stress was repeated. Trees root systems were partially excavated in 2007, and root architecture was characterized. Deep planting did not affect trunk diameter growth over 8 years. Survival was 100% for the first 5 years; however, one 30 cm below grade tree died after flooding in 2004 and another died after the 2006 flooding. Photosynthesis was monitored during the 2004 flooding and all trees experienced decline in photosynthetic rates. There was an apparent slight delay in the decline for trees with excavated root collars and those planted at grade. Girdling roots reduced trunk taper and occurred primarily on unremediated trees planted 30 cm below grade. Selected individual roots were excavated and followed from the root ball and were observed to gradually rise to the upper soil regions. Analysis of roots emerging from excavation trench faces indicated that vertical root distribution at approximately 1.25 m from the tree trunks was the same regardless of planting depth. Longterm consequences of planting below grade are discussed.

Estimation of forest biophysical characteristics in Northern Michigan with SIR-C/X-SAR

A three-step process is presented for estimation of forest biophysical properties from orbital polarimetric SAR data. Simple direct retrieval of total aboveground biomass is shown to be ill-posed unless the effects of forest structure are explicitly taken into account. The process first involves classification by (1) using SAR data to classify terrain on the basis of structural categories or (2) a priori classification of vegetation type on some other basis. Next, polarimetric SAR data at L- and C-bands are used to estimate basal area, height and dry crown biomass for forested areas. The estimation algorithms are empirically determined and are specific to each structural class. The last step uses a simple biophysical model to combine the estimates of basal area and height with ancillary information on trunk taper factor and wood density to estimate trunk biomass. Total biomass is estimated as the sum of crown and trunk biomass. The methodology is tested using SIR-C data obtained from the Raco Supersite in Northern Michigan on Apr. 15, 1994. This site is located at the ecotone between the boreal forest and northern temperate forests, and includes forest communities common to both. The results show that for the forest communities examined, biophysical attributes can be estimated with relatively small rms errors: (1) height (0-23 m) with rms error of 2.4 m, (2) basal area (0-72 m/sup 2//ha) with rms error of 3.5 m/sup 2//ha, (3) dry trunk biomass (0-19 kg/m/sup 2/) with rms error of 1.1 kg/m/sup 2/, (4) dry crown biomass (0-6 kg/m/sup 2/) with rms error of 0.5 kg/m/sup 2/, and (5) total aboveground biomass (0-25 kg/m/sup 2/) with rms error of 1.4 kg/m/sup 2/. The addition of X-SAR data to SIR-C was found to yield substantial further improvement in estimates of crown biomass in particular. However, due to a small sample size resulting from antenna misalignment between SIR-C and X-SAR, the statistical significance of this improvement cannot be reliably established until further data are analyzed. Finally, the results reported are for a small subset of the data acquired by SIR-C/X-SAR.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Size-dependent Allometry of Tree Height, Diameter and Trunk-taper

The allometry of tree height with respect to trunk diameter and the allometry of trunk diameter with respect to distance from the top of the tree (i.e. trunk taper) were determined for 27 Robinia pseudoacacia trees differing in age and size growing in an open field. The allometric (scaling) exponent for height was > 1 for small and young trees and decreased to 2/3 and then 1/2 as tree size and age increased. Similarly, the exponent for taper was > 1 near the tips of young and old trunks and converged onto values of 2/3 and 1/2 toward the base of mature tree trunks. These observations indicate that a single 'optimal mechanical design principle' (i.e. elastic, stress or geometric self-similarity) neither holds true throughout the lifetime of R. pseudoacacia trees, nor does a single design principle govern the taper of a trunk throughout its entire length. Rather, over the course of growth and development, the allometry of R. pseudoacacia tree height and trunk taper progressively changes, complying with geometric self-similarity for young plants (and young portions of old plants) and subsequently giving the appearance of elastic or stress self-similarity as plants (or portions of plants) get older and therefore larger. Analyses of published (and new) data suggest that the conclusions drawn for R. pseudoacacia trees are likely to hold true for other tree species because stem growth in diameter is 'indeterminate' whereas growth in overall tree height is asymptotic and therefore essentially 'determinate'.

ROOTSTOCK INFLUENCE ON FRUIT TREE ARCHITECTURE

Rootstock influence on tree architecture may be seen in a variety of expressions. Above ground effects include canopy volume and shape, crotch angles, branch display angles, relative distribution of long shoots and spurs, internode length, relative distribution of fruit buds and spurs, and trunk taper. Below the graft union, effects include relative distribution of fine vs. coarse roots, total root mass, and numbers, nature and distribution of burrknots. Many of these phenomena are indirect effects that stare from induction of fruiting by the rootstock, e.g., early fruit production induced by the rootstock will result in reduced canopy volume, reduced aboveground total mass, flatter branch display angles, and reduced root mass. The rootstock also plays a major role in the duration of shoot extension growth; by influencing the production of growth regulators in the shoot tip, the rootstock indirectly influences the inhibit ion of lateral buds and therefore the production of feathers.