Effects of irregular stand structure on tree growth, crown extension and branchiness of plantation-grown<i>Pinus patula</i>

Ackerman, Simon; Ackerman, Pierre; Seifert, Thomas

doi:10.2989/20702620.2013.846722

Cited by 12 publications

(10 citation statements)

References 22 publications

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“…Depending on the position of the branch, there was also potential variability in growth and metabolic rate among branches due to environmental factors. We also used the needle biomass to predict the branch biomass in the allometric model, rather than direct measurement, expecting it to be more accurate than DBH for these trees where release from competition would increase branchiness ( Mäkinen and Colin 1998 , Ackerman et al 2013 ). If, in this case, we substantially overestimated the branch masses, this would also have caused an overestimation in the label recovery in the branches.…”

Section: Discussionmentioning

confidence: 99%

Stem injection of 15N-NH4NO3 into mature Sitka spruce (Picea sitchensis)

et al. 2014

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Stem injection techniques can be used to introduce 15N into trees to overcome a low variation in natural abundance and label biomass with a distinct 15N signature, but have tended to target small and young trees, of a variety of species, with little replication. We injected 98 atom% 15N ammonium nitrate (NH4NO3) solution into 13 mature, 9- to 13-m tall edge-profile Sitka spruce trees in order to produce a large quantity of labelled litter, examining the distribution of the isotope throughout the canopy after felling in terms of both total abundance of 15N and relative distribution of the isotope throughout individual trees. Using a simple mass balance of the canopy alone, based on observed total needle biomass and modelled branch biomass, all of the isotope injected was accounted for, evenly split between needles and branches, but with a high degree of variability both within individual trees, and among trees. Both 15N abundance and relative within-canopy distribution were biased towards the upper and middle crown in foliage. Recovery of the label in branches was much more variable than in needles, possibly due to differences in nitrogen allocation for both growth and storage, which differ seasonally between foliage and woody biomass.

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Section: Discussionmentioning

confidence: 99%

Stem injection of 15N-NH4NO3 into mature Sitka spruce (Picea sitchensis)

et al. 2014

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“…In the case of saw-timber production, thinning practices influence the quality of the logs produced at end of rotation for conversion into sawmill-ready merchandised logs. Thinnings from below are practiced in industrial plantations like those in South Africa, (von Gadow & Bredenkamp 1992;Ackerman et al 2013). This practice aims to ensure trees of poor form and those that are smaller than desired are removed while balancing the requirement for even tree spacing.…”

Section: Tree Distributions and Uniformitymentioning

confidence: 99%

“…Industrial saw-timber plantation management prescriptions are aimed at producing uniform sized trees through good establishment techniques and silvicultural interventions that are timeous and result in evenly spaced trees (Sterba & Amateis 1998;De Moraes Gonçalves et al 2004;Ackerman et al 2013). In the case of saw-timber production, thinning practices influence the quality of the logs produced at end of rotation for conversion into sawmill-ready merchandised logs.…”

Section: Tree Distributions and Uniformitymentioning

confidence: 99%

“…This practice aims to ensure trees of poor form and those that are smaller than desired are removed while balancing the requirement for even tree spacing. Even with these silvicultural and harvesting interventions, stand heterogeneity does still occur, often due to intra-stand variability i.e., slope, soil differences and the presence of rocks limiting soil depth , delayed replanting of dead trees (blanking) at establishment (Pallett 2005) and mismatched thinning practices (Ackerman et al 2013). This leads to the distributions of tree sizes with greater variability or skewness and with a high coefficient of variation (CV) that can lead to reduced harvesting productivity (Pettersson 2017).…”

Section: Tree Distributions and Uniformitymentioning

confidence: 99%

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Understanding the Influence of Tree Size Distribution on the CTL Harvesting Productivity of Two Different Size Harvesting Machines

Ackerman

Bekker

Astrup

et al. 2022

Preprint

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Tree size determines harvester productivity. Stand management determines tree size distributions. Understanding the effect of tree size distribution on harvesting productivity is central for optimizing management of operations. To investigate tree size distribution on harvester productivity, productivity functions for a medium and larger-sized harvesters were applied to harvester derived tree size distributions from 35 clearfelled pine stands. These functions were applied to a normal distribution of trees covering the same tree size ranges. Productivity differences were analysed on a stand-by-stand basis. Results showed that for the large harvester, productivity rates remained constant (67.1 vs 67.6 m3 PMH− 1) indicating relatively little sensitivity to variations in tree size distributions. Although the standard deviation (SD) halved from 11.6 to 5.6 in the case of the uniform tree distribution. The smaller harvesters, productivity decreased by 15% from 47.3 to 40.1 m3 PMH− 1 and the coefficient of variation (CV) by 6% in the same transition to a uniform distribution. Further investigation was done on more skewed tree size distributions, a family of nine Weibull distributions was generated, representing combinations of three mean DBH classes (25cm, 30 cm, and 35cm) and three levels of CV (15%, 20%, 25%), for each DBH class. Results clearly indicate that different distribution shapes have different effects on different machine sizes, and that a low CV correlates to a higher productivity in larger tree sizes. A more uniform tree size distribution also provides more predictable results (lower CV), which would promote machine scheduling and result in fewer discrepancies on production rates.

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“…As displayed in Figure 1, each swath had an edge row of trees (row 6), adjacent to an access row (row 7), which had been felled previously at an age of 8 years, during routine thinnings. Consequently (Table 1), all swaths contained a similar number of edge trees, which were potentially larger in size due to having greater resource allocation (Ackerman et al 2013.…”

Section: Study Layoutmentioning

confidence: 99%