The reliability of tree crown position classification

Nicholas, N. S.; Gregoire, T. G.; Zedaker, Shepard M.

doi:10.1139/x91-095

Cited by 32 publications

(8 citation statements)

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“…Ten plots with a size of 600 m 2 (20 m × 30 m) were set up, and DBH, tree height, height to crown base (HCB) and crown width (four directions) for each tree were measured in each plot. After that, all the trees were divided into three social status classes including dominant, mean and suppressed trees according to the widely adopted system (Kraft class) described by Nicholas et al [20], since the stands had been thinned three times and no dying trees existed. For each social status class, 1-2 trees in each plot (34 trees in total) were sampled for stem analysis (Table 2).…”

Section: Sampling and Measurementmentioning

confidence: 99%

Horizontal and Vertical Distributions of Heartwood for Teak Plantation

Yang

Zhao

et al. 2020

Forests

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Tectona grandis is a valuable timber species with heartwood that is used worldwide. Most of the previous studies on its heartwood and sapwood have focused on dominant or mean trees, while trees with different social status might show different vertical and horizontal distributions of heartwood and sapwood. Studies on their heartwood and sapwood properties could be conducive to increasing heartwood yield at stand level. In 31-year-old plantations of T. grandis in southwest Guangxi, China, the trees were divided into three groups including dominant, mean and suppressed trees. Stem analysis was conducted for sampled trees in each of these groups to explore the differences in the horizontal and vertical distribution of their heartwood and sapwood. The results indicated that the heartwood radius, heartwood and sapwood areas of T. grandis showed significant differences in horizontal and vertical directions among trees of different social status. Heartwood began to form when xylem radius was 2-3 cm, and the heartwood radius ratio tended to be stable when the xylem radius reached about 8 cm. Heartwood radius and area, sapwood area and section heartwood volume all decreased with increasing tree height. The ratios of heartwood radius and area were relatively stable for sections under 50% of tree height. The sapwood width did not vary largely in horizontal and vertical directions among the three social status tree groups, which mainly fluctuated in the range of 1-4 cm. The heartwood volume proportions for dominant, mean and suppressed trees were 60%, 55% and 51%, respectively. There was a significant exponential relationship between heartwood volume and diameter at breast height (DBH) regardless of social status. The model HV = 0.000011 × DBH 2.9787 (R 2 = 0.8601) could accurately estimate heartwood volume for all T. grandis with different social statuses at this age. These findings could provide evidence for stand management and high-quality and large-sized timber production of T. grandis.Forests 2020, 11, 225 2 of 12 T. grandis has been in China for nearly 200 years, and has now been extensively planted in more than 60 counties or cities in 10 provinces of southern China, with a planting area of 35,000 hectares [8].Heartwood normally determines the value of wood [9], while sapwood is closely correlated with the physiological functions of trees [10]. There are a number of references on the heartwood of dominant or mean trees for T. grandis. For example, Pérez and Kanninen [11] studied the effects of thinning intensities on the heartwood volume of dominant T. grandis trees; Tewari and Mariswamy's [1] study showed that the proportion of heartwood increased while sapwood proportion was almost constant with increasing diameter at breast height (DBH) for T. grandis. In addition, Fernández-Sólis et al. [12] predicted the heartwood formation process of T. grandis based on randomly selected trees in each age class. However, mean and suppressed trees also account for a large proportion in stand [13] and their role in wood productio...

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Section: Sampling and Measurementmentioning

confidence: 99%

Horizontal and Vertical Distributions of Heartwood for Teak Plantation

Yang

Zhao

et al. 2020

Forests

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“…As a result, primarily the largest diameter A. balsamea, which tend to grow more rapidly than P. rubens early in stand development [51], were retained during thinning and smaller individuals were removed, which would further narrow the size distribution. Another possible explanation is that the subjectivity of crown class determination [35] is exacerbated when plots that have been precommercially thinned are scrutinized during field measurements.…”

Section: Discussionmentioning

confidence: 99%

“…For each of these trees, measurements included DBH; bark thickness, measured at breast height on the north and east sides of the tree; height; height to the lowest live branch. Crown class designations were given to each tree [19,22,35]. Two increment cores per tree were taken 90…”

Section: Field Measurementsmentioning

confidence: 99%

Leaf Area and Structural Changes after Thinning in Even-AgedPicea rubensandAbies balsameaStands in Maine, USA

DeRose

Seymour

2012

International Journal of Forestry Research

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We tested the hypothesis that changes in leaf area index (LAI m2 m−2) and mean stand diameter following thinning are due to thinning type and residual density. The ratios of pre- to postthinning diameter and LAI were used to assess structural changes between replicated crown, dominant, and low thinning treatments to 33% and 50% residual density in even-agedPicea rubensandAbies balsameastands with and without a precommercial thinning history in Maine, USA. Diameter ratios varied predictably by thinning type: low thinnings were <0.7, crown thinnings were >0.7 but <1.0, and dominant thinnings were >1.0 . LAI change was affected by type and intensity of thinning. On average, 33% density reduction removed <50% of LAI, whereas 50% density reduction removed >50% of LAI. Overall reduction of LAI was generally greatest in dominant thinnings (54%), intermediate in crown thinnings (46%), and lowest in low thinnings (35%). Upon closer examination by crown classes, the postthinning distribution of LAI between upper and lower crown classes varied by thinning history, thinning method, and amount of density reduction.

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“…: see Miller and Clover 1991). With practice, observers can become reasonably consistent (minimizing repeat sampling error) at categorizing or estimating the condition of crowns of even very large trees (Zedaker and Nicholas 1991;Nicholas et al 1991). However, a source of variation that has not been addfessed is observer bias.…”

Section: Variation In Efficacy Measuresmentioning

confidence: 99%

Sample-size needs for forestry herbicide trials

Zedaker¹,

Grégoire²,

Miller³

1993

Can. J. For. Res.

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needs for forestry herbicide trials. Can. J. For. Res. 23: 2153Res. 23: -2158 Forest herbicide experiments are increasingly being designed to evaluate smaller treatment differences when comparing existing effective treatments, tank mix ratios, surfactants, and new low-rate products. The ability to detect small differences in efficacy is dependent upon the relationship among sample size. type I and II error probabilities, and the coefficients of variation of the efficacy data The common sources of variation in efficacy measurements and design considerations for controlling variation ate reviewed, while current shortcomings are clarified. A summary of selected trials estimates that coefficients of variation often range between 25 and lOO%, making the number of observations necessary to detect small differences very large, especially when the power of the test (1 -l3) is considered. Very often the power of the test has been ignored when designing experiments because of the difficulty in calculating f3. An available program for microcomputers is introduced that allows researchers to examine relationships among sample size, effect size, and coefftcients of variation for specified designs, a and p. This program should aid investigators in planning studies that optimize experimental power to detect anticipated effect sizes within resource constraints. ZEDAKER, S.M., GRE~~IFUZ, T.G., et MILER, J.H. 1993. Sample-size needs for forestry herbicide trials. Can. J. For. Res. 23 : 2153-2158. Les experiences sur les herbicides forestiers. sent de plus en plus structtmfes pour evaluer de petites diff&ences entne les traitements lorsqu'on compare les traitements actuellement utilis& les rapports des m&anges dam les reservoirs, les surfactants et les nouveaux produits utilis& 8 faible dose. La cap&u5 de d&ecter de p&es differences d'effkaciti d&pend de la relation entre la dimension des &iantillons, des eneurs en probabik? de types I et II et des coeffkients de variation des doM6es d'effrcacid. Les sources communes de variation dans les mesurea d'efIicacit6, et les consid&ations de structure pour contiler la vatiatio~ sont revis& pendant que les dkfauts courants sont clarifi&~ A l'aide d'un sununaim d'l%&S s&ctio~&s, on estime que les coefficients de variation se situent souvent eatre 25 et 100%. ce qui n&es&e un t&s grand nombre d'observations pour d&e&r de pet&es differences surtout lorsque la puissance du test (1 -B) est consid&&. Tti?s souvent la puissance du test, a &? &nor& dans la structure des experiences a cause de la difficuld & cakuler p. Nous inuoduisens un prograuuue disponible sur mko-oniinateur qui permet aux chercheurs d'examiner lcs relations entre la' dimension des kchaatillons, les effets de la dimension et des coefficients de variition pour des structures do~&s,

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The reliability of tree crown position classification

Cited by 32 publications

References 0 publications

Horizontal and Vertical Distributions of Heartwood for Teak Plantation

Horizontal and Vertical Distributions of Heartwood for Teak Plantation

Leaf Area and Structural Changes after Thinning in Even-AgedPicea rubensandAbies balsameaStands in Maine, USA

Sample-size needs for forestry herbicide trials

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