Modelling crown width–diameter relationship for Scots pine in the central Europe

Sharma, Ram P.; Bílek, Lukáš; Vacek, Zdeněk; Vacek, Stanislav

doi:10.1007/s00468-017-1593-8

Cited by 63 publications

(90 citation statements)

References 75 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Most of the existing CR models have included the measures describing the effects of competition (e.g., stand basal area, crown competition factor, and spacing index), the effects of size of trees (e.g., diameter, height, height-to-diameter ratio, and stand age), and the effects of site characteristics (e.g., altitude, slope, and aspect), but not the measures that describe the effects of intra-or inter-species interactions and canopy height differentiation on the CR variation. The effects of species mixture on tree and stand characteristics have been thoroughly analyzed in several studies [42,44,48,56,[58][59][60]. These studies confirm that species-mixing effect on tree characteristics is highly significant; therefore, this cannot be disregarded when measurements from mixed stands are used.…”

Section: Introductionmentioning

confidence: 87%

“…Site quality, stand development stage, and stand density or competition may have significant effects on the crown of trees [8,[40][41][42][43][44]49,69]. Considering this, we evaluated several tree and stand measures for their potential contributions to the CR variation.…”

Section: Tree and Stand Measuresmentioning

confidence: 99%

“…We also calculated the relative spacing index (RSI), which is defined by RSI = √ 10, 000/N/HDOM [11,20,74,75]. We assumed RSI as an effective stand density measure for determining the thinning specification, because it includes stocking and combined effect of site quality and stand development stage through N and HDOM, respectively [11,44,76].…”

Section: Tree and Stand Measuresmentioning

confidence: 99%

“…All tree-and stand-level competition measures were computed using the measurements regardless of species. There can be a significant effect of species mixture on tree growth and stand dynamics [44,48,56,[58][59][60]. We also included a variable (basal area proportion of the species of interest: BAPRO) that describes species mixing effect on the CR variation.…”

Section: Tree and Stand Measuresmentioning

confidence: 99%

“…Considering the necessity of the crown models for decision-making in forestry, a number of studies that involved tree-based crown models have been carried out, including crown diameter models [39][40][41][42][43][44], crown shape models [45], crown rise models [46], crown spread ratio models [47], crown projection ratio models [48], and crown ratio models [8,[49][50][51][52][53]. The CR models are much more important than any other models of the crown measures for forest management [8,24].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Generalized Nonlinear Mixed-Effects Individual Tree Crown Ratio Models for Norway Spruce and European Beech

Sharma

Vacek

2018

Forests

Self Cite

View full text Add to dashboard Cite

Tree crowns are commonly measured to understand tree growth and stand dynamics. Crown ratio (CR—crown depth-to-total height ratio) is significantly affected by a number of tree- and stand-level characteristics and other factors as well. Generalized mixed-effects CR models were developed using a large dataset (measurements from 14,669 trees of Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus sylvatica (L.)) acquired from permanent research plots in various parts of the Czech Republic. Among several tree- and stand-level variables evaluated, diameter at breast height, height to crown base, dominant height, basal area of trees larger in diameter than a focal tree, relative spacing index, and variables describing the effects of species mixture and canopy height differentiation significantly contributed to CR variation. We included sample-plot-level variations caused by randomness in the data and other stochastic factors into the CR models using the mixed-effects modeling approach. The logistic function, which predicts the values between 0 and 1, was chosen to develop the generalized CR mixed-effects model. A large proportion of the CR variation (R2adj ≈ 0.63 (Norway spruce); 0.72 (European beech)) was described by generalized mixed-effects model without significant residual trends. Testing the CR model against a part of the model fitting dataset confirmed its high prediction precision. Our CR model can be useful for growth simulation using inventory databases that lack crown measures. Other potential implications of our CR models in forest management are mentioned in the article.

show abstract