Modelling tree crown-to-bole diameter ratio for Norway spruce and European beech
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TL;DR: In this article, the authors used a mixed-effects model to predict the crown-to-bole diameter ratio (CDBDR), which is a ratio of maximum crown width to diameter at breast height.
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Abstract: Crown dimensions are correlated to growth of other parts of a tree and often used as predictors in growth models. The crown-to-bole diameter ratio (CDBDR), which is a ratio of maximum crown width to diameter at breast height (DBH), was modelled using data from permanent sample plots located on Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus sylvatica L.) stands in different parts of the Czech Republic. Among various tree and stand-level measures evaluated, DBH, height to crown base (HCB), dominant height (HDOM), basal area of trees larger in diameter than a subject tree (BAL), basal area proportion of the species of interest (BAPOR), and Hegyi’s competition index (CI) were found to be significant predictors in the CDBDR model. Random effects were included using the mixed-effects modelling to describe sample plot-level variation. For each species, the mixed-effects model described a larger part of the variation of the CDBDR than nonlinear ordinary least squares model with no trend in the residuals. The spatially explicit mixed-effects model showed more attractive fit statistics [conditional R2 ≈ 0.73 (spruce), 0.78 (beech)] than its spatially inexplicit counterpart [conditional R2 ≈ 0.71 (spruce), 0.76 (beech)]. The model showed that CDBDR increased with increasing HDOM – a measure that combines the stand development stage and site quality – but decreased with increasing HCB and competition (increasing BAL and CI), and decreasing proportions of the species of interest (increasing BAPOR). For both species, the spatially explicit mixed-effects model should be a preferred choice for a precise prediction of the CDBDR. The CDBDR model will have various management implications such as determination of spacing, stand basal area, stocking, and planning of appropriate species mixture.
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Citations
Modelling individual tree height–diameter relationships for multi-layered and multi-species forests in central Europe
TL;DR: In this paper, a generalized nonlinear mixed-effects height-diameter (H-D) model was proposed for estimating forest yield and biomass, and simulation of the vertical stand structures.
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Mixed vs. monospecific mountain forests in response to climate change: structural and growth perspectives of Norway spruce and European beech
Zdeněk Vacek,Anna Prokůpková,Stanislav Vacek,Daniel Bulušek,Václav Šimůnek,Vojtěch Hájek,Ivo Králíček +6 more
TL;DR: In general, mixed stands can achieve higher production potential, diversity and especially resistance to climate extremes and air pollution in relation to climate change in the water-sufficient highland and mountain areas of the Czech Republic.
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A Nonlinear Mixed-Effects Height-to-Diameter Ratio Model for Several Tree Species Based on Czech National Forest Inventory Data
TL;DR: In this article, a nonlinear mixed-effects HDR model applicable to several tree species was developed using the Czech national forest inventory data comprising 13,875 sample plots and 348,980 trees.
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Systematic Review of the Roost-Site Characteristics of North American Forest Bats: Implications for Conservation
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Generalized Nonlinear Mixed-Effects Individual Tree Diameter Increment Models for Beech Forests in Slovakia
TL;DR: In this article, the authors developed both age dependent and age independent diameter increment models using long-term research sample plot data collected from both monospecific and mixed stands of European beech (Fagus sylvatica L.) in the Slovak Republic.
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Modelling growing space requirements for some tropical forest tree species
TL;DR: In this paper, the importance of crown data in improving the reliability of growth models for stand management has long been established, but such data are scarce for tropical forests, and such data is not available for tropical plantations.
Applications of the crown diameter–stem diameter relationship for different species of broadleaved trees
TL;DR: The relationship between crown diameters and stem diameters was investigated in this article, showing that the relationship is very close to being linear, with an r2 value higher than 0.8.