Additive crown width models comprising nonlinear simultaneous equations for Prince Rupprecht larch (Larix principis-rupprechtii) in northern China

Fu, Liyong; Xiang, Wei; Wang, Guangxing; Hao, Kaijie; Tang, Shouzheng

doi:10.1007/s00468-017-1600-0

Cited by 7 publications

(7 citation statements)

References 31 publications

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“…To optimize the structure and promote the growth of the forest, a slight under-tending treatment (e.g., removing less than 15% of smaller trees and only those with less economic value) was implemented in 2014. The remaining two sites are the natural secondary forest (Plot c) and natural oak (Q. mongolica) forest (Plot d), located in Maoershan Forest Farm (127°18′-127°41′E, 45°2′-45°18′N), which covers an area of 26,496 ha, with a south-north length of approximately 30 km and an east-west width of 20 km [29]. It is located in a low-altitude area of the Zhangguangcai Mountains, approximately 80 km from Harbin city, the capital of Heilongjiang Province.…”

Section: Case Study Areasmentioning

confidence: 99%

“…The tree crown is the main site for a series of important physiological activities of forests and trees, such as photosynthesis and respiration; thus, the size, structure, and distribution of the canopy can comprehensively reflect the growth vigor and development trend of trees. Previous studies have indicated that the crown size usually increases significantly with tree diameter, presenting a typical sigmoid tendency [29,30]. To eliminate the preference of tree vigor indices, the ratio of crown width with respect to DBH was employed to evaluate tree vigor:…”

Section: Nonspatial Structural Parametersmentioning

confidence: 99%

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Optimizing Forest Spatial Structure with Neighborhood-Based Indices: Four Case Studies from Northeast China

Dong

Wei

Liu

2020

Forests

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The fine-scale spatial patterns of trees and their interactions are of paramount importance for controlling the structure and function of forest ecosystems; however, few management techniques can be employed to adjust the structural characteristics of uneven-aged mixed forests. This research provides an accurate, efficient, and impersonal comprehensive thinning index (P-index) for selecting candidate harvesting trees; the index was proposed by weighting the commonly used quantitative indices with respect to stand fine-scale structures, competition status, tree vigor, and tree stability. The applications of the proposed P-index in evaluating and simulating the process of thinning operations were examined using four 1-ha mapped plots with different forest types, namely, natural secondary forest, natural pine-broadleaved mixed forest, natural larch-birch mixed forest, and natural oak forest, which were widely distributed across the Heilongjiang Province in Northeast China. The results indicated that the proposed P-index could effectively affect the structural differentiations between different forest types and alternative thinning intensities. The marginal benefits of alternative thinning intensities on the integrated forest structure indicated that removing 10% of the trees from the plots might be the optimal thinning intensity from the perspective of optimizing stand structure, in which the P-index values could be increased by approximately 5%–11% for the four tested plots. The main conclusion from this paper was that the proposed P-index could be used as a quantitative tool to manage uneven-aged mixed forests.

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Section: Case Study Areasmentioning

confidence: 99%

Section: Nonspatial Structural Parametersmentioning

confidence: 99%

Optimizing Forest Spatial Structure with Neighborhood-Based Indices: Four Case Studies from Northeast China

Dong

Wei

Liu

2020

Forests

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“…In the first place, we considered whether a generic model could be developed for the four CR of each species as in other studies (Fu et al 2017b;Fu et al 2017c;Lei et al 2018). However, we believe that various tree species or even directions of CR may have diverse growth trends, especially in natural forests.…”

Section: Preparation Before Modelingmentioning

confidence: 99%

“…The plasticity and phototropism of the crown allow for optimal canopy filling by growing into vacant growth spaces (Jucker et al 2015;Krůček et al 2019;Longuetaud et al 2013). Therefore, the four CR usually possess different growth and development characteristics that tend to form asymmetrical or irregular crowns (Fu et al 2017b;Kong et al 2021;Thorpe et al 2010). The understanding of the growth characteristics of the CR in four directions is critical for assessing the health and competitiveness of trees (Thorpe et al 2010), simulating canopy cover and radiative transfer (Cescatti 1997;Gill et al 2000), and understanding the susceptibility of trees to windthrow (Skatter and Kucera 2000).…”

Section: Introductionmentioning

confidence: 99%

“…The understanding of the growth characteristics of the CR in four directions is critical for assessing the health and competitiveness of trees (Thorpe et al 2010), simulating canopy cover and radiative transfer (Cescatti 1997;Gill et al 2000), and understanding the susceptibility of trees to windthrow (Skatter and Kucera 2000). However, most of the developed models related to the crown still assumed consistent developmental trends in all directions of the crown, leading to identical models being used to simulate crown properties in all directions (Fu et al 2017b;Fu et al 2017c;Gao et al 2021;Lei et al 2018).…”

Section: Introductionmentioning

confidence: 99%

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Two new methods applied to crown width additive models: a case study for three tree species in Northeastern China

Wang

Jiang

Xin

et al. 2023

Annals of Forest Science

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Key message The non-linear seemingly unrelated regression mixed-effects model (NSURMEM) and generalized additive model (GAM) were applied for the first time in crown width (CW) additive models of larch (Larix gmelinii Rupr.), birch (Betula platyphylla Suk.), and poplar (Populus davidiana Dode). The crown radii in four directions (CR) exhibited different growth trends and responded differently to tree size and competition variables. In the absence of calibration, GAM was more accurate than NSURMEM for CR and CW predictions. Context Crown radii in four directions (CR) and crown width (CW) are fundamental indicators used to describe tree crowns. The complexity of the CR growth in four directions of different tree species in natural forests is often ignored. There is logical additivity among CR and CW that is also often overlooked. Furthermore, the existing methods applied to CW additive models have some drawbacks. Aims We aim to: (i) evaluate the utility of two new methods in developing CW additive models for larch (Larix gmelinii Rupr.), birch (Betula platyphylla Suk.), and poplar (Populus davidiana Dode) in natural secondary forests of Northeastern China; and (ii) explore the growth patterns of CR in four directions to gain important ecological insights. Methods The non-linear seemingly unrelated regression mixed-effects model (NSURMEM) and generalized additive model (GAM) were used to develop CW additive models and to explore crown growth patterns. The predictive ability of the additive models was evaluated using leave-one-plot-out cross-validation (LOOCV). Results At a fair level without calibration, GAM provided slightly better results than NSURMEM. The response of the four CR to tree size and competition variables is different and may be non-uniform due to complex stand conditions and tree growth strategies. Conclusion The newly provided methods applied to additive models are available for external datasets. GAM is recommended in the absence of calibration. This study has important implications for the understanding of natural forest dynamics and decision-making for critical stand management.

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Developing nonlinear additive tree crown width models based on decomposed competition index and tree variables

et al. 2023

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Additive crown width models comprising nonlinear simultaneous equations for Prince Rupprecht larch (Larix principis-rupprechtii) in northern China

Cited by 7 publications

References 31 publications

Optimizing Forest Spatial Structure with Neighborhood-Based Indices: Four Case Studies from Northeast China

Optimizing Forest Spatial Structure with Neighborhood-Based Indices: Four Case Studies from Northeast China

Two new methods applied to crown width additive models: a case study for three tree species in Northeastern China

Developing nonlinear additive tree crown width models based on decomposed competition index and tree variables

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