scholarly journals Comparison of various growth functions for predicting long-term stand development associated with different initial spacing in 64-year-old Japanese cedar (Cryptomeria japonica (L.f.) D. Don) plantations

2021 ◽  
Vol 64 (1) ◽  
pp. 87-97
Author(s):  
Che-Yu Shih ◽  
Tian-Ming Yen ◽  
Ya-Nan Wang
Keyword(s):  
Cryptomeria Japonica ◽  
Stand Density ◽  
Japanese Cedar ◽  
Growth Patterns ◽  
Growth Potential ◽  
Stand Development ◽  
Initial Growth ◽  
Growth Functions ◽  
Initial Spacing

Establishing a plantation with varied distances between trees is one way to control stand density in an initial growth stage. Understanding how stand growth patterns are influenced by initial spacing can help maximize growth and yield. The purpose of this study was to examine the long-term effects of different patterns of initial tree spacing on stand development. A spacing trial with five initial distances, namely, treatments I: 1×1 m, II: 2×2 m, III: 3×3 m, IV: 4×4 m, and V: 5×5 m, was established in 1950 in Japanese cedar (Cryptomeria japonica (L.f.) D. Don) plantations in central Taiwan, managed by the Experimental Forest of National Taiwan University. Each treatment had three repetitions, and all plots were surveyed from 1955 to 2014, with eight records for each time series. We simultaneously employed six growth functions to predict stand basal area growth for each plot and assessed their predictability using the root mean square error (RMSE) as a criterion. Consequently, a total of twelve plots covering all treatments except treatment I, each with six RMSEs resulting from various models, were obtained. The repeated measures analysis of variance approach was adopted to compare predictability among models. The Richards growth function performed the best compared to all the other models. As a result, this model was used to analyse stand development following different initial spacing. We found that the predicted curves could effectively exhibit the growth patterns resulting from different initial spacing. Moreover, the parameters help explain some characteristics of stand development, such as growth potential and maximum growth rate achieved (t max). As a result, a clear trend emerged, showing that, with decreasing initial spacing, the growth potential increased and the t max decreased. These results provided valuable information for managing the stand density of this conifer.

scholarly journals Evaluation of Individual Distance-Independent Diameter Growth Models for Japanese Cedar (Cryptomeria japonica) Trees under Multiple Thinning Treatments

Forests ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 344 ◽  
Author(s):  
Keiko Fukumoto ◽  
Tomohiro Nishizono ◽  
Fumiaki Kitahara ◽  
Kazuo Hosoda
Keyword(s):  
Forest Management ◽  
Tree Growth ◽  
Cryptomeria Japonica ◽  
Growth Models ◽  
Japanese Cedar ◽  
Diameter Growth ◽  
Model Accuracy ◽  
Thinning Intensity ◽  
Diameter Growth Models

Understanding the tree growth process is essential for sustainable forest management. Future yields are affected by various forest management regimes such as thinning; therefore, accurate predictions of tree growth are needed under various thinning intensities. This study compared the accuracy of individual-level distance-independent diameter growth models constructed for different thinning intensities (thinning intensity-dependent multiple models: TDM model) against the model designed to include all thinning intensities (thinning intensity-independent single model: TIS model) to understand how model accuracy is affected by thinning intensity. We used long-term permanent plot data of Japanese cedar (Cryptomeria japonica) stands in Japan, which was gathered from four plots where thinning was conducted at different thinning intensities: (1) intensive (41% and 38% of trees removed at 25 and 37 years old, respectively), (2) moderate (38% and 34%), (3) light (32% and 34%), and (4) no thinning. First, we specified high interpretability distance-independent competition indices, and we compared the model accuracy both in TDM and TIS models. The results show that the relative spacing index was the best competition index both in TDM and TIS models across all thinning intensities, and the differences in the RMSE (Root mean square error) and rRMSE (relative RMSE) in both TDM and TIS models were 0.001–0.01 cm and 0.2–2%, respectively. In the TIS model, rRMSE varied with thinning intensity; the rRMSE was the lowest for moderate thinning intensity (45.8%) and the highest for no thinning (59.4%). In addition, bias values were negative for the TIS model for all thinning intensities. These results suggest that the TIS model could express diameter growth regardless of thinning intensities. However, the rRMSE had varied with thinning intensity and bias had negative values in the TIS model. Therefore, more model improvements are required for accurate predictions of long-term growth of actual Japanese cedar stands.

Long-term growth analyses of Japanese cedar trees in a plantation: neighborhood competition and persistence of initial growth deviations

2006 ◽  
Vol 11 (4) ◽  
pp. 217-225 ◽  
Author(s):  
Takashi Masaki ◽  
Shigeta Mori ◽  
Takuya Kajimoto ◽  
Gaku Hitsuma ◽  
Satoshi Sawata ◽  
...  
Keyword(s):  
Japanese Cedar ◽  
Initial Growth ◽  
Growth Analyses ◽  
Neighborhood Competition

scholarly journals Auf dem Weg zum Gebirgsplenterwald: Kurzzeiteffekte von Durchforstungen auf die Struktur subalpiner Fichtenwälder | On the way to a mountain selection forest:Short-term effects of thinning on the structure of subalpine spruce forests (reviewed paper)

2005 ◽  
Vol 156 (12) ◽  
pp. 456-466 ◽  
Author(s):  
Hansheinrich Bachofen ◽  
Andreas Zingg
Keyword(s):  
Spatial Distribution ◽  
Stand Density ◽  
Stand Development ◽  
Protective Function ◽  
Spruce Forests ◽  
Density Index ◽  
Thinning Operations ◽  
Stand Density Index ◽  
Improve Stability

Stand structures and stand stability in unmanaged Norway spruce forests in the Swiss mountains may decline and their protective function against natural hazards will thus be put at risk. They are being subjected to thinning operations to improve stability and, in the long-term, to transform them into mountain selection forests. On pairs of research plots – thinned and not thinned – we will closely follow the stand development. Preliminary results indicate that the best variables to describe the effectiveness of the applied treatment to the stand structures are the h/d ratio,the spatial distribution and the stand density index.

scholarly journals Impacts of Long-Term Diameter-Limit Harvesting on Residual Stands of Red Spruce in Maine

2004 ◽  
Vol 21 (2) ◽  
pp. 69-73 ◽  
Author(s):  
Kerry A. Sokol ◽  
Michael S. Greenwood ◽  
William H. Livingston
Keyword(s):  
Positive Selection ◽  
Growth Rates ◽  
Growth Patterns ◽  
Growth Potential ◽  
Red Spruce ◽  
Growing Stock ◽  
Spruce Stands ◽  
Selection Harvesting ◽  
Residual Tree

Abstract Diameter-limit harvesting has long been suspected as a dysgenic forestry practice, but a conclusive, practical demonstration of the effects of this selection technique on residual tree performance is lacking. To determine the effects of repeated diameter-limit harvesting on the phenotypes of residual trees, we compared radial growth patterns of residual red spruce trees (with ages greater than 100 years) after diameter-limit harvests with those of residual trees in stands subjected to positive selection harvesting. After nearly 50 years of repeated harvesting, residual trees in the diameter-limit stands were nearly 40% smaller and had grown 32% slower than residual trees in positive selection stands. Furthermore, diameter-limit residuals were initially smaller and remained significantly smaller than positive selection residuals throughout their lifespan, despite major release events. After release, the diameter-limit trees responded with increased growth rates, but the increase was relatively small. Growth rates were consistently and significantly lower for diameter-limit residuals until the final 20 yr when growth rates in each treatment converged. Our results indicate that red spruce stands subjected to repeated diameter-limit harvesting will develop progressively less valuable growing stock with limited growth potential.

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