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Article

Thinning Increases Individual Tree Growth While Reducing the Growth Heterogeneity of Lodgepole Pine

by
Mostarin Ara
*,
Bradley D. Pinno
,
Francis Scaria
,
Robert E. Froese
and
Mike Bokalo
Alberta School of Forest Science and Management, University of Alberta, 751 General Services Building, Edmonton, AB T6G 2H1, Canada
*
Author to whom correspondence should be addressed.
Forests 2023, 14(6), 1091; https://doi.org/10.3390/f14061091
Submission received: 13 April 2023 / Revised: 13 May 2023 / Accepted: 17 May 2023 / Published: 25 May 2023
(This article belongs to the Section Forest Ecology and Management)
Browse Figures
Versions Notes

Abstract

:
The positive effect of thinning on individual tree growth is well known, but the subsequent growth dynamics of individual trees over a rotation is relatively unknown, even though this is critical for interpreting actual thinning effects. Therefore, in this study, we aimed to investigate the thinning response of individual tree growth dynamics of lodgepole pine (Pinus contorta var. latifolia) over rotation using an individual tree growth model. We used data from an operational site to use as input to the Mixedwood Growth Model, an individual tree growth model, to simulate tree growth throughout the rotation. Overall, we found that thinning increased the absolute growth of individual trees and reduced the growth heterogeneity throughout the rotation. Combining pre-commercial thinning prior to commercial thinning provided maximum growth and less growth variability in individual trees. The positive effect of thinning was immediate and declined with time since thinning with most of the responses occurred within the first 10–15 years of thinning.

1. Introduction

Intraspecific competition is a key variable in tree growth and is influenced by several factors including initial spacing [1]. Thinning is commonly used to reallocate growing space to the residual trees, resulting in reduced competition between trees for available resources [2]. Thinning can lead to an increase in the merchantable volume production of logs and financial benefit [3,4]. Moreover, commercial thinning may also provide an early financial return to forest managers by providing access to raw materials earlier in the rotation. A general assumption is that by redistributing growing space and reducing competition for resources, thinning improves the growth efficiency of the residual trees (i.e., higher growth rates than same-sized trees of unthinned stands) [5]. Results from a wide range of thinning experiments generally support this assumption. However, there are also a range of outcomes where thinning increased mortality due to wind damage, water stress [6,7], and stagnant residual tree growth [8]. Therefore, it is very difficult to generalise the thinning response since the thinning response of individual trees can vary depending on the stand characteristics, site characteristics, species, and thinning method [9,10].
In addition, the neighborhood condition created by thinning [11,12], including initial tree size and growth rate of trees prior to thinning [13,14] can influence the growth of residual trees after thinning. After reducing competition through thinning, trees generally show an increased growth rate; however, the growth rate might vary across tree sizes due to differences in resource use and uptake efficiency [15]. For example, larger trees might obtain a greater share of resources compared to smaller trees and suppress the growth of individual small trees. Therefore, a better understanding of how individual trees across the size distribution respond to the post-thinning condition would be of use in developing thinning prescriptions.
The thinning response of individual trees can be described in three phases. In the first phase, tree growth increases for a few years after thinning, and reaches the maximum in the second phase, followed by a slow decrease in growth in the last phase [16,17]. Therefore, time since thinning is an important consideration when evaluating thinning responses [18,19]. By taking the time since thinning into account, it is possible to evaluate the growth difference in individual trees between thinned and unthinned stands at different time intervals. This will provide an opportunity to evaluate thinning responses over time, such as when the maximum growth rate is obtained by thinning, when it declines, and whether the benefit of thinning remains throughout the duration of the rotation or diminishes after a certain time period. Earlier studies evaluated the thinning response of individual trees after a long interval since thinning, whereas most growth increases happen between three and six years after thinning [16,17,18]. This means that the evaluation of thinning response after a long interval of thinning likely does not capture important growth dynamics of individual trees. Despite the available literature on thinning response to individual trees across the globe, limited knowledge is available on the long-term dynamics of individual tree growth response to thinning.
Although thinning is a common practice in many countries and its general effects are well known, it is a relatively new practice in western Canada [20,21], due to real or perceived policy barriers [22] and uncertainty in the benefits of thinning such as residual tree growth response. This is especially true in western Canada during the transition from basic reforestation to more intensive forest management on public land [23]. However, the absence of long-term data from manipulated experiments makes it difficult to answer some of the essential questions related to the thinning response. Therefore, while waiting for the data from long-term experiments, simulation with a forest decision support system could provide estimates of production and stand dynamics over a full rotation.
Lodgepole pine (Pinus contorta var. latifolia) is native to North America and is the most economically important tree species in Alberta, Canada. However, there is a pending midterm timber supply shortage in Alberta due to past natural disturbances and a shrinking forestry land base giving rise to recent research on the thinning response of lodgepole pine. Recent studies have shown the effect of thinning (both pre-commercial (PCT) and commercial thinning (CT)) on the growth and productivity of lodgepole pine at the stand level [24,25,26]. However, the thinning response of individual trees and their growth dynamics over time has not been addressed intensively, especially with different thinning intensities and combinations of PCT and CT. Thinning intensities are one of the most important factors affecting growth response after thinning [27,28,29]. Additionally, PCT and a combination of PCT + CT positively affect the growth of individual trees [30]. Therefore, evaluating different thinning combinations will help forest managers select thinning strategies based on their specific management goals. The main aim of this paper was to evaluate the long-term growth dynamics of individual lodgepole pine trees in Alberta, Canada, addressing the following research questions:
  • How do contrasting thinning treatments and time since thinning affect the individual tree diameter growth and height diameter ratio of lodgepole pine?
  • Does thinning equally benefit all the trees in the residual stands and how does the variability of tree growth change over time since thinning?

2. Materials and Methods

2.1. Study Area and Experimental Design

Data from operational forestry field sites dominated by lodgepole pine in the upper foothills and sub-alpine ecological subregions of western Alberta were used to conduct the study (Figure 1). The stands were naturally regenerated after commercial felling in 1961–1964. A pre-commercial thinning was conducted on half of the stands at ages 17–19 (1981–1983). The initial treatments during PCT were:
01. Control: no-PCT;
02. PCT: to approximately 2500 trees ha−1.
Each treatment was replicated in 11 stands and the stand size ranged between 5 and 45 ha. Based on the species composition, harvest year, and evidence of thinning, a total of 22 stands were selected out of 100 candidate stands. The sites were manipulated with a pre-determined experimental design and there was no difference in site characteristics between treatments.
Measurements of the stands were carried out in 2022 when the average stand age was 58 years. Inventory was conducted at the plot level with six temporary circular sample plots (100 m2) established within each stand. The plots were established in equal intervals of 50 m distances along the grid (50 × 50 m) starting from a corner of the stand. Further caution was taken to avoid the edge effect by establishing plots at least 30 m away from roads, other stands, creeks, and so on.

2.2. Data Collection and Analysis

We measured the diameter at breast height (1.3 m) of individual trees (DBH > 5.1 cm, according to the criteria of permanent growth and yield sampling design in Alberta, Canada) https://www.alberta.ca/permanent-sample-plots-program.aspx#jumplinks-1 (accessed on 23 May 2023) and the height of five sample canopy trees from each plot. Canopy trees were selected according to tree size (DBH), with a higher probability for larger trees. We calculated the height of the remaining trees from the measured diameter using an ecoregional equation [31]. Site index (SI, top height in m, base age 50) was estimated from the site index simulator in the GYPSY Pass tool [32] using field-measured top height and total age of the stand.
In this study, we simulated six alternative management scenarios to develop the stands over the long term to evaluate the growth response of individual trees to management alternatives. We used the unthinned control stands and PCT stands as a base to simulate different management alternatives and then followed these with CT, leaving either 600 or 800 trees ha−1 (Table 1).
Using the last field measurement, the growth of individual trees was projected to year 100, including future thinning, for each management scenario. The projections were made using the Mixedwood Growth Model (MGM) [http://www.MGM.ualberta.ca (accessed on 23 May 2023)]. MGM is a deterministic, distance-independent, individual tree growth model developed and validated at the University of Alberta for the western boreal region of Canada [33,34].
MGM is a “height-driven model” that uses regional site index curves to predict the maximum potential height increment for each tree. The trees are first ranked by social status (diameter) with annual individual tree height and diameter growth estimated using allometric allocation functions and empirically derived functions to account for the effects of competition from overtopping trees to obtain competition-adjusted height increment and diameter increment. Under this approach, dominant trees grow quickly and are more likely to survive. Suppressed trees grow slowly and are less likely to survive. MGM requires input on the site (e.g., site index), plot size, individual tree species, breast height or total age, height, and diameter. With this approach, tree level height, diameter, tree factor, basal area, and volume are updated annually. Then, tree-level characteristics are summarised for each stand to determine the stand-level height, diameter, density, basal area, and volume.
In this study, we constructed an individual tree list for each stand (in our case, 11 unthinned controls and 11 PCT) using the latest inventory data (2022) to use as input for MGM. The simulation of individual tree lists was carried out separately for each management scenario (control, CT_800, CT_600, PCT, PCT_CT_800, and PCT_CT_600). The simulation of tree growth started at age 58, and a virtual thinning operation was conducted at age 60 with different intensities and strategies (Table 1). During thinning, a proportional thinning (removing trees from all diameter classes) was conducted first to simulate the loss of 20% of the basal area from extraction trails. This was immediately followed by a thinning from below (removing trees with the smallest diameter first) until the desired number of trees per hectare was achieved. For example, in CT_800, trees were removed until the tree density reached 800 trees ha−1.
Tree growth was defined by the periodic absolute diameter growth between two successive measurement periods by an individual tree. For consistency, the growth was annualized by dividing the observed periodic growth by the measurement interval. The same procedure was used to calculate the growth of the 400 largest individual trees in the stands. We selected the 400 largest trees as a response variable because of their potential to be future crop trees. Moreover, the height-diameter ratio (HDR) is an indication of stand stability; the lower the value of HDR, the higher the stand stability. The height-diameter ratio of the individual trees was also determined for different scenarios over time to see the dynamics of tree stability over time in different thinning scenarios. Furthermore, the Gini coefficient was calculated to measure the growth inequality of individual trees over time in different thinning scenarios. The Gini coefficient ranges from 0 to 1, where 0 indicates that all trees are equal in size and 1 is the perfect inequality. The greater the value of the Gini index, the higher the inequality. The Gini coefficient was quantified by using the function gini of the R package ineq [35]. The analysis was conducted in R statistical package version 4.0.3 [36].

3. Results

Overall, the growth rate of individual trees was greater in thinned stands than unthinned stands, and the positive thinning effect remained over the rotation for all treatments, although decreasing over time (Figure 2A, Table 2). Thinning resulted in an immediate (just after thinning) increase in the diameter growth of individual trees by approximately 7–15 times compared to unthinned stands, depending on the treatments (Appendix A). The majority of the growth response to the thinning occurred within 10–15 years after thinning. However, even 40 years after thinning, individual tree DBH growth was still approximately 1.5–2 times higher compared to the unthinned stands (Appendix A). The order of average individual tree growth by treatment was: PCT_CT_600 > CT_600 > PCT_CT_800 > CT_800 > PCT > Unthinned control (Figure 2A).
The diameter growth in the 400 largest trees was greatest with the combination of PCT and CT (PCT_CT_800 and PCT_CT_600). PCT had a similar initial growth to PCT + CT after thinning but only persisted for 10 years after thinning. Although the growth in the biggest trees in PCT stands was higher than the control after thinning, it went back near to the control 25 years afterthinning. Additionally, 15 years after thinning, the growth in individual trees in PCT and CT stands was almost the same (Figure 2B). CT-only resulted in a slight increase in diameter growth in the 400 largest trees over that seen in the controls.
The inequality in diameter growth (Gini index) of individual trees was larger in the unthinned stands compared to the thinned stands (Figure 3). The lowest inequality in individual tree growth was observed in PCT_CT_600 stands, followed by CT_600, CT_800, and PCT_CT_800. The inequality in individual tree growth in PCT stands was lower than in control stands but higher than in other thinned stands. Overall, the growth inequality in individual trees decreased over time in thinned stands but increased in unthinned stands. Moreover, the height–diameter ratio (HDR) of individual trees was lower in the thinned stands compared to the unthinned stands, but in all treatments, there was a trend in increasing HDR of individual trees since the time of thinning. Among thinning treatments, HDR was lowest in the combined PCT_CT_600 treatments and highest in PCT stands (Figure 3).

4. Discussion

Thinning is clearly predicted to increase the growth in individual lodgepole pine trees, but the response to the thinning varied between thinning strategies, intensity, and time since thinning. Our predicted thinning response is supported by earlier studies from other tree species and ecosystems [24,27] and can be explained by the spacing factor [37,38,39]. Trees with more growing space simply have greater access to resources and therefore grow more [37,38,39].
However, there was a difference in individual tree growth rates between different thinning treatments in our stands. We observed that, even when accounting for the same stand density, the stands with PCT prior to CT (PCT_CT_800 or 600) had higher individual tree growth compared to stands with no PCT prior to CT (CT_800 or 600). This means that in stands with CT with prior PCT, individual trees maintained their increased earlier growth obtained from PCT [40,41] in current stands (PCT_CT_800 or 600). Therefore, the positive growth effect of PCT was additive to the growth benefits of CT. This means that to maximize individual tree growth, PCT should be conducted prior to CT.
Furthermore, the combination of PCT + CT increased the growth in the largest trees compared to the stands with only CT (CT_600 or CT_800). Additionally, CT-only resulted in a slight increase in the diameter growth in the 400 largest trees over that seen in the controls. After PCT, due to competition release and an increase in available resources, faster growth of the largest trees in the stand is very common [42,43,44]. This indicates that in the young stage, due to competition release, the biggest trees have a faster growth response [45].
The increased growth in the largest trees after thinning has been shown in some stands where the stand age was below 30 [27,46]. Trees do not respond to late CT as much as they do to early CT [47,48], especially after age 50 [47]. In our stands, we simulated CT at age 60, when the biggest trees had likely already reached their maximum growth potential and might not respond to competition release very well.
Individual tree growth was immediate after thinning and showed a negative trend in growth with increasing time since thinning. The immediate positive growth might occur due to the removal of smaller trees from the stand. Therefore, the average diameter of individual trees increased. Moreover, the negative trend in growth might indicate that lodgepole pine reached its maximum growth potential prior to CT and the growth rate had already started to decrease. A similar trend was observed in loblolly pine and Douglas-fir [19]. A study on loblolly pine showed that it reached its maximum growth potential at age 10 [49] and started to show a negative relationship between age and biomass assimilation from age 14 [50]. Additionally, a late thinning was conducted in the stand in which trees might not respond very well. Because of the above-mentioned reasons, we might not observe the three-phase pattern of thinning responses in tree growth [16,17]. Rather we found an immediate increase in growth due to thinning type effect and a negative trend.
We found lower diameter growth inequality in individual trees in thinned stands compared to unthinned stands. This means that thinning from below created more uniform growing conditions for trees in thinned stands than for trees in unthinned stands [19,51,52]. The decrease in growth inequality after thinning indicates that the residual smaller trees (intermediate dominance classes) have greater absolute diameter growth from thinning than larger trees [52,53,54]. Moreover, reducing the range of tree size reduces the variability in the size-inherent ability of a tree to acquire resources or utilize them efficiently [55]. This means thinning from below in our stands lowered growth variability by reducing the range of tree size. The decreasing trend in growth variability over time in thinned stands could be due to having retained trees belonging to the intermediate dominance classes, which may result in a relatively greater response to thinning than dominant classes over time [56].
Examining stand stability following thinning, we observed a lower height–diameter ratio of individual trees in thinned stands compared to unthinned stands, which is supported by other studies [27,57]. However, in the case of a positive relationship between higher thinning intensity and lower HDR, the risk associated with storm and wind damage needs to be kept in mind [58,59] during the practical implementation of these findings.
Theoretically, simulating thinning operations is possible in MGM due to the nature of the model (individual tree growth), and MGM provides a set of common removal rules for thinning. However, the model has not been tested yet to evaluate its performance to simulate the thinning response. Therefore, we do not know how accurately MGM captures the thinning response. Because of this uncertainty related to the model’s performance, we might over- or underestimate the thinning response. Additionally, the thinning response at the tree level in MGM likely depends on the effect of the thinning prescription on the reduction factor in the model, which represents the effect of inter-tree competition. Since the growth reduction factors in MGM depend on the basal area of trees larger than a tree being simulated, it might be expected that thinning from below will have little to no effect on the projected growth of the residual trees since the basal area in larger trees is not affected by thinning. Additionally, by thinning from below, we removed the trees that had the highest reduction factor, which will certainly reduce the variability in forecast diameter growth. This means lower heterogeneity in individual tree growth in thinned stands might also be influenced by the model structure.
However, we simulated a proportional thinning representing thinning corridors before simulating thinning from below. This means the lower heterogeneity in tree growth is not solely a result of model structure. Furthermore, by proportional thinning, we increased the uncertainty related to the model’s capability to analyze spatial modeling. Therefore, all the uncertainties related to the model and modeling need to be kept in mind during the interpretation and implementation of the thinning forecast.

5. Conclusions

Overall, simulated thinning increased the growth response of individual trees and reduced the growth variability between individual trees with the positive benefits of thinning remaining throughout the rotation. However, the positive effect of thinning on the growth of individual trees started to decline with increasing time since thinning. Our simulated thinning findings indicate that if maximizing the individual tree size is the goal of forest management, then thinning is a recommended practice. Moreover, based on our findings, pre-commercial thinning prior to commercial thinning is required for the maximum benefit of tree growth. Our research findings can be used to inform forest managers developing thinning prescriptions to increase individual tree growth.

Author Contributions

Conceptualization, M.A. and B.D.P.; methodology, M.A. and B.D.P.; formal analysis, M.A.; visualization, M.A.; Data collection, F.S.; Data analysis, M.B.; writing—original draft preparation, M.A.; writing—review and editing, B.D.P., F.S., R.E.F. and M.B.; supervision, B.D.P. and R.E.F.; funding acquisition, B.D.P. All authors have read and agreed to the published version of the manuscript.

Funding

The research was funded by West Fraser Mills—Hinton Wood Products and the Forest Resource Improvement Association of Alberta.

Data Availability Statement

Data are available from the corresponding author subject to privacy restrictions.

Acknowledgments

The authors would like to thank all the people who were involved in establishing the operational site and also the field crew, and Ethan Ramsfield and Stephania Hinse, who assisted in data collection.

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. All authors have read and agreed to the published version of the manuscript.

Appendix A

Table
Table A1. The Increment in Individual Tree Growth in Thinned Stands Compared to Unthinned Control Stands. For Example, the Value of PCT at 0 (Time since Thinning) is 7.45, Meaning Individual Tree Growth is 7.45 Times Higher in PCT Stands Compared to Unthinned Control Stands. See Figure 2 for the Description of All Treatment.
Table A1. The Increment in Individual Tree Growth in Thinned Stands Compared to Unthinned Control Stands. For Example, the Value of PCT at 0 (Time since Thinning) is 7.45, Meaning Individual Tree Growth is 7.45 Times Higher in PCT Stands Compared to Unthinned Control Stands. See Figure 2 for the Description of All Treatment.
Time since ThinningPCTCT_800CT_600PCT_CT_800PCT_CT_600
07.459.8611.9511.6515.13
55.257.438.818.3910.77
103.314.575.435.106.41
152.013.684.334.024.98
202.363.233.783.484.27
251.8182.963.453.163.84
301.752.773.222.873.54
351.952.643.062.773.33
401.891.551.951.652.17

Appendix B

Forests 14 01091 g0a1 550
Figure A1. Diameter Distribution of Individual Trees at Age 65 (5 Years after Thinning) with Different Treatments. See Figure 2 for the Description of the Treatment. The Dashed Lines Show the Mean Diameter of Each Stand.
Figure A1. Diameter Distribution of Individual Trees at Age 65 (5 Years after Thinning) with Different Treatments. See Figure 2 for the Description of the Treatment. The Dashed Lines Show the Mean Diameter of Each Stand.
Forests 14 01091 g0a1

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Forests 14 01091 g001 550
Figure 1. Location of the operational site and schematic distribution of the stands. Each rectangle represents one stand, and one dot represents one plot. Green dots indicate plots from control stands and yellow dots indicate plots from PCT stands.
Figure 1. Location of the operational site and schematic distribution of the stands. Each rectangle represents one stand, and one dot represents one plot. Green dots indicate plots from control stands and yellow dots indicate plots from PCT stands.
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Forests 14 01091 g002 550
Figure 2. Tree level absolute diameter growth of unthinned and thinned stands over the time since thinning. (A) shows the tree-level absolute growth (average) of all trees and (B) shows the absolute growth (average) of the 400 biggest trees. Here, control = no thinning, CT_600 = commercial thinning leaving 600 trees ha−1, CT_800 = commercial thinning leaving 800 trees ha−1, PCT = stand with only PCT, PCT_CT_600 = stand with PCT prior to commercial thinning with 600 trees ha−1, and PCT_CT_800 = stand with PCT prior to commercial thinning with 800 trees ha−1.
Figure 2. Tree level absolute diameter growth of unthinned and thinned stands over the time since thinning. (A) shows the tree-level absolute growth (average) of all trees and (B) shows the absolute growth (average) of the 400 biggest trees. Here, control = no thinning, CT_600 = commercial thinning leaving 600 trees ha−1, CT_800 = commercial thinning leaving 800 trees ha−1, PCT = stand with only PCT, PCT_CT_600 = stand with PCT prior to commercial thinning with 600 trees ha−1, and PCT_CT_800 = stand with PCT prior to commercial thinning with 800 trees ha−1.
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Forests 14 01091 g003 550
Figure 3. Gini index of diameter growth rate and height diameter ratio of individual trees in unthinned and thinned stands over the time since thinning. See Figure 2 for the description of all treatments/scenarios.
Figure 3. Gini index of diameter growth rate and height diameter ratio of individual trees in unthinned and thinned stands over the time since thinning. See Figure 2 for the description of all treatments/scenarios.
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Table
Table 1. Initial treatment, simulated treatment, and stand a description of the site with lodgepole pine. Here, control = no thinning, CT_600 = commercial thinning leaving 600 trees ha−1, CT_800 = commercial thinning leaving 800 trees ha−1, PCT = stand with only PCT, PCT_CT_600 = stand with PCT prior to commercial thinning with 600 trees ha−1, and PCT_CT_800 = stand with PCT prior to commercial thinning with 800 trees ha−1.
Table 1. Initial treatment, simulated treatment, and stand a description of the site with lodgepole pine. Here, control = no thinning, CT_600 = commercial thinning leaving 600 trees ha−1, CT_800 = commercial thinning leaving 800 trees ha−1, PCT = stand with only PCT, PCT_CT_600 = stand with PCT prior to commercial thinning with 600 trees ha−1, and PCT_CT_800 = stand with PCT prior to commercial thinning with 800 trees ha−1.
Initial TreatmentsSimulated TreatmentsAverage Number of Trees ha−1
Before ThinningAfter Thinning
ControlControl20792079
CT_8002079800
CT_6002079600
PCTPCT13771377
PCT_CT_8001377800
PCT_CT_6001377600
Table
Table 2. The average diameter and range of diameter (minimum and maximum) of individual trees at age 58, age 60 (before and after thinning), and 5 years after thinning. The diameter distribution of individual trees after 5 years of thinning is available in Appendix B. See Figure 2 for the description of the treatments.
Table 2. The average diameter and range of diameter (minimum and maximum) of individual trees at age 58, age 60 (before and after thinning), and 5 years after thinning. The diameter distribution of individual trees after 5 years of thinning is available in Appendix B. See Figure 2 for the description of the treatments.
TreatmentMean Diameter and Range of Diameter (cm)
Age 58Age 60Age 65
Before ThinningAfter Thinning
Control13.30
Range: 5.1–30		13.74
Range: 5.5–30.58		13.74 (no thinning)
Range: 5.5–30.58		14.40
Range: 5.97–31.47
CT_80013.30
Range: 5.1–30		13.74
Range: 5.5–30.58		17.64
Range: 13.37- 30.58		18.56
Range: 14.11–31.47
CT_60013.30
Range: 5.1–30		13.74
Range: 5.5–30.58		18.56
Range:14.73–30.58		19.56
Range: 15.53–31.47
PCT16.04
Range: 5–30.4		16.51
Range: 5.38–31.26		16.51 (no thinning)
Range:5.38–31.26		17.27
Range: 5.97–32.58
PCT_CT_80016.04
Range: 5–30.4		16.51
Range: 5.38–31.26		18.43
Range: 12.20–31.26		19.28
Range: 12.97–32.57
PCT_CT_60016.04
Range: 5–30.4		16.51
Range: 5.38–31.26		19.96
Range: 15.36–31.26		20.85
Range:16.09–32.57
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MDPI and ACS Style

Ara, M.; Pinno, B.D.; Scaria, F.; Froese, R.E.; Bokalo, M. Thinning Increases Individual Tree Growth While Reducing the Growth Heterogeneity of Lodgepole Pine. Forests 2023, 14, 1091. https://doi.org/10.3390/f14061091

AMA Style

Ara M, Pinno BD, Scaria F, Froese RE, Bokalo M. Thinning Increases Individual Tree Growth While Reducing the Growth Heterogeneity of Lodgepole Pine. Forests. 2023; 14(6):1091. https://doi.org/10.3390/f14061091

Chicago/Turabian Style

Ara, Mostarin, Bradley D. Pinno, Francis Scaria, Robert E. Froese, and Mike Bokalo. 2023. "Thinning Increases Individual Tree Growth While Reducing the Growth Heterogeneity of Lodgepole Pine" Forests 14, no. 6: 1091. https://doi.org/10.3390/f14061091

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