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Article

Wood Basic Density Assessment of Eucalyptus Genotypes Growing under Contrasting Water Availability Conditions

by
Juan Pedro Elissetche
1,2,3,
Rosa M. Alzamora
1,3,
Yosselin Espinoza
4,
Verónica Emhart
5,
Matías Pincheira
5,
Alex Medina
5 and
Rafael Rubilar
3,4,*
1
Departamento de Manejo de Bosques y Medio Ambiente, Facultad de Ciencias Forestales, Universidad de Concepción, Concepción 4030000, Chile
2
Centro de Biotecnología, Universidad de Concepción, Concepción 4030000, Chile
3
Centro Nacional de Excelencia para la Industria de la Madera (CENAMAD), Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Santiago 8320000, Chile
4
Cooperativa de Productividad Forestal, Departamento de Silvicultura, Fac. Ciencias Forestales, Universidad de Concepción, Concepción 4030000, Chile
5
Forestal Mininco S.A., Avenida Alemania 751, Los Ángeles 4440000, Chile
*
Author to whom correspondence should be addressed.
Forests 2024, 15(1), 185; https://doi.org/10.3390/f15010185
Submission received: 13 November 2023 / Revised: 11 December 2023 / Accepted: 12 December 2023 / Published: 17 January 2024
(This article belongs to the Section Wood Science and Forest Products)
Browse Figures
Review Reports Versions Notes

Abstract

:
Limited research exists on wood properties in E. nitens × E. globulus hybrid genotypes grown in water-limited conditions generated by the climate change influence in Mediterranean areas. The EUCAHYDRO project aimed to assess environmental stress impacts on eucalyptus genotypes, including responses to reduced water availability, and to evaluate wood density and resistance using the non-destructive drill resistance technique. This study focused on 10-year-old E. nitens × E. globulus hybrids and Eucalyptus badjensis Beuzev. & Welch, revealing that low irrigation led to a 13% (p < 0.05) decrease in diameter and a 6.5% (p > 0.05) increase in wood density for the hybrids. On the contrary, E. badjensis demonstrated a noteworthy 22% increase in wood density (p < 0.05), while showing a corresponding 0.6% growth increase (p > 0.05), as measured by the diameter at breast height. Drill resistance measurement results indicated that E. nitens × E. globulus’ amplitude ranged from 20.1% to 26.6%, while E. badjensis’ ranged from 20.8% to 27.2%. The study revealed a high correlation between resistance amplitude and wood density, with coefficients of 0.97 observed for E. nitens × E. globulus and 0.84 for E. badjensis (p < 0.05). These findings fall within the range reported in similar studies involving Eucalyptus spp. The primary focus of the research was to assess the growth potential and wood quality of novel Eucalyptus spp. under conditions of water limitation. The study also explored the utility of drill resistance as a predictive measure for evaluating wood density as an indicator of wood quality.

1. Introduction

The significance of planted forests is growing in the worldwide provision of wood for various purposes, including the development of new construction products, the supply of fiber for the pulp and paper industry, as well as the textile industry. Additionally, these forests contribute to the production of fuel for energy. Furthermore, planted forests play a crucial role in providing non-timber forest products, such as ecosystem services related to water, biodiversity, landscape, and recreation [1]. Additionally, they provide valuable environmental services such as reducing land degradation and capturing CO2 to mitigate climate change [2,3,4]. However, the challenges posed by climate change, including rising temperatures, increased CO2 and O3 concentrations, ultraviolet radiation, and changes in precipitation patterns, significantly impact the physiology and growth of trees, thereby affecting wood properties for various end-uses [5]. In a study conducted on Eucalyptus globulus Labill. and Eucalyptus nitens plantations in the southeastern region of Tasmania, Downes et al. [6] observed that when constraints on tree growth are alleviated, such as improved water availability, a distinct shift in growth rates becomes evident. This pattern continues until another limiting factor once again hinders further growth. These findings emphasize the intricate connection between the growth of tree stems and the water status of the trees, with fluctuations in xylem water potential directly influencing variations in stem diameter. White et al. [7] further emphasize the importance of water availability in a study when exploring the hypothesis that practices like thinning and nitrogen fertilization can increase the amount of wood produced per unit of water consumed (evapotranspiration) in E. globulus plantations. In the course of their investigation, White et al. [7] introduced the concept of “plantation water productivity”. This concept, linked to specific genotypes, amalgamates the influences of management techniques, site-specific characteristics, and climatic conditions on both production and evapotranspiration. On the other hand, Searson et al. [8] conducted a study involving various Eucalyptus species under contrasting water availability conditions, and they established a connection between changes in the internal wood anatomy and wood basic density. They observed a significant variation (p < 0.05) in the case of E. grandis and E. sideroxylon, while no significant variation was noted in E. occidentalis. The rationale behind this observation lies in the influence of periods with limited water availability, which exerts an impact on the vessel anatomy and their ability to transport water in two out of the three Eucalyptus species, which in turn affects various wood properties for industrial usage.
The relationship between growth, wood formation, and climate and soil variables is strongly influenced by temperature changes and the availability of soil water, which in turn affect the length of the growing season [9,10]. In light of these factors, which affect productivity, competitiveness, and adaptability to climate change, pulp producers in countries like Chile and Brazil have been evaluating the behavior of eucalyptus species under soil and climatic gradients that affect fiber morphology and other wood quality characteristics.
Numerous studies have examined the effects of edaphoclimatic variables on wood properties. Ibanez et al. [11] and Maherali et al. [12] demonstrated that species with higher wood density tend to thrive in low rainfall environments, while Clough et al. [13] reported an increase in wood basic density in regions with higher temperatures. However, Kunstler et al. [14] pointed out that fast-growing species generally have lower wood density. Therefore, when breeding trees for growth and wood quality, it is crucial to consider the performance of genotypes under the effects of climate change and varying resource availability, particularly under conditions of limited water availability [15].
Wood density is a key property widely used to assess wood quality for numerous applications. It is an integrative attribute that enables the evaluation of physical and mechanical properties and is a commercially significant heritable property in wood production [16]. Esther de Lima et al. [9] conducted a study on the effects of edaphoclimatic variables on the wood basic density and productivity of 18 Eucalyptus clones in Brazil. They concluded that rainfall, temperature, and maximum vapor pressure deficit are the primary explanatory variables influencing individual trees and stand characteristics. Barbosa et al. [17] reported similar results when exploring the influence of environmental factors on wood properties and the growth of E. urograndis (hybrid between E. grandis and E. urophylla) clones in Minas Gerais, Brazil. Rocha et al. [18] conducted a study to examine the basic wood density, biomass, and growth behavior of four different Eucalyptus spp. clones planted in 11 locations across Brazil. In this case, the main goal was to represent a wide range of climatic conditions and investigate the potential of using meteorological variables to estimate basic wood density. The research spanned a four-year period from 2012 to 2015, during which various climatic factors such as precipitation, maximum vapor-pressure deficit, water deficit in the soil, temperature, and precipitation seasonality were used to characterize the regions. The study findings revealed that the drier locations generally exhibited lower wood volume and stem biomass but higher basic wood density. This higher wood density was associated with a reduction in the growth rate of the Eucalyptus clones in those areas. Additionally, the researchers performed a hierarchical grouping of the sites and conducted a linear regression analysis to identify the most influential meteorological variables in estimating basic wood density. The results indicated that the maximum vapor-pressure deficit and water deficit in the soil were the most significant variables in this estimation process. In summary, Rocha et al. [18] demonstrated that the climatic variations significantly influenced the wood basic density, biomass, and growth behavior of Eucalyptus spp. clones. The study underscores the importance of considering meteorological factors in estimating wood density and understanding its potential implications for industrial applications and forest management in the context of climate change. In the same way, Almeida et al. [19] assessed the impact of various climate variables on the wood density of a specific E. urophylla clone over a 4–5 year period across 12 sites in Brazil. The main finding of the Almeida et al. [19] study indicated that the influence of climate on wood density became more significant after the third year of growth. In addition, among the climate variables analyzed, the average air temperature exhibited the strongest correlation with the wood density of E. urophylla. Moreover, the cross-site climatic gradient played a more crucial role in the variation of wood density for E. urophylla than the variability observed among different years. The study highlights the importance of considering climate variables, especially mean air temperature, when studying and managing E. urophylla plantations. Taking into account the influence of silviculture, Candel et al. [20] discovered that climate variables and silvicultural practices, such as thinning, had an impact on the annual stem radial growth of Pinus sylvestris. This effect was observed at two distinct sites in northern Spain characterized by varying levels of drought, resulting in increased ring width and wood density. The key findings of the study indicated that thinning played a role in mitigating changes in wood density caused by drought or reduced site water availability. Intriguingly, these findings suggest that thinning practices may contribute to promoting uniform wood quality despite the influence of climate variability and drought. However, it is important to note that projecting these results onto Eucalyptus spp. would require further research.
Conventional methods for assessing wood density were primarily destructive, expensive, and time-consuming, limiting the number of samples that can be obtained and processed [21]. However, non-destructive sampling techniques and innovative assessment methodologies have significantly increased the number of individual trees sampled and potential traits to be evaluated [22]. Drill resistance measurements have become a common method for predicting wood basic density in standing trees. The Resistograph is a specialized tool used in forestry and wood science to assess the quality of standing trees non-destructively. It involves drilling a small-diameter needle or probe into the tree’s stem, and the resistance encountered during the drilling is recorded and graphically represented as a drill resistance profile, providing information about the density and structural integrity of the wood within the tree [23]. The basic principle is that the total energy required to penetrate the bark and wood tissues at a specific location on the tree trunk isclosely related to the physical properties of the wood [22,23,24,25,26,27,28].
In the context of climate change, the drill resistance method can be a valuable tool to study the impact of changing climatic conditions on tree growth and wood quality. Some potential applications include climate-induced changes in wood density. Climate change can lead to variations in temperature, precipitation, and other environmental factors that affect tree growth. The drill resistance method can help measure wood density in standing trees, and these data can be correlated with historical climate data to understand how changing climatic conditions influence wood density and quality [29].
This study aimed to evaluate the growth, wood basic density, and drill penetration resistance of E. nitens × E. globulus hybrids, along with one E. badjensis genotype, under varying water availability conditions.
The E. nitens × E. globulus hybrid poses a significant challenge for the pulpwood Chilean industry, and therefore, early evaluation of climate adaptability and wood quality has become crucial for determining suitable planting sites and specific genotypes. On the other hand, E. badjensis has garnered recognition as a promising species for production in environments with low temperatures and limited water availability. This species is characterized by its tall stature, narrow leaves, and rough, fibrous bark at the base, while its trunk and branches feature smooth and light-colored bark. According to the literature from Brazil and South Africa, E. badjensis is a species that readily sprouts, which is advantageous for short rotation regimes [30,31]. Swain and Gardner [31], and Thompson [32] indicate that E. badjensis possesses favorable wood attributes for pulping, non-timber uses, and the production of essential oils for pharmaceutical and industrial applications [31,32].
Additionally, the study aimed to assess the effectiveness of drilling resistance measurements as a rapid indirect tool for predicting wood density in the evaluated genotypes. This research holds particular significance in clonal forestry, where understanding the responses of different genotypes to environmental factors is of utmost importance, considering climate change’s potential impact on wood production and characteristics, especially since these aspects are crucial for industrial applications.

2. Materials and Methods

2.1. Experimental Location and Site Information

This study is based on a large-scale experiment called “EUCAHYDRO” investigating water use and carbon fixation of mediterranean Eucalyptus genotypes.
The experiment was established in 2013 in the forestry nursery “Carlos Douglas”, which belongs to the company Forestal Mininco S.A., located 9.6 Km south of Yumbel, Biobío region, central south Chile (37°8′0.01″ S, 72°27′34.70″ W) (Figure 1).
Comprehensive details regarding site characteristics, experimental design, establishment, and management of this trial can be found in the research conducted by Rubilar et al. [33]. Their study primarily centered on evaluating the stability of volume growth for various genotypes under different water availability conditions. It aimed to discern whether genetics or resource availability played a more significant role as drivers of volume growth, leaf area, and growth efficiency across sites characterized by varying atmospheric demand and soil types.
The experiment conducted by Rubilar et al. [33] involved 30 high-ranking Eucalyptus genotypes selected from the tree breeding programs of two major industrial forest companies, CMPC and ARAUCO. These genotypes included seventeen cuttings and two seedlings of Eucalyptus globulus, six cuttings of E. nitens × globulus hybrids, two seedlings of Eucalyptus nitens, and single cuttings of Eucalyptus camaldulensis × E. globulus, E. badjensis, and Eucalyptus smithii. The genotypes were planted in a randomized complete factorial block design with three replicates under two contrasting irrigation treatments (low and high) during the dry summer season (November to March). The “low irrigation” treatment maintained soil water availability between the permanent wilting point (PWP) and 25% above PWP, while the “high irrigation” treatment maintained soil water availability from 75% of field capacity (FC) to FC. The planting spacing was set at 2 × 3 m. Table 1 illustrates the irrigation regime during the nine years of the experiment.
For detailed information on the silvicultural treatments, refer to Rubilar et al. [33]. Due to limitations imposed by the pandemic and available resources, the present study will specifically focus on the E. nitens × E. globulus hybrids and E. badjensis.
E. nitens × E. globulus, also known commercially as “Gloni” is a hybrid species produced in Chile and southern Brazil. In Chile, its development was after successful controlled pollination techniques in 1991, which resulted in hybrids suitable for the growing conditions and Kraft pulping requirements of the Santa Fe Group mill [34]. The development of hybrid clones aimed to maximize yield gains and fiber quality while achieving better adaptability and uniformity of plantations across various site conditions [35].

2.2. Drill Resistance Measurements

Drill resistance measurements were conducted on 25 individual trees, considering the diameter distribution of each genotype in the experiment. Specifically, nineteen E. nitens × globulus hybrids (from four selected varieties) and six E. badjensis trees (corresponding to a single variety) were drilled bark-to-bark at the diameter at breast height (DBH) level, which ranged from 1.3 to 1.4 m. The length of the wood core ranged from 10 to 20 cm, and it was extracted at a height of 1.3 m (DBH). The drill process utilized an “IML-RESI Power Drill PD400 (Instrumenta Mechanik Labor GmbH, Wiesloch, Germany), equipped with a drilling needle measuring 1.5 mm in diameter (with a 3 mm drill bit head) and a maximum drilling depth of 40 cm. The instrument generated a graphical representation of wood resistance to penetration, known as a “drill resistance profile”, based on the energy consumed by the electric engine and the friction encountered during the rotation of the drill (expressed as amplitude). The drilling speed was standardized at 100 cm per minute for all measurements, and the resistance profiles were stored in the electronic unit for subsequent retrieval using the PD-Tools Pro software 1.22 provided by the manufacturer. The drilling resistance measurements underwent adjustments using the software provided at (https://forestquality.shinyapps.io/EucalyptResiProcessor/, accessed on 20 July 2022), as described by Downes et al. [24].
To determine wood basic density, samples were obtained using a 12 mm increment borer at a height of 1.3 m from the same trees. The estimation of basic wood density (ρk) followed the TAPPI T258 om-94 [36], which involves calculating the ratio between the oven dry weight and the green volume of the samples, expressed as weight per unit volume. The water displacement method was employed to estimate the green wood volume (Vmax), following the approach outlined by Olesen [37]. The drying process involved placing the samples in an oven at 105 °C until they reached a moisture content (MC) of 0% (m0). Finally, all dried wood samples were weighed using a high-precision scale with an accuracy of ±0.001 g in the laboratory.

2.3. Data Analyses

We conducted mean test and correlation analyses to investigate differences in growth (DBH, cm) and wood basic density (WBD, kg/m3) when having low and high irrigation. In addition, we explored the connections between drill resistance measurements and basic wood density. These analyses were performed for each individual tree, as well as for specific taxonomic groups and taxonomic groups with different irrigation treatments. All statistical analyses were carried out using R version 3.4.4.

3. Results

3.1. Growth and Wood Basic Density

The average wood basic density (WBD) for E. nitens × E. globulus and E. badjendis were 523 and 471 kg/m3, respectively, while the average diameter at breast height (DBH measured at 1.3 m tree height) was 17 cm for E. nitens× E. globulus and 16 cm for E. badjendis
Figure 2 presents the mean values of wood basic density (WBD) and diameter at breast height for E. nitens × E. globulus clones and E. badjendis growing under low and high irrigation. As we see, the average values are higher for E. nitens × E. globulus in both low and high irrigation; however, the error values represented by the standard deviation are also higher in E. nitens× globulus than E. badjendis.
We conducted a t-test for independent samples for DBH (cm) and WBD (kg m−3), comparing the conditions with and without irrigation. The results indicated significant differences between the mean values (p < 0.05) for WBD and DBH when analyzing the low irrigation condition.
Pearson correlations between DBH (cm) and WBD (kg m−3) for E. nitens × E. globulus hybrids growing under low irrigation was −0.713 (p < 0.05) and under high irrigation was −0.041 (p > 0.05). For E. badjensis, the same correlations were −0.967 (p < 0.05) under low and −0.127 (p > 0.05) under high irrigation.
We analyzed the relationship between individual tree wood basic density (WBD; kg m−3) and diameter at breast height (DBH; cm) for both E. nitens × E. globulus and E. badjensis genotypes under high and low irrigation conditions. In the case of E. badjensis, the trees growing with high irrigation presented WBD values superior to the group average of 471 kg m−3.
Conversely, trees subjected to low irrigation exhibited a negative correlation with the diameter at breast height (DBH) and a wood basic density (WBD) value below the group average. It is essential to note that the sample size was restricted to six trees, preventing the establishment of definitive conclusions regarding this species.
In the case of the hybrid, the average WBD was 522 kg m−3 and the genotype with the better performance was clone number 5, which consistently presented a WBD higher than the average of the clones from HI (506 kg m−3) and LI (539 kg m−3). Figure 3 illustrates the trend on WBD and DBH for the hybrid.

3.2. Wood Basic Density and Drill Resistance Measurements

The amplitude range (drill resistance) of the E. nitens × E. globulus hybrids ranged from 20.1 to 26.6%, while for E. badjensis, the amplitude range was 20.8%–27.2% (Table 2). Under high irrigation, the amplitude values ranged from 21 to 22% and the wood basic density ranged from 400 to 450 kg m−3. Under low irrigation, the amplitude values ranged from 25 to 27 and the basic wood basic density values ranged from 450 to 500 kg m−3.
A positive correlation was observed between wood basic density (kg m−3) and mean amplitude (%) for all genotypes, where the Pearson correlation coefficient for E. nitens × E. globulus was 0.84 (p < 0.05) and for E. badjensis, 0.97 (p < 0.05). In the case of E. badjendsis, the amplitude values were strongly affected by irrigation conditions (Figure 4). Contrastingly, the E. nitens × E. globulus hybrids’ amplitude values were not related to irrigation conditions.
Previous studies have consistently shown strong correlations between mean resistograph amplitude (%) and wood basic density (WBD) in Eucalyptus species. Carrillo et al. [38] observed correlation coefficients of 0.84 (p < 0.05) for E. globulus and 0.85 (p < 0.05) for E. nitens, indicating a robust relationship between these variables. Similarly, Lima et al. [39] found moderate to high correlations between mean amplitude and WBD in 16-year-old Eucalyptus hybrid clones.
Barría et al. [40] reported a correlation coefficient of 0.65 between WBD (measured at 1.3 m height) and amplitude for Pinus radiata (D. Don). These findings further support the existence of significant associations among mean resistograph amplitude and wood basic density in Eucalyptus species and P. radiata. Thus, our results validate that tools based on resistography provide accurate values for wood density estimates in Eucalyptus spp.

4. Discussion

As noted by Booth [1], Eucalyptus spp. plantations are renowned for their rapid growth and adaptability, with over 110 species introduced in more than 90 countries. Their capacity to flourish in diverse environmental settings, particularly in Mediterranean, dry tropical, and subtropical regions, is well-recognized. However, the impact of climate change, specifically concerning alterations in water availability and temperature stress, has the potential to influence their productivity and wood quality for various applications.
In the context of Chile, the hybrid E. nitens × E. globulus has demonstrated promising performance; nevertheless, it is imperative to investigate how this hybrid responds to evolving climatic conditions, especially concerning water availability. It is worth emphasizing that the decision to create this hybrid from both species was largely motivated by the limited frost tolerance of Eucalyptus globulus and the superior frost resistance of E. nitens, as highlighted by Medina et al. [35].
This study delved into an analysis of four genotypes of the E. nitens × E. globulus hybrid. The findings revealed that a reduction in irrigation resulted in a significant decline in growth (p < 0.05), while there was an increase in basic wood density, although this change did not reach statistical significance (p > 0.05). Comparable results were reported by Searson et al. [8] concerning Eucalyptus occidentalis, where the wood basic density increased under water-limited conditions, albeit without statistical significance (p > 0.05).
Hence, although our observations regarding the E. nitens × E. globulus hybrid align with the trend of increased wood basic density under water-limited conditions, as reported by Rocha et al. [18] in their investigation of four distinct Eucalyptus spp. clones planted across 11 different locations in Brazil, as well as Ibañez et al. [11] when sampling wood density in 1580 trees belonging to 175 species across nine sites (eight 1 ha plots) located in dry, mesic, and humid forests in New Caledonia, and by Wimmer et al. [41] in their study of the growth of six-year-old E. nitens within a two-hectare plantation in southeastern Tasmania, our results did not reach statistical significance.
However, it is important to mention that this result represents the initial data on the hybrid performance regarding wood basic density under water restrictions in Chile, and it reveals that all clones exhibit promising outcomes in terms of increasing wood basic density (p > 0.05) when reducing irrigation. Moreover, it is remarkable that although three of the clones experienced a decline in growth under low irrigation, this one did not achieve statistical significance (p > 0.05). The current investigation examined an irrigation gradient ratio averaging 1:5, which contrasts with Ibañez et al. [11] consideration of ratios up to 1:13 and White et al. [7] who used a 1:9 ratio. In contrast, Rocha et al. [18] experimented with a ratio of 1:2.5 for available water gradients. All these studies obtained significant differences (p < 0.05) in wood basic density, with a consistent trend of increasing wood basic density with increasing water limitations.
Conversely, E. badjensis exhibited a significant increase in wood basic density under low irrigation conditions (p < 0.05) and no significant differences in growth (p > 0.05), which is a promising outcome for exploring this species in a more wider range of climatic variability, especially those places with low temperature and water-limited conditions.
There is limited reported information of E. badjensis growing in Chile; however, a study conducted in Chile by Emhart et al. [42] aimed to evaluate new Eucalyptus species’ resistance to pests and adaptability to climate change. The reported wood density of E. badjensis ranged from 499 to 503 kg m−3 which was slightly lower than that of E. nitens, used as a control, which fluctuated between 546 and 553 kg m−3. In terms of pulp yield, E. badjensis exhibited a range of 48.4% to 53.3%, while the values for E. nitens ranged from 50.6% to 52%. Nevertheless, our data on the growth and wood density performance of this species is limited. Despite this limitation, there is potential for it to contribute to studies that investigate its responses to growth and wood quality under various climate and soil conditions.
In situations assessing the quality of wood in standing trees, and when making informed decisions about introducing new tree species, it becomes increasingly important to continuously and swiftly evaluate the potential effects of climate change on forest plantations. In this context, employing tools such as resistography provides a distinct advantage for rapidly and accurately evaluating wood basic density and its adaptability to environmental shifts [22,43]. The results of our study affirm the potential of resistography for the rapid assessment of wood basic density since correlations are in the range reported by comparable studies [38], as well as its reaction to reduced water availability scenarios under suitable experimental conditions or across diverse environmental gradients [19].

5. Conclusions

In recent years, there has been a growing body of literature focusing on climate change’s effect on wood quality in forest plantations, particularly the wood density. In general, for Eucalyptus spp., drier locations with specific climatic conditions tend to have a higher wood density but slower growth rates, which can have implications for forest management and industrial use of Eucalyptus wood. However, these relationships may not apply to hybrid species; thus, in the case of this research, there were no differences in the wood basic density of E. nitens × E. globulus between low and high irrigation (p > 0.05). In the case of growth, represented by the DBH, the expected reduction was observed and statistically significant between low and high irrigation for the average condition of the clones.
Differently, E. badjensis presented the expected trend of an increase in the average wood basic density under low irrigation conditions (p < 0.05), but no significant difference in the variable DBH. While our analysis was limited to just six E. badjensis trees, constituting a statistically weak sample, we uncovered evidence that encourages further exploration of this species’ performance across a broader range of climate and soil scenarios. This finding is particularly interesting since E. badjensis has been reported as suitable for its pulp production and ease of sprouting, which is a great advantage for plantations intended for energetic purposes. Additionally, the study reported for first time information of drill resistance and its correlation with wood density for the hybrid and the E. badjensis spp.

Author Contributions

Conceptualization, J.P.E., R.R. and R.M.A.; Data curation, J.P.E. and R.M.A.; Formal analysis, J.P.E. and R.M.A.; Funding acquisition, R.R., V.E. and A.M.; Investigation, R.R., M.P. and Y.E.; Methodology, R.R., V.E. and A.M.; Project administration, R.R. and Y.E.; Resources, V.E. and M.P.; Software, R.M.A. and J.P.E.; Supervision, R.R. and R.M.A.; Validation, R.R. and V.E.; Visualization, R.R.; Writing—original draft, R.M.A. and J.P.E.; Writing—review and editing, R.R. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the government of Chile via CONICYT Fondecyt Regular Project 1190835, CMPC S.A., and the Chilean National Commission for Scientific and Technological Research with Project Grand ANID BASAL FB210015.

Data Availability Statement

Data are contained within the article.

Acknowledgments

All authors thank the Mininco Forest Company, Forest Productivity Cooperative at Universidad de Concepción.

Conflicts of Interest

Authors Verónica Emhart, Matías Pincheira and Alex Medina were employed by the company Forestal Mininco S.A. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Forests 15 00185 g001
Figure 1. Carlos Douglas forest nursery location in the Biobío, VIII Region.
Figure 1. Carlos Douglas forest nursery location in the Biobío, VIII Region.
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Figure 2. Average wood basic density (kg m−3) and standard deviation values for the hybrid clones of E. nitens × E. globulus, and E. badjendis in low (LI) and high irrigation (HI) conditions. Different letters indicate significant differences (p < 0.05).
Figure 2. Average wood basic density (kg m−3) and standard deviation values for the hybrid clones of E. nitens × E. globulus, and E. badjendis in low (LI) and high irrigation (HI) conditions. Different letters indicate significant differences (p < 0.05).
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Figure 3. Wood basic density (WBD, kg m−3) and diameter at breast height (DBH, cm) for the five hybrid E. nitens × E. globulus clones in low and in high irrigation. Different letters (A,B) indicate statistical difference between high irrigation and low irrigation (p < 0.05).
Figure 3. Wood basic density (WBD, kg m−3) and diameter at breast height (DBH, cm) for the five hybrid E. nitens × E. globulus clones in low and in high irrigation. Different letters (A,B) indicate statistical difference between high irrigation and low irrigation (p < 0.05).
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Figure 4. Linear regression between mean resistograph amplitude measurements and wood basic densities at DBH for (a) E. badjensis and (b) E. nitens × E. globulus genotypes. Filled circles correspond to individual trees growing with low irrigation and open circles to individual trees with high irrigation.
Figure 4. Linear regression between mean resistograph amplitude measurements and wood basic densities at DBH for (a) E. badjensis and (b) E. nitens × E. globulus genotypes. Filled circles correspond to individual trees growing with low irrigation and open circles to individual trees with high irrigation.
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Table 1. Annual rainfall and irrigation regime treatments water additions at the experimental site from 2014 to 2022.
Table 1. Annual rainfall and irrigation regime treatments water additions at the experimental site from 2014 to 2022.
YearRainfall
(mm yr−1)		Irrigation Regime (mm yr−1)
LowHigh
201413021855
2015110283384
2016782195552
201797250837
2018116258295
201983397203
2020105348216
2021107245230
202297262352
Average102873347
Minimum7821855
Maximum1302195837
Standard deviation16051230
Table 2. Amplitude, diameter at breast height (DBH, cm), and wood basic density (WBD, (kg m−3) means and standard deviation (SD) values for E. badjensis and E. nitens × globulus genotypes.
Table 2. Amplitude, diameter at breast height (DBH, cm), and wood basic density (WBD, (kg m−3) means and standard deviation (SD) values for E. badjensis and E. nitens × globulus genotypes.
Low Irrigation (LI)MeanStandard
Deviation		MinimumMaximum
E. badjensis
Amplitude (%)25.631.3524.6827.17
DBH (cm)16.034.3413.0021.00
WBD (kg m−3)516.8021.53495.27538.33
E. nitens × E. globulus
Amplitude (%)23.422.1520.4826.60
DBH (cm)15.942.0413.6020.10
WBD (kg m−3)560.1158.11484.50654.08
High irrigation (HI)
E. badjensis
Amplitude (%)21.120.7020.6221.92
DBH (cm)15.932.0614.5018.30
WBD (kg m−3)424.9922.84400.52445.74
E. nitens × E. globulus
Amplitude (%)22.352.0620.1126.54
DBH (cm)17.921.8414.6020.20
WBD (kg m−3)516.3042.59457.58581.40
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Elissetche, J.P.; Alzamora, R.M.; Espinoza, Y.; Emhart, V.; Pincheira, M.; Medina, A.; Rubilar, R. Wood Basic Density Assessment of Eucalyptus Genotypes Growing under Contrasting Water Availability Conditions. Forests 2024, 15, 185. https://doi.org/10.3390/f15010185

AMA Style

Elissetche JP, Alzamora RM, Espinoza Y, Emhart V, Pincheira M, Medina A, Rubilar R. Wood Basic Density Assessment of Eucalyptus Genotypes Growing under Contrasting Water Availability Conditions. Forests. 2024; 15(1):185. https://doi.org/10.3390/f15010185

Chicago/Turabian Style

Elissetche, Juan Pedro, Rosa M. Alzamora, Yosselin Espinoza, Verónica Emhart, Matías Pincheira, Alex Medina, and Rafael Rubilar. 2024. "Wood Basic Density Assessment of Eucalyptus Genotypes Growing under Contrasting Water Availability Conditions" Forests 15, no. 1: 185. https://doi.org/10.3390/f15010185

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