Hybrid Plantations Research Articles

Variations in soil carbon, nitrogen, and phosphorus concentrations and stoichiometry with stand age in Acacia hybrid plantations in Southern Vietnam

Abstract. Chau M, Quy N, Xu X, Hung B, Cuong LV, Ngoan T, Nguyen T. 2024. Variations in soil carbon, nitrogen, and phosphorus concentrations and stoichiometry with stand age in Acacia hybrid plantations in Southern Vietnam. Biodiversitas 25: 565-573. Soil Carbon (C), Nitrogen (N), and Phosphorus (P) contents are the three most critical soil nutrient elements required for plant growth and development, and their ecological stoichiometric ratios are significant indicators for understanding soil nutrient balance and cycling. This study was conducted to probe variations in the soil organic C (SC), total N (SN), and total P (SP) contents and stoichiometry at five soil depths (0-20, 20-40, 40-60, 60-80, and 80-100 cm) in Acacia hybrid plantations of five different ages (2-, 4-, 6-, 8-, and 10-year-old plantations) in Langa-Dongnai Forestry Company, Southern Vietnam. The results showed that forest age and soil depth substantially impacted soil nutrient contents and their stoichiometric characteristics. The concentrations of SC, SN, and SP as well as C/N, C/P, and N/P ratios increased as the forest stand age increased. The contents of SC, SN, and SP reduced with soil depth, indicating an obvious soil “surface-aggregation” phenomenon. The nutrient restriction varied based on forest stand development, shifting from restricted nitrogen in the earlier growth periods of trees to restricted phosphorus in the later growth periods. The findings demonstrate that to resolve the issue of restricted availability of these nutrient indexes, additional nitrogen should be supplied during earlier growth periods and additional phosphorus during later growth periods. The results further emphasize the importance of understanding SC, SN, and SP interactions and nutritional limitations and provide relevant theoretical support for sustainable Acacia hybrid plantation management in the Southern region.

Developing production models and analyzing timber production variation of Acacia hybrid plantations on different sites in Dong Nai province

The objective of this study was to analyze the variation in timber production in Acacia hybrid plantations based on age and different sites. Data were collected from 50 standard plots (25 × 20 m) of different plantation ages ranging from 2 to 10 years. The site condition of Acacia hybrid plantations were assessed using 5 site indices from I to V. Site index functions were developed from the height of 50 dominant trees at the age of 10. Production functions at the average tree level were constructed using data from 50 trees at age 10. The research results showed that 5 site indices of Acacia hybrid plantations had values of 28, 25, 22, 19 & 16 m, respectively. Timber production of Acacia hybrid plantations has changed markedly with age and site indices. The age of 2 could be the time when diameter and height of Acacia hybrid plantations change from the fast growing stage to the slow growing stage. By the age of 5, the timber volume of Acacia hybrid plantations changes from the fast growing stage to the slow growing stage. The average timber productivity of 10 year old Acacia hybrid plantations on 5 site indices from I đến V was 38.8, 28.6, 20.2, 13.6, & 8.5 m3/ha per year, respectively. The age of quantitative maturity of Acacia hybrid plantations on 5 site indices was 9 years of age.

Modeling the stem taper functions for Acacia hybrid in Dong Nai province

The objective of this study was to construct appropriate stem taper functions at the individual tree level of Acacia hybrid plantations. The stem taper functions were constructed from 150 sample trees at the age of 3 - 10 years in which their diameter at breast height ranged from 4 - 24 cm. The appropriate stem taper functions were constructed and tested from 2 forms of candidate functions. The form 1 was a multivariable stem taper function and form 2 was a single-variable stem taper function. The research results showed that the deviation of the multivariable outsidebark stem taper function was 19.0% and 42.2% smaller than that of the single-variable function of order 7 and order 2, respectively. Similarly, the deviation of the multivariable inside-bark stem taper function was 13.6% and 32.8% smaller than that of the single-variable stem taper function of order 7 and order 2, respectively. Accuracy of multi-order single-variable stem taper functions was improved by constructing for each diameter class.

Models for biomass expansion factor of acacia hybrid (A. auriculiformis* A. mangium) plantations in the Southern region, Vietnam

Acacia hybrid is one of the favorably fast-growing species which is bring to potential benefits of agro-ecological and socio-economic sectors in Vietnam. The main objective of this study was to develop well-fitted models for estimating biomass expansion factor (BEF) for Acacia hybrid plantations. Fifty-four samples of Acacia hybrid trees from 2 to 10 years of age were collected from Acacia hybrid plantations in the Southern part of Vietnam. Total dry biomass including stems, branches and leaves were used to estimate an average value of BEF. The BEF value was calculated by taking the dry aboveground biomass (W) divided by the volume of merchantable tree woods over their barks (Vm). Twelve allometric equations were fitted by constructing regression models between BEF and inventory variables including diameter at breast height (DBH), height (H) and age (A). Consequently, the average value of BEF was 1.11 ton/m3. The BEF value had a strongly negative relationship with DBH, height and age in which the BEF value decreased as these three parameters increased. Two best fitted models for estimating a BEF value of Acacia hybrid (A. auriculiformis * A. mangium) plantations included: BEF = 1.99865 - 0.15400*DBH - 0.02123*H + 0.18210*A; and BEF = 3.01307 - 2.44459*ln(DBH) - 0.10171*DBH -2.06212*ln(H) + 1.54556*ln(DBH*H*A). Estimated values of above-ground biomass by utilizing the fitted BEF values from two these models were similar. Results of the study indicated that use of a fitted BEF model is fundamental to obtain reliable estimates of biomass and CO2 equivalent for Acacia hybrid plantations.

The stem borer Zeuzera multistrigata Moore (Lepidoptera, Cossidae): a serious pest undermining Eucalyptus plantations in Northern Vietnam

Zeuzera multistrigata Moore, 1881 (Lepidoptera: Cossidae) is a dangerous stem borer that damages the Eucalyptus plantations in Vietnam. Field surveys in Lao Cai and Phu Tho provinces in 2022 showed that Z. multistrigata frequently damaged Eucalyptus hybrid plantations (clone DH32-29) at the age of 16‒28 months with damage incidence ranging from 16.93 to 28.74% and the damage index from 0.49 to 1.08. This study showed that three E. urophylla clones (PN3d, PN46, PN54) were not damaged by Z. multistrigata, and five clones (PN10, PN21, PN24, PN47, PN108) were less damaged. Further studies are recommended to screen tolorance Eucalyptus varieties and develop an integrated pest management plan for this pest.

Detection of genetic identity for hybrid Populus x canadensis trees along the Seyhan River

Populus x canadensis hybrids play an important role for the commercial poplar cultivation with good growth performance and adaptability in the world. Hybrid clones introduced the different region of Turkey replaced the native stands of Populus nigra gradually. Along the Seyhan River there are many mature and young hybrid poplar trees despite of less number of P. nigra as a result of hybrid plantations growing near the river. To detect the genetic identity of hybrid trees, 17 microsatellite markers were studied. Out of ten hybrid trees, seven trees had the different genotype. From the results of current study it is seen that hybrid poplar species reproduce at larger distances from the plantation sites and colonize riparian habitat thereby competing for resources with the native P. nigra species and threaten the genetic diversity of the species with genetic pollution via intogression. From the field trip observation and obtained genetic results, conservation of the native P. nigra trees is an important requirements to prevent the reduction of effective population size and population density. Establishing more seed sources of black poplar over the river stretch could provide the establishment of mainly pure black poplar seedlings nearby the parental stands.

Developing a Yield Table and Analyzing the Economic Feasibility for Acacia Hybrid Plantations in Achieving Carbon Neutrality in Southern Vietnam

To achieve the goal of carbon neutrality, overseas plantation projects have been conducted in several countries, including Vietnam. In the present study, stand growth models and a yield table were developed and used to analyze the economic feasibility of Acacia hybrid plantations in southern Vietnam. Diameter at breast height, tree height, and number of trees were determined in the field; basal area, mean height, dominant tree height, stand density, and stand volume were estimated using in situ data. The initial number of trees increased for five years and reached 4947 trees ha−1; tree numbers then decreased to 1987 trees ha−1 until the stands reached ten years of age. The highest current annual increment of stand volume was shown to be 46.23 m3 ha−1 yr−1 when stands were 7 years old. For 7 years of stand age, the net present value was USD 1566/ha, and the internal rate of return was 13%, exceeding the market interest rate (4%). Therefore, an A. hybrid plantation is a reasonable proposition for an overseas plantation project in southern Vietnam and the growth models will be useful for the management of an A. hybrid plantation.

Potential effects of soil chemical and biological properties on wood volume in Eucalyptus urophylla × Eucalyptus grandis hybrid plantations and their responses to different intensity applications of inorganic fertilizer.

Long-term and high-intensity application of inorganic fertilizer leads to a strong variation of soil characteristics. The changes in soil chemical and biological properties can significantly affect the yield of Eucalyptus plantation. However, the mechanism of soil chemical properties affecting wood volume mediated by biological factors is not clear. The purpose of this study was to identify which soil properties were affected by different fertilization intensities and to disentangle the dominant factors affecting Eucalyptus volume. After clear felling evergreen broad-leaved forest, a Eucalyptus plantation was established that was coppiced every 5 years and fertilized every year. Within this plantation, areas with different treatments were established. These treatments were a 5-year growth period (low); two times 5-year growth period (medium); and three times 5-year growth period (high). In each treatment area and in a nearby evergreen broad-leaved forest (EBLF Control), five sample plots per treatment were set up. Various biological and chemistry analyses (18 in total) were related to determining the most important path and index for optimizing Eucalyptus plantation. The analysis of variance of enzyme activity and microbial biomass showed that the soil biological characteristics decreased over 10 years of plantation, and the enzyme activity was close to the state of EBLF control in medium, while the microbial biomass failed to return to its original state during continuous planting. Redundancy analysis results show that there was a strong correlation in chemical indicators and biological characteristics. Partial least square structural equation model showed that total phosphorus, nitrate nitrogen, urease, catalase, and microbial biomass nitrogen and phosphorus were the most influential soil biochemical factors, and the indirect effect of chemical properties on volume was achieved by microorganisms through enzyme activity. Continuous planting and large-scale application of inorganic fertilizer would lead to a decrease in plantation yield and fertilizer utilization efficiency and would affect the microbial biomass and enzyme activity by destroying the stability of soil chemical properties.

Impacts and trapping of ambrosia beetles Euwallacea fornicatus and E. similis in Acacia plantations in Vietnam

There are over two million hectares of Acacia plantations in Vietnam and loss from infestations of ambrosia beetles is of increasing concern. In this study, we first determined the key taxa and the extent of damage, and then identified effective trap and lure combinations for trapping adult beetles, and finally quantified the seasonality of flight of Euwallacea for informing pest management decisions. Based on analysis of the mitochondrial cytochrome c oxidase subunit I gene, the greatest threats were confirmed as Euwallacea fornicatus and E. similis (Coleoptera: Curculionidae), which are native to Southeast Asia but known as invasive species in South Africa and elsewhere. The damage incidence of Euwallacea ranged from 16.7% to 34.9% in Acacia plantations throughout Vietnam. There were no significant differences in the numbers of beetles captured between the three trap types (plastic bottles, funnels and panels). Ethanol and quercivorol were more effective as lures than cubeb oil, α-pinene or a distilled water control. Trapping from June 2020 to May 2021 revealed a bimodal frequency of E. fornicatus and E. similis in A. mangium and Acacia hybrid plantations, with captures peaking in April (spring) and October (autumn). These findings can be applied to develop early detection and trapping control programmes for Euwallacea in Acacia plantations in Vietnam and elsewhere.

Reliable Bio Technology using ERP System

RELIABLE BIO TEHCNOLOGIES COMPANY is an ISO 9001 : 2015 certified agriculture based company. The company was founded in 2015. Over these years, the company has earned a reputation that has a unique combination of quality, value, trust and reliability. It has three divisions of Hybrid plantation, Bio Organic Manure and Transport. In last four years it has spread all over Madhya Pradesh, Chhatisgarh and Rajasthan at a very rapid pace. The company has pioneered the concept of direct marketing in agricultural sector talking the product to farmers directly by field staff of the company.

Species Diversity and Distribution Characteristics of Calonectria in Five Soil Layers in a Eucalyptus Plantation.

The genus Calonectria includes pathogens of various agricultural, horticultural, and forestry crops. Species of Calonectria are commonly collected from soils, fruits, leaves, stems, and roots. Some species of Calonectria isolated from soils are considered as important plant pathogens. Understanding the species diversity and distribution characteristics of Calonectria species in different soil layers will help us to clarify their long-term potential harm to plants and their patterns of dissemination. To our knowledge, no systematic research has been conducted concerning the species diversity and distribution characteristics of Calonectria in different soil layers. In this study, 1000 soil samples were collected from five soil layers (0–20, 20–40, 40–60, 60–80, and 80–100 cm) at 100 sampling points in one 15-year-old Eucalyptus urophylla hybrid plantation in southern China. A total of 1037 isolates of Calonectria present in all five soil layers were obtained from 93 of 100 sampling points. The 1037 isolates were identified based on DNA sequence comparisons of the translation elongation factor 1-alpha (tef1), β-tubulin (tub2), calmodulin (cmdA), and histone H3 (his3) gene regions, as well as the combination of morphological characteristics. These isolates were identified as C. hongkongensis (665 isolates; 64.1%), C. aconidialis (250 isolates; 24.1%), C. kyotensis (58 isolates; 5.6%), C. ilicicola (47 isolates; 4.5%), C. chinensis (2 isolates; 0.2%), and C. orientalis (15 isolates; 1.5%). With the exception of C. orientalis, which resides in the C. brassicae species complex, the other five species belonged to the C. kyotensis species complex. The results showed that the number of sampling points that yielded Calonectria and the number (and percentage) of Calonectria isolates obtained decreased with increasing depth of the soil. More than 84% of the isolates were obtained from the 0–20 and 20–40 cm soil layers. The deeper soil layers had comparatively lower numbers but still harbored a considerable number of Calonectria. The diversity of five species in the C. kyotensis species complex decreased with increasing soil depth. The genotypes of isolates in each Calonectria species were determined by tef1 and tub2 gene sequences. For each species in the C. kyotensis species complex, in most cases, the number of genotypes decreased with increasing soil depth. The 0–20 cm soil layer contained all of the genotypes of each species. To our knowledge, this study presents the first report of C. orientalis isolated in China. This species was isolated from the 40–60 and 60–80 cm soil layers at only one sampling point, and only one genotype was present. This study has enhanced our understanding of the species diversity and distribution characteristics of Calonectria in different soil layers.

DETERMINING AN APPROPRIATE AGE FOR ESTIMATING SITE INDEX OF Acacia hybrid PLANTATIONS IN SOUTHEASTERN VIETNAM

This article introduces the research results of a site index classification for Acacia hybrid plantations in Dong Nai Province. The objectives of this study were to (i) determine a baseline age of Acacia hybrid plantations to establish their site indices and (ii) develop site index curves for Acacia hybrid plantations. Three standard plots were established for each age group of 1-10 years with 111 trees per plot; 108 trees were measured for the estimation of growth criteria. Three trees were used for tree truncation, and truncated trees did not count for the estimation of tree growth criteria. In this study, the site index (SI) for Acacia hybrid plantations was divided into three levels according to the total height of the dominant trees. The heights collected from 108 trees were used to build the functions of the SI, and three truncated trees were used to examine the possibilities of the functions of SI. Research results showed that the appropriate baseline age of Acacia hybrid plantations at Dong Nai Province is 8 years. The site indices of hybrid plantations were divided into three site levels of I, II, and III, corresponding to heights of 24, 20 and 16 m, respectively. To improve the effectiveness of Acacia hybrid plantation businesses, owners should focus on growing plantations at site index levels of I or II.

DETERMINING AN APPROPRIATE AGE FOR ESTIMATING SITE INDEX OF Acacia hybrid PLANTATIONS IN SOUTHEASTERN VIETNAM

This article introduces the research results of a site index classification for Acacia hybrid plantations in Dong Nai Province. The objectives of this study were to (i) determine a baseline age of Acacia hybrid plantations to establish their site indices and (ii) develop site index curves for Acacia hybrid plantations. Three standard plots were established for each age group of 1-10 years with 111 trees per plot; 108 trees were measured for the estimation of growth criteria. Three trees were used for tree truncation, and truncated trees did not count for the estimation of tree growth criteria. In this study, the site index (SI) for Acacia hybrid plantations was divided into three levels according to the total height of the dominant trees. The heights collected from 108 trees were used to build the functions of the SI, and three truncated trees were used to examine the possibilities of the functions of SI. Research results showed that the appropriate baseline age of Acacia hybrid plantations at Dong Nai Province is 8 years. The site indices of hybrid plantations were divided into three site levels of I, II, and III, corresponding to heights of 24, 20 and 16 m, respectively. To improve the effectiveness of Acacia hybrid plantation businesses, owners should focus on growing plantations at site index levels of I or II.

Contribution of Small-Scale Acacia Hybrid Timber Production and Commercialization for Livelihood Development in Central Vietnam

Forming a backbone of the wood supply in Vietnam, approximately 50% of plantation areas are managed by individual households. Of the planted species, the Acacia (Acacia auriculiformis A. Cunn. ex Benth. × Acacia mangium Willd) hybrid is one of the most preferred by timber growers. Yet, information on the potential of this timber species for rural livelihoods is lacking. Taking Nam Dong and Phu Loc districts in Thua Thien Hue province as case studies, this paper aimed to explore the (i) characteristics of small-scale Acacia hybrid timber producers; (ii) contribution of Acacia hybrid timber production and commercialization to rural livelihoods; and (iii) socio-economic and contextual factors which determine the income from Acacia hybrid timber. We applied a mixed-methods approach including review of secondary data, interviews of 26 key informants, eight focus group discussions, direct observations and a survey of 300 Acacia hybrid producer households selected through multistage and purposive sampling. Qualitative and quantitative data were analyzed using thematic, descriptive and inferential statistics, such as variance analysis, correlation analysis and Bayesian model average (BMA) analysis. The results demonstrated the diversity of socio-economic characteristics, resource access and management as well as determinants of timber income of small-scale timber producers between the cases. Accounting for 33–56% of total household income, Acacia hybrid timber plantations played a crucial role in the current livelihood system. Nevertheless, timber income was skewed toward the wealth status of timber producers and ranged between 327 USD/household and 3387 USD/household in Nam Dong and between 397 USD/household and 9460 USD/household in Phu Loc district. Despite the substantial contribution the income from Acacia hybrid plantations could make to local poverty reduction, it was the main contributor to the overall income inequality. While this income source reduced the Gini coefficient by 1% in Nam Dong, it increased the Gini coefficient by 18% in Phu Loc district. Our study can be of interest for further policy interventions focusing on sustainable reforestation and livelihood development in Vietnam.

Nondestructive Tree Stem and Crown Volume Allometry in Hybrid Poplar Plantations Derived from Terrestrial Laser Scanning

Abstract Accurate and frequently updated tree volume estimates are required for poplar plantations, which are characterized by fast growth rate and short rotation. In this study, we tested the potential of terrestrial laser scanning (TLS) as a reliable method for developing nondestructive tree volume allometries in poplar plantations. The trial was conducted in Italy, where 4- to 10-year-old hybrid plantations were sampled to develop tree crown volume allometry in leaf-on conditions, tree stem volume, and height-diameter allometries in leaf-off conditions. We tested one-entry models based on diameter and two-entry models based on both diameter and height. Model performance was assessed by residual analysis. Results indicate that TLS can provide accurate models of tree stem and crown volume, with percentage of root-mean-square error of about 20 percent and 15 percent, respectively. The inclusion of height does not bring relevant improvement in the models, so that only diameter can be used to predict tree stem and crown volume. The TLS-measured stem volume estimates agreed with an available formula derived from harvesting. We concluded that TLS is a reliable method for developing nondestructive volume allometries in poplar plantations and holds great potential to enhance conventional tree inventory and monitoring. Study Implications: Terrestrial laser scanning (TLS) is a technique that allows nondestructive measurement of the three-dimensional structure of a tree with high precision and low cost. The ability of TLS to measure both tree crown volume and tree position can be effective to test optimal spacing requirements and also to test innovative schemes such as mixed or polycyclic poplar plantations. The spatially explicit nature of TLS measurements allows better integration with different remotely sensed sensors, which can be used in combination with TLS, enabling a multiscale assessment of poplar plantation structure with different levels of detail, enhancing conventional tree inventory and supporting effective management strategies.

A Genome-Wide Association Study for Resistance to the Insect Pest Leptocybe invasa in Eucalyptus grandis Reveals Genomic Regions and Positional Candidate Defense Genes.

The galling insect, Leptocybe invasa, causes significant losses in plantations of various Eucalyptus species and hybrids, threatening its economic viability. We applied a genome-wide association study (GWAS) to identify single-nucleotide polymorphism (SNP) markers associated with resistance to L. invasa. A total of 563 insect-challenged Eucalyptus grandis trees, from 61 half-sib families, were genotyped using the EUChip60K SNP chip, and we identified 15,445 informative SNP markers in the test population. Multi-locus mixed-model (MLMM) analysis identified 35 SNP markers putatively associated with resistance to L. invasa based on four discreet classes of insect damage scores: (0) not infested, (1) infested showing evidence of oviposition but no gall development, (2) infested with galls on leaves, midribs or petioles and (3) stunting and lethal gall formation. MLMM analysis identified three associated genomic regions on chromosomes 3, 7 and 8 jointly explaining 17.6% of the total phenotypic variation. SNP analysis of a validation population of 494 E. grandis trees confirmed seven SNP markers that were also detected in the initial association analysis. Based on transcriptome profiles of resistant and susceptible genotypes from an independent experiment, we identified several putative candidate genes in associated genomic loci including Nucleotide-binding ARC- domain (NB-ARC) and toll-interleukin-1-receptor-Nucleotide binding signal- Leucine rich repeat (TIR-NBS-LRR) genes. Our results suggest that Leptocybe resistance in E. grandis may be influenced by a few large-effect loci in combination with minor effect loci segregating in our test and validation populations.

Effect of harvest residue management on soil properties of Eucalyptus hybrid and Acacia mangium plantations planted on steep slopes in northern Vietnam

Burning harvest residues during site preparation can compromise the soil-nutrient stock in short-rotation plantations, but this practice remains common in northern Vietnam. This study compared the effect of two contrasting harvest-residue treatments (burning vs retention) on soil total carbon (TC), total nitrogen (TN), extractable P (ext-P), exchangeable K (exch-K) and bulk density (BD) of two adjacent randomised complete-block trials, one of Eucalyptus hybrid (Eucalyptus urophylla × E. pellita) and the other of Acacia mangium planted on steep slopes. Harvest-residue management had no effect on soil properties of either E. hybrid or A. mangium two years after planting. Soil pH in E. hybrid increased and exch-K in A. mangium decreased during the first year; ext-P decreased over time in both species though this was only significant in the residue-retention treatment in A. mangium. Slope significantly influenced pH and TC of E. hybrid and TC and TN of A. mangium. It appeared that slope position and correlative factors such as surface runoff and erosion had led to the observed distribution of some soil properties along the steep slope.

Floristic and Phenological Analysis of Ground Vegetation Growth under <i>Eucalyptus hybrid</i> and <i>Dalbergia sissoo</i> Plantation

The present study deals with phytosociological and phenology of ground vegetation in Eucalyptus hybrid and Dalbergia sissoo plantation in Haridwar forest division. The total number of plant species were recorded as 39, 35, 28 in E. hybrid and 29, 25, 23 in D. sissoo during rainy, winter and summer season respectively. Chrysopogon fulvus was dominating the community grown under E. hybrid plantation by having maximum value of IVI and co-dominating by Arundinella nepalensis . However Parthenium hysterophorus was dominated by Cynodon dactylon and Oxalis corniculata . the phenological study of ground vegetation revealed that majority of annuals flowers fruit and produced their seeds in rainy season while fruiting and seed maturation in a number of perennial are activated during winter.

Above-ground Biomass Allometric Equation and Dynamics Accumulation of Eucalyptus Camaldulensis and Acacia Hybrid Plantations in Northern Thailand

In order to supply biomass energy in Thailand, fast-growing trees like Eucalyptus and Acacia are large plantations in the region. However, there are few studies on related topics such as biomass growth versus time and tree partitioning. The objectives of the study are to develop biomass equations and characterize biomass dynamics accumulation for E. camaldulensis , E. camaldulensis coppice, and A . hybrid. The study plantation area is 960 hectares in Lampang and Lamphun province, Northern Thailand. The planted density is 1666 trees ha -1 . A total of 221 trees for destructive sampling were randomly selected from thirteen sites. Allometric biomass equations for tree components are developed by regressing the diameter at breast height (DBH), tree height (H) and a combination of these. The results show that DBH alone is an optimal predictor variable for all studied species. However, the combination of DBH and H is more accurate than DBH alone. The models show that the total estimated above-ground biomass (AGB) production is 62.78 t ha -1 and 48.87 t ha -1 at the age of 5 years of E. camaldulensis and A . hybrid, respectively. The total estimated AGB production of E. camaldulensis coppice is 18.21 t ha -1 at 3 years of age. The equations developed in the study can be used to estimate the growth of the three species under the same growing conditions: topography, tree growth dimensions, and plantation density.

Comparisons of Four Methods for Thinning Eucalyptus Hybrid Coppice Shoots in Brazil

Both manual and semi-mechanized systems are used for operations involved in coppice remodeling. Thus, there is a paradigm about the higher yield of semi-mechanized operations compared to manual operations. However, the small volume of research on this subject does not present data which is capable of confirming this hypothesis. Thus, the present study aimed to perform a technical analysis of costs, quality and productivity of different methods for conducting regrowth in Eucalyptus grandis x Eucalyptus urophylla hybrid plantations under coppice regeneration in areas of forest fostering. The experiment was conducted under a completely randomized design with four treatments (sprouting methods) and four replications in plots of 360m² each. The methods used were: brushcutter, sickle, machete and hand digger. An F-test (p <0.05) was performed to verify the differentiation between treatments for a given characteristic after verifying the normal distribution of data and homogeneity of variances. The means were compared by analysis of variance at the 5% significance level to analyze if there was significant difference between the operating times in the analyzed methods. An estimate of the costs per hectare was subsequently obtained in each offspring method and the quality of the operation was evaluated by observing the frequency of damage to the remaining trunk. The mean operation time of the methods did not differ significantly (p> 0.05). The brushcutter presented the highest cost per hectare (US$ 40,06/ha-1) and the excavator presented the lowest (US$ 18,65/ha-1). Spreading with the brushcutter presented the lowest percentage of mechanical damage (6.88%) and the sickle obtained the highest (20.63%). It was concluded that the operation with brushcutter was the method that provided the highest productivity, but has the highest operational cost, making the method with brushcutter, advantageous for its low cost, associated with a satisfactory productivity.