Assessment of crown woody biomass in <Emphasis Type="Italic">Eucalyptus grandis</Emphasis> and <Emphasis Type="Italic">E. globulus</Emphasis> plantations

Young trees were harvested to explore non-destructive methodologies to estimate live branch dry weights in young fast-growing Eucalyptus species under different spacing and fertilizer treatments. Branch growth can vary with silvicultural management such as spacing, fertilizing and thinning, and over relatively short periods in response to environmental conditions. Many published regressions based on standard measurements of height and diameter are site, age and treatment specific. The aim of this study was to improve our capacity to predict woody crown dry weight, based on stem measurements, and to minimize (or eliminate) treatment effects on the resulting model. In young trees, branches are temporary support structures for foliage and are often discarded as the base of the green crown rises. As temporary structures they represent an investment of biomass and nutrient elements, and are subject to selection pressures to maximize the return on investment by the tree. Trees were harvested from existing plantation experiments located in south-eastern Queensland for E. grandis W. Hill ex Maiden (ranging from 0.28 to 15.85 m in height, to 5 years old) and south-western Australia for E. globulus Labill. (0.10–34.4 m in height, to 10.2 years) in order to examine the impact of spacing, nitrogen and phosphorus fertilization on early growth. Relationships to estimate crown woody biomass from non-destructive measurements were developed, and these relationships tended to have different slopes and intercepts for trees with predominantly juvenile foliage and those with intermediate or adult foliage. Dry weight of whole-crown live branch wood (W_branch) was related to heights and/or diameter at breast height (D_BH), but the regressions parameters were different, depending on treatment. The relationships became more generic (i.e. less dependent on treatment effects) between W_branch and stem sectional area at the height of the base of the green crown (SA_CB), consistent with the pipe model theory (R² > 0.91 for the two species for trees with intermediate/adult leaves). However, W_branch was more closely related again to the stem volume above the base of the green crown and treatment effects were not significant (V_Con,gc, R² > 0.93). Branches exit the stem below the green crown, and for E. grandis the best relationship was on stem volume above the lowest live branch (V_Con,llb, R² 0.94). Limited sampling from four other species with similar or contrasting crown characteristics indicated that the relationship could be applied quite generally. Individual E. grandis branch woody dry weight was closely related to the conical volume of the main (first order) branch (V_con,br, R² 0.98₎. The whole crown equivalent, branch woody dry weight plus stem dry weight above the lowest live branch, was also closely related to the stem volume within the woody crown (V_Con,llb, R² 0.97–0.99). While the slope of this relationship was still significantly different between trees with juvenile and intermediate/adult foliage, it had a similar form, suggesting that trees with juvenile foliage allocated a different proportion of their woody biomass within the crown to branches than older trees.     

Understanding the naturalization of <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> in Portugal: a comparison with Australian plantations

Despite the potential utility of a biogeographical approach to understanding the naturalization of exotic species, studies using this approach are scarce. Eucalyptus globulus is an economically important Australian tree species that has become naturalized in a number of countries where it was introduced. Portugal is an ideal territory to study the naturalization of E. globulus owing to: a long introduction history, the antipodal location compared to Australia and the large cultivated area. Wildling density was assessed in 116 E. globulus plantations in central Portugal through 213 transects established along plantation borders. Boosted regression trees were used to model the influence of plantation-scale variables. Results from this survey were compared with data obtained in plantations from seven Australian regions, where a similar sampling protocol had been used. In Portugal, wildlings were more abundant in plantations that were: located in moist aspects, coppiced, with older tree stems and corresponding to intermediate site growth indexes. The overall density (127 plants ha^?1) was 14.9 times higher than in the Australian estate, but this ratio was reduced to 3.1 in a more comparable subset of unburnt, first rotation plantations. A generalized linear model fitted using a dataset combining the two surveys showed that country influenced wildling density, together with plantation rotation and stem age. These results provide insights into the naturalization of a widely cultivated tree species, pointing to a fundamental role of the introduction history, possibly acting along with the biogeographical characteristics of the introduced range.     

A case study of <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> fingerprinting for breeding

• Introduction  

Tree genetic improvement programs usually lack, in general, pedigree information. Since molecular markers can be used to estimate the level of genetic similarity between individuals, we genotyped a sample of a Portuguese Eucalyptus globulus breeding population—a reference population of 125 individuals—with 16 microsatellites (SSR).     

Non-aerated liquid culture promotes shoot organogenesis in <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> Labill

Eucalyptus is very recalcitrant to in vitro culture. In this research, an efficient shoot organogenesis system was developed using 60-day-old plants of Eucalyptus globulus grown in vitro and non-aerated liquid medium to improve shoot proliferation. Cultures were initiated with hypocotyls and leaf segments from plantlets cultivated on semisolid ½ MS modified medium supplemented with 4.44 µM 6-Benzyladenine (BA) and 16.1 µM 1-Naphthaleneacetic acid (NAA). Calli were transferred to shoot induction medium, with either 0.5 or 2.7 µM NAA. Shoot multiplication was carried out on 4.44 µM BA + 0.5 µM NAA medium, and semisolid and non-aerated liquid systems were compared for improving shoot proliferation. Rooting of adventitious shoots was evaluated on medium containing NAA or Indole-3-butyric acid -IBA (5 and 16 µM). Callogenesis was obtained from both types of explants, although shoot formation was only obtained from leaf-derived calli. Shoot proliferation on 4.44 µM BA + 0.5 µM NAA resulted in the most shoots/callus. Non-aerated liquid medium was more efficient in promoting shoot multiplication (53.5 shoots/callus) than was semisolid medium (28.5 shoots/callus). Levels of phenolic compounds were significantly reduced in the shoots cultivated in liquid medium. Efficient rooting (76%) was obtained using 16 µM IBA.     

Selective herbicides for establishment of <Emphasis Type="Italic">Eucalyptus benthamii</Emphasis> plantations

Competition control is essential for successful eucalyptus plantation establishment, yet few selective herbicides have been identified. Five herbicides, flumioxazin, imazamox, imazapic, oxyfluorfen, and sulfometuron methyl, were evaluated at either pre- or post-weed emergence timing for selective weed control in the establishment of Eucalyptus benthamii, a frost-tolerant species showing promise for commercial plantations in the southeastern United States and southern Brazil. Herbicides were applied at two or three rates and compared to a non-treated control and to near-complete weed control obtained with repeated glyphosate directed sprays. Herbicides were most efficacious when applied prior to weed emergence, at 2 weeks after planting 16-week-old containerized eucalyptus seedlings. Pre-emergence imazapic treatments resulted in broad-spectrum and persistent weed control, with 77–82% bare-ground at 60 days after treatment, but both pre- and post-emergence applications of imazapic caused excessive eucalyptus injury at the highest rate tested. Imazapic, sulfometuron, and imazamox were most effective for grass control. Both timings of flumioxazin were effective for forb control at the early assessment. All pre-emergence treatments enhanced stem volume compared to the non-treated control, but post-emergence treatments did not, suggesting the need for early weed control to facilitate E. benthamii growth. Pre-emergence applications of medium and high sulfometuron, low imazapic, high imazamox, and high oxyfluorfen rates increased stem volume four-fold to six-fold compared to the non-treated control. Repeated glyphosate directed sprays increased stem volume nearly three-fold compared to the control. These results confirm one early report of flumioxazin effectiveness and identify imazamox and imazapic as new selective herbicides for eucalyptus culture.     

Weeds in <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> subsp. <Emphasis Type="Italic">maidenii</Emphasis> (F. Muell) establishment: effects of competition on sapling growth and survivorship

The effect of herbaceous vegetation on growth and survival was assessed in planted eucalyptus saplings grown under four levels of weed cover. Seedlings of Eucalyptus globulus subsp. maidenii were planted with 0 (W0), 25 (W25), 50 (W50) and 100% (W100) weed cover. Weed species composition and aboveground biomass was determined. Soil water content was evaluated by the gravimetric method. Seedling leaf area, diameter and height were evaluated at planting and during the 3 months following establishment. Tree height, diameter and stem volume was estimated at 12, 24 and 36 months. First year tree survival was recorded. The ratio of cumulative stem growth under W100: cumulative stem growth under W0 was used to measure competitive performance. Regression analysis was used to determine competition thresholds. Weeds seriously threaten the growth of E. globulus subsp. maidenii. Early negative effects of competition on growth were evident as from the second month after establishment, and both seedlings and 1-year-old saplings were more affected than 2- and 3-year-old ones. A “minimum-response threshold” was determined near 500 kg/ha (corresponding to W25 cover). No clear effect was found between sapling survival and weed biomass.     

Biomass and nutrient allocation to aboveground components in fertilized <Emphasis Type="Italic">Eucalyptus saligna</Emphasis> and <Emphasis Type="Italic">E. urograndis</Emphasis> plantations

The objective of this study was to evaluate biomass allocation and nutrient pools in aboveground biomass components in 18-month-old plantations of Eucalyptus saligna and E. urophylla × E. grandis (i.e. E. urograndis) in Brazil. The plantations were established by pulp companies in a large area comprising three soil types (Acrisols, Vertisols and Leptosols) in the grassland biome in southern Brazil, and an operational regime of planting and maintenance fertilization was used to ensure full availability of nutrients. Vertisols showed the highest availability of soil nutrients, and the P and Ca concentrations in aboveground biomass were also highest in this type of soil. The nutritional status of both species indicates great consumption of nutrients, particularly of P, K and Ca. At this early age, canopy biomass components still made the largest relative contribution, although debarked stem biomass already accounted for 41.5% and 37.4 of total aboveground biomass in E. saligna, and E. urograndis, respectively. Nutrient concentrations in biomass components were similar across species. For all macronutrients, except Ca and Mg, the concentration gradient followed the order wood < bark < branches < leaves. For all micronutrients, except Cu, the concentration gradient followed the order wood < branches ≈ bark < leaves. At the plantation stage studied, i.e. before canopy closure, the importance of the components as nutrient pools followed the order leaves > branches > wood > bark. The branches hold the majority of Ca reserves in biomass and are a very important pool of Mg, K, P and B. The bark makes a small contribution to total biomass, but stores a similar amount of Ca as leaves, being the second major pool after the branches. Comparison of the nutrients supplied by fertilization and the amounts stored in soil and aboveground indicates that the operational dose should be adjusted to each type of soil after further experimental fertilizer trials, as the supply of N and P appears to be too high, particularly for Vertisols. This is leading to the immobilization of P in biomass components that are not of importance in the biological or biochemical nutrient cycles, thus increasing the risk of larger exports of P during biomass removal.     

Evaluation of a process-based ecosystem model for long-term biomass and stand development of <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> plantations

Versatile process-oriented ecosystem models are discussed as promising tools for the analyses of ecosystem services beyond wood yield, such as catchment water yield, sequestration of carbon and greenhouse gas balances. However, long-term yield simulation is often regarded as a weakness of such versatile models. In this context, we present a multiple response evaluation of the modular, process-based forest growth model MoBiLE-PDT based on mensurational data from 38 permanent sample plots in commercial Eucalyptus globulus plantations in Australia followed from establishment to 8 years of stand age. MoBiLE-PDT is based on the PnET-N-DNDC model and considers nitrogen availability and drought stress dynamically in dependence on tree and stand properties as well as on climate and deposition. New tree dimensions are calculated directly from carbon allocated to sapwood and mortality is derived from stand density. Towards the end of the rotation, model efficiency E was 0.58 for stand volume (m³ ha⁻¹) and 0.54 for aboveground biomass (t C ha⁻¹). In a comparison with similar forest growth models evaluated against the same data only one had a better model efficiency, whereas MoBiLE-PDT was the most versatile model for the analyses of ecosystem services. Due to its modular structure, further model extensions for more ecological applications are easily possible.     

Establishment of native <Emphasis Type="Italic">Eucalyptus pauciflora</Emphasis> and exotic <Emphasis Type="Italic">Eucalyptus nitens</Emphasis> on former grazing land

The success of tree plantings in agricultural landscapes within dry and variable rainfall regions is often below expectations. The aims of this study were to investigate techniques for establishing a local native species (Eucalyptus pauciflora) and an exotic species (E. nitens) in the Midlands of Tasmania, a tree-denuded region that has been grazed for over 100 years in Australia. We established trials at the Sorrel Springs and Woodland Park properties. We compared six establishment techniques: control; understorey nurse planting; spot burn; mulch; tree-guard and; self-watering tree-guard. Three months, 1 and 6 years after planting we measured tree height, health index and mortality. At Sorrell Springs tree-guarded treatments had greater height than other treatments at year one, but there were no effects of treatment at year six on height, health or mortality. At Woodland Park mulch, burn and tree-guarded treatments had greater height 1 and 6 years after planting. At year six tree-guarded treatments had lower mortality than other treatments. At Sorrell Springs height of E. nitens was greater than E. pauciflora at year one but not at year six. At Woodland Park height of E. nitens was generally greater at year six but having almost double the incidence of mortality relative to E. pauciflora. We conclude that expensive tree-guarding is only warranted where high browse pressure is expected and that on such sites species with tough leaves that are resistant to browsing should be considered. Further that in environments marginal for growing trees, best practice establishment technique is generally as effective as additional treatments of understorey nurse planting, spot burning or mulching.     

Effects of <Emphasis Type="Italic">Eucalypt</Emphasis> and <Emphasis Type="Italic">Acacia</Emphasis> plantations on soil water in Sumatra

Indonesia’s pulp and paper industry needs a large area of sustainably grown plantations to support its continued development. Acacia mangium has been the key species underpinning the pulp and paper industries in Sumatra, however increased disease pressure on A. mangium is expected to require large-scale conversion of Acacia plantations to Eucalyptus in the near future. The effect of such a large scale change in plantation species on soil moisture, for both tree production, and catchment hydrology is unknown. In this study we sought to characterize the impacts of plantation species (Acacia or Eucalyptus) and nitrogen management, on soil moisture, soil water depletion and depth to groundwater under stands of Acacia mangium and Eucalyptus pellita over the first 2–3 years after establishment. The study was conducted in experiments at four sites in Sumatra, Indonesia. Soil moisture and soil water depletion were not influenced by plantation species or fertilizer treatment. Soil moisture content and soil water depletion were strongly influenced by shallow groundwater at two of the four sites, however depth to groundwater did not influence stem growth. Results from the field trials cautiously suggest that large scale conversion of Acacia mangium to Eucalypt species in these regions is unlikely to result in increased moisture stress, nor is conversion of plantation species likely to lead to substantial differences in catchment hydrology. This study demonstrated the importance of conducting multi-site studies when investigating biophysical relationships in forest/plantation systems.     

Effects of inbreeding on population mean performance and observational variances in <Emphasis Type="Italic">Eucalyptus globulus</Emphasis>

• ? Mean performance and variances were studied in self (SELF), open pollinated (OP) and unrelated polymix (POL) crosses of common parentage in Eucalyptus globulus.
• ? Inbreeding depression for survival (SURV) and basal area per hectare (BAH) was the highest reported for a SELF eucalypt population, increasing with age to reach 74 and 77%, respectively, over 10 years.
• ? Inbreeding depression in the OP was 36% for SURV and 32% for BAH at age 10 years, and estimates of outcrossing rate from BAH were stable across ages, averaging 0.56. In contrast, OP inbreeding depression for stem diameter (DBH) of survivors decreased with age and few selfs appeared to survive to 10 years.
• ? There was more variation in DBH between and within SELF than POL families, with variance ratios consistent with rare and partially recessive deleterious alleles causing inbreeding depression.
• ? The OP variances were initially more similar to the SELF population but converged to the POL population after 10 years.
• ? It is argued that when outcrossing rates are low, as in the present case, inbreeding depression will be a significant force countering local adaptation in forest trees.

     

Successful <Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated transformation of <Emphasis Type="Italic">Populus tomentosa</Emphasis> with apple <Emphasis Type="Italic">SPDS</Emphasis> gene

The problem of salinized soils has become one of the most serious constraints to agricultural and forest productivity. With the purpose of enhancing salt stress tolerance of Populus tomentosa, we transformed this tree species with spermidine synthase （SPDS） genes derived from an apple by an Agrobacterium-mediated method. Four transgenic clones were confu＇med by PCR and Southern blot analysis. As well, the expression of introduced SPDS genes was analyzed by real-time quantitative PCR.     

Weed control measures in Christmas tree plantations of <Emphasis Type="Italic">Abies nordmanniana</Emphasis> and <Emphasis Type="Italic">Abies lasiocarpa</Emphasis> on agricultural land

Abies nordmanniana and Abies lasiocarpa, established for Christmas tree production in southwestern Norway (58°44′N, 5°38′E), were treated with different weed control methods, including chemicals, use of black plastic mulch, grass or clover as ground cover, living mulch and mechanical hoeing. Ground cover with black plastic mulching resulted in the best growth and quality in A. lasiocarpa; the least favourable treatment was when grasses were allowed to grow close to the trees. Unless measures were taken to remove this competing vegetation, the ground cover grew over the trees, smothering 94% of them. A. nordmanniana plants grew to the same height on plots with no weed control as on plots with thorough weed eradication. Stem diameter decreased on plots with ground vegetation compared to seedlings grown in the weed-free environment. The use of Trifolium repens as ground cover decreased height growth by 30% compared to thorough weed control. Both grasses and clover sown as living mulch, damaged the trees more than did natural weed vegetation.     

<Emphasis Type="Italic">In vitro</Emphasis> morphogenic response of leaf sheath of <Emphasis Type="Italic">Phyllostachys bambusoides</Emphasis>

Nodal segments from secondary branches of saplings of Phyllostachys bambusoides were inoculated in MS medium to assess the in vitro morphogenic response of leaf sheath through the induction to callogenesis by Picloram(4-amino-3,5,6-trichloropicolinic acid) at different concentrations of carbohydrate under the same conditions with presence or absence of luminosity.In our experiment,secondary explants were kept in MS medium containing 8.0 mg·L-1 of Picloram for the callus formation.Calluses were transferred in MS medium supplemented with sucrose,fructose and glucose(control,2%,4% and 6%).Results show that Picloram induced the callogenesis in leaf sheath.The secondary embryogenesis was formed in yellow-globular callus.The sucrose as carbohydrate source in the absence of light was more efficient to induce rhizogenesis.Glucose was more efficiency in the presence of light.Callogenic induction and further embryogenesis evidenced the competence and determination of leaf sheath cells.     

Response of <Emphasis Type="Italic">Eucalyptus camaldulensis</Emphasis> and <Emphasis Type="Italic">Acacia mangium</Emphasis> kraft pulp in different ECF bleaching options

In this study, the response of Eucalyptus camaldulensis and Acacia mangium kraft pulp to different options of ECF bleaching was investigated. Oxygen-delignified pulps of both species having similar kappa number (c.a. 12) were used. Both the pulps were prebleached using conventional ClO₂ stage (D₀), combined use of ClO₂ and O₃ (DZ), hot acid treatment before D₀ (A_hotD₀) and hot acid treatment before (DZ) i.e., A_hot(DZ), hot ClO₂ treatment (D_HT) and A_hot followed by D_HT (A_hotD_HT). All prebleached pulps were finally bleached to 90%+ ISO brightness using D₁ option. The overall benefits of other options were not considerable compared to D₀ and (DZ). From the ClO₂ consumption point of view, for a certain species, the option A_hot(DZ) was the best. Instead of D₁ in final bleaching, pressurized hydrogen peroxide (PO) was also investigated in the case of D₀ and (DZ) prebleached pulps. (PO)-bleached pulp produced higher brightness stability but lower viscosity compared to D₁.     

<Emphasis Type="Italic">Quercus suber</Emphasis> forest and <Emphasis Type="Italic">Pinus</Emphasis> plantations show different post-fire resilience in Mediterranean north-western Africa

Key message

In the African rim of the Western Mediterranean Basin, cork oak forests and pine plantations coexist. Under similar fire regimes, cork oak forest is more resilient in terms of habitat structure (canopy, understory, and complexity of vegetation strata) than pine plantation. By contrast, both woodland types show similar resilience in plant species composition. Resilience in habitat structure varies between the two woodland types because of the resprouting and seeding strategies of cork oak and pine species, respectively. These differences can be relevant for the conservation of biodiversity of forested ecosystems in a future scenario of increased fire frequency and scale in the Mediterranean basin.

Context

Wildfires have major impacts on ecosystems globally. In fire-prone regions, plant species have developed adaptive traits (resprouting and seeding) to survive and persist due to long evolutionary coexistence with fire. In the African rim of the Western Mediterranean Basin, cork oak forest and pine plantation are the most frequently burnt woodlands. Both species have different strategies to respond fire: cork oak is a resprouter while pines are mostly seeders.

Aims

We have examined the hypothesis that pine plantations are less resilient in habitat structure (canopy, understory, diversity of vegetation strata) and plant composition than cork oak woodlands.

Methods

The habitat structure and plant species composition were measured in 30 burnt and 30 unburnt 700-m transects at 12 burnt sites from north-western Africa, where the two forest types can coexist. Habitat structure and plant species composition were compared between burnt and unburnt transects from cork oak and pine plantation woodlands with generalized linear mixed models and general linear models.

Results

The results showed significant interaction effect of fire and forest type, since cork oak forest was more resilient to fire than was pine plantation in habitat structure. By contrast, both forest types were resilient to fire in the composition of the plant communities, i.e., plant composition prior to fire did not change afterwards.

Conclusion

The higher structural resilience of cork oak forest compared to pine plantation is related to the resprouting and seeding strategies, respectively, of the dominant tree species. Differences in the responses to fire need to be considered in conservation planning for the maintenance of the Mediterranean biodiversity in a future scenario of changes in fire regime.

     

Application of the 3PG forest growth model to a <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> plantation in Northwest Spain

This paper presents an assessment of the ability of the 3PG process-based model to simulate height (h) and diameter at breast height (DBH) growth in three plots located in a Eucalyptus globulus plantation on the Atlantic coast of Galicia (Northwest Spain). The obtained results show how this model estimates adequately height (h) and DBH growth, and determination coefficients (R ²) between observed data and data predicted by the model are always higher than 0.97, root mean square error (RMSE) of 0.45–1.05 cm in DBH and 0.46–0.85 in h, and a model efficiency (EF) close to 1 (0.98–0.99). In order to improve the results predicted by the model, we propose modifying the nS and fullCanAge parameter values given by default so as to adjust growth rates in the plantation to the weather conditions in the site. The ability of the model to discriminate growth rates in the three plots must be noted, even when plots are located in the same plantation and they only show differences in aspects related to site factors. Given the obtained results in the three plots used in this study, its simplicity and the small number of parameters needed as input data, the 3PG model stands out as a very useful tool for forest plantation management.     

Insecticidal properties of <Emphasis Type="Italic">Thymus persicus</Emphasis> essential oil against <Emphasis Type="Italic">Tribolium castaneum</Emphasis> and <Emphasis Type="Italic">Sitophilus oryzae</Emphasis>

Red flour beetle Tribolium castaneum (Herbst) and rice weevil Sitophilus oryzae (L.) are considered to be the major insect pests in storage. Essential oils from aromatic plants are recognized as proper alternatives to fumigants. Thymus persicus (Ronniger ex Rech. f.) is one of these plants that have medicinal properties and is indigenous to Iran. The essential oil was obtained from aerial parts of the plant and analyzed by GC and GC–MS. Carvacrol (44.69%) and thymol (11.05%) were the major constituents of the oil extracted. In this experiment, fumigant toxicity of the essential oil was studied against T. castaneum, S. oryzae at 27 ± 1°C and 60 ± 5% RH in dark condition. The adult insects were exposed to the concentrations of 51.9, 111.1, 207.4 and 370.4 μl/l air to estimate median lethal time (LT₅₀) values. The fumigant toxicity was increased in response to increased essential oil concentrations. The LT₅₀ values at the lowest and the highest concentrations tested were ranged from 28.09 to 13.47 h for T. castaneum, and 3.86 to 2.30 h for S. oryzae. It was found that S. oryzae adults were much more susceptible to the oil than T. castaneum. After 24 h of exposure, the LC₅₀ values (95% fiducial limit) for T. castaneum and S. oryzae were estimated to be 236.9 (186.27–292.81) and 3.34 (2.62–4.28) μl/l air, respectively. These results suggest that T. persicus essential oil merits further study as potential fumigant for the management of these stored-product insects.     

Modeling of sapwood and heartwood delignification kinetics of <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> using consecutive and simultaneous approaches

Eucalyptus globulus sapwood and heartwood were delignified at 130°, 150°, or 170°C by kraft pulping. Pulp yields of heartwood were lower than those of sapwood (46.5% vs. 50.4% at 170°C). Delignification was modeled using consecutive and simultaneous kinetic models. The modeling was similar for heartwood and sapwood, and either approach could be used, with both yielding good correlations between experimental and model data. The consecutive model identified two delignification phases with similar reaction rates and activation energies for heartwood and sapwood at 150° and 170°C. At 130°C only one phase was identified. Three reactive types of lignin fractions were identified using the simultaneous model, without differences between heartwood and sapwood. Their reaction rates were 0.152, 0.138, and 0.003 min⁻¹ at 170°C, and the activation energies were 132, 119, and 102 kJ.mol⁻¹. The presence of heartwood did not influence the kinetic development of delignification. The negative impact of heartwood in pulping is related to the higher content of extractives (9.8% vs. 3.9% in heartwood and sapwood) and to their influence on the process, namely in the heating-totemperature phase when a substantial mass loss occurs (30% vs. 20% for heartwood and sapwood).