Annual Diameter Increment Research Articles

Peeler core and slabwood fibre properties for Pinus radiata D.Don pulp production

Background: Pulp production based on Pinus radiata D.Don is constantly improving the value recovery of logs. One example is using the peeler cores and slabwood derived from sawing and peeling processes to produce pulp. However, these two raw materials have not been characterised for their fibre properties. Methods: We report on four wood fibre quality attributes derived from peeler cores and slabwood, directly influencing pulp quality and pulping process: fibre length (mm), fibre width (µm), fines content (%), and coarseness (µg/m). This pilot study sampled two P. radiata stands grown on different sites and early silvicultural regimes in the Araucanía Region of Chile. Analysis of wood fibre consisted of three trees per stand, and six discs per tree: two at the bottom, two at breast height (1.3 m), and the last two at 5.23 m height. Results: The trajectory of mean annual increment in diameter at breast height (MAI) and periodic annual increment in diameter at breast height (PAI) for trees in the two stands aligned with their respective site qualities and silvicultural regimes. In Stand 1, with a site index of 36, and Stand 2, with a site index of 31, the average proportions of juvenile wood (measured at 1.3 m) were 50% and 53%, respectively. Thus, despite weed control and fertiliser application in Stand 1, there was no increase observed in the proportion of juvenile wood. There were significant differences in fibre properties between peeler core and slabwood, and these differences were present across the range of tree heights and diameters (p<0.05). While there were no statistically significant differences among disc positions, significant distinctions emerged between stands and wood types. The interaction between these factors was also found to be statistically significant (p<0.05). Conclusions: Our study suggests that adding these two materials into the mix for producing pulp would have positive implications due to pulp from peeler core is more suitable for printing and writing grades and addition of mature wood from slabwood, could improve strength properties of paper manufacture. However, it is necessary to test the optimal proportion for the final mix.

Variation of Physical and Mechanical Properties of Pinus Sylvestris L. Wood in the Boreal Zone of the European Northeast

The study considers variational aspects of physical and mechanical properties of Scots pine (Pinus sylvestris L.) wood depending on conditions and growth areas in the boreal zone of the European Northeast. Anatomical traits of xylem and its strength properties were analyzed. Based on the data received, statistical processing of the material was carried out using correlation and multivariate analysis. The impact of hazardous air emissions on variation of linear dimensions in structural elements of the annual height increment in the trunk diameter was estimated. A varying nature of the influence of environmental factors on the formation of strength properties of P. sylvestris wood in growth areas was attested. The variation value of basic wood density decreases as soil and hydrological conditions of growth improve. A significant negative correlation between basic wood density and distance to sources of hazardous air emissions in the areas of concentration of industrial enterprises was established. The results of multivariate analysis make it possible to reveal the weight of the influence of environmental factors and biometric characteristics of wood on volumetric and strength properties of pine wood. Growth in the impact zone of air emissions from large industrial enterprises in the study area does not produce a significant effect on the dynamics of wood strength properties, taking into account various growth conditions. For Scots pine growing in the European Northeast, the study determined a significant impact of the size and structure of the annual height increment of the trunk in terms of diameter, as well as the position of the wood sample in terms of trunk volume, on strength properties of pine wood.

Genotype x environment interaction and climate sensitivity in growth and wood density of European larch

European larch is an ecologically and economically important tree species planted across a wide range of environments. Understanding its response to the rapidly changing climate is essential to developing efficient gene resource management strategies in line with the assisted migration methodology. In this study, we quantified the genotype x environment interaction (GxE) of a larch provenance in a multi-environmental trial analysis using factor analytic (FA) modeling. We analyzed the mean annual height increment (MAI-H), the mean annual diameter increment (MAI-DBH), and wood density (PP). Additionally, we evaluated the effect of several environmental variables on these traits. The genetic correlations between sites varied from −0.53 to 0.99, −0.87 to 0.99, and −0.17 to 0.99 for MAI-H, MAI-DBH, and PP, respectively. This indicates the presence of low to high GxE. The growth traits showed more GxE signal than wood density. Narrow-sense heritability estimates were 0.41, 0.16, and 0.35 for MAI-H, MAI-DBH, and PP, respectively. The FA modeling of order 2 explained 77.4%, 67.9%, and 77.3% of the genetic variance for MAI-H, MAI-DBH, and PP, respectively. For MAI-H, the latent regression plots for the predicted site means indicate a significant positive correlation with the first factor loading. At the individual genotype level, the latent regression plots indicated high levels of GxE, especially for growth traits. Significant and relatively high correlations were found between several EVs and the factor loadings of the FA models, suggesting their possible influence on the genotypic performance across environments. Regarding MAI-H, elevation, averaged monthly mean temperature, precipitation seasonality, and stand age were correlated with the first factor loading. Annual temperature range with both the first and second factor loadings. For MAI-DBH, the mean diurnal range was correlated with the first factor loading. In the case of PP, we found that elevation was correlated with the second factor loading. Overall, this approach successfully modeled the GxE and identified environmental variables likely affecting it. Therefore, we conclude that this methodology is a valuable tool for selecting suitable genotypes adapted to specific environmental conditions.

Size of sampling units aproppriate for management level forest inventory in Eastern Amazon, Brazil

This study aimed to indicate the ideal sample size for continuous forest inventories in the tropical forest in Amapá. Data were obtained from a monitoring inventory started in 2010 and completed in 2016, in five permanent sampling units of 100m x 100m with an inclusion level of DBH ≥ 10cm. Randomly allocated sample subunits with five different dimensions ranging from 400 m2 to 1600 m2 were simulated within these units. The measurement times of each sampling unit, from the first to the last three, were timed. Dimensions were analyzed for their accuracy and relative efficiency. Given the above and depending on the purpose of the inventory, the standard sampling unit of 1 ha (100 m x 100 m) is recommended for the inventory variables. The 20 m x 20 m (400 m2) square sampling unit was the most suitable for monitoring growth variables (annual increment in diameter, basal area, and volume), indicating that these sampling units for continuous inventories can become an essential alternative for use in monitoring inventory in the region.

Comparison of carbon content between plantation and natural regeneration seedlings in Durango, Mexico.

Forest plantations and natural forests perform a relevant role in capturing CO2 and reducing greenhouse gas concentrations. The objective of this study was to compare the diameter increment, biomass and carbon accumulation in a plantation of Pinus durangensis and a naturally regenerated stand. The data were collected from 32 circular plots of 100 m2 (16 plots in the planted site and 16 in naturally regenerated area). At each plot, the diameter at the base (cm) and height (m) of all seedlings were measured using a Vernier and tape measure, and a seedling was destructively sampled collecting one cross-section at the base of the stump. The annual ring-width increment of each sampled seedling was recorded to obtain its diameter at the base and estimate annual aboveground biomass and carbon accumulation through allometric equations. The response variables were evaluated using mixed-effects ANOVA models. Results indicated that there were significant differences (P ≤ 0.05) on annual tree-ring width growth, biomass and carbon accumulation. The plantation seedlings showed significantly higher growth rates, biomass and carbon accumulation at most evaluated years. After 7 years of growth the lines of current annual increment (CAI) and mean annual increment (MAI) in basal diameter for both the plantation and the natural regeneration have not yet intersected. Both forest plantations and naturally regenerated stands of the studied tree species may be suitable alternatives to promote CO2 capture and increase timber production.

Soil fertility and drought interact to determine large variations in wood production for a hyperdominant Amazonian tree species

IntroductionThe productivity of the Amazon Rainforest is related to climate and soil fertility. However, the degrees to which these interactions influence multiannual to decadal variations in tree diameter growth are still poorly explored.MethodsTo fill this gap, we used radiocarbon measurements to evaluate the variation in tree growth rates over the past decades in an important hyperdominant species, Eschweilera coriacea (Lecythidaceae), from six sites in the Brazilian Amazon that span a range of soil properties and climate.ResultsUsing linear mixed-effects models, we show that temporal variations in mean annual diameter increment evaluated over a specific time period reflect interactions between soil fertility and the drought index (SPEI-Standardized Precipitation and Evapotranspiration Index).DiscussionOur results indicate that the growth response of trees to drought is strongly dependent on soil conditions, a facet of forest productivity that is still underexplored, and which has great potential for improving predictions of future tropical tree growth in the face of projected climate change.

Evolução da severidade do cancro e qualidade de fuste no crescimento do mogno-africano

Abstract The objective of this work was to investigate the influence of the qualitative traits canker severity and stem quality on the mean annual increment (MAI) in diameter, total height, and stem height of an African mahogany (Khaya grandifoliola) stand. The study area is located in the state of Minas Gerais, Brazil, where continuous forest inventories were conducted over six years for data collection. Given the nonparametric characteristic of the data, an aligned rank transform analysis of variance was performed for each factor, and the averages were compared by Dunn’s multiple test. There was no significant effect of the interaction between the classes of canker severity and stand age. Increased canker severity has a significant effect on MAI values, causing reductions of 13% in diameter, 11% in total height, and 21% in stem height in trees from the highest canker severity class, when compared with the healthy ones. Age interacts significantly with stem quality, and MAI values tend to be similar in younger trees, differing over time in the oldest ones. In addition, the highest MAI values are recorded in trees with the best stem classification.

Socio-economic and ecological outcomes of a community-based restoration of peatland swamp forests in Peninsular Malaysia: A 5Rs approach

Restoration of degraded forest lands is a global priority that aims to restore ecosystems and their functions in ways that provide multiple socio-economic benefits. The Selangor State Forestry Department (SSFD) of peninsular Malaysia in collaboration with an NGO, local people and other stakeholders had been implemented a community-based restoration of degraded peat swamp forest (1000 hectare) programme in Raja Musa Forest Reserve, North Selangor since 2008. However, socio-economic and ecological impacts of this restoration programme are yet to study fully. In this pioneer study, we followed 5Rs approach to peatland restoration and assessed rewetting status (R1), reduction of fire incidences (R2), revegetation (R3), revitalization (R4) and reporting and monitoring (R5) to understand socio-economic and ecological outcomes of the programme. Data on R1, R2, R3 (restoration approach), R4 (qualitative data on socio-economic outcomes) and R5 (management actions and stakeholders’ participation) were collected through four focus group discussions, five key informant interviews, review of NGO’s documents and a stakeholders’ workshop. Quantitative data on R4 (local peoples’ willingness to contribute (WTC) and socio-economic impact (e. g. benefits, education, awareness) were collected through structured interviews of 200 randomly selected households in four surrounding villages. Data on R3 (ecological outcomes- survival rate and growth of planted trees, status of natural regeneration) were gathered through a series of vegetation survey. Restoration project created jobs (e. g. patrolling) and small business (e. g. forest nursery) opportunities for local people, and enhanced tourism, nature education and research in RMFR thus contributed to locals’ socio-economic development (R4). Local people were WTC to tree planting and maintenance (69 %), canal blocking and maintenance (26 %), forest vigilance (34 %), fire control (35 %), trail construction (27 %), and education and awareness creation (40%) voluntarily without remuneration (R1, R2, R3). The SSFD and NGO adopted an innovative approach of PSF restoration where volunteers (local people and other stakeholders) participated in canals blocking to keep PSF wetted, monthly tree planting events, and education and awareness creation campaigns (R1, R3). Canal blockings helped to maintain a mean ground water level of − 24.96 cm. Due to continuous motivation and awareness creation among surrounding villagers, fire incidents in RMFR were reduced (R2). Between 2008 and 2019, 323.72- hectare plantations were developed mainly with Euodia redlevi tree species and few trees of Shorea leprosula, Myristica lowiana and M. pruinose (R3). Selection of species was done by the SSFD and NGO without input from local people (R5). The mean survival percentage of planted trees was 65%. Mean annual increment (MAI) of diameter and height of E. redlevi decreased from younger plantations (3-year) toward older ones (5-, 7-year) (R3). Overall, MAI (dbh and height) across four tree species between age groups was found significantly different (p = 0.001). Regeneration study identified 16 tree species with an average density of 17,798. E. redlevi was dominant, but only 10.6 % of its regeneration attained young tree stage (R3). Suggestions are made to expedite restoration with diverse tree species (R3) with effective participation of local people (R5) and to ensure post-planting maintenance for greater survival of planted trees (R1, R2, R3).

Allometric models for estimating aboveground biomass of young Norway spruce trees in the Western Carpathians, Slovakia

Abstract In the period of climate change, it is necessary to have biomass models for trees of all sizes to make precise estimations of biomass forest stocks to quantify carbon sequestration by forest cover. Therefore, we created allometric models of aboveground biomass in young Norway spruce (Picea abies [L.] Karst.) trees including main components, i.e. stem, branches and needles. The models used 200 sampled trees from 10 sites located in the central part of the Western Carpathians in Slovakia. The models, i.e. allometric regression relations implemented stem base diameter (diameter d0) and/or tree height. Moreover, using the derived allometric relations and a constant annual diameter increment of 10 mm, we calculated quasi-annual aboveground biomass production with regard to diameter d0. While stem had the largest contribution to aboveground biomass, followed by needles and branches, a different situation was revealed for the annual aboveground biomass production with the largest share of needles followed by stem and branches. Finally, we implemented the allometric models in a specific forest stand, where repetitive measurements were performed within 14 consecutive years. The results showed for example nearly 650 kg of the aboveground biomass per 102 m2 at the stand age of 10 years. The new biomass models can be applied to estimate the aboveground biomass stock in Norway spruce dominating stands in the Western Carpathians. Since the models are based on both diameter d0 and tree height a user can choose which variable is more suitable for particular conditions.

Effects of Climate and Drought on Stem Diameter Growth of Urban Tree Species

Urbanization and climate change are two inevitable megatrends of this century. Knowledge about the growth responses of urban trees to climate is of utmost importance towards future management of green infrastructure with the aim of a sustainable provision of the environmental ecosystem services. Using tree-ring records, this study analyzed growth response to climate by stem diameter at breast height (DBH) of 1178 trees in seven large cities worldwide, including Aesculus hippocastanum L. in Munich; Platanus × hispanica Münchh. in Paris; Quercus nigra L. in Houston; Quercus robur L. in Cape Town; Robinia pseudoacacia L. in Santiago de Chile, Munich, and Würzburg; and Tilia cordata Mill. in Berlin, Munich, and Würzburg. Climate was characterized following the de Martonne aridity index (DMI). Overall, trees showed an 8.3% lower DBH under arid than humid climate at the age of 100. Drought-tolerant tree species were overall not affected by climate. However, R. pseudoacacia showed a lower diameter when growing in semi-dry than humid climate. In contrast, drought-sensitive tree species were negatively affected by arid climate. Moreover, the effect of drought years on annual diameter increment was assessed. P. × hispanica and R. pseudoacacia appeared as the most drought-resistant species. The highest sensitivity to drought was detected in T. cordata and Q. robur. A. hippocastanum and Q. nigra showed a lower diameter growth during drought events, followed by a fast recovery. This study’s findings may contribute to a better understanding of urban tree growth reactions to climate, aiming for sustainable planning and management of urban trees.

The Dynamics of Secondary Mangrove Forests in Bintuni Bay, West Papua after Harvested on the First 30-Year Rotation Cycle

Mangrove forests in Bintuni Bay, West Papua, Indonesia, have been managed for timber extraction since 1988 to produce wood chips using a 30-year rotation cycle. The first rotation cycle was completed, resulting in secondary mangrove forests with various stand ages (1–30 years). A large-scale forest inventory was conducted for all harvested blocks to recognize actual standing stock for the 2021–2030 management plan. A total of 434 quadrat plots (20 m x 20 m) covering 17.36 ha each were used to observe forest standing stock. The results present the dynamics of secondary mangrove forests after the initial rotation cycle. At the end of the first cycle (30-year-old stand), secondary mangrove forests provided a volume of 290.12 m3 ha-1 and potential extractable biomass of 203.03 ton ha-1 with mean diameter, basal area, and stem density of 16.91 cm, 29.18 m2 ha-1, and 1,370 stem ha-1, respectively. Annual increment of volume, biomass, and diameter were estimated to be 9.67 m3 ha-1 year-1, 6.77 ton ha-1 year-1, and 0.56 cm year-1, consecutively. The dynamics of secondary mangrove forests could provide significant information in the context of the management plan and implementation of the silviculture system to ensure the sustainability of utilization in managed mangrove forests. Keywords: Forest regeneration, Silviculture, Standing stock, Sustainable management, Timber utilization

PRUNING Araucaria angustifolia FOR KNOT-FREE TIMBER PRODUCTION

Although A. angustifolia is currently economically unimportant, the worldwide trend of conservation through the sustainable use of natural resources together with an intense discussion of governmental regulations and the recent results of genetic breeding started in the 1970s are delivering promising perspectives for a new wave of plantations. This study aimed to determine optimal pruning strategies by evaluating the diameter and height growth of young A. angustifolia trees as affected by different pruning intensities. Pruning quality in terms of occlusion and defect-core size were also investigated. At the age of 6 years, the pruning experiment was started by conducting six different pruning intensities, named after the number of whorls left after pruning (0, 2, 4, 6, and 8), as well as unpruned (U) trees as a control. From the results obtained in the present study, it was concluded that pruning intensity had a significant negative effect on the growth of young A. angustifolia trees. Diameter was more affected than height growth. Pruning young A. angustifolia trees for knotty-free timber production must be conducted keeping 8 whorls after the intervention if no negative effect in current annual increment in diameter is to be observed when compared to unpruned trees. A defect core of 15 cm seems to be a feasible target for the species regarding optimal pruning intensity to avoid losses in diameter growth. This is strongly dependent on a fast occlusion process, which, in turn, is a result of a careful pruning technique.

Evaluation of individual-tree growth models for Picea abies based on a case study of an uneven-sized stand in southern Sweden

ABSTRACT To develop recommendations for tree selection in Continuous Cover Forestry (CCF), access to valid tools for simulating growth at individual tree-level is necessary. To assist efforts to develop such tools, in this study, long-term observation data from two uneven-sized Norway spruce plots in southern Sweden are used to evaluate old and new individual-tree growth models (two established Swedish models, two new preliminary models and included as a reference, a Finnish model). The plots’ historical management records and site conditions are the same, but their last thinning treatment differs. Observed diameter increment at tree-level is investigated in relation to treatment. Individual tree growth residuals of tested models are evaluated in relation to tree diameter, treatment, projection length and sensitivity to the predictor mean stand age. Furthermore, the relations between displayed residuals and basal area local competition are analysed. The analyses indicate that active thinning made annual diameter increment independent of tree diameter above a threshold level, while the absence of thinning supported a concave relationship. All tested models displayed a significant linear bias leading to overestimation of small trees’ growth and increasing underestimations of larger trees’ growth with tree diameter. All distance-independent models displayed residual trends related to local competition.

Examining approaches for modeling individual tree growth response to thinning in Norway spruce

Using periodic measurements from permanent plots in non-thinned and thinned Norway spruce (Picea abies (L.) H. Karst.) stands in Norway, individual-tree growth models were developed to predict annual diameter increment, height increment, and height to crown base increment. Based on long-term data across a range of thinning regimes and stand conditions, alternative approaches for modeling response to treatment were assessed. Dynamic thinning response functions in the form of multiplicative modifiers that predict no effect at the time of thinning, a rapid increase followed by an early maximum before the effect gradually declines to zero could not be fitted to initially derived baseline models without thinning related predictors. However, alternative approaches were used and found to perform well. Specifically, indicator variables representing varying time periods after thinning were statistically significant and behaved in a robust manner as well as consistent with general expectations. In addition, they improved overall prediction accuracy when incorporated as fixed effects into the baseline models for diameter and height to crown base increment. Further, more simply, including exponentially decreasing multiplicative thinning response functions improved prediction accuracy for height increment and height to crown base increment. Irrespective of studied attribute and modelling approach, improvement in performance of these extended models was relatively limited when compared to the corresponding baseline models and more pronounced in trees from thinned stands. We conclude that the largely varying and often multi-year measurement intervals of the periodic data used in this study likely prevented the development of more sophisticated thinning response functions. However, based on the evaluation of the final models’ overall performance such complex response functions may not to be necessary to reliably predict individual tree growth after thinning for certain conditions or species, which should be further considered in future analyses of similar nature.

Individual-tree growth models for Sitka spruce (Picea sitchensis) in Iceland

Sitka spruce (Picea sitchensis) is one of the main tree species used in forestry in Iceland, growing well in all parts of the country. In view of the importance of Sitka spruce in Iceland, there is need for a reliable growth model that will support multifunctional forest management and planning. This study developed growth models for Sitka spruce using data from permanent sample plots established by the Icelandic Forest Service between 1970 and 2020. The measurement interval on the plots varied from 3 to 16 years. To deal with irregular measurement intervals, an optimization approach was used to recover models for annual diameter increment and survival rate. The aim was to find parameters for diameter increment and survival models that would minimize the difference between the measured and simulated diameter distributions of the plots at the end of the measurement interval (when the simulation begins from the diameter distribution at the beginning of the interval). To enable the simulation of stand development, models for dominant height development and tree height were also developed.

Analysis of growth and vitality class of Ulin (Eusideroxylon zwageri T. et B.) on Sempaja Arboretum East Kalimantan

The purpose of this study was to determine the growth and vitality class of Ulin stands after the age of 17 years at Sempaja Arboretum, Samarinda East Kalimantan. Collecting data by measuring all species of Ulin which were planted in the arboretum area of 2.5 ha covering diameter/circumference, tree height, and trunk condition in 2020. The growth analysis approach used individual tree increment calculations, while the vitality class and social dynamic assessment were based on the IUFRO classification. The results showed that in the arboretum Sempaja found 82 stems of Ulin which planted as a result of ex-situ conservation activities. The tree’s growth distribution after 17 years was wide both based on the diameter, namely 1.5-11.72 cm, and height, namely 2.4-16.21 m. Based on the mean annual diameter increment (MAId) is 0.09-0.69 cm. yr-1, the height increment (MAIh) is 0.14-0.95 m. yr-1 and volume increment (MAIvol) is 0.00002-0.006 m3.yr-1. The vitality value of Ulin was classified into three classes, meanwhile, the dynamic social was divided into two classes. Based on this assessment, the stand is dominated by trees with average growth and trees requiring maintenance in their development. These results provide input for the need for silvicultural maintenance for the Ulin stand, especially in the management of Sempaja arboretum.

Restoration of degraded forest reserves in Ghana

Deforestation in Ghana has led to a forest loss of almost 20% from 9,924,000 ha in 1990 to 7,986,000 ha today. To restore degraded lands, Forest Landscape Restoration has become a critical approach globally. This study was conducted in Ghana focusing on the examples of two forest landscape restoration projects in the Pamu Berekum Forest Reserve: 10-year-old mixed-stands of two to four native tree species and an exotic species stands, including Triplochiton scleroxylon, Terminalia ivorensis, Ceiba pentandra, Nauclea diderrichii and Cedrela odorata at Pamu Berekum 1 and 4-year-old Tectona grandis and 2-year-old Gmelina arborea monoculture stands at Pamu Berekum 2. Estimates of productivity in the restored forests are described, as well as the effects of the restoration on provision of ecosystem service and benefits obtained by local communities. Stand productivity was assessed as mean annual increment of diameter and height, biomass production, and standing volume. For ecosystem services, carbon stocks were calculated for the restored forests; other ecological benefits, as well as financial benefits, were obtained through interviews with fringe communities. The results indicate that FLR can be implemented successfully using different models provided that local communities are involved during the planning and implementation of interventions. When all stands were projected to 10 years, results show higher productivity in T. grandis (331.77 m3 ha-1) and G. arborea stands (1,785.99 m3ha-1) compared to mixed stand (160.41 m3 ha-1). The Gmelina arborea stand was more productive and had higher carbon stocks (1,350.10 Mg ha-1) relative to the T. grandis stand (159.89 Mg ha-1). Both restoration projects were found to deliver important benefits and ecosystem services at the local and national levels, including direct and indirect benefits. The results provide an example for forest/environmental managers on how FLR might be implemented to create multiple benefits at different levels from local communities to the national level. Thus, these results may be useful for guiding successful restoration activities within the context of the ongoing global Forest Landscape Restoration efforts.

The growth Shorea leprosula Miq. on various slopes and directions of slopes in Gunung Dahu Research Forest, Bogor

Shorea leprosula Miq is a Dipterocarps forest plantation that has the prospect of being developed because it is a fast-growing species with high economic value. Given its commercial importance, this study was conducted to analyze the effect of slope class and slope direction on growth. Data were collected using the census method on S.leprosula stands with a spacing of 2m x 2m and 4m x 8m. The direction of the slope is determined based on the configuration of the slope according to the cardinal directions, while the slope of the land is determined based on the classification of the slope class of the land. The results showed that the slope class, slope direction, and the interaction between factors had a significant effect on the growth of S.leprosula. The interaction between the slope class and the direction of the slope produces the highest average annual increment of diameter in the flat slope class with the direction of the slope facing north, which is 1.79 m / year while the highest annual increment of the total average height is in the very steep slope class with to the slope facing to the north at 0.82 m / year.

Growth modeling of Carapa guianensis and Tetragastris altissima for improved management in native forests in the Amazon

In forests of the Amazon biome, Sustainable Forest Management Plans are based on technical guidelines. Such legislation provides for a cutting cycle that can vary from 25 to 35 years and a minimum cutting diameter of 50 cm. In view of the above, the present research aimed to evaluate the accuracy of regression models for the projection of growth in diameter and to calculate the t by diametric class for trees of the species C. guianensis and T. altíssima. Four models with fixed effects were tested and best model was selected as the base model for the incorporation of random effects. The best fixed-effect model was Pienaar and Schiver. Thus, structures of variance and autocorrelation were added to this model to correct heteroscedasticity and autocorrelation. Finally, the time of passage for each species studied was calculated. The average annual increment in diameter estimated with the Pienaar and Schiver model with fixed effect was 0.38 cm.year−1 for C. guianensis and 0.46 cm.year−1 for T. altissima. Using the Pienaar and Schiver model with a random effect, the average annual diameter increase varied from 0.31 to 0.58 cm.year−1 for C. guianensis and from 0.37 to 0.65 mm.year−1 for T. altissima. Results showed that the estimated cutting cycle varied from 24 to 45 years for the species C. guianensis and from 21 to 38 years for the species T. altissima. Thus, using the cutting time of 25 to 35 years and a minimum cutting diameter of 50 cm for these species, can lead to incorrect decisions about the intensity of logging or the appropriate length of the cutting cycle. The growth and production models depict a synthesis of the growth dynamics of the forest, allowing to providing fundamental information for the definition of planning strategies, such as the establishment of a cutting cycle and an exploration intensity more compatible with the growth rate of the forest and for each species.

A review of kowhai (Sophora spp.) and its potential for commercial forestry

Background: Demand for imported sawn timbers in New Zealand has increased over the last decade, reflecting the lack of New Zealand-grown, naturally durable timber in the domestic market. Therefore, a market opportunity exists for sustainably grown, naturally durable timbers in New Zealand for specialty applications. Kowhai (Sophora spp.) are New Zealand native tree species, known for their bright, yellow flowers and reported to produce coloured, naturally durable heartwood.Methods: Information on kowhai was collated from literature, focusing on their potential for commercial forestry. The taxonomic relationships, species descriptions, establishment, and growth rates of kowhai were examined, along with timber properties and historical uses, as well as medicinal applications. The review identified potential market opportunities for kowhai and key areas for further research.Results: Kowhai refers to eight different Sophora species that are endemic to New Zealand. Kowhai is easily established and the different species hybridise readily. While growth and form of kowhai varies with species, site, and management, examples of straight single-stemmed trees and annual diameter increments exceeding 20 mm have been found. Kowhai timber properties might be comparable to those of teak (Tectona grandis L.f.). Kowhai contains alkaloids, a class of compounds used in pharmaceutical applications. The species have been used for timber and traditional medicine by Maori in the past, while European settlers used kowhai for their durable and flexible timber.Conclusions: Kowhai could be established as a sustainable, domestic source of high-quality timber and substitute imported specialty timbers in New Zealand on account of their natural durability, strength, stiffness, colour, and density properties. The residues could support a secondary industry, as a source of alkaloids for pharmaceutical applications or natural dyes. Key areas that require further study include growth rates and silviculture, mechanical timber properties, machining/processing characteristics, natural durability and cytisine levels in kowhai, as well as the cultural, economic, and ecological framework required for a commercial kowhai forestry industry. Lack of literature on, and expertise in the use of native timbers in general are barriers to promoting native species for commercial forestry in New Zealand.