Fiber- and fine fractions-derived effects on pulp quality as a result of mechanical pulp refining consistency

High-yield pulping of wood chips using low-consistency (LC) refining in combination with primary-stage high-consistency (HC) refining has previously been shown to produce paper with quality parameters (tensile strength and light-scattering coefficient) commonly targeted for newsprint with significantly less refining energy input than using only HC refining. However, questions remain on the differences in the refining action between the two refiner types and for high-yield pulping, the refiner energy demand is a crucial process parameter. Therefore, fines- and fiber-fraction development in HC and LC refining has been studied in detail using Bauer-McNett fractionation, and the respective tensile strengths of the different fractions have been compared. Quantitative and qualitative (morphological) characteristics of the isolated fine fractions have also been analyzed in detail using a newly developed automated fluorescence microscopy method and scanning electron microscopy. The results suggest the difference in LC/HC pulp properties (strength and optical) is partly derived from deviating fiber and fines morphologies and mass balances. The quality of the fines generated during HC and LC refining also differs. LC-refined pulps contain thinner fibrillar fines (thread-like) and HC-refined pulps broader fibrils such as lamellae-type fines. Flake-like fines from the outer fiber wall decreased in relative amount with energy input.     

Growth and yield of coffee plants in agroforestry and monoculture systems in Minas Gerais, Brazil

This research compared coffee plants (Coffea arabica L.) grown in an agroforestry and monoculture systems. Data were collected during two years, on vegetative growth, reproductive development, nutritional status and yield of coffee, besides monitoring air temperature and the tree growth. All trees in agroforestry system increased in growth, resulting in a reduction in the magnitude of the diurnal temperature variation and also maximum temperature. Coffee plants in agroforestry system had less branch growth and leaf production, more persistent and larger leaves, and presented earlier flowering, with a smaller number of productive nodes and flower buds, leading to smaller berry yield than plants in monoculture system. In both systems, the coffee plants showed adequate leaf nutrient levels, except for P and K. The yield of 2443 kg ha^-1 of coffee from the monoculture was greater than 515 kg ha^-1 of coffee from the agroforestry system.     

Characteristics of sugar maple wood surfaces machined with the fixed-oblique knife pressure-bar cutting system

Oblique cutting differs from orthogonal cutting by an inclination given to the knife edge, which induces several changes on tool geometry, cutting forces, as well as on the quality of machined surfaces. In this work, a pressure bar was used during oblique cutting to reduce the occurrence of torn grain. The effects of cutting depth, rake angle, and oblique angle on cutting forces and surface quality were studied. Surface topography, cell damage and wetting properties were used to assess surface quality. All force components were increased by increasing cutting depth and decreasing rake and oblique angles. The lateral force, however, increased as the oblique angle increased. The surface roughness increased with increasing the lateral cutting force. Higher cutting depths and oblique angles tended to provide higher surface roughness, while higher rake angles tended to reduce surface roughness. The pressure bar was not always able to completely prevent the occurrence of defects when cutting against the grain. The occurrence of machining defects increased at higher cutting depths and oblique angles. As the rake angle decreased, the type of machining defect tended to change from torn grain to slight fuzzy grain. Moreover, the best wetting properties were obtained at lower rake angles, as they induced higher surface roughness. A 25° rake angle, a 30° oblique angle, and thinner cutting depths should be preferred to reduce dependence on ulterior sanding.     

Merchantable volume system for pedunculate oak in northwestern Spain

A model is required for accurate estimation of the merchantable volume of pedunculate oak (Quercus robur L.) trees in Galicia, northwestern Spain. Accordingly, the purpose of the present study was to obtain equations for predicting merchantable volumes and stem profiles of individual trees. For this reason, two compatible and four non-compatible volume systems were initially evaluated and fitted to data from 251 destructively sampled trees which were collected in stands located throughout the area of distribution of the species in Galicia. The outliers were removed to provide a data set of measurements from 3 090 sections, which was then available for fitting. A second-order continuous autoregressive error structure was used to account for autocorrelation. Comparison of the models was carried out using overall goodness-of-fit statistics and box plots of residuals against relative height or diameter class. The compatible volume system of Fang et al. [22] provided the best compromise in describing the stem profile and estimating merchantable height, merchantable volume and total volume and is therefore recommended for pedunculate oak stands in Galicia.     

Multiple-use forest planning model for second-growth forests of roble–raulí–coihue (genus <Emphasis Type="Italic">Nothofagus</Emphasis>)

Second-growth natural forests of roble–raulí–coihue are an important resource that must be managed from a multiple-use perspective. The objective of this work is to develop a thinning and harvest scheduling model for this type of forests aiming at maximizing profit while maintaining areas with minimum levels of biodiversity and landscape protection. The proposed model is based on a linear programming approach and incorporates constraints on timber yield flow and biodiversity levels as well as on clearcutting in high visibility areas. The evolution of forest diversity along the planning horizon has been modeled and both biodiversity and landscape indicators have been calculated. The model allows for the assessment of the physical and economic effects of management decisions, providing optimal resource allocation solutions for different scenarios and marginal values both for the land resource and for activities, such as biodiversity conservation or landscape protection, leading to the provision of non-market outputs.     

Characterizing the setting of cement when mixed with cork, blue gum, or maritime pine, grown in Portugal II: X-ray diffraction and differential thermal analyzes

It is already known by the scientific and industrial communities that lignocellulosic substrates are, to a certain extent, inhibitors of the hydration reaction of cement. The extent to which and how they influence such reactions is still a matter of debate. Several techniques, such as calorimetry, i.e., the measurement of the heat evolved or obtaining temperature profiles during the hydration, the determination of extractive contents of lignocellulosic substrates and their relation with the characteristics of the hydration curves, or even testing of the mechanical properties of the wood-cement composites, have been used in previous research. This study complements past research using two techniques that have been used in the analysis of cement hydration but are not usually applied to lignocellulose-cement mixes, namely X-ray diffraction (XRD) and differential thermal analysis (DTA). The raw materials for this study were three lignocellulosic materials of Portuguese origin: cork (the bark of Quercus suber L.), blue gum (Eucalyptus globulus Labill.), and maritime pine (Pinus pinaster Ait); and Portland cement. The two techniques allowed tracking of the evolution of the main cement constituents during hydration. It was found that all the lignocellulosic substrates had detrimental effects on cement hydration. The blue gum exhibited the fastest hydration kinetics in the initial stage of reaction, but was then overtaken by cork, which at the end gave the highest hydration conversion amongst the three lignocellulosic substrates. Although pine caused the slowest initial hydration kinetics, with the passage of time its effect approached that of blue gum. At the end of the hydration period, specimens containing either species had similar quantities of hydration reaction products. The DTA and XRD results were consistent and are in good agreement with the temperature profiles and compatibility indexes reported in a previous work.     

Population dynamic and management of <Emphasis Type="Italic">Pinus oocarpa</Emphasis> and <Emphasis Type="Italic">Tabebuia rosea</Emphasis> within silvopastoral systems in Central America

Silvopastoral systems—the management of trees within pastures from natural regeneration or planting—are a strategy to promote sustainable livestock systems and ecosystems services. Timber is one of the products from these systems with potential to increase family revenues. The management of natural regeneration and population dynamics of trees is a feasible way to harvest timber and maintain environmental services. In this research, we modeled the population dynamics of Pinus oocarpa and Tabebuia rosea, two important timber species of silvopastoral systems in Central America. The results showed that farmers manage a significant density of different tree species from natural regeneration. However, only the species with well-known uses or desired services are allowed to remain. The natural regeneration is more impressive in silvopastoral systems with natural grass than those with exotic grass. Farming practices, for instance use of fire for weed control, are the main reasons for low rates of natural regeneration in pastures with exotic grass. The models of population dynamics for both species showed that the sustainable timber harvest plans are a viable activity in pasturelands under natural-regeneration management plans. Innovative farmers are willing to adopt silvicultural practices and management of population dynamics to increase timber revenues and sustainability if forestry regulations for sustainable use of trees in farms are simplified.     

The decreased competition in expanding versus mature juniper woodlands is counteracted by adverse climatic effects on growth

World-wide deforestation is being reversed in Mediterranean continental areas, where abandonment of traditional practises favours the expansion of valuable habitats, like Juniperus thurifera woodlands. We hypothesised that pre-existing trees facilitate establishment in expanding woodlands, whereas in mature woodlands, competition leads to patch disaggregation. We compared the imprint of these processes on growth, demographic and spatial structure of expanding and mature J. thurifera woodlands. We selected plots where we geopositioned, aged and quantified the morphological characteristics of all trees. In the mature woodland, trees arranged in clumps and randomly in the expanding woodland. Competition negatively affected growth, was greater in the mature woodland and led to disaggregation of juvenile clumps. Differences in growth between the mature and the expanding woodland disappeared in climatically unfavourable years, suggesting that adverse climate constrains growth more in expanding than in mature woodlands. We suggest that change in the dispersal agents and a decrease of facilitation underlay differences in spatial patters between the expanding and the mature woodland. Observed effective recruitment in less than 30?years into the expanding woodland evidenced that propagule arrival and sapling survival do not constrain woodland expansion. Furthermore, growth of juveniles established in these new areas is favoured by reduced intra-specific competition. However, we expect growth in expanding woodlands to be negatively impacted by climate change. We conclude that under current global change scenario, conservation of J. thurifera woodlands is favoured by changes in land use, but greater frequency and severity of drier than usual episodes could hamper natural reforestation.     

Evaluating the behaviour of vertical structure indices in Scots pine forests

? Stand structure indices would appear to be good surrogate measures for biodiversity in forest ecosystems.

? The vertical structure of Pinus sylvestris L. stands in Central Spain was analysed in order to evaluate their structural diversity. A comparison between two forests with similar ecological conditions but managed under different silvicultural systems was conducted in order to analyse changes in diversity at different stages of stand development. Height diversity was quantified using two non-spatially explicit indices (Shannon’s index and STVI) as well as two spatially explicit indices (Gadow’s differentiation index and the Structure complexity index). A new diversity index was then proposed, based on the sum of square roots of height differences (SQRI).

? Correlations between all vertical structure indices were highly significant. All indices showed that height diversity was greater in the forest with the longer regeneration period and where less intensive thinnings were applied throughout the rotation. Diversity was highest in uneven-aged stands and in the period between the regeneration stage and the first thinning. Thinning from below accounted for the decrease in vertical structure complexity throughout the rotation in even-aged stands.

? The results show that height distribution along with successional stage data enhance the analysis of vertical diversity since structural complexity is highly related to the silvicultural practices that are carried out at different ages.