Diffuse Reflectance Infrared Fourier Transform Spectroscopy (Drift) and Color Changes of Artificial Weathered Wood

Short-term (22.7 h) accelerated weathering was performed on black cherry (Prunus serotina), soft maple (Acer saccharinum), and red oak (Quercus rubra) using a 2-h ultraviolet (UV) light irradiation and 0.3-h water spray regime. Contributions to the wood surface color change from changes in lightness, chroma, and hue were observed, and variations existed among wood species. Chemical modifications on wood surfaces were monitored semi-quantitatively by using Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT). Band intensities at 1170 cm-1, 1510 cm-1, and 1740 cm-1 were used to follow the photodegradation on the wood surface during the 22.7-h accelerated weathering. Linear correlation was observed between the ratio of band intensity at 1740 cm-1 relative to the band intensity at 1170 cm-1, and the color change or the lightness modification. Results from this study clearly indicated that the rates of weathering/photodegradation of wood are influenced by wood species. Soft maple and red oak exhibit similar weathering rate (0.048) and higher than that of black cherry (0.031)

Developments in undergraduate wood science education at Stellenbosch University, South Africa

In South Africa, Stellenbosch University (SU) is the designated provider of Bachelor, Master and Doctorate level qualifications in Forestry and Wood Products Science. SU provides educational programs to both mechanical (sawmilling, preservation, composite products, furniture, etc.) and the chemical (pulp & paper) processing sectors. To ensure academic quality, SU regularly has her academic programs assessed externally. In 2000, several changes to the then existing 4 year B.Sc. Wood Science program were recommended. A restructured SU undergraduate program, similar to the B.Sc. Wood Products Processing program at the University of British Columbia (UBC), Vancouver, Canada, was consequently introduced in 2003. That same year, to provide more support to this effort, a partnership between UBC, SU and the Nelson Mandela Metropolitan University, the SA institution responsible for the National Diploma and Bachelor of Technology degrees in similar subjects, was established. The objective was to develop and deliver successful tertiary programs in value-added wood product processing education for South Africa and later, for other African countries as well. A Wood Products Processing Education Project, implemented in 2004 and running until mid 2010, funded by the respective partner institutions and the Canadian International Development Agency (CIDA) through the University Partnership in Cooperation and Development Program, was established. In addition to curriculum developments based on the UBC model, module content was modified to address relevant South African conditions. To make modules accessible to part-time students and members of industry off-campus, conversion of several Wood Products Science modules into e-learning format was implemented.A concise overview of Wood Science education at Stellenbosch University is given and the implementation and progress of the CIDA project at SU is briefly discussed. Solutions to the educational needs of the SA pulp & paper sector are also highlighted

Correlation between drying defects, their parameters and moisture gradient in kiln-dried, south african grown Eucalyptus Grandis poles

Non-destructive testing for drying defects in Eucalyptus grandis utility poles would be highly advantageous. These defects can negatively affect creosote preservative treatment and in-service performance. The objective of this study was to assess correlations between drying defects such as surface checking, honeycombing, collapse, their parameters and moisture content (MC) gradient in poles, to possibly find a simple and quick but reliable method to assess internal and external drying defects. Defects and moisture content gradients were measured in 39 kiln-dried E. grandis poles. After measuring surface check length, width and depth using a measuring tape, a ruler and a depth gauge, destructive sampling at the theoretical ground line (TGL) was done to measure the MC gradient between the shell and core of poles. Digital image analysis of cross-sections of discs cut at TGL was used to measure honeycomb check width, length and area, as well as counting individual closed surface checks. Collapse was assessed using qualitative methods. Results showed that honeycombing and collapse were positively, and surface checking and MC gradient were negatively correlated. Surface check width, length and depth were also correlated. Honeycomb count, check width, length and area were strongly correlated. It was concluded that measuring any of these surface check and/or honeycomb parameters may give meaningful deductions about the extent of surface checking and honeycombing respectively

The variation of microfibril angle in South African grown Pinus patula and its influence on the stiffness of structural lumber

Reduction in the rotation ages of softwood saw log plantations in South Africa is causing increased proportions of low stiffness sawn lumber at final harvest. It has been shown for some species that the microfibril angle (MFA) of the S2 layer of tracheids is strongly related to the modulus of elasticity (MOE) of wood, even more so than wood density, especially in wood formed during juvenile growth. The objectives of this study were to describe the variation in MFA in young Pinus patula trees and to determine the relationship between MFA and the dynamic MOE of sawn Pinus patula lumber. Thirty 16-20 year old trees from six compartments from the Mpumalanga escarpment were processed into discs and lumber. MFA, density and ring width were measured at two height levels using Silviscan 3. The average annual ring MFA varied between 7 o and 29o; the pattern of variation depending mainly on height level and the ring number from the pith. The MFA in P. patula followed the same within-tree variation trends as in New Zealand-grown Pinus radiata but the average MFA was lower in absolute terms and differences between height levels were less pronounced. MFA and density exhibited highly significant Pearson correlations of 0.73 and 0.70 respectively with board dynamic MOE. A multiple regression model, which included MFA, density and ring width, explained 71% of the variation in the dynamic MOE of boards. A sensitivity analysis on the model showed that MFA and density had approximately similar influences on predicting the dynamic MOE of Pinus patula boards.Sawmilling South Africa and the NRF’s THRIP programme.http://www.tandfonline.com/loi/tsfs202016-04-30hb201

The prediction of the flexural lumber properties from standing South African-grown Pinus patula trees

Pinus patula is the most intensively planted conifer in the tropics and subtropics. The increased proportion of corewood that results when rotation ages of pine plantations are shortened has become a wood quality factor of growing concern worldwide. The purpose of this study was to develop empirically based models for predicting the flexural properties of the wood produced from relatively young P. patula trees. Models were based on the properties of standing trees, and their effectiveness was evaluated at board, tree, and compartment levels. Sample material was obtained from 170 P. patula trees, 16–20 years old, established in 17 compartments on the Mpumalanga escarpment of South Africa. Multiple regression models were developed, which managed to explain 68, 60, and 95 % of the variation in the dynamic modulus of elasticity (MOE) on individual boards, trees, and compartments levels, respectively. At compartment level, 80 % of the variation in the 5th percentile MOR value could be explained by the model. Sensitivity analyses showed that site index at base age of 10 years, acoustic time of flight, wood density, and ring width were influential variables in the MOE models. The models indicated that tree slenderness during early growth seems to play a major role in determining the dynamic MOE and MOR of lumber. This is in agreement with Euler’s buckling theory and the bending stress theory. The results from this study indicated that the MOEdyn and MOR of lumber can be accurately predicted on especially a compartment level. The predictive models developed can be used as management tools to improve operational decisions around tree breeding, silvicultural practices, and rotation ages.Sawmilling South Africa, the South African National Research Foundation’s THRIP program and Komatiland Forests.http://link.springer.com/journal/103422016-01-30hj201

Chaos and crises in a model for cooperative hunting: A symbolic dynamics approach

In this work we investigate the population dynamics of cooperative hunting extending the McCann and Yodzis model for a three-species food chain system with a predator, a prey, and a resource species. The new model considers that a given fraction sigma of predators cooperates in prey's hunting, while the rest of the population 1-sigma hunts without cooperation. We use the theory of symbolic dynamics to study the topological entropy and the parameter space ordering of the kneading sequences associated with one-dimensional maps that reproduce significant aspects of the dynamics of the species under several degrees of cooperative hunting. Our model also allows us to investigate the so-called deterministic extinction via chaotic crisis and transient chaos in the framework of cooperative hunting. The symbolic sequences allow us to identify a critical boundary in the parameter spaces (K, C-0) and (K, sigma) which separates two scenarios: (i) all-species coexistence and (ii) predator's extinction via chaotic crisis. We show that the crisis value of the carrying capacity K-c decreases at increasing sigma, indicating that predator's populations with high degree of cooperative hunting are more sensitive to the chaotic crises. We also show that the control method of Dhamala and Lai [Phys. Rev. E 59, 1646 (1999)] can sustain the chaotic behavior after the crisis for systems with cooperative hunting. We finally analyze and quantify the inner structure of the target regions obtained with this control method for wider parameter values beyond the crisis, showing a power law dependence of the extinction transients on such critical parameters

Reproductive isolation between two populations of Aglaoctenus lagotis , a funnel-web wolf spider

Aglaoctenus lagotis (Lycosidae: Sosippinae) is a spider that, in contrast to the predominant wandering habit of the family, constructs funnel webs. The species is widely distributed throughout the Neotropics and is credited with high levels of intraspecific variation. Here, we evaluate whether reproductive isolating barriers operate between some populations of A. lagotis. We used heterotypic encounters between individuals from two distant localities: southern Uruguay (SU) and Central Argentina (CA). Additionally, we used spiders from an ntermediate locality, western Uruguay (WU), where both forms of the species overlap (SU.WU was used to describe individuals from WU reminiscent of those from SU; and CA.WU was used to describe individuals from WU reminiscent of those from CA). No copulations occurred between SU and CA individuals, whereas a single and atypical copulation occurred between SU.WU and CA.WU individuals. Attacks (only by females on males) were rare. In tests of choice based on silk cues, SU males did not prefer homotypic cues but almost did not court CA females, whereas CA males preferred homotypic cues but usually courted heterotypic females. These findings, with a previously reported temporal asynchrony between populations, suggest the occurrence of reproductive isolation between both spider forms and a speciation process favoured by the wide distribution and plasticity of the species.Fil: González Pérez, María de la Macarena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Diversidad Animal I; ArgentinaFil: Peretti, Alfredo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Diversidad Animal I; ArgentinaFil: Costa, Fernando G.. Instituto de Investigaciones Biológicas "Clemente Estable"; Urugua