Stiffness and checking of <Emphasis Type="Italic">Eucalyptus nitens</Emphasis> sawn boards: genetic variation and potential for genetic improvement

A trial was undertaken to assess the extent to which variation in sawn-board quality traits of plantation-grown Eucalyptus nitens is under genetic control and amenable to genetic improvement. Five hundred and sixty trees from 129 families and three central Victorian races were sampled from an open-pollinated progeny trial in Tasmania, Australia. Acoustic wave velocity (AWV) was assessed on standing trees and sawlogs. Wedges from disks extracted from sawlogs were assessed for basic density and checking. Processed boards from 496 of the trees were assessed for board stiffness (static modulus of elasticity, MOE), and internal and surface checking. Genetic differences among races were significant for AWV and MOE traits. The Southern race had the highest mean values for these traits. Significant additive genetic variation within races was observed in all traits, demonstrating that the quality of plantation-grown E. nitens boards could be improved through breeding. Estimated narrow-sense heritabilities were 0.85 for standing-tree AWV, 0.71 for log AWV, 0.37 for board MOE, and ranged from 0.20 to 0.52 for checking traits. A strongly positive genetic correlation (r _g = 1.05) was observed between standing-tree AWV and board MOE, indicating that AWV could be used as a selection trait to improve E. nitens board stiffness. The genetic correlation between basic density and board MOE was also positive (r _g = 0.62). However, a significant and adverse genetic correlation (r _g = 0.61) was identified between basic density and surface check length. Wood stiffness and checking traits were more-or-less genetically independent, and genetic correlations between surface and internal checking were positive but only moderate (r _g = 0.48–0.52).     

Control of matric water potential (ψm) in immobilised cultures of cyanobacteria

Abstract Three simple methods are described that permit cells of cyanobacteria, immobilised on filter supports, to be subjected to matric water stress that leads to a downshift in nitrogenase activity. In Nostoc commune , a desiccation-tolerant form, nitrogenase activity is more sensitive to water stress than the intracellular ATP pool. When it is dried rapidly to −99.5 MPa, nitrogenase activity ceases within 30 min while the ATP pool is maintained at 16.07 pmol ATP ·μg protein⁻¹. During short-term incubation, decreasing ψ _m from −0.10 to −23.1 MPa may result in an increased rate of CO₂ uptake.     

Interactive Effects of N Deposition, Land Management and Weather Patterns on Soil Solution Chemistry in a Scottish Alpine Heath

Nitrogen (N) deposition and land management practices can have profound impacts on the structure and functioning of alpine ecosystems occupying headwaters of major river systems. Such impacts have the potential to result in loss of N to surface waters and acidification, both of which could have serious consequences for water quality and downstream habitats. We present results from a 6-year study of Calluna-dominated alpine heathland in Scotland, designed to assess the interactive effects of N addition (0 and 50 kg N ha^?1 y^?l), simulated accidental fire and grazing on soil solution chemistry. Both N addition and to a lesser extent burning had significant effects on soil solution chemistry, whereas grazing had no significant impact. Soil solution nitrate (NO₃ ^?) and ammonium (NH₄ ⁺) concentration showed a rapid response to N addition and N addition also resulted in acidification of soil solution. A ‘flush’ of base cations, which normally buffer soil from the acid effects of deposited N, accompanied the excess N released from the soil to soil solution. The N treatment had no effect on dissolved organic carbon (DOC), however, concentrations were significantly (14%) lower at the burned plots. In addition to treatment effects, temporal analysis of data from control plots demonstrated that soil solution chemistry was influenced by extremes in weather conditions. Peak NO₃ ^? concentrations were observed in soil solution following the cold winter of 2000–2001 when there were frequent freeze/thaw events. A large pulse of base cations was lost from the soil following the dry year of 2003. These weather-induced responses potentially exacerbate the treatment effects observed in this study.     

How do animal territories form and change? Lessons from 20 years of mechanistic modelling

Territory formation is ubiquitous throughout the animal kingdom. At the individual level, various behaviours attempt to exclude conspecifics from regions of space. At the population level, animals often segregate into distinct territorial areas. Consequently, it should be possible to derive territorial patterns from the underlying behavioural processes of animal movements and interactions. Such derivations are an important element in the development of an ecological theory that can predict the effects of changing conditions on territorial populations. Here, we review the approaches developed over the past 20 years or so, which go under the umbrella of ‘mechanistic territorial models’. We detail the two main strands to this research: partial differential equations and individual-based approaches, showing what each has offered to our understanding of territoriality and how they can be unified. We explain how they are related to other approaches to studying territories and home ranges, and point towards possible future directions.     

Rare British marine fishes-identification and conservation

Methods of recording and categorizing rare British marine fishes and their habitats are described. Information is stored on a database designed for maximum flexibility, cross-referencing, multiple word search and key word search facilities. Examples are given and discussed in relation to species and habitat protection.     

Fluorescence spectroscopy of 9-anthroyloxy fatty acids in solvents

A series of anthroyloxy fatty acid (AF) fluorescent probes, with the anthroyloxy group covalently linked at various positions along the alkyl chain, were studied in solvents exhibiting a wide range of polarity and hydrogen-bond donor (H_d) and acceptor (H_a) ability. These probes were sensitive to the solvent polarity as reflected by the Stokes' shift observed in steady state fluorescence. As determined by multi-linear regression analysis of the observed Stokes' shift and solvent parameters, such as orientation polarizability (Δf), H_d and H_a of the solvents, all the probes were sensitive to the H_d of solvents but were not affected by the H_a of solvents except the 2-AF. Due to the proximity of the polar headgroup to the fluorophore, it appears that some intramolecular hydrogen-bonding is present in 2-AF, an interaction that is sensitive to the pH of the solvent, but is less sensitive to the H_d and H_a of the solvents. Fluorescence lifetimes measured by the multi-frequency phase-modulation technique in mixtures of hexane and ethanol reflect a modified Stern-Volmer behavior suggesting the second solvent, ethanol, specifically interacts with the probe, in part through collisional quenching. Also, the lifetime data were sensitive to very low concentrations of the second solvent (0–0.1%, by vol.). The results from this study provide insight into the intrinsic differences between the different AF positions that must be taken into consideration while investigating the dynamics of lipid bilayer systems. Moreover, this study illustrates the utility and resolving power of lifetime based measurements needed for the interpretation of heterogeneous biophysical environments.