Prioritising sites for pollinators in a fragmented coastal nectar habitat network in Western Europe

Landscape Ecology - Habitat loss and fragmentation contribute significantly to pollinator decline and biodiversity loss globally. Conserving high quality habitats whilst restoring and connecting...     

The frictional behaviour of wood

Summary The work described was primarily concerned with determining the more important variables affecting friction between wood and steel, but friction between wood and non-ferrous materials including wood itself was also investigated briefly. Deviations from the classical laws of friction were of interest, the most significant being variation of friction coefficient with sliding speed. With an increase in sliding speed up to 4 m/sec the curves for highly polished steel showed undulations, but with unpolished surfaces there was a monotonic reduction, somewhat greater in wet wood than dry. Other important factors, interacting with sliding speed, were steel roughness and wood moisture content. Effects of load, nominal contact area and fibre direction were minor. The results appear to be adequately explained in terms of adhesion and lubrication.A world wide selection of species was tested, and it appears that the nature and amount of extractives in most woods is such that they have similar friction coefficients except on very smooth steel, and only a few greasy species, have significantly lower coefficients. For most air-dry wood in contact with unpolished steel, the coefficient decreases from a static value about 0.65 to a value about 0.4 at 4 m/sec. For wet wood, the corresponding values are about 0.7 and 0.15.Coefficients of friction between wood and wood were similar to those between wood and rough steel, and those between wood and other materials varied in a manner which may be related to strength of adhesion.

---

Zusammenfassung Die ursprüngliche Zielsetzung der Arbeit, die Untersuchung der wesentlichen Einflußgrößen auf die Reibung zwischen Holz und Stahl wurde durch Einbeziehung von Nichteisen-Metallen und der Reibung zwischen Holz und Holz erwitert. Als bemerkenswert stellten sich die Abweichungen von den klassischen Reibungsgesetzen heraus, am auffallendsten die Änderung der Reibung mit der Vorschubgeschwindigkeit. Beim Anstieg der Vorschubgeschwindigkeit bis zu 4 m/s zeigten die Kurven für hochglanzpolierten Stahl Unstetigkeiten, während bei unpoliertem Stahl ein gleichförmiger Abfall eintrat, der bei nassem Holz etwas größer war als bei trockenem. Weitere wichtige Einflußgrößen waren Stahlart und Holzfeuchtigkeit. Die Wirkungen von Normaldruck, Kontaktfläche und Faserrichtung waren von untergeordneter Bedeutung. Die erzielten Ergebnisse lassen sich in etwa gleicher Weise durch Begriffe aus den Gebieten der Adhäsion oder der Schmierung beschreiben.Es wurde angestrebt, möglichst alle wichtigen Holzarten der Welt zu erfassen. Man kann sagen, daß die Inhaltsstoffe der meisten Hölzer nach Art und Menge zu ziemlich ähnlichen Reibungskoeffizienten führen, ausgenommen bei sehr glatten Stahlarten. Nur wenige fetthaltige Holzarten weisen deutlich niedrigere Reibungskoeffizienten auf. Für lufttrockenes Holz und unpolierten Stahl fällt der Koeffizient von 0,65 für Haftreibung auf 0,40 für gleitende Reibung bei 4 m/s Vorschubgeschwindigkeit. Bei nassem Holz lauten die entsprechenden Werte 0,70 und 0,15. Die Reibungskoeffizienten zwischen Holz und Holz waren ähnlich denen zwischen Holz und rauhem Stahl; diejenigen zwischen Holz und anderen Materialien variierten so, daß ein Zusammenhang mit den Adhäsionskräften anzunehmen ist.

     

Movement and habitat use of the freshwater catfish (Tandanus tandanus) in a remnant floodplain wetland

Knowledge of the movement and habitat use of fishes is important in identifying and understanding the causes of population declines and predicting how populations are likely to respond to management interventions. In this study, radiotelemetry was used to examine the spring and summer movement and habitat use patterns of the freshwater catfish (Tandanus tandanus) in a remnant wetland to inform the development of recovery actions for this threatened species. Twenty‐one adult fish were tagged and released within Tahbilk Lagoon, Victoria, Australia, in September 2009. Fish were located every 1–2 weeks between September 2009 and February 2010, a period which coincides with the spawning period for the species. Eleven of the fish were also tracked every 2 h for 68 consecutive hours in December 2009 to examine diel movements. The study revealed that freshwater catfish make extensive use of cover (e.g. wood and macrophytes) and typically have limited ranges (median total linear range and 90% linear range 599 and 173 m respectively), although they occasionally moved more extensively (up to 1.5 km) between floodplain and riverine habitats. Fish moved over much greater areas at night compared with during the day. There was also evidence of sex‐specific variation in movement, with a trend for greater movement of female fish at night compared with males. The results of the study suggest that strategies that protect macrophyte and wood habitats and improve connectivity between riverine and floodplain habitats are likely to be important in maintaining and restoring remnant populations of this species.     

Norsesquiterpene glycosides in bracken ferns (Pteridium esculentum and Pteridium aquilinum subsp. wightianum) from Eastern Australia: reassessed poisoning risk to animals

Austral bracken Pteridium esculentum contains three unstable norsesquiterpene glycosides: ptaquiloside, ptesculentoside, and caudatoside, in variable proportions. The concentration of each of the glycosides was determined in this study as their respective degradation products, pterosin B, pterosin G and pterosin A, by HPLC-UV analysis. Samples of P. esculentum collected from six sites in eastern Australia contained up to 17 mg of total glycoside/g DW, with both ptaquiloside and ptesculentoside present as major components accompanied by smaller amounts of caudatoside. Ratios of ptaquiloside to ptesculentoside varied from 1:3 to 4:3, but in all Australian samples ptesculentoside was a significant component. This profile differed substantially from that of P. esculentum from New Zealand, which contained only small amounts of both ptesculentoside and caudatoside, with ptaquiloside as the dominant component. A similar profile with ptaquiloside as the dominant glycoside was obtained for Pteridium aquilinum subsp. wightianum (previously P. revolutum ) from northern Queensland and also P. aquilinum from European sources. Ptesculentoside has chemical reactivity similar to that of ptaquiloside and presumably biological activity similar to that of this potent carcinogen. The presence of this additional reactive glycoside in Australian P. esculentum implies greater toxicity for consuming animals than previously estimated from ptaquiloside content alone.     

Selecting representative reserve systems in remote areas: A case study in the Nullarbor region, Australia

We present a procedure for the selection of a network of reserves representing the biological diversity of a large and biologically poorly known region. The quantitative analysis gives equal weighting to a wide array of different species: mobile and sessile, long-lived and ephemeral, heterothermic and homeothermic, etc.

Sampling was based on quadrats that were positioned through the region using a stratified random strategy. This provided a presence-absence matrix of the species composition at each quadrat. Numerical pattern analysis was used to identify 14 species assemblages and to re-order the sites and species in the data matrix. The geographic pattern of each assemblage throughout the region was described by contouring assemblage richness, the isolines being the proportion of the number of species in each assemblage. The data matrix was re-examined. Some assemblages exhibit several gradients in species composition. For example, a 0·1 isoline in the east may represent a different 10% of species than a 0·1 isoline in the west. Other assemblages exhibit only a single gradient in species composition.

The results were used to select the optimum positions of reserves needed to represent the compositional diversity of each of the 14 species assemblages.

Limited field checking confirmed the predicted isolines in assemblage compositional richness to a satisfactory extent.     

Amelioration of a hardsetting Alfisol through deep mouldboard ploughing, gypsum application and double cropping. I. Soil physical and chemical properties

Contrasting soil management techniques were applied to a hardsetting red-brown earth (Alfisol) used for flood-irrigated wheat (Triticum aestivum) production at Trangie, N.S.W., Australia. The individual and combined effects of deep mouldboard ploughing to a depth of 0.45 m, gypsum application (5 t ha⁻¹) and double cropping upon aggregate stability, bulk density, porosity, cone index and the non-limiting water range were evaluated. Dispersion and slaking of the surface soil were unaffected by the treatments when measured at the end of the second year of the experiment. Approximately 60% of the soil mass in the 0–0.15 m layer slaked on wetting, whereas less than 1% of the soil dispersed. Organic carbon (OC) levels of the surface soil were not affected by double cropping or gypsum application, but were reduced by mouldboard ploughing from 0.9% to 0.6% OC. The relationship between OC and macroaggregate (more than 250 μm) stability indicated that large increases in OC beyond 0.7% OC were required for relatively small increases in aggregate stability. Mouldboard ploughing increased clay content of the upper 0.15 m of the soil from 22% to 27%. This was associated with an increase in the frequency and depth of cracking which, however, diminished over time. The non-limiting water range (NLWR) was expanded in the uppermost 0.1 m by gypsum application from 0.15–0.30 to 0.09–0.28 m³ m⁻³. Mouldboard ploughing expanded the NLWR at a depth of 0.2 m. Penetrometer resistance, on average, exceeded the critical value for wheat root growth at a water content of 0.15 m³ m⁻³, which is substantially higher than the wilting point (0.09 m³ m⁻³). Excessive resistance to penetration as opposed to inadequate aeration or water availability is the main agronomic impediment in these soils, at least in the initial stages of crop development. Penetration resistance within the 0.05–0.3 m layer was reduced during a drying cycle in the order: mouldboard ploughing>gypsum>double cropping. The reduced penetration resistance associated with mouldboard ploughing was due to higher water content to a depth of 0.2 m and reduced bulk density below this depth.     

Amelioration of a hardsetting Alfisol through deep mouldboard ploughing, gypsum application and double cropping. III. Crop production and profitability

Deep mouldoard ploughing to 0.45 m, gypsum application (5 t ha⁻¹), and double cropping were evaluated, alone and combined, as ameliorants for a hardsetting red-brown earth (Alfisol). The double cropped treatment consisted of winter wheat (Triticum aestivum) and a summer forage crop consisting of sudax (Sorghum sudanese) intersown with cowpea (Vigna unguiculata). This paper describes the effect of these treatments on crop development, yield, crop-water relations and economic returns. Crop emergence was not affected by any treatment. Mouldboard ploughing significantly increased wheat grain yield from 1.86 to 2.15 t ha⁻¹, in 1984, but not in 1985. Yield was also increased from 5.18 to 5.68 t ha⁻¹ as a result of gypsum addition in 1985—after no significant difference in 1984. Double cropping significantly increased yield (by 0.6 t ha⁻¹) in 1985. Greater increases were obtained with the summer cropping phase where higher evaporative demand during the summer would have aggravated soil structural problems associated with hardsetting. Sudax-cowpea dry matter yields were increased from 13.6 to 17 t ha⁻¹ and from 13.0 to 17.5 t ha⁻¹ during summer 1984–1985 by gypsum and mouldboard ploughing, respectively. The higher yields are attributed to increased water storage and depletion, and reduced soil strength for the mouldboard ploughed and gypsum main treatments. No interactions were found between the main treatments, except at the end of the 1985 winter cropping phase when there was a negative interaction between mouldboard ploughing and gypsum application for dry matter, equivalent root length and yield. The yield increases associated with mouldboard ploughing did not persist beyond the second year of the experiment. Double cropping combined with mouldboard ploughing (Mb+DC) was the most profitable treatment, whereas mouldboard ploughing with gypsum (Mb+G) was the least profitable for the crops grown in this experiment.     

Evidence from tag recapture experiments that fish learn to avoid fishing gear

We found evidence that tagging induced trap shyness in snapper (Pagrus auratus), i.e., tagged fish had a reduced probability of recapture by the method by which they had originally been caught. Tagging experiments in 1985 and 1994 involving single release over a short period and single recapture were conducted on a closed population (SNA 1: East Northland-Hauraki Gulf-Bay of Plenty). Initial capture was by trawling and by line fishing, while recapture over an extended period included other methods. A test for trap shyness that removed the possible effects of spatial and fish size heterogeneity gave a significant result for both years. The data suggested that the trap shyness effect might have been smaller for trawl-released fish than for line-released fish. However, we estimated a single trap shyness factor (0.71). There was also some evidence for attenuation of trap shyness over time.     

Axial pressures generated by the earthworm Aporrectodea rosea

Summary The axial forces generated by the earthworm Aporrectodea rosea were measured by directing the earthworm to tunnel into soil discs mounted on an electronic balance connected to a datalogger. The area over which the force acted was estimated from the size of the hole created by the tunnelling. The maximum force recorded by an individual worm was 0.760 N and the mean maximum value was 0.465 N. The maximum pressures recorded was 116.5 kPa, while the mean maximum pressure was 72.8 kPa. These axial pressures are approximately one-tenth of the maximum axial pressure recorded for plant roots. The statistical distribution of activity as the worms tunnelled through the soil discs was analysed. Pressures recorded were well in excess of physiologically measured pressures and the generation of forces within muscles to achieve these pressures was calculated by some assumptions. It was estimated that there is a maximum tension in the circular muscles of 0.15 N per segment of the worm.     

Lead, cadmium, and fluoride levels in market milk and infant formulas in Canada

Lead, cadmium, and fluoride were determined in 68 samples of market milk and about 115 infant formulas. Mean and median levels (ranges) in ng/g found for cow milk were as follows: lead, 1.12, 1.19 (0.01-2.48); cadmium, 0.10, 0.039 (0.005-0.74); and fluoride, 41, 40 (7-86). In canned, ready-to-use formulas, lead, cadmium, and fluoride levels averaged 37.3, 1.50, and 840 ng/g, respectively. In concentrated liquid formulas, the respective levels were 21, 3.54, and 600 ng/g. In powder formula concentrates, respective levels were 73.7, 6.78, and 1130 ng/g. On the basis of this study and literature data, lead levels in market milk exceeding 5 ng/g appeared to signify contamination of the milk either directly or via the cow. For formulas considered on an as-consumed basis, lead levels exceeding about 10-15 ng/g were attributed to contamination from either the can used to store the formula or the formula ingredients. Infant formulas in lead-free cans contained about 1.7 ng/g of lead on a ready-to-use basis. Milk-based formulas contained about 0.26 ng/g of cadmium on a ready-to-use basis. Soy-based or milk-free formulas contained about 8-15 times more cadmium than did milk-based formulas. Canadian and U.S. ready-to-use formulas contained 900 and 230 ng/g fluoride, respectively, and this difference was attributed to the level of fluoride in the processing water used by the manufacturers.