Showing papers by "Swedish University of Agricultural Sciences published in 1989"
TL;DR: The protein resembles other cell-wall-associated proteins on Gram-positive bacteria in that it appears to be anchored in the cell membrane via its C-terminal end, and contains a proline-rich repeating unit outside the membrane anchor.
Abstract: Binding of cells of Staphylococcus aureus to fibronectin, which may represent a mechanism of host tissue adherence, involves a fibronectin-receptor protein present on the bacterial surface. Cloning of a gene coding for a staphylococcal fibronectin-binding protein and construction of a fusion protein with fibronectin-binding properties was previously reported from our laboratory. We have now sequenced the gene and deduced a primary sequence of the fibronectin-binding protein. The protein resembles other cell-wall-associated proteins on Gram-positive bacteria in that it (i) appears to be anchored in the cell membrane via its C-terminal end, (ii) contains a proline-rich repeating unit outside the membrane anchor, and (iii) contains a long (36-amino acid) signal sequence at the N terminus. The fibronectin-binding activity has been localized to a domain composed of a 38-amino acid unit repeated completely three times and partially a fourth time; the identity between the three 38-amino acid sequences varies from 42 to 87%. Three synthetic peptides mimicking the structure of each 38-amino acid unit were constructed. All three peptides interacted with fibronectin, as indicated by their ability to inhibit binding of fibronectin to staphylococcal cells, whereas an unrelated 37-amino acid peptide showed no inhibitory activity.
415 citations
TL;DR: A method to screen lactobacilli for production of unique antimicrobial substances and the discovery of reuterin is described, capable of inhibiting growth of species representing all bacterial genera tested thus far.
Abstract: Lactobacillus reuteri resides in the gastrointestinal tract of humans, swine, poultry and other animals. Resting cells of this species convert glycerol into a potent, broad-spectrum antimicrobial substance termed reuterin. Reuterin is a low molecular weight, neutral, water soluble compound, capable of inhibiting growth of species representing all bacterial genera tested thus far, including: Escherichia, Salmonella, Shigella, Proteus, Pseudomonas, Clostridium and Staphylococcus. Also affected, but to a lesser degree, are lactic acid bacteria belonging to the genera Streptococcus, Pediococcus, Leuconostoc, and Lactobacillus. In this report we describe a method to screen lactobacilli for production of unique antimicrobial substances and the discovery of reuterin.
318 citations
TL;DR: In the case of private goods, individuals reveal their preferences in the market place as discussed by the authors, but no similar market mechanism exists in public goods, and therefore it is difficult to compute the average willingness to pay when only yes and no responses are available.
Abstract: In the case of private goods, individuals reveal their preferences in the market place. No similar market mechanism exists in the case of public goods. However, one obvious possibility is to ask people about their maximal willingness to pay for public goods or government expenditure (Johansson 1987, 1990, Miller). In some recent contingent market valuation studies people instead have been asked to accept or reject a specified amount of money for a change in the provision of a public good; different subsamples are confronted with different "bids." The resulting "yes" and "no" responses usually are analyzed by logit or probit techniques (e.g., Johansson and Kristrom). This raises the question of how to compute the average willingness to pay when only yes and no responses are available. This point was advanced by Hanemann in his seminal 1984 paper on welfare evaluations with discrete responses; see also Hanemann (1987). However, we believe a minor imperfection in Hanemann's presentation may confuse and mislead practitioners. Hanemann's approach assumes that negative bids cannot occur but at the same time gives the impression that it also applies to models that allow for negative bids. We also extend Hanemann's discussion of the choice of money measure in cost-benefit analysis.
312 citations
TL;DR: In vitro investigations revealed that the enzyme preparation solubilized pentosans, increasing the relative viscosity of buffer extracts from enzyme-supplemented diets, which probably was primarily responsible for the observed improvements in digestibility and production results.
Abstract: A total of 360 1-d-old broiler chickens were fed on a diet based on rye and wheat in equal proportions without or with supplementation of increasing levels (0.11, 0.22, 0.44 and 0.88 g/kg) of a technical enzyme preparation containing pentosanase and beta-glucanase activities. In vitro investigations revealed that the enzyme preparation solubilized pentosans, increasing the relative viscosity of buffer extracts from enzyme-supplemented diets. Enzyme supplementation generally improved body-weight by approximately 27% at day 15 and 15% at day 27, increased feed intake by 15 and 8% respectively, and improved feed conversion efficiency by 10 and 5% respectively. There was also a decreased occurrence of sticky droppings. Enzyme supplementation increased the digestibility of organic matter, crude protein (nitrogen x 6.25) and starch measured in the last third of the small intestine, and of organic matter and crude fat measured in excreta. Solubilization of insoluble pentosans by the enzyme included led to negative digestibility values for soluble pentosans in the small intestine at the higher levels of supplementation. Most of the dietary fibre degradation observed occurred before the middle section of the small intestine, with some degradation of soluble fibre in the caeca and colon. The solubilization and disruption of feed endosperm cell walls by enzyme supplementation probably was primarily responsible for the observed improvements in digestibility and production results.
285 citations
TL;DR: Ammonia volatilization, nitrogen immobilization, carbon decomposition and formation of volatile fatty acids were investigated in a laboratory incubation experiment with fresh poultry manure, to which increasing amounts of straw were added as mentioned in this paper.
Abstract: Ammonia volatilization, nitrogen immobilization, carbon decomposition and formation of volatile fatty acids was investigated in a laboratory incubation experiment with fresh poultry manure, to which increasing amounts of straw were added.
278 citations
TL;DR: The structure of the active site of ribulose-bisphosphate carboxylase described here should provide a rational basis for attempts to improve the efficiency of the enzyme by genetic engineering.
Abstract: Ribulose-bisphosphate carboxylase catalyses the key carboxylation reaction of photosynthetic carbon fixation, but also the competing oxygenase reaction of photorespiration. The structure of the active site of ribulose-bisphosphate carboxylase described here should provide a rational basis for attempts to improve the efficiency of the enzyme by genetic engineering.
237 citations
TL;DR: In this article, an empirical sink function describing water extraction by roots is proposed, where water uptake is given as a function both of the potential transpiration rate and a weighted stress index which accounts for the effects of the vertical distributions of roots and soil water content.
223 citations
TL;DR: In this article, the authors used soil cores from F/H layers in a Norway spruce (C:N=31) and a Scots pine stand in central Sweden were treated in the laboratory for 55 days with deionized water (control), weak H2SO4 (successively applied as 72 mm of acid rain of pH 3.1), strong H 2 SO4 (applied as a single high dose of pH 1), and lime CaCO3.
Abstract: The aim was to determine if changes in C and N mineralization after acidification and liming could be explained by changes in the soil organism biomass. Intact soil cores from F/H layers in a Norway spruce (C:N=31) and a Scots pine (C:N=44) stand in central Sweden were treated in the laboratory for 55 days with deionized water (control), weak H2SO4 (successively applied as 72 mm of acid rain of pH 3.1), strong H2SO4 (applied as a single high dose of pH 1), and lime CaCO3. Strong acidification reduced C mineralization and increased net N mineralization in both soils. Weak acidification resulted in similar but less pronounced effects. Liming initially stimulated C mineralization rate, but the rates declined, indicating that an easily available C source was successively used up by the microorganisms. Liming also increased net N mineralization in the C:N=31 humus, but not significantly in the C:N--44 humus. Strong acidification generally affected the amounts of FDA-active fungal hyphae, nematodes and enchytraeids more than the other treatments did. The increases in net N mineralization after acidification and liming could only partly be explained by the decreases in biomass N in soil organisms. Mineralization of biomass N from killed soil organisms could at the most explain up to about 30% of the increase in net N mineralization after strong acidification. Most of the effects on N mineralization seemed to depend on the fact that acidification reduced and liming increased the availability of C and N to the microorganisms. Furthermore, acidification seemed to reduce the incorporation of N from dead organisms into the soil organic matter and, thereby, make the N compounds more readily available to microbial decomposition and mineralization.
198 citations
TL;DR: Volatile metabolites from a number of rhizosphere pseudomonads prevented lettuce root growth in a seedling bioassay and one of these metabolites was identified as cyanide, which was related to consistently higher levels ofrhizosphere cyanide in comparison with S97-treated plants and control soils.
Abstract: Volatile metabolites from a number of rhizosphere pseudomonads prevented lettuce root growth in a seedling bioassay. One of these metabolites was identified as cyanide. Direct contact between rhizobacteria and plant roots produced, with one exception, similar responses. However, not all cyanogenic isolates were plant-growth-inhibitory rhizobacteria. When grown in liquid culture, cyanogenic strains produced an average of 37 nmol HCN ml−1 over a 36-h period and inhibition of root growth occurred at concentrations as low as 20 nmol ml−1. Cyanogenic strains introduced into sand or soil also produced HCN. Two cyanogenic strains ofPseudomonas fluorescens, one (5241) a plant-growth inhibitory rhizobacterium and the other (S97) a plant-growth-promotory rhizobacterium, were used to treat bean and lettuce seedlings prior to planting in soil. Lettuce dry weight was reduced by 49.2% (day 28) and 37.4% (day 49) when inoculated with S241 whereas S97 increased growth initially (+64.5% at day 28, no difference from control at day 49). Equivalent figures for inoculated bean plants were: −52.9% and −65.1% (5241); +40.7% and +23.3% (S97). A more detailed experiment using only bean plants confirmed these contrasting affects. Inhibition by S241 was related to consistently higher levels of rhizosphere cyanide in comparison with S97-treated plants and control soils. S241 also survived in the rhizosphere at higher densities and for a longer period of time than S97. The possible contribution of rhizobacterial cyanogenesis to plant growth inhibition is discussed.
194 citations
TL;DR: It is suggested that suckling can be regarded as a special case of foraging and that the young themselves decide to stop suckling as a result of an optimal foraging decision, and the sow could affect this decision by acting so as to increase the cost:benefit ratio of suckling.
184 citations
TL;DR: The attraction of bark and ambrosia beetles as well as associated beetles to α-pinene and ethanol was studied in field experiments with flight barrier traps to reflect dissimilarities in the release of the two substances among the various types of breeding material to which the species are adapted.
Abstract: The attraction of bark and ambrosia beetles as well as associated beetles to α-pinene and ethanol was studied in field experiments with flight barrier traps. α-Pinene and ethanol were released individually and as combinations in approximately 1∶1 or 1∶10 ratios and at four different release rates. Ethanol attractedTomicus piniperda (L.),Hylurgops palliatus (Gyll.),Trypodendron lineatum (Oliv.),Hylastes cunicularius Er.,H. brunneus Er.,H. opacus Er., andAnisandrus dispar (F.) (Scolytidae);Glischrochilus quadripunctatus (L.) andEpuraea spp. (Nitidulidae);Thanasimus formicarius (L.) (Cleridae); andRhizophagus depressus (F.) (Rhizophagidae). α-Pinene attracted all these species with the exception ofT. lineatum, H. cunicularius, andA. dispar. Combinations of a-pinene and ethanol resulted in synergistically increased attraction of all species with the exception ofH. opacus andA. dispar. A. dispar, the only hardwood-associated species in the study, was repelled by α-pinene. Both the release rates and the ratio at which the two substances were released influenced the response of the beetles. The differences in response between the beetle species seem to reflect dissimilarities in the release of the two substances among the various types of breeding material to which the species are adapted.
TL;DR: In this paper, critical loads for N deposition are derived from an ecosystem's anion and cation balance assuming that the processes determining ecosystem stability are soil acidification and nitrate leaching.
Abstract: Critical loads for N deposition are derived from an ecosystem's anion and cation balance assuming that the processes determining ecosystem stability are soil acidification and nitrate leaching. Depending on the deposition of S, the parent soil material, and the site quality critical N deposition rates will range between 20 to 200 mmol m−2 yr−1 (3 to 14 kg ha−1 yr−1) on silicate soils and reach 20 to 390 mmol m−2 yr−1 (3 to 48 kg ha−1) on calcareous soils.
TL;DR: The findings seem compatible with alveolar collapse during anaesthesia, causing shunt, whereas the absence of clearly low VA/Q regions questions the role of airway closure as the major disturbance of gas exchange.
Abstract: Ventilation-perfusion relationships were studied by the multiple inert gas elimination technique in seven horses while they were conscious and during inhalation anaesthesia with halothane. A generally good match between ventilation and perfusion was found in the conscious, standing horse. During anaesthesia a huge shunt developed, ie perfusion of completely unventilated lung regions, both in dorsal and left lateral recumbency and whether the horse was breathing spontaneously or mechanically ventilated. The shunt was significantly greater and the arterial oxygen tension (PaO2) significantly lower in dorsal than in left lateral recumbency. Little or no perfusion of low VA/Q regions was observed during anaesthesia, whether ventilation was spontaneous or mechanical. Positive end-expiratory pressure (PEEP) did not significantly improve PaO2 or reduce the shunt. Selective mechanical ventilation of dependent lung regions with PEEP reduced the shunt markedly, an effect that was not achieved by conventional mechanical ventilation with general PEEP. The findings seem compatible with alveolar collapse during anaesthesia, causing shunt, whereas the absence of clearly low VA/Q regions questions the role of airway closure as the major disturbance of gas exchange.
TL;DR: The amino acid sequence of glycolate oxidase from spinach has been fitted to an electron density map of 2.0 A nominal resolution and the structure has been refined using the restrained parameter least-squares refinement of Hendrickson and Konnert.
TL;DR: In this paper, the authors analyzed the geometry of the eight-stranded beta-sheets and the packing of the residues at the center of the barrel, showing that not all proteins with this fold are related by evolution, but that they represent a common favorable solution to the structural problems involved in the creation of closed beta barrel.
Abstract: Alpha/beta barrel structures very similar to that first observed in triose phosphate isomerase are now known to occur in 14 enzymes. To understand the origin of this fold, we analyzed in three of these proteins the geometry of the eight-stranded beta-sheets and the packing of the residues at the center of the barrel. The packing in this region is seen in its simplest form in glycolate oxidase. It consists of 12 residues arranged in three layers. Each layer contains four side chains. The packing of RubisCO and TIM can be understood in terms of distortions of this simple pattern, caused by residues with small side chains at some of the positions inside the barrel. Two classes of packing are found. In one class, to which RubisCO and TIM belong, the central layer is formed by a residue from the first, third, fifth, and seventh strands; the upper and lower layers are formed by residues from the second, fourth, sixth, and eighth strands. In the second class, to which GAO belongs, this is reversed: it is side chains from the even-numbered strands that form the central layer, and side chains from the odd-numbered strands that form the outer layers. Our results suggest that not all proteins with this fold are related by evolution, but that they represent a common favorable solution to the structural problems involved in the creation of a closed beta barrel.
TL;DR: It is reported that in a long-term field experiment with artificial rockpools, interspecific competition between three common rock-pool zooplankton species led to increased local extinction rates, implying that inter specific competition is likely to limit the regional richness of species in the rockpool metapopulation system.
Abstract: THE importance of interspecific competition for the distribution and abundance of organisms has been hotly debated during the last decade1-7. Although many field experiments have shown effects of interspecific competition on abundance and reproduction1,3, there is no unequivocal experimental evidence that interspecific competition can influence rates of local extinction in the field. Here I report that in a long-term field experiment with artificial rockpools, interspecific competition between three common rock-pool zooplankton species led to increased local extinction rates. In addition, studies of the distributional dynamics of the species in natural rockpools also showed that interspecific competition increases extinction rates. These results imply that interspecific competition is likely to limit the regional richness of species in the rockpool metapopulation system. MacArthur and Wilson8 were the first to suggest that an increase in extinction rate per species with an increase in the number of species could influence species richness on islands. Moulton and Pimm9 found that this was so among birds introduced to the Hawaiian islands, but the present study is the first field experiment providing unequivocal evidence of the effect.
TL;DR: It is concluded that birds have the potential to heavily modify the interaction between bilberry and insect larvae.
Abstract: The bilberry (Vaccinium myrtillus L.), is the dominant plant in the field layer of many boreal forests in northern Sweden. It is utilized by several herbivorous insect larvae as food (i.e. Lepidoptera: Geometridae, Tortricidae and Hymenoptera: Symphyta). Total density of insect larvae was 63% lower where birds had access to larvae compared to exclosures. Larvae with a feeding behaviour which exposes them to birds (geometrids and sawflies) showed a pronounced reduction in density when exposed to bird predators. Density of larvae with a concealed feeding behaviour (tortricids) was unaffected by birds. The frequency of larval damage to bilberry annual shoots was significantly higher in areas where larval density was high due to exclusion of birds. I concluded that birds have the potential to heavily modify the interaction between bilberry and insect larvae.
TL;DR: In this paper, a 2-yr pot experiment was conducted to investigate the relationship between Cd levels in soil and those in plants and the amount of Cd added to the soil (0 to 5 mg kg−1 soil).
Abstract: Adsorption of Cd by two soils and its uptake by perennial ryegrass (Lolium perenne) and winter rape (Brassica napus) as a function of pH (pH 4 to 7) and the amount of Cd added to the soil (0 to 5 mg kg−1 soil) were studied in a 2-yr pot experiment. In the soils, the more soluble fractions of Cd increased as the pH was lowered. Increasing the pH from 5 to 7 by adding CaO invariably reduced the Cd-content of ryegrass plants, but this decrease was less consistent where the pH had only been increased to 6. In some cases, acidifying the soil with S to reach a pH of 4 also led to a decrease in plant Cd-content. The Cd-content of rapeseed plants was markedly higher at pH 4 than at pH 5. Plant damage at low pH was observed in this crop. Water-leachable and CaCl2-extractable soil Cd levels as well as plant uptake were higher in the sand soil than in the clay soil, whereas 1M NH4AcO (buffered at pH 4.8 and 7) extracted roughly equal amounts from both soils. Adding more Cd to the soil did not change the relation between Cd levels in soil and those in plants; instead the amounts of Cd in both increased in direct proportion to the amounts added. Fixation of added Cd apparently did not occur continuously at any pH or Cd-level during the 2-yr period, but seasonal variations in solubility and uptake were observed.
TL;DR: The mechanisms that enable horses to achieve higher maximal rates of O2 consumption (VO2max) than steers are identified and the mechanisms used to achieve it are the same as observed in smaller pairs of mammalian species with large variation in aerobic capacity.
Abstract: This study investigated mechanisms used by horses and steers to increase O2 uptake and delivery (VO2) from resting to maximal rates and identified the mechanisms that enable horses to achieve highe...
TL;DR: Analysis of in vivo-labelled soluble proteins by two-dimensional gel electrophoresis revealed several low temperature — or ABA — induced proteins, which where not produced in non-acclimated plants, suggesting that they might be directly involved in the frost hardening process in A. thaliana.
Abstract: Exogenously applied abscisic acid (ABA) induced frost hardening of Arabidopsis thaliana (L.) Heynh. The freezing tolerance of A. thaliana plantlets treated with ABA (15 mg/l) at a non-acclimating temperature (20 °C) appeared to increase even more rapidly than following a low temperature (4 °C) acclimation. Analysis of in vivo-labelled soluble proteins by two-dimensional gel electrophoresis revealed several low temperature - or ABA - induced proteins, which where not produced in non-acclimated plants. A subset of these proteins was induced by both low temperature and ABA treatments, suggesting that they might be directly involved in the frost hardening process in A. thaliana.
Journal Article•
TL;DR: There was a tendency for bitches treated with antibiotics at the time of mating or during early pregnancy to have a higher pregnancy rate and a larger litter size, and for breed differences in pregnancy rate, although not significant.
Abstract: In this study 470 bitches were inseminated; 405 with fresh semen into the cranial vagina and 65 with frozen semen transcervically into the uterus. The pregnancy rate was 65.7% with fresh semen and 41.5% with frozen. When corrected for stage of oestrus at the time of insemination and for semen quality the pregnancy rate was 83.8% with fresh semen and 69.3% with frozen semen. The pregnancy rate improved with an increase in the number of inseminations. Inseminations with fresh semen before the time of ovulation (less than 17.3 nmol progesterone/l) were often successful. With frozen semen the peripheral plasma level of progesterone at the time of insemination was greater than 30 nmol/l in all but 1 of the bitches that became pregnant. This difference is assumed to be attributable to a longer survival time of several days for fresh semen than for frozen-thawed semen. Cytological scoring was a satisfactory method for determining the stage of oestrus when using fresh semen, but more precise methods are needed when using frozen semen. Semen quality was difficult to correlate with fertility. Pregnancies were obtained with fresh semen of inferior quality, although the litter size was smaller. With frozen semen no pregnancies resulted when the semen quality was poor. Litter size was estimated to be 21.5% smaller in bitches inseminated with fresh semen compared with naturally mated bitches. Litter size in bitches inseminated with frozen semen was 23.3% smaller than in bitches inseminated with fresh semen. Puppy deaths occurred in 35.5% of the litters in this study. The overall puppy death rate during the first 3 weeks of life was 11.9%. Although not statistically significant, there was a tendency for bitches treated with antibiotics at the time of mating or during early pregnancy to have a higher pregnancy rate and a larger litter size. There was also a tendency for breed differences in pregnancy rate, although not significant.
TL;DR: The large variations in relative growth rate observed after inoculation with different fungi demonstrated that the mycobiont has a substantial influence over the proportion of host photosynthate allocated for maintaining the symbiosis.
Abstract: SUMMARY
Ectomycorrhizal and control Pinus sylvestris L. seedlings were grown under steady-state nutritional conditions in a semi-hydroponic system. Free access to balanced low concentrations of mineral nutrients did not inhibit mycorrhiza formation. The large variations in relative growth rate observed after inoculation with different fungi demonstrated that the mycobiont has a substantial influence over the proportion of host photosynthate allocated for maintaining the symbiosis. Analyses with 14C-tracer demonstrated that photosynthesis was considerably enhanced in mycorrhizal seedlings, even though N and Mg concentrations were similar in mycorrhizal and uninoculated seedlings. Although translocation and respiration were highly variable, they were enhanced in some seedlings. Nutrition had no demonstrable effects on shoot or root carbohydrate content, but auxin (IBA and IAA) treatments increased the carbohydrate concentrations. Several auxin treatments also accelerated translocation and respiration, but their effects on photosynthesis were variable. The results contradict some of the basic tenets in Bjorkman's (1942) carbohydrate theory, while providing circumstantial evidence in favour of Slankis's (1973) hormone hypothesis.
TL;DR: Efforts to infiltrate degraded wood pieces with high levels of lignin peroxidase showed the enzyme to be restricted to superficial regions of wood decay and to penetrate wood cell walls only where the wall structure had been modified, suggesting a possibility for a close substrate-enzyme association during wood cell wall degradation.
Abstract: The distribution of lignin peroxidase during degradation of both wood and woody fragments by the white rot fungus Phanerochaete chrysosporium was investigated by using anti-lignin peroxidase in conjunction with postembedding transmission electron microscopy and immuno-gold labeling techniques. The enzyme was localized in the peripheral regions of the fungal cell cytoplasm in association with the cell membrane, fungal cell wall, and extracellular slime materials. In solid wood, lignin peroxidase was detected in low concentrations associated with both superficial and degradation zones within secondary cell walls undergoing fungal attack. A similar but much greater level of extracellular peroxidase activity was associated with wood fragments degraded by the fungus grown under liquid culture conditions optimal for production of the enzyme. Efforts to infiltrate degraded wood pieces with high levels of lignin peroxidase showed the enzyme to be restricted to superficial regions of wood decay and to penetrate wood cell walls only where the wall structure had been modified. In this respect the enzyme was able to penetrate characteristic zones of degradation within the secondary walls of fibers to sites of lignin attack. This suggests a possibility for a close substrate-enzyme association during wood cell wall degradation. Images
TL;DR: Based on a model of bound glycolate to the authors' structure, it is proposed that the following residues are important in the catalytic reaction: Arg-257, Tyr-24, and Tyr-129 for binding the substrate, and His-254 for abstracting a proton from the C2 atom of the substrate.
TL;DR: The ability of piglets to peacefully make social bonds with other piglets has clear implications for the pig industry.
TL;DR: These results are consistent with a long-standing hypothesis that behavioral responses to essential oil components characteristic of the larval food plants have facilitated host shifts in the genus Papilio.
Abstract: Black swallowtail females laid more eggs on plant models treated with contact stimulants and volatiles from carrot leaves than on models treated only with contact stimulants. The volatiles enhanced landing rates and females alighted more frequently on artificial leaves treated with host volatiles than on adjacent control leaves. Volatiles from cabbage, a nonhost, inhibited landing rates on artificial leaves treated with carrot contact stimulants. Examination of antennae revealed two major types of sensilla, believed to be olfactory in function. Electroantennogram preparations responded more strongly to carrot volatiles than to cabbage volatiles and several shared responses at particular retention times to carrot volatile components eluting from a gas chromatograph. Our results are consistent with a long-standing hypothesis that behavioral responses to essential oil components characteristic of the larval food plants have facilitated host shifts in the genus Papilio.
TL;DR: It is concluded that they also oviposited again in the stumps, giving rise to a new generation emerging during autumn of the third season and spring of the fourth season after cutting.
Abstract: Age composition, seasonal occurrence, sexual development and flight muscle condition were investigated in populations of Hylobius abiets collected on a clear-cut area during three consecutive years after cutting. Weevils that had been reproductive during any previous season were classified as old and distinguished from young weevils based on the degree of elytral scale wear. Collections were made from late April until early October. Weevils developed their flight muscles before reaching sexual maturity. The proportion of young and old weevils with well-developed flight muscles was already high by the beginning of May. None of the examined young weevils emerging during autumn had well-developed flight muscles or mature reproductive organs. A large proportion of the weevils arriving at the fresh clear-cutting overwintered and remained there throughout the following season. It is concluded that they also oviposited again in the stumps, giving rise to a new generation emerging during autumn of the third season and spring of the fourth season after cutting.
Zusammenfassung
Alter, Geschlechtsreife und jahreszeitliches Auftreten des Grosen Braunen Russelkafers Hylobius abietis (L.)
Auf Kahlschlagen in Mittelschweden wurden wahrend der ersten drei Jahre nach dem Abtrieb das jahreszeitliche Auftreten von Hylobius abietis untersucht sowie Altersstruktur, Geschlechtsreife und Zustand der Flugmuskulatur in den Populationen. Kafer, die sich schon in fruheren Jahren vermehrt hatten, wurden als alt klassifiziert und von jungen Kafern auf Grund des Zustandes der Deckflugelbe-schuppung unterschieden. Die Kafer wurden von Ende April bis Anfang Oktober an Fangknuppeln eingesammelt.
Keiner der im Herbst gefangenen und untersuchten Jungkafer hatte eine gut entwickelte Flugmus-kulatur oder ausgereifte Geschlechtsorgane. Die Kafer entwickelten ihre Flugmuskulatur bevor sie die Geschlechtsreife erreichten. Schon Anfang Mai hatte ein hoher Anteil der Kafer eine gut entwickelte Flugmuskulatur. Ein groser Anteil der Kafer, die in den frischen Kahlschlag eingewandert waren, uberwinterten und blieben wahrend der ganzen folgenden Vegetationsperiode auf der Flache. Es wird angenommen, das sie auch wieder Eier in die Stubben und Wurzeln legten und damit eine neue (Schwester-)Generation anlegten, die im Herbst des dritten und im Fruhjahr des vierten Jahres nach dem Kahlschlag ausschlupfte.
TL;DR: The results suggest that the sows were able to adjust their nest site choice and nest-building behaviour according to the prevailing external conditions, indicating that the behaviour is under feed-back regulation.
TL;DR: In this paper, the authors measured the gradient of wind, temperature and humidity in a sparse pine forest at Jadra»s in Sweden, and found that the wind and temperature gradients of the forest top level are very similar to those of the ground level.
Abstract: Measurements of gradients of wind, temperature and humidity and of the corresponding turbulent fluxes have been carried out over a sparse pine forest at Jadra»s in Sweden. In order to ascertain that correct gradient estimates were obtained, two independent measuring systems were employed: one system with sensors at 10 fixed levels on a 51 m tower and another with reversing sensors for temperature and humidity, covering the height interval 23 to 32 m. Turbulent fluxes were measured at three levels simultaneously. Data from three field campaigns: in June 1985, June 1987 and September 1987 have been analyzed. The momentum flux is found on the average to be virtually constant from tree top level, at 20 to 50 m. The average fluxes of sensible and latent heat are not so well behaved. The ratio of the non-dimensional gradients of wind and temperature to their corresponding values under ‘ideal conditions’ (low vegetation) are both found to be small immediately above the canopy (about 0.3 for temperature and 0.4 for wind). With increasing height, the ratios increase, but the values vary substantially with wind direction. The ratios are not found to vary systematically with stability (unstable stratification only studied). The ratio of the non-dimensional humidity gradient to the corresponding non-dimensional potential temperature gradient (equivalent to k
h
/k
w
) is found to be unity for (z − d)/L
v
less than about −0.1 and about 1.4 for near neutral stratification, but the scatter of the data is very large.