Classification and ecological characterization of coniferous forest phytogeocoenoses of Hokkaido,Japan

Coniferous forest phytogeocoenoses of Hokkaido Island, Japan, were studied to classify them based on vegetation characteristics, to analyse their soils, to correlate the vegetation and soil characteristics, and to provide some ecological interpretation for the phytogeocoenosis differentiation and establishment. Five forest types were distinguished based on the vegetation structure, each of which was comparable to plant association of Krajina (1960); 1. the moss type, 2. the Sasa kurilensis type, 3. the Sasa senanensis type, 4. the Carex sachalinensis type, and 5. the Dryopteris crassirhizoma type. Soil base status indicated by pH, electric conductivity, amount of calcium and magnesium, and base saturation showed a fair correlation with the forest types. The forest types were, therefore, arranged along a soil nutritional gradient. The moss type developed in the least fertile habitats whereas the Dryopteris crassirhizoma type in the most fertile habitats, and others were in between the two. It was suggested that in the island, where climate was humid with excess of soil water throughout a year, soil nutritional regime, more specifically availability of bivalent cations which tended to be removed by the excessive soil water, seemed to be a critical factor to differentiate and establish the forest types.This study was financially supported by the Science Research Grant of the (Monbusho) Japanese Goverment (Grant No. 60540422).     

A synecological investigation of Matteuccia struthiopteris — dominanted stands in Western Norway

This investigation is based on phytosociological and ecological analyses of stands dominated by M. struthiopteris within its main distributional area in Western Norway. The distribution and floristical composition of such stands are related to different environmental parameters such as regional climate, soil and topography. The data are analysed by numerical methods, of which two-way indicator species analysis (TWINSPAN), canonical correspondence analysis (CCA), and simple discriminant functions (DISCRIM) are the most useful. Few stands occur in areas where the mean July temperature is below 12.0 °C, and where the mean January temperature is higher than 0 °C. The soil is rich in metal cations, with a base saturation mostly higher than 50% in the B-layer. Based on a TWINSPAN classification of the 230 investigated stands, 9 different groups (types) are distinguished. Many stands have a tree layer of Alnus incana, while stands with a canopy of Betula pubescens, Fraxinus excelsior and Ulmus glabra are considered to be marginal sites for M. struthiopteris. The types described are interpreted as belonging to the Pruno padi-Alnetum incanae, Alno incanae-Fraxinetum excelsioris and Alno incanae-Ulmetum glabrae associations within the Alno-Ulmion alliance. The floristic composition of the quadrats is highly correlated with the altitude/temperature gradient. The other important factor is interpreted to be soil moisture. Soil richness is poorly correlated with the floristic composition of the different stands. Several stands represent a regeneration stage after cessation in cultivation, while others appear to have been very little influenced by human activity.     

Introduction into the ecosystem of the North Sea: Hydrography,biota, and food web relationships

The North Sea, one of the most productive of the earth's seas and oceans, is also surrounded by some of earth's most densely populated and heavily industrialized regions. A growing number of signals are being received which indicate that this valuable ecosystem is increasingly under stress. This has generated a corresponding increase in concern over the steps to be taken to protect the North Sea. While there are divergent views on what constitutes an ‘ideal’ North Sea, there is a general recognition that any decisions that are made should be based on a good understanding of this ecosystem. The intention of this paper is to give an overview of what is presently known, and to identify areas where more studies are needed. A brief summary of the hydrography and the biota of the North Sea is given. Biotic and abiotic structure justify partitioning the North Sea into three ecologically different regions: southern, central, and northern. For the most part, neither the top predators,e.g. marine birds and mammals, nor the macroalgae and sea grasses are included in this overview.     

Neuroethology of olfactory preference development

Young mammals come to approach the odor of their mother, a response that facilitates their survival during early life. Young rats induce a cascade of events in their mother to induce the emission of her odor. The pups increase circulating prolactin levels, which increases food intake and the emission of large quantities of cecotrophe containing the maternal odor. This odor is synthesized by the action of cecal microorganisms and changes with maternal diet. The diet-dependence of the odor requires the pups to acquire their attraction to the odor postnatally. The acquisition of this preference occurs when an odor is paired with the tactile stimulation that pups receive during maternal care. The action of the tactile stimulation appears to be mediated by noradrenaline. The development of this type of olfactory attraction is accompanied by changes in the regions of the olfactory bulb that are responsive to the attractive odor. Metabolic, anatomical, and neurophysiological changes in response to the attractive odor emerge in such regions of the bulb after early olfactory preference training. © 1992 John Wiley & Sons, Inc.     

The roles of temperature and food quality in affecting the performance of the alder aphid, Pterocallis alni

Six successive summer generations of the alder aphid (Pterocallis alni (DeGeer) (Homoptera: Callaphididae)) were reared simultaneously in the field and under controlled temperature conditions in the laboratory. The growth and reproduction of each generation were recorded. The available food quality for the aphids was measured by weekly analysis of foliar soluble nitrogen concentrations. Although there was a significant change in leaf soluble nitrogen during the season, the decline was only 23% and this did not appear to have an adverse effect on the performance of this aphid. Instead, the major environmental factor affecting the aphid is temperature. This is evidenced by the facts that when aphids were reared at constant temperatures, there were no differences in generation performance, even though food quality varied seasonally. In addition, all generations of the aphid posess the same number of ovarioles, indicating that there is no pre-programmed anticipation of a seasonal deterioration in food quality in this aphid species.

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Résumé P. alni DeGeer (Homopt. Callaphididae) vit sur Alnus glutinosa Gaertner pendant toute l'année. L'aulne étant un arbre fixant l'azote, cette étude a été entreprise pour examiner la croissance et la reproduction de ce puceron sur cet arbre afin d'expliquer les changements de la dynamique de sa population. 6 générations successives estivales ont été élevées dans la nature et en température constante au laboratoire. La qualité de l'aliment a été mesurée chaque semaine par une microkjeldahl analyse des concentrations foliaires en azote soluble. La qualité de l'aliment varie saisonnière, mais ne diminue que de 23%; elle semble n'avoir que peu d'effets sur le puceron, puisque la fécondité dans la nature n'est réduite que pendant une génération. Quand la température est maintenue constante, il n'y a pas de différences entre les performances des différentes générations de pucerons. Ainsi, les changements saisonniers dans la croissance et la reproduction des pucerons sont provoqués par la température et non par la qualité de l'aliment.

     

Temperature effects on bioenergetics of growth, assimilaton efficiency and thyroid activity in juvenile varand lizards

When varanid lizards, Varanus niloticus, were allowed to select their preferred body temperature (c. 34°C) they exhibited swifter growth, larger food intake and superior efficiency of conversion when compared with animals restricted to a maximum body temperature of 24°C. At the higher temperature the animals also exhibited a higher metabolic rate and increased thyroid activity, while those at the lower temperature lostproportionately more energy via respiration. A complete energy budget over a period of 6 weeks is presented.     

Kinetics of nitrogen and phosphorus release in varying food supplies byDaphnia magna

Rates of nitrogen and phosphorus release from individualDaphnia magna were determined by measuring ammonia and soluble reactive phosphorus in successive 10-min incubations in small (0.05 ml) vessels after the animals were removed from their food. Release rates of both nutrients were generally highest initially and decreased with time after removal. The ratio of nitrogen to phosphorus released increased with time after animals were removed from an artificial detritus/bacterial food; ratios were lower and changed with time less for animals fed algae. These data suggest errors may be introduced by assumptions of constant stoichiometry for nutrient release in varying environments.GLERL Contribution No. 268     

The growth of rhododendrons in containers in soil,treated with either CaCO3, Ca(OH)2 or CaSO4

Summary Rhododendrons were grown in containers for a period of six and a half years (six growth cycles) in soil mixes which contained liberal amounts of either CaCO₃, Ca(OH)₂ or CaSO₄.No evidence was obtained to suggest that the plants were sensitive to liming of the soil or to excessive applications of calcium. The only reaction observed was a leaf chlorosis and veinal necrosis which developed for a brief period following the heavy application of CaSO₄ in the fifth season. The application of Ca(OH)₂ raised the pH throughout the soil profile to over 7, and CaSO₄ induced a consistent increase in leaf calcium.     

The relation between spruce monoculture and incipient podzolisation in ochreous brown earths of the Belgian Ardennes

Summary The effects of coniferous monoculture on the distribution of C, Fe and Al in the upper horizons of brown ochreous earths of the Belgian Ardennes were investigated by comparing 5 soil profiles developed under an 80 year old spruce stand with another 5 profiles developed under a climactic broad-leaved forest (beechwood).Organic carbon, Fe and Al were extracted with 0.1N NaOH/Na-tetraborate solution buffered at pH 9.7: recent studies have shown that this extraction is particularly appropriate for the detection of incipient podzolisation in brown earths-brown podzolic soils intergrades.Even if most of the classic podzolisation indexes fail to illustrate differences, nevertheless our results show that fulvic acids and organo-ferric complexes are present in significantly greater amounts in the upper part of the cambic (B)₁ horizon of the soils developed under conifers. Moreover, this podzolic tendancy is confirmed by the weathering patterns of the clay minerals in the A₁(B) horizons developed under spruces, i.e. a more pronouced weathering of chloritic layers than those observed in the beechwood soil, with a correlative genesis of more abundant smectite-like minerals. One may therefore conclude that the change in the humus type (moder to mor) after the planting of spruce trees, has been sufficient, within the local climatic and edaphic context, to promote incipient podzolisation.