Mild Winter Climate Research Articles

Comparison of Gremmeniella abietina isolates from Pinus sylvestris and Pinus contorta in terms of conidial morphology and host colonization

SummaryGremmeniella abietina isolates from Pinus contorta in northern Sweden produced, in vitro, shorter conidia with fewer septa compared with isolates from Pinus sylvestris in the southern part of the country. After mycelial inoculation of shoots with G. abietina isolates from both host species, the resulting necroses were longer in P. sylvestris than in P. contorta. Keeping seedlings in artificial mild winter climate or detaching shoots from the seedling before inoculation caused longer necroses. No host specificity in colonization was found. Isolates from P. sylvestris caused longer necroses than did isolates from P. contorta, and both types of isolates caused longer necroses in P. sylvestris than in P. contorta. The differences found between the two G. abietina populations probably reflect regional variation in the fungus.

Zur Lebensgeschichte der Gattung Helleborus L. (Ranunculaceae)

Summary The growth form and growth rhythm of seven Helleborus species of different sections are investigated on the basis of cultivated plants and herbarium specimens. Special attention is drawn to germination, plant development, radication, stem morphology, leaf sequence, inflorescences, and innovation. H. foetidus is an allo-homorhizous, evergreen, chamaephytic, short-living perennial with dicyclic to pleiocyclic, slightly rhythmically growing stems, many-flowered inflorescences and bracteose hypsophylls. In the mountains of Mallorca, dwarfed, long-living pleiocormous perennials grow which approach shrubs. H. argutifolius is an evergreen rhizomatous perennial with dicyclic, strongly rhythmically growing stems, inflorescence buds, many-flowered inflorescences and bracteose hypsophylls. H. lividus is an evergreen rhizomatous perennial with dicyclic, continuously growing stems without inflorescence buds, and with several-flowered inflorescences and frondose-bracteose hypsophylls. H. niger is an evergreen rhizomatous perennial with basal leaves, very few-flowered, geophilous inflorescences and bracteose hypsophylls. H. orientalis is an evergreen rhizomatous perennial with basal leaves, few-flowered inflorescences and frondose hypsophylls. H. viridis is a summergreen rhizomatous perennial with basal leaves, few-flowered inflorescences and frondose hypsophylls. H. vesicarius is a rhizomatous perennial with monocyclic stems, few basal and cauline leaves, green in winter to spring, several-flowered inflorescences and frondose hypsophylls. In view of morphological character progressions, the results are discussed under consideration of all species and further features, and of the relations to environment and distribution. In conclusion, a hypothetical phylogenetic tree of the genus is presented (fig. 29). The pinnate-palmate leaves of H. vesicarius are considered to be primitive. The pedate leaf, typical to the genus, is derived from it. An additional pedate division of the leaf segments occurs in H. multifidus and related species. The ternate leaf of H. lividus and H. argutifolius is interpreted as neoteny. The generally accepted groups, Caulescentes and Scapigeri, are understood as grade groups. The species belonging to the Caulescentes, with elongated, leafy, usually dicyclic stems grow in the mild winter climate of the Mediterranean-Atlantic range. Derived from this group, the Scapigeri with their basal leaves are, for the most part, submediterranean to south-temperate plants of deciduous forests. The development of a scape is explained by the strict growth rhythm of these species: The inflorescence buds are transferred underground and develop very fast in early spring. The whole part above the leaves belongs to the reproductive region. The scales at the base of the scape are referred to as hypsophylls, which adopt the function of bud scales and have a vaginal structure. In accordance with their environment and distribution, the evergreen H. lividus and H. foetidus are characterized by a vegetation period beginning in autumn and a continual inflorescence development with a long flowering period. They develop no, or only loose, inflorescence buds. On the other hand, H. argutifolius develops compact inflorescence buds that unfold quickly, but not before January. The relatively short flowering period of the Scapigeri is delayed even further towards spring. Among them, the summergreen species have a clearly defined winter rest period. The wintergreen H. vesicarius, though, demonstrates a clearly Mediterranean growth cycle with a rest period in summer. The Sicilian plants of H. multifidus subsp. bocconei diverge considerably in growth rhythm and leaf sequence from the species, and need further morphological and taxonomical investigation. In order to achieve a more natural classification, the genus is differentiated according to the structure of the hypsophylls into two new subgenera, s ubgen . Helleborus with undivided, bracteose hypsophylls, and subgen. Helleborastrum (Spach) W erner & E bel with divided, frondose hypsophylls.

Effects of increased discharge on benthic invertebrates in a regulated river

AbstractBenthic animal densities, biomass and production were studied in a weir basin and the upstream adjacent riffle area in a regulated west Norwegian river in 1988 and 1989. In years of normal discharge, such as 1988, water from a large part of the catchment area is transferred to a hydroelectric power station in another watershed, and the discharge at the study site is low. In 1989 heavy precipitation and a mild winter climate caused surplus production of hydroelectric power. Consequently large amounts of stored water had to be released as overflow at the dam. On a yearly basis the discharge at the study site was 4.8 times higher in 1989 than 1988, whereas peak values were 12.0 and 54.0 m3 s−1 in 1988 and 1989, respectively. The change in flow regime resulted in reduced biomass and faunal changes. Biomass was high during 1988 and the first months of 1989. Corresponding to the flow increase in June 1989 the biomass in the weir basin was reduced from 7.1 to 2.2 g dw m 2 and from 8.0 to 0.8 g dw m−2 at the two studied transects. The mean biomass in the autumn period was 270 and 800% higher at the two transects in 1988 compared to 1989. A great part of the biomass reduction was caused by reduced densities of the chironomids Stictochironomus pictulus and Chironomus melanotus. The mean autumnal densities of these two species were reduced from 4400 to 170 ind. m2 and from 876 to 2 ind. m2, respectively. An increase in the biomass was recorded for rheophilic insect larvae, such as the stoneflies Leuctra fusca and Capnia pygmaea. On the other hand lentic caddis larvae such as Apatania spp. and Oxyethira spp. were reduced. Mean benthic animal production of the weir basin was reduced from 22.3 g dw m−2 yr−1 in 1988 to 12.5 g dw m −2 yr−1 in 1989. In a riffle upstream of the weir basin the production was reduced from 9.1 to 3.9 g dw m−2 yr −1 in the same period. The faunal change is explained by an altered physical environment and destruction of lentic habitats.

Life‐History Theory in the Nonbreeding Period: Trade‐Offs in Avian Fat Reserves?

We tested the hypothesis of optimal winter fat storage in birds. The hypothesis predicts that when the survivorship benefits (fasting capacity) but not the survivorship costs (higher cost of flight, lowered agility, increased exposure to predators) of fat are eliminated by predictable resources (e.g., tree— and shrub—borne food), species will be leaner than species exploiting unpredictable resources (e.g., ground—borne food subject to sudden covering by snow). The predicted pattern was found in an earlier study of avian communities in central North America, while snowfall is frequent. Here we tested the predictions of the hypothesis that (1) when ground—and tree—feeding guilds are compared between geographic regions of harsh and mild winter climate, only ground—feeders will have relatively high fat reserves, resulting in a significant guild ° climate interaction term in a two—way analysis of variance, and (2) ground— and tree—foraging guilds will both show low fat reserved in a mild winter environment. To test these predictions, visible subcutaneous fat class was measured in both guilds in Wisconsin and Michigan (harsh winter environments) and southwestern British Columbia, northwestern Washington, and Tennessee (mild winter environments). Both predictions were supported. We suggest that small birds wintering in North America approach local optima in energy storage strategy and winter survivorship. The energy storage strategy thus appears to be a major life—history trait in the nonbreeding period. The trade—off between the costs and benefits of winter fat has two potential implications for understanding population limitation. First, trade—offs that reduce reserves can lead to lower survival in severe winter weather than would occur at maximum fat levels. Second, our study suggest that individual birds are sensitive to, and can control, both predation and starvation risks. Recent theory of population limitation indicates that as food abundance declines, birds feed to avoid starvation, but at the expense of increase mortality from predation. Together these studies suggest that populations are limited by interacting (predation, food supply) instead of single (food supply) factors. Study of trade—offs used by individuals to maximize survival can provide unique perspectives on population limitation.

Seasonal changes in the carbohydrate content of two cultivars of asparagus

The annual changes in carbohydrate content in the roots of two cultivars of asparagus ( Asparagus officinalis L. cultivar UC 157 and cultivar ‘Junon’) grown in the relatively mild winter climate of Israel were studied. During the autumn (August–November) when the ferns senesce and the subsequent winter dormant season (November–February) the roots were characterized by a constant and significant decrease in fructan content in both cultivars, contributing to a loss of over 30% of the stored fructans. During the harvest (February–April) there was a further decline in root fructan content. During the post-harvest period of fern growth, as the unharvested ferns develop and expand, the root fructan content declined to its lowest levels. Following this, there was a sharp and continuous increase in root fructan levels, as well as a transient increase in sucrose levels for the following three summer months (May–August). The general pattern of root carbohydrate changes was similar in the two cultivars, although there were differences of possible physiological significance.

A Novel Passive Solar Greenhouse Based on Phase-Change Materials

Abstract A novel concept for a passive solar greenhouse for regions with mild winter climates is described. The concept was tested with a 66-m2 prototype greenhouse. The roof of the greenhouse was made of modular double-layered transparent panels filled with a latent heat-storage material. During both night and day, the thermal performance of the test building was significantly better than that of the control glass house. The main drawback of the proposed method is that the light intensity is low in the morning until the solid Latent Heat Storage Material (LHSM) is completely melted. Therefore, practical application of this method is restricted to specific crops and climate regions.

Analysis of the direct gain concept for non-conditioned buildings

Based on periodic solutions of the dimensionless heat conduction equations, an analytical model is developed to study the direct gain passive heating concept for non-conditioned buildings. The effect of multireflections inside the building has also been taken into account. Numerical calculations are also carried out for a mild winter climate (New Delhi, India) and a harsh winter climate (Boulder, Colo.,U.S.A.). The results indicate that, for a mild winter climate, a floor area equal to that of the glazed area is able to provide comfortable conditions, while for a harsh winter climate, the floor area/glazed area ratio may be 1 2 or 3 4 , and auxiliary energy also has to be used.

Winter temperature control in a non-airconditioned building with non-convective roof pond

This paper presents an investigation of the internal thermal environment of a building having a non-convective roof pond. A self consistent periodic heat transfer analysis has been developed to evaluate the indoor heat flux and the resultant inside air temperature. The effects of air ventilation/infiltration, furnishings (assumed to be isothermal masses) and the basement ground heat storage have been incorporated in the analysis. Numerical computations, corresponding to a typical winter day at New Delhi, have been made to illustrate the analytical results. It is found that the placement of a non-convective roof pond of about 10 cm depth considerably enhances the heat flux entering the living space and increases the indoor temperature to comfortable conditions in mild winter climates.

Condensation and mould growth in dwellings—parametric and field study

This paper presents a parametric study of the surface condensation problem in dwellings, which shows that in coastal regions with mild winter climate, absorbed surface condensation is probably unavoidable. The actual extent and severity of mould growth problems, which are due to the invisible surface condensation, were studied by means of a post-occupancy survey in 200 dwellings. Statistical analysis revealed that the major factors which affect the mould problem are: location and orientation of the dwellings, occupancy density, cooking habits and type of wall covering.

Using solar energy to heat water in low income housing

SYNOPSIS The NBRI originally developed a pipe type integral solar water heater for use in low income dwellings. This design was subsequently adapted by a number of manufacturers to suit manufacturing procedures and utilise more durable materials. The integral unit is relatively inexpensive and simple to install and operate. Its solar efficiency is high but it has the disadvantage that the water in the unit cools during the night. The integral unit unit is inherently frost resistant in a mild winter climate because of the large waterways and small exposed surface area. Those units currently available are water and hail resistant and are of durable construction. The integral solar water heater, when used as a stand-alone water heating system, is much more cost-effective than the alternative of an electrical geyser or a geyser combined with a solar water heater.

Zur Solifluktionsgrenze in den Gebirgen Japans

Concerning the solifluction boundary in the mountains of Japan. Japan may be divided into four periglacial morphological regions (fig. 2). Region 1 is an area of cool winters and heavy snowfall where periglacial forms seldom appear and then hardly ever below the timber-line. Region 2, in central Hokkaido, has a cold winter climate. In most parts the terrain in gently sloped and strongly influenced by peri glacial processes. Region 3 is distinguished by a cool winter climate and little snowfall. Here, periglacial forms are not widely spread, but they reach far below the timber-line, e. g. in central Honshu by approx. 800 metres and in north-east Hokkaido by approx. 1200 metres. In region 4, an area with a mild winter climate, periglacial forms are of little importance. In Japan the appearance of periglacial forms at a relativ ely low altitude and below the timber-line is related to the marked seasonal differences of temperature. At a level where woods can thrive in warm and humid summers, peri glacial forms (especially sorted steps, -rings, -nets and stripes) may appear in relatively cold winters, provided that the soil is not protected by dense plant or snow cover. Therefore the lower boundary of the periglacial stage in Japan is more difficult to define than in European mountain ranges; it also has a different qualitative significance. The knowledge gained as a result of investigations in Ja pan is compared with that of conditions in the north-eastern Appalachians, where the climate is very similar to that of Japan in region 3. Here, too, periglacial forms appear regularly within the upper woods. As a preliminary hypothesis it is assumed that within the perenially humid, temperate and subtropical climate zones one may generally differentiate between the following regions (fig. 3): 1. Mountain ranges with a difference of less than 15 ?C between the average temperature of the warmest and cold est months (temperature amplitude) and a lower boundary of the periglacial stage above the timber-line. 2. Mountain ranges with a temperature amplitude be tween 15? and 22 ?C and a lower boundary of the peri glacial stage at the altitude of the timber-line. 3. Mountain ranges with a temperature amplitude above 22 ?C and a lower boundary of the periglacial stage below the timber-line, i. e. with periglacial forms appearing regu larly within the upper woods. So far mountain ranges of region 3 have been studied the least.

Biology of the Adult Hemerobius pacificus1

The influence of temperature and photoperiod on reproduction of the predator Hemerobius pacificus Banks was studied in the laboratory. Short photoperiods (8–12 h) and a relatively low temperature (18.3°C) were found to be favorable for mating, fecundity, fertility and longevity. A life table is presented for these conditions. The adults lived a mean of 72 days (maximum 147 days). They deposited a mean of 715 eggs/♀ (maximum 2554 eggs); fertility was 92.0% until a week before death. The mean generation time was 6.1 weeks. Reproduction occurred at temperatures as low as 4.4°C. Mating and fecundity decreased at a constant temperature of 23.9°C, even under a short photoperiod. Estival diapause, which would protect this predator from hot summer climates could not be induced. It is concluded that H. pacificus is adapted to areas of California which have mild winter climates.

Freezing Resistance of Trees in North America with Reference to Tree Regions

Dormant one—year—old twigs of about 70 tree species were collected during mid—winter from five tree regions in North America (Rocky and Western Mountain, Northern, Pacific Coast, Southeastern Coast, and Central and Eastern Lowlands). The twigs were artificially hardened in a regime of sub—freezing temperatures between —3 degrees C and —10 degrees C for 24 days to induce maximum freezing resistance. Four Northern species, Populus tremuloides, Populus balsamifera, Betula papyrifera and Larix laricina had the greatest freezing resistance of the species tested. They resisted freezing to —80 degrees C and even immersion in liquid nitrogen (—196 degrees C) following prefreezing to —15 degrees C. Most of the Northern and Rocky and Western Mountain conifers survived freezing between —60 degrees and —80 degrees C while several species from the Pacific and SoutheasternCoast regions, which have relatively mild humid winter climates, were hardy to only among —15 degrees C. The ranges of some Pacific Coast species such as Pseudotsuga menziesii, Thuja plicata and Tsuga heterophylla extend into the mountainous inland. Samples collected from inland sites were found to be much hardier than those from the coast. A similar trend was observed in the various collections of Tsuga heterophylla from northern, central and southern areas along the Pacific Coast. Winter minimal temperatures are among the important factors setting the northern boundaries of the natural ranges of many forest tree species. However, Populus deltoides and Salix nigra from locations with temperate or moderate winter climates survived freezing to at least —50 degrees C irrespective to their native habitats. In these species, winter minimal temperatures do not appear to be the principal factor governing geographic distribution.