Cool Temperatures (cool + temperature)

Distribution by Scientific Domains


Selected Abstracts


Seasonal and inter-stream variations in the population dynamics, growth and secondary production of an algivorous fish (Pseudogastromyzon myersi: Balitoridae) in monsoonal Hong Kong

FRESHWATER BIOLOGY, Issue 9 2009
GRACE Y. YANG
Summary 1.,Balitorid loaches are widespread and highly diverse in Asian streams, yet their life history and ecology have received little attention. We investigated seasonal (wet versus dry season) and spatial variation in populations of algivorous Pseudogastromyzon myersi in Hong Kong, and estimated the magnitude of secondary production by this fish in pools in four streams (two shaded and two unshaded) over a 15-month period. 2.,Mean population densities of P. myersi ranged from 6.0 to 23.2 individuals m,2, constituting more than half (and typically >70%) of benthic fishes censused. Abundance was c. 25% greater in the wet season, when recruitment occurred. Significant density differences among streams were not related to shading conditions and were evident despite small-scale variations in P. myersi abundance among pools. Mean biomass varied among streams from 0.85 to 3.87 g ash-free dry weight (AFDW) m,2. Spatial and seasonal patterns in biomass and density were similar, apart from some minor disparities attributable to differences in mean body size among populations. 3.,All four P. myersi populations bred once a year in June and July, and life spans varied from 24 to 26 months. Populations consisted of three cohorts immediately after recruitment but, for most of the study period, only two cohorts were evident. Cohort-specific growth rates did not differ significantly among streams but, in all streams, younger cohorts had higher cohort-specific growth rates. 4.,Secondary production of P. myersi estimated by the size-frequency (SF) method was 2.7,11.5 g AFDW m,2 year,1 and almost twice that calculated by the increment-summation (IS) method (1.2,6.6 g AFDW m,2 year,1). Annual P/B ratios were 1.17,2.16 year,1 (IS) and 2.73,3.22 year,1 (SF). Highest production was recorded in an unshaded stream and the lowest in a shaded stream, but site rankings by production did not otherwise match shading conditions. Wet-season production was six times greater than dry-season production, and daily production fell to almost zero during January and February. Cool temperatures (<17 °C) may have limited fish activity and influenced detectability during some dry-season censuses. Estimates of abundance and annual production by P. myersi are therefore conservative. 5.,Comparisons with the literature indicate that the abundance and production of P. myersi in Hong Kong was high relative to other benthic fishes in tropical Asia, or their temperate counterparts in small streams. Manipulative experiments are needed to determine the influence of P. myersi, and algivorous balitorids in general, on periphyton dynamics and energy flow in Asian streams. [source]


Postnatal growth and reproductive biology of Rhinolophus hipposideros (Chiroptera: Rhinolophidae)

JOURNAL OF ZOOLOGY, Issue 3 2004
Guido Reiter
Abstract The timing of birth and postnatal growth in lesser horseshoe bats Rhinolophus hipposideros were studied during 2000 and 2001 at three maternity roosts located in the provinces of Carinthia and Salzburg, Austria. Postnatal growth curves for length of forearm and body mass were determined separately for the different colonies and years. Cooler weather during June 2001 coincided with a median birth date that was 8 days later than in 2000, whilst the difference between colonies was 4 and 5 days, respectively, for the pooled data of both years. Cool temperatures in June also coincided with a longer duration of the parturition period. Postnatal growth rates were higher than in most other bat species but differences between years and colonies were considerable. These differences may be attributed to the ambient roost temperatures, whereby the young of two cooler roosts showed significantly reduced growth rate during 8 days of cool weather in 2000. Moreover, later born and therefore smaller pups were more strongly affected by low temperatures than earlier born and larger ones. The mean length of forearm of young lesser horseshoe bats at the beginning of September equalled that of adult bats, whilst their body mass was still lower. Non-volant juveniles did not cluster following the nightly emergence of adult females, and a preferred location within the roosts could not be identified. High and very low roost temperatures, however, did have an influence on the location of non-volant young in the colonies. [source]


Flowering phenology of myrtaceous trees and their relation to climatic, environmental and disturbance variables in northern New South Wales

AUSTRAL ECOLOGY, Issue 2 2000
B. Law
Abstract Patterns of flowering phenology, which represent a partial description of food availability for nectarivores, are described for 20 species of myrtaceous trees on the mid-north coast of New South Wales (NSW), Australia. Data were recorded monthly between 1982 and 1992 across 23 sites that comprise a variety of local environmental conditions and disturbance histories. Flowering periodicity and intensity were highly variable between species and sites, ranging from annual flowering to no flowering over the 10-year period. Cool temperatures prior to floral budding was a strong predictor of flowering for nine species. Extraordinary climatic events also influenced flowering. The period of greatest flowering for all species combined occurred 9 months after the highest monthly rainfall recorded in the survey (March 1985). An 18-month extreme drought led to poor flowering in Corymbia variegata, Eucalyptus acmenoides, Eucalyptus grandis and Eucalyptus resinifera, but recovery after the drought broke was rapid. In contrast to climate, few site-based environmental variables explained the intersite variation in flowering performance of the tree species. Site disturbance from logging at two sites during the survey did not influence flowering in the remaining canopy over following years. No species showed a negative correlation with a history of recent logging, and direct comparisons, between large- and medium-sized trees, of the percentage of foliage in flower showed no differences for any species. At the scale of a timber production forest, the negligible effect of tree size (if >10 cm diameter at breast height over bark), and high stem density resulting from selective logging, leave about half of the net harvestable area producing flowers at a similar density to unlogged forest. However, larger trees flowered more frequently than medium-sized trees in C. variegata (medium: every 5.9 years; large: every 2.3 years) and there was a trend in this direction for 13 of 17 species. Low-intensity burns and wildfires caused differing amounts of crown scorch, sometimes resulting in bud loss, but most species flowered at prefire levels 1,3 years after the disturbance. Eucalyptus microcorys and Angophora costata flowered poorly at sites that experienced frequent low-intensity burns. Regionally, blossom shortages occur through a combination of spatial and temporal patchiness in flowering and the clearing of those species that occurred on soils preferred for agriculture. On the north coast of NSW, these shortages commonly occur from late winter to spring. Species that flower reliably in this period include Eucalyptus robusta, Eucalyptus tereticornis and Eucalyptus siderophloia in late winter and E. siderophloia and E. acmenoides in spring. [source]


Relative importance of microhabitat, plant form and photosynthetic physiology to carbon gain in two alpine herbs

FUNCTIONAL ECOLOGY, Issue 2 2001
M. J. Germino
Abstract 1.,The effects of microhabitat and plant form on sunlight interception, leaf temperatures, frost occurrence and photosynthesis were evaluated for Caltha leptosepala DC and Erythronium grandiflorum Pursh. Both plants are perennials that commonly emerge from alpine snowbanks where the combination of cool temperatures and strong sunlight is among the most extreme for vascular plants. 2., Caltha leptosepala occurred in microsites where colder air accumulates, and has larger, less inclined and more densely clustered leaves compared to E. grandiflorum (which has two steeply inclined leaves). 3.,These differences in microsite and plant form led to leaf temperatures below 0 °C on 70% of nights during the summer growth season in C. leptosepala, compared to only 38% in E. grandiflorum. Leaves of C. leptosepala warmed more slowly on mornings following frosts compared to E. grandiflorum, due to less aerodynamic coupling between leaf and air temperature, and also a 45% smaller ratio of sunlit to total leaf area due to mutual shading among leaves. 4.,As a result, night frost did not affect subsequent CO2 assimilation (A) in E. grandiflorum, while frostless nights and warmer mornings led to 35% greater A in C. leptosepala in the early morning. 5.,There were no appreciable differences in the temperature and light response of photosynthesis between the two species. The apparent quantum yield of A declined only ,8% in both species following frost and exposure to strong sunlight, indicating little adjustment of photosynthetic physiology. 6.,Greater daily carbon gain probably occurs for E. grandiflorum because of its plant form and microclimate, rather than differences in photosynthetic physiology. [source]


Air temperatures at Armagh Observatory, Northern Ireland, from 1796 to 2002

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 8 2005
C. J. Butler
Abstract Three independent mean temperature series for Armagh Observatory, covering the period 1796,2002 have been calibrated and corrected for the time of reading and exposure. Agreement between the three series is good in regions of overlap. With a short gap in the Armagh data from 1825 to 1833 filled by data from two stations in Dublin, the resulting series is the longest for the island of Ireland and one of the longest for any single site in the British Isles. Over the past 207 years, we note that temperatures in Armagh, in all seasons, show a gradual overall trend upwards. However, there are seasonal differences: summer and spring temperatures have increased by only half as much as those in autumn and winter. This is partly due to the exceptionally cold winters and autumns experienced prior to 1820. Relative to the overall trend, warm periods occurred in Ireland, as in other parts of Europe, in the mid-19th century, in the mid-20th century and at the end of the 20th century. Relatively cool temperatures prevailed in the early 19th century, in the 1880s and in the 1970s. Thus, if the baseline against which current temperatures are compared were moved from the late 19th century to include the earlier warm period, the apparent warming at the end of the late 20th century would be correspondingly reduced. A gradual decline in the daily temperature range at Armagh since 1844 may have resulted from higher minimum temperatures associated with increased cloudiness. A 7.8 year periodicity is identified in winter and spring mean temperatures at Armagh, which is probably a consequence of the North Atlantic oscillation. Copyright © 2005 Royal Meteorological Society [source]


The Effects of Plant Population Density on the Growth and Chemical Composition of Lablab purpureus Grown for Fodder Production in a Semi-Arid Region

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 2 2001
Y. Shehu
Lablab purpureus was grown in two 6-month field experiments in the Savannah region of Africa, with high rainfall and hot temperatures in the first 2 months, followed by low rainfall and cool temperatures until harvesting in January. The experiments evaluated the effects of plant population density (PPD), using rows at 70-, 110- and 150-cm intervals, on the yield and nutritive value of the crop, and the effect of an interim harvest on response to PPD. Lablab yield ha,1 was increased to a greater extent by an increase in PPD from 110 to 70 cm interrow spacing than by an increase from 150 to 110 cm, and yield plant,1 decreased as PPD increased to a greater extent for double-harvested than for single-harvested plants. This suggested that high PPD in the early stages of growth is important to promote high crop yields in this environment, probably because it mitigates drought effects in autumn. The effects of PPD on herbage composition were small and suggested that plant maturity had not been greatly affected by density. It is concluded that the maintenance of plant cover in the early stages of growth is important for high yields in the Savannah region, which can be achieved by an interrow spacing of no more than 70 cm and avoidance of an interim harvest. Die Einflüsse der Bestandesdichte auf Wachstum und chemische Zusammensetzung von Lablab purpureus im Anbau zur Futterproduktion in einer semiariden Region Lablab purpureus wurde in zwei 6 Monate andauernden Feldexperimenten in der Savannenregion von Afrika angebaut, wobei hoher Regenfall und hohe Temperaturenin den ersten beiden Monaten, gefolgt durch niedrigen Regenfall und kühle Temperatur bis zur Ernte im Januar vorherrschten. Die Experimente wurden im Hinblick auf die Einflüsse der Bestandesdichte (PPD) ausgewertet, wobei Reihenabstände von 70, 110 und 150 cm hinsichtlich des Ertrages und des Nährwertes des Bestandes und des Einflusses auf eine Zwischenernte in Abhängigkeit von PPD untersucht wurden. Der Lablab -Ertrag/ha war stärker durch Zunahmen in PPD von 110,70 cm Reihenabständen erhöht als bei Abständen von 150,110 cm; in diesem Fall nahm der Ertrag je Pflanze mit einer Zunahme von PPD für zweifache Ernte stärker zu als bei Pflanzen mit einmaliger Aberntung. Dies lässt vermuten, dass hohe PPD in frühen Stadien des Wachstums bedeutend ist für die Förderung des Bestandesertrages in dieser Umwelt, da wahrscheinlich Trockeneinflüsse im Herbst abschwächt werden. Die Einflüsse von PPD auf die Spross-Zusammensetzung war gering und lässt vermuten, dass die Pflanzenreife kaum von der Bestandesdichte abhängig ist. Es wird angenommen, dass der Halt der Pflanzenbedeckung in den frühen Stadien des Wachstums Bedeutung für hohe Erträge in der Savannenregion hat; dies kann mit Reihenabständen nicht über 70 cm und dem Vermeiden einer Zwischenernte erreicht werden. [source]


Low-temperature photosynthetic performance of a C4 grass and a co-occurring C3 grass native to high latitudes

PLANT CELL & ENVIRONMENT, Issue 7 2004
D. S. KUBIEN
ABSTRACT The photosynthetic performance of C4 plants is generally inferior to that of C3 species at low temperatures, but the reasons for this are unclear. The present study investigated the hypothesis that the capacity of Rubisco, which largely reflects Rubisco content, limits C4 photosynthesis at suboptimal temperatures. Photosynthetic gas exchange, chlorophyll a fluorescence, and the in vitro activity of Rubisco between 5 and 35 °C were measured to examine the nature of the low-temperature photosynthetic performance of the co-occurring high latitude grasses, Muhlenbergia glomerata (C4) and Calamogrostis canadensis (C3). Plants were grown under cool (14/10 °C) and warm (26/22 °C) temperature regimes to examine whether acclimation to cool temperature alters patterns of photosynthetic limitation. Low-temperature acclimation reduced photosynthetic rates in both species. The catalytic site concentration of Rubisco was approximately 5.0 and 20 µmol m,2 in M. glomerata and C. canadensis, respectively, regardless of growth temperature. In both species, in vivo electron transport rates below the thermal optimum exceeded what was necessary to support photosynthesis. In warm-grown C. canadensis, the photosynthesis rate below 15 °C was unaffected by a 90% reduction in O2 content, indicating photosynthetic capacity was limited by the capacity of Pi -regeneration. By contrast, the rate of photosynthesis in C. canadensis plants grown at the cooler temperatures was stimulated 20,30% by O2 reduction, indicating the Pi -regeneration limitation was removed during low-temperature acclimation. In M. glomerata, in vitro Rubisco activity and gross CO2 assimilation rate were equivalent below 25 °C, indicating that the capacity of the enzyme is a major rate limiting step during C4 photosynthesis at cool temperatures. [source]


Capsule Treatments to Enhance Seedling Emergence of Gaura neomexicana ssp. coloradensis

RESTORATION ECOLOGY, Issue 1 2005
L. M. Burgess
Abstract Management of riparian vegetation is difficult because these communities are frequently impacted by herbivores, invasive weeds, and altered hydrologic regimes. Multiple and intertwined factors affecting rare species recruitment are particularly difficult to identify. Gaura neomexicana ssp. coloradensis Munz (Gaura) is a short-lived perennial forb endemic to riparian areas in mixed-grass prairies of Wyoming, Nebraska, and Colorado, U.S.A. It became a federally listed threatened species in October 2000. Because the species is a recruitment-limited monocarpic perennial, we studied the effects of six capsule-collection dates, a 2-month cool-moist stratification, 24-hr leaching, and 24-hr imbibition on Gaura seedling emergence. Seedling emergence did not vary with collection date. Capsules collected from Gaura plants grown at the Bridger Plant Materials Center in Montana exhibited greater emergence than capsules harvested from endemic populations near Cheyenne, Wyoming, suggesting that maternal plant growing conditions impact dormancy. Because cool-moist stratification enhanced seedling emergence of Gaura and leaching did not, sufficient moisture during cool temperatures may be more critical than leaching of germination inhibitors as might occur with normal stream flows. Spring flooding may enhance Gaura recruitment by increasing the availability of riparian sites that are inundated during periods of cool temperatures. If so, hydrologic and climatic regimes must be considered in restoring the unique conditions needed for germination of this rare riparian endemic. [source]