scholarly journals Germination at Extreme Temperatures: Implications for Alpine Shrub Encroachment

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 327
Author(s):  
Susanna E. Venn ◽  
Rachael V. Gallagher ◽  
Adrienne B. Nicotra
Keyword(s):  
Geographic Distribution ◽  
Shrub Encroachment ◽  
Shrub Species ◽  
Ambient Temperatures ◽  
Average Temperature ◽  
Alpine Shrub ◽  
Maximum Temperatures ◽  
Gradient Plate ◽  
High Elevations ◽  
Germination Niche

Worldwide, shrub cover is increasing across alpine and tundra landscapes in response to warming ambient temperatures and declines in snowpack. With a changing climate, shrub encroachment may rely on recruitment from seed occurring outside of the optimum temperature range. We used a temperature gradient plate in order to determine the germination niche of 14 alpine shrub species. We then related the range in laboratory germination temperatures of each species to long-term average temperature conditions at: (1) the location of the seed accession site and (2) across each species geographic distribution. Seven of the species failed to germinate sufficiently to be included in the analyses. For the other species, the germination niche was broad, spanning a range in temperatures of up to 17 °C, despite very low germination rates in some species. Temperatures associated with the highest germination percentages were all above the range of temperatures present at each specific seed accession site. Optimum germination temperatures were consistently within or higher than the range of maximum temperatures modelled across the species’ geographic distribution. Our results indicate that while some shrub species germinate well at high temperatures, others are apparently constrained by an inherent seed dormancy. Shrub encroachment in alpine areas will likely depend on conditions that affect seed germination at the microsite-scale, despite overall conditions becoming more suitable for shrubs at high elevations.

Photoperiod and Temperature Influence on Flower Initiation and Development for Euphorbia pulcherrima Grown Under Florida Conditions

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 509a-509
Author(s):  
C.E. Wieland ◽  
J.E. Barrett ◽  
D.G. Clark ◽  
G. J. Wilfret
Keyword(s):  
Subsequent Development ◽  
Flower Initiation ◽  
Euphorbia Pulcherrima ◽  
Floral Initiation ◽  
Temperature Influence ◽  
Average Temperature ◽  
Long Day ◽  
Time To Initiation ◽  
Growth Room ◽  
Maximum Temperatures

Four poinsettia cultivars were grown in glass greenhouses in Gainesville, Fla., in the Fall 1997 to evaluate differences in floral initiation and subsequent development. Three means of regulating photoperiod were 1) natural days 2) long-day lighting to 6 Oct. and then natural days (lights out) 3) long-day lighting to 6 Oct., and then short-day conditions by black cloth for 15 h (black cloth). At 2-day intervals, sample meristems were collected and examined for initiation of reproductive development. Average minimum and maximum temperatures during the first two weeks of October were 22 and 29 °C, respectively, with an average temperature of 25.3 °C. The overall average temperature was 23.2 °C from planting to anthesis. Differences in anthesis dates among cultivars were primarily due to time to initiation vs. rate of development. Under natural days, `Lilo' initiated first on 8 Oct. and `Freedom', `Peterstar', and `Success', followed by 6, 8, and 18 days, respectively. Lights out resulted in `Lilo' initiating 17 Oct., followed by `Freedom', `Peterstar', and `Success' initiating 7, 12, and 15 days later, respectively. Differences between cultivars in time of initiation was reduced under black cloth, where `Lilo' initiated 14 Oct., followed by `Freedom' 2 days later, and `Peterstar' and `Success' 7 days afterward. Initiation was positively correlated to visible bud and anthesis. First color was positively correlated to initiation and visible bud, with the exception of `Lilo'. Growth room studies conducted using various high temperatures and photoperiods indicated similar trends.

Phenological development and seasonal distribution of the rutherglen bug, Nnysius vinitor Bergroth (Hemiptera: Lygaeidae), on various hosts in Victoria, south-eastern Australia

1988 ◽  
Vol 78 (4) ◽  
pp. 673-682 ◽  
Author(s):  
Garrick McDonald ◽  
A. Mark Smith
Keyword(s):  
Rapid Development ◽  
Early Spring ◽  
Common Source ◽  
Body Temperatures ◽  
Ambient Temperatures ◽  
Polygonum Aviculare ◽  
Developmental Thresholds ◽  
Eastern Australia ◽  
Weed Hosts ◽  
Maximum Temperatures

AbstractPopulations of Nysius vinitor Bergroth were studied from 1979 to 1982 in two weed hosts, Arctotheca calendula and Polygonum aviculare, and eight irrigated sunflower crops in a summer cropping area of northern Victoria, Australia. The spring generation began with the adults colonizing flowering A.calendula plants in September and concluded with the rapid development of late stage nymphs and an exodus of adults from these plants from mid-November to December. Gradual invasion of sunflowers occurred mostly in late December and reached a peak at flowering, after which nymphs appeared. P. aviculare attracted adults from February and hosted a number of overlapping generations until winter. The weed sustained diminishing numbers of adults through the winter, except in 1982, when a further generation produced an early spring peak. Immigrant populations were regarded as a common source of adults for initiating the spring and summer generations. The rate of development of N. vinitor in spring was more rapid than that predicted by phenological simulation based on ambient temperatures and laboratory-derived day-degree estimates. This was attributed to increased body temperatures through absorption of solar radiation, and the simulation model was adjusted by increasing daily minimum and maximum temperatures by 1·3 and 5·5°C for young and older instars, respectively. This suggested that older nymphs have lower developmental thresholds or are better able to optimize body temperatures.

scholarly journals Temperature and Wetness-Duration Requirements for Grape Leaf and Cane Infection by Phomopsis viticola

Plant Disease ◽  
2003 ◽  
Vol 87 (7) ◽  
pp. 832-840 ◽  
Author(s):  
O. Erincik ◽  
L. V. Madden ◽  
D. C. Ferree ◽  
M. A. Ellis
Keyword(s):  
Disease Severity ◽  
Correlation Coefficients ◽  
Phomopsis Viticola ◽  
Average Temperature ◽  
Growing Seasons ◽  
Wide Range ◽  
Maximum Temperatures ◽  
Rain Events ◽  
Grape Leaf ◽  
The Relationship

In 1998 and 1999, controlled-environment studies were conducted in growth chambers to determine the temperature and wetness-duration parameters required for leaf and cane infection of grape by Phomopsis viticola. Greenhouse-grown ‘Catawba’ (Vitis labrusca) and ‘Seyval’ (French hybrid) grapes were inoculated with P. viticola and incubated at constant temperatures of 5, 10, 15, 20, 25, 30, and 35°C and at wetness durations of 5, 10, 15, and 20 h for each temperature. Data from each cultivar were analyzed by nonlinear regression analysis to determine the relationship between disease severity and temperature and wetness duration. A generalized form of the Analytis Beta model was found to provide the best fit to the data. Disease severity on leaves and canes increased with increasing wetness duration at most temperatures. Minimum and maximum temperatures for infection were around 5 and 35.5°C, respectively. Optimum temperatures for leaf and cane infection were between 16 and 20°C. In the 2000 and 2001 growing seasons, the generalized Beta model was validated in ‘Catawba’ and ‘Seyval’ vineyards by inoculating vines during natural rain events. Average temperature and hours of wetness for each event and inoculation were recorded and used in the model equation to predict disease severity on leaves and internodes. Correlation coefficients between observed disease severities following field inoculations and predicted disease severities for both cultivars were between 0.71 and 0.81 and always significant (P < 0.01). These results indicate that the model reliably predicted leaf and cane infection on both cultivars over a wide range of wetness durations and temperatures. The model may be useful in developing disease-forecasting systems for Phomopsis cane and leaf spot on grapes.

scholarly journals Does Shrub Encroachment Indicate Ecosystem Degradation? A Perspective Based on the Spatial Patterns of Woody Plants in a Temperate Savanna-Like Ecosystem of Inner Mongolia, China

Forests ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1248
Author(s):  
Xiao Wang ◽  
Lina Jiang ◽  
Xiaohui Yang ◽  
Zhongjie Shi ◽  
Pengtao Yu
Keyword(s):  
Inner Mongolia ◽  
Woody Plants ◽  
Plant Cover ◽  
Distribution Patterns ◽  
Research Area ◽  
Shrub Encroachment ◽  
Point Pattern Analysis ◽  
Point Pattern ◽  
Shrub Species ◽  
Degraded Ecosystems

Shrub encroachment, i.e., shrub emergence or an increase in woody plant cover, has been widely observed in arid and semiarid grasslands and savannas worldwide since the 2000s. However, until now, there has been a clear division of opinion regarding its ecological implications. One view is that shrub encroachment is an indicator of ecological degradation, and the other is that shrub encroachment is a sign of the restoration of degraded ecosystems. This division leads to completely different judgments about the states and transition phases of shrub-encroached ecosystems, which further affects decisions about their conservation and management. To determine whether ecosystems experiencing shrub encroachment are degrading or are in a postdegraded restoration stage, the spatial distributions and interactions of woody plants after shrub encroachment were investigated in this study. An Ulmus pumila-dominated temperate savanna-like ecosystem with significant shrub encroachment in the Otindag Sandy Land, Inner Mongolia, China, was selected as the research area, and woody plants were surveyed within a 25-hectare (500 × 500 m) plot. Spatial point pattern analysis was employed to analyze the distribution patterns of the woody plants. The results indicated different patterns for U. pumila trees, i.e., a random distribution pattern for old trees (with a diameter at breast height (DBH) of more than 20 cm) and aggregated distribution patterns for medium (5 cm ≤ DBH < 20 cm) and juvenile trees (DBH < 5 cm) at scales of 0–9 and 0–12 m, respectively. For most shrubs, there was significant aggregation at a scale of 0–6 m. However, there were significant negative relationships between old U. pumila trees (DBH ≥ 20 cm) and most shrub species, such as Caragana microphylla and Spiraea aquilegifolia. In contrast, there were positive relationships between juvenile trees (DBH < 5 cm) and most shrub species. These results suggest that, to some extent, shrub encroachment may have disrupted the normal succession pattern in the U. pumila community in this area, and without conservation, the original tree-dominated temperate savanna-like ecosystem may continue to deteriorate and eventually become a shrub-dominated temperate savanna-like ecosystem.

scholarly journals Changes in climate conditions and their effects on production and reproduction of medium yielding cows in temperate continental climate

2019 ◽  
Vol 69 (4) ◽  
pp. 264-275
Author(s):  
Silviu-Ionuţ Borş ◽  
Iulian Ibănescu ◽  
Emesse Balla ◽  
Alina Borş
Keyword(s):  
Artificial Insemination ◽  
Climate Changes ◽  
Dairy Farm ◽  
Reproductive Parameters ◽  
Climate Conditions ◽  
Ambient Temperatures ◽  
North Eastern ◽  
Hot Season ◽  
Maximum Temperatures ◽  
Continental Climate

The increased air temperature combined with the reduction of rainfall during hot season impairs the capacity of cows to maintain the optimal body temperature. This study tested the hypothesis that climate changes affect the medium yielding cows in temperate continental climate. The productive-reproductive parameters of 8607 milking cows from a dairy farm in North-eastern Romania were examined and correlated with changes in ambient temperatures and rainfall between the years of 1983 and 2010. We observed that the number of artificial inseminations served to cows showed a decreasing trend. The reduction in this parameter was significantly influenced by the increase in the average and maximum temperatures during hot season associated with the reduction in rainfall, as shown by regression analysis. Other studied parameters such as milk production, calving to conception interval, calving to first artificial insemination interval and conception rates at first, second and more than two services were not related to the changes in average annual temperatures, annual temperatures amplitude and annual precipitation quantities. This study suggests that, although present, the effects of climate changes on some productive-reproductive parameters of medium yielding cows in geographic areas with temperate continental climate are not as dramatic as described in other studies.

Elevational Correlates of Speciation and Intraspecific Geographic Variation in Plumage in Andean Forest Birds

The Auk ◽  
1985 ◽  
Vol 102 (3) ◽  
pp. 556-579 ◽  
Author(s):  
Gary R. Graves
Keyword(s):  
Species Richness ◽  
Geographic Variation ◽  
Intraspecific Variation ◽  
Geographic Distribution ◽  
Ecological Factors ◽  
Geographic Range ◽  
Forest Birds ◽  
Elevational Distribution ◽  
The Mean ◽  
High Elevations

Abstract Intraspecific variation in plumage was used to test the null hypotheses that geographic variation in 280 species of elevationally restricted Andean forest birds is independent of elevation and is not a function of patchy geographic distribution. Both null hypotheses were rejected. At most taxonomic levels, geographic variation in plumage was correlated positively with both the mean of its elevational distribution and the size of its geographic range. Vertical amplitude of elevational distribution was not a significant predictor of geographic variation in plumage in most taxa. Independent of these elevational correlates, patchily distributed species showed significantly more geographic variation than continuously distributed species. These results show that geographic variation and presumably ongoing speciation phenomena are greater at higher elevations. The decreased species richness at high elevations may be attributable to a higher rate of extinction from catastrophic disturbance as well as to ecological factors that limit sympatry in newly formed species.

Patch mosaic cyclic succession associated with the growth and senescence of an alpine shrub

2016 ◽  
Vol 64 (2) ◽  
pp. 111 ◽  
Author(s):  
Danielle C. McPhail ◽  
Jamie B. Kirkpatrick
Keyword(s):  
Vegetation Change ◽  
Root Competition ◽  
Shrub Species ◽  
Central Plateau ◽  
Clear Sky ◽  
Patch Mosaic ◽  
Dead Material ◽  
Alpine Shrub ◽  
Floristic Variation ◽  
Sky Conditions

Endogenously-induced cyclic vegetation change has been associated with the life cycle of shrub species, resulting in mosaic or linear patterning in vegetation. We investigated whether mosaic cyclic succession was taking place in Richea acerosa (Lindley) F.Muell. alpine heath on the Central Plateau of Tasmania, Australia by determining the variation in species composition associated with different growth characteristics of the shrub and by monitoring shrubs in plots over 11 years. Temperatures below and adjacent to shrubs were measured in clear sky conditions to determine if microclimatic variation was associated with structural and floristic variation. Species richness was higher outside than inside the shrubs, and was further depressed by an increasing proportion of dead material in the shrub. However, Poa saxicola R.Br. appeared to be protected by the prickly foliage of R. acerosa and also preferentially occurred among the mass of dead stems that characterised the centre of older plants. There was a strong floristic shift associated with the development of the shrub. The live cover of individual shrubs remained constant in all plots over the 11 years, while plots initially dominated by senescent plants contained young plants and vice-versa. The live part of the shrubs moderated temperatures. However, root competition and protection from grazing seem likely to have made a major contribution to the shifting conditions associated with the mosaic cyclic succession.

Packaging of High Burnup UO2 and MOX Spent Fuel Considering Temperature Restrictions in the Near Field of a Repository

1997 ◽  
Vol 506 ◽  
Author(s):  
D.F. McGinnes ◽  
J. W. Schneider
Keyword(s):  
Near Field ◽  
Management Program ◽  
High Level Waste ◽  
Heat Output ◽  
Spent Fuel ◽  
Ambient Temperatures ◽  
Heat Loading ◽  
High Burnup ◽  
Maximum Temperatures ◽  
High Level

ABSTRACTThe direct disposal of spent fuel is one of the options considered in the Swiss high level waste management program. One of the important questions, within this program, is the heat generation from high-burnup UO2and MOX spent fuels. Depending on the repository boundary conditions (e.g. ambient temperatures at depth, thermal properties of the host rock etc.), on the maximum temperatures allowed in the near field and on the heat output of the fuel, it may not always be possible to completely fill the conceptual waste canister. The aim of this paper is to address the potential loading of spent fuel into canisters for different possible repository heat loading restrictions

scholarly journals Climatic and Altitudinal Influences on Variation in Macaca Limb Morphology

2011 ◽  
Vol 2011 ◽  
pp. 1-18 ◽  
Author(s):  
Karen J. Weinstein
Keyword(s):  
Partial Correlation ◽  
Principal Component ◽  
Interspecific Variation ◽  
Climatic Conditions ◽  
Ambient Temperatures ◽  
Interspecific Variations ◽  
Large Joint ◽  
Small Joint ◽  
High Elevations ◽  
Limb Morphology

This study compares limb lengths and joint diameters in the skeletons of six macaque species (Macaca assamensis, M. fascicularis, M. fuscata, M. mulatta, M. nemestrina, and M. thibetana) from a broad range of habitats and climates in order to test whether ambient temperatures, latitude, and altitude influence interspecific variation in limb morphology in this widely dispersed genus. Analysis of variance, principal component analysis, and partial correlation analysis reveal that species from temperate latitudes and high elevations tend to have short limbs and large joint diameters for their sizes while species from tropical latitudes and low elevations tend to have long limbs and small joint diameters. Interspecific variations in intra- and interlimb length proportions also reflect phylogeny and subtle differences in locomotion. The results of this study suggest that climatic conditions are important factors among many ecological variables that influence limb morphology in this geographically widespread genus.

Influence of season and environment on fertility of goats in a hot-arid environment

2002 ◽  
Vol 138 (1) ◽  
pp. 97-102 ◽  
Author(s):  
M. MELLADO ◽  
C. A. MEZA-HERRERA
Keyword(s):  
Arid Environment ◽  
Conception Rate ◽  
Maximum Temperature ◽  
Mean Annual Precipitation ◽  
Ambient Temperatures ◽  
Northern Mexico ◽  
Average Maximum ◽  
Average Maximum Temperature ◽  
Maximum Temperatures ◽  
Breeding Efficiency

Conception rate and prolificacy of dairy and crossbred goats under intensive conditions in an arid environment of northern Mexico (26° 06′ 15′′ N; maximum temperature throughout the year 12–42 °C, mean annual precipitation 186 mm, and RH <40% year-round) were examined with respect to season of mating, ambient temperature and rainfall at mating. The database contained 4194 natural services. Conception of goats inseminated with average maximum ambient temperatures >34 °C was significantly higher (P<0·01) than conception of goats inseminated when the average maximum temperature 3 days before breeding was <34 °C. The warmest season favoured conception rate (70% in spring; P<0·01) as compared to cooler seasons (62% and 64% for summer and autumn, respectively). Conception rate of goats bred when rain was present was 14 percentage points lower (P<0·01) compared to mating with no rain. When maximum temperatures on the day of mating were >34 °C, cooler temperatures 1 to 3 days before or after the day of mating were associated with a significant increase in the number of kids born. When the maximum temperature at mating was >36 °C, prolificacy for goats exposed to higher or lower temperatures 1 day before mating was 1·56 and 1·65, respectively (P<0·05). Similarly, when the maximum temperature at mating was 34–36 °C, prolificacy was higher for goats exposed to cooler temperatures as compared to warmer temperatures 1 day (1·64 v. 1·49; P<0·01) or 3 days (1·63 v. 1·48; P<0·01) after mating, with respect to the temperature on the day of mating. Conclusions were that conception rate was not compromised in non-lactating Alpine, Toggenburg, Granadino and Nubian goats subjected to high environmental temperature in an arid region, but the occurrence of rain at mating depressed breeding efficiency of these animals. Additionally, an increment in litter size is expected with cooler temperatures before or after hot days at time of mating.

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