Altitudinal Variation in the Photosynthetic Characteristics of Snow Gum, Eucalyptus pauciflora Sieb. Ex Spreng. VII. Relationship Between Gradients of Field Temperature and Photosynthetic Temperature Optima in the Snowy Mountains Area

1978 ◽  
Vol 26 (1) ◽  
pp. 111 ◽  
Author(s):  
RO Slatyer
Keyword(s):  
Close Agreement ◽  
Temperature Response ◽  
Lapse Rate ◽  
Maximum Temperature ◽  
Temperature Function ◽  
Preferred Temperature ◽  
Field Temperature ◽  
Effective Selection ◽  
Wave Conversion ◽  
Temperature Optima

Elevational gradients of several field temperature parameters were examined and compared with estimated and observed photosynthetic temperature optima for a range of elevational populations of E. pauciflora. The gradient of maximum temperature (9.68°km-1) was found to be very close to the dry adiabatic lapse rate, regardless of whether annual, seasonal or monthly conditions were examined. In contrast, the gradient of minimum temperature (2.06°km-1) was much flatter and was affected by topographic location, particularly at sites exposed to nocturnal temperature inversions. The gradient of the square-wave conversion of the day-time temperature curve (Tsqw), found previously to be useful in mediating the photosynthetic temperature response, was intermediate in slope, 7.20°km-1. The gradient of the phytotron-derived preferred temperature for photosynthesis, Tpref (6.26°km-1), was very close to that for Tsqw. The acclimation coefficient, α, showed no apparent change with elevation. Estimates of field photosynthetic temperature optima, based on Tpref, α and Tequiv (which was the value of Tsqw averaged for 10 days prior to the date of measurement) were in close agreement with measured values. The close agreement between the gradients of Tpref and Tsqw, together with the effectiveness of estimation of field temperature optima by means of Tequiv suggested that a temperature function resembling Tsqw may exert effective selection pressure on the photosynthetic temperature response of E. pauciflora in this environment.

Altitudinal Variation in the Photosynthetic Characteristics of Snow Gum, Eucalyptus pauciflora Sieb. ex Spreng. VI. Comparison of Field and Phytotron Responses to Growth Temperature

1977 ◽  
Vol 4 (6) ◽  
pp. 901 ◽  
Author(s):  
RO Slayter
Keyword(s):  
Growth Temperature ◽  
Temperature Response ◽  
Net Photosynthesis ◽  
Equivalent Temperature ◽  
Temperature Optimum ◽  
Response Curves ◽  
Preferred Temperature ◽  
Practical Applications ◽  
Field Temperature ◽  
Temperature Optima

A procedure for estimating field photosynthetic temperature optima from phytotron temperature response data, for elevational populations of E. pauciflora, is developed. It utilizes the principle that each population has a preferred temperature, Tpref, and an acclimation coefficient, α, which can be determined from phytotron-derived temperature response curves, and which enable the photosynthetic temperature optimum observed in a particular field temperature regime (Test) to be estimated from the expression Test = Tpref - α(Tpref - Tequiv), where Tequiv is a field temperature equivalent, in terms of its effect on the photosynthetic temperature optimum, to a known phytotron growth temperature. Application of the procedure to sets of field and greenhouse data suggests that when Tpref and α are based on phytotron day growth temperatures, and when Tequiv is based on the proposition that a square-wave conversion of the field day-time temperature curve is equivalent to the phytotron day growth temperature, estimates of field and greenhouse temperature optima can be made which give good agreement with observed values. The agreement is best when active, current-year tissue is used as a basis of the field observations and when single leaves rather than shoots are used for field measurements. The procedure is also used to compare actual rates of net photosynthesis, Pamb, obtained from field and phytotron studies, when both are plotted against equivalent temperature. Using this procedure, the large apparent differences between rates of net photosynthesis observed in the field and in the phytotron can be considerably reduced. This suggests that the notion of equivalent temperature may provide a useful means of minimizing the effects of physical, temperature-related differences in comparing field and phytotron responses, thereby widening the range of practical applications of phytotron experiments.

Altitudinal Variation in the Photosynthetic Characteristics of Snow Gum, Eucalyptus pauciflora Sieb. ex Spreng. V. Rate of Acclimation to an Altered Growth Environment

1977 ◽  
Vol 4 (4) ◽  
pp. 595 ◽  
Author(s):  
RO Slayter ◽  
PJ Ferrar
Keyword(s):  
Control Level ◽  
High Elevation ◽  
Maximum Temperature ◽  
Daily Maximum Temperature ◽  
Daily Maximum ◽  
Temperature Optimum ◽  
Preferred Temperature ◽  
Growth Environment ◽  
Temperature Optima ◽  
Maximum Minimum

Established, field-grown, seedlings of Eucalyptus pauciflora were transferred from high- and low- elevation field sites to a controlled-environment greenhouse in Canberra (maximum/minimum daily temperature range 26/15°) and the pattern of photosynthetic acclimation observed. Levels of net photosynthesis, Pamb, intracellular resistance rI, and leaf gas-phase resistance to CO2 transfer (r1) were monitored, as were the temperature optima for these parameters. Acclimation proceeded most rapidly in the material grown at the warmer, low-elevation, site (955 m), and in the low-elevation population. Daily maximum/minimum temperatures at this site for the 10 days prior to transfer averaged 23/11°. With this material, levels of, and the temperature optimum for, Pamb reached control levels within 6 days of transfer from the field environment. By comparison, Pamb in the high-elevation population grown at the high-elevation (tree-line) site (1910 m) where the 10-day temperature averaged 15/7°, did not reach control levels until 14 days after transfer, and the temperature optimum for Pamb required 20 days to reach the control level. In general, the patterns of change in rI and r1 paralleled those in Pamb. Both the level of physiological activity in the field, and the temperature differences between the field and greenhouse environment, appeared to affect the rate of acclimation. Immediately after transfer from the field, the temperature optima of the high-and low-elevation populations were close to the daily maximum temperature of the respective field environments. The temperature optimum of the high-elevation material grown at the low-elevation site was intermediate in value. At the conclusion of the acclimation period, the temperature optima of both high-elevation populations had converged to a value similar to that of the high-elevation control (about 22°); similarly, the temperature optimum of the low-elevation populations had reached the level of the low-elevation control (27°) These various temperature optima are interpreted on the basis that each population has a 'preferred' temperature which can be modified by different effective growth temperatures to yield different optima in different thermal environments. In the field, the effective temperature appears to be intermediate between the prevailing maximum and minimum temperatures.

Temperature/light interactions and the effect of seed source on germination of annual ryegrass (Lolium rigidum Gaud.) seeds

1976 ◽  
Vol 27 (6) ◽  
pp. 779 ◽  
Author(s):  
D Gramshaw
Keyword(s):  
Constant Temperature ◽  
Day Length ◽  
Maximum Temperature ◽  
Annual Ryegrass ◽  
Lolium Rigidum ◽  
Average Temperature ◽  
Seed Sources ◽  
Alternating Temperature ◽  
Germinating Seeds ◽  
Temperature Optima

Germination of Lolium rigidum seeds, in the light (12 hr day length) and in the dark, was studied at constant and alternating (12/12 hr) temperatures in the range 8–35°C. Seeds had after-ripened for 22 weeks. Different constant temperature optima for germinability were found: 27° in light and 11° in dark. Germinability at alternating temperatures in darkness was determined solely by the minimum temperature of the alternation, and there was no response to thermoperiodicity per se. In contrast, light and alternating temperature appeared to interact to increase germinability, although the highest germinability occurred only when the maximum temperature was close to the optimum constant temperature, i.e. about 27°. Germination in both light and dark was most rapid where either the constant or the average temperature of an alternating regime was between 18 and 29°. Below 18° germination rates decreased markedly, and at 8°, rates were one-third of those at 18°. Seeds germinated more slowly in light than in darkness at all temperatures, but the differences were small relative to the effects of low temperatures.In another study, seeds collected from plants naturalized in eight different localities in the cereal belt of Western Australia and subsequently planted together in two contrasting environments were examined for germinability at 24/12°C in light and dark 18 weeks after harvest. Dark germinability differed between seed sources but not between planting sites, and ranged between 78 and 93%. Exposure of germinating seeds to light substantially alleviated dormancy in seeds from all sources.

scholarly journals A 1D RCE Study of Factors Affecting the Tropical Tropopause Layer and Surface Climate

2019 ◽  
Vol 32 (20) ◽  
pp. 6769-6782 ◽  
Author(s):  
Sally Dacie ◽  
Lukas Kluft ◽  
Hauke Schmidt ◽  
Bjorn Stevens ◽  
Stefan A. Buehler ◽  
...  
Keyword(s):  
Water Vapor ◽  
Climate Models ◽  
Temperature Response ◽  
Global Climate Models ◽  
Lapse Rate ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Surface Climate ◽  
Ozone Profile ◽  
Convective Adjustment

Abstract There are discrepancies between global climate models regarding the evolution of the tropical tropopause layer (TTL) and also whether changes in ozone impact the surface under climate change. We use a 1D clear-sky radiative–convective equilibrium model to determine how a variety of factors can affect the TTL and how they influence surface climate. We develop a new method of convective adjustment, which relaxes the temperature profile toward the moist adiabat and allows for cooling above the level of neutral buoyancy. The TTL temperatures in our model are sensitive to CO2 concentration, ozone profile, the method of convective adjustment, and the upwelling velocity, which is used to calculate a dynamical cooling rate in the stratosphere. Moreover, the temperature response of the TTL to changes in each of the above factors sometimes depends on the others. The surface temperature response to changes in ozone and upwelling at and above the TTL is also strongly amplified by both stratospheric and tropospheric water vapor changes. With all these influencing factors, it is not surprising that global models disagree with regard to TTL structure and evolution and the influence of ozone changes on surface temperatures. On the other hand, the effect of doubling CO2 on the surface, including just radiative, water vapor, and lapse-rate feedbacks, is relatively robust to changes in convection, upwelling, or the applied ozone profile.

scholarly journals Anthropogenic and Natural Radiative Forcing: Positive Feedbacks

2018 ◽  
Vol 6 (4) ◽  
pp. 146 ◽  
Author(s):  
Jean-Louis Pinault
Keyword(s):  
Surface Temperature ◽  
Radiative Forcing ◽  
Rossby Waves ◽  
Temperature Response ◽  
Heat Fluxes ◽  
Lapse Rate ◽  
Positive Feedbacks ◽  
Long Period ◽  
Sea Surface Temperature Anomalies ◽  
The Impact

This article is based on recent work intended to estimate the impact of solar forcing mediated by long-period ocean Rossby waves that are resonantly forced—the ‘Gyral Rossby Waves’ (GRWs). Here, we deduce both the part of the anthropogenic and climate components within the instrumental surface temperature spatial patterns. The natural variations in temperature are estimated from a weighted sum of sea surface temperature anomalies in preselected areas of subtropical gyres representative of long-period GRWs. The temperature response to anthropogenic forcing is deduced by subtracting the climate component from the instrumental temperature. Depending on whether the inland regions are primarily impacted by latent or sensible heat fluxes from the oceans, positive feedbacks occur. This suggests that the lapse rate and the high troposphere cloud cover have a driving role in the amplification effect of anthropogenic climate forcing, while specifying the involved mechanisms.

scholarly journals The Influence of Hyporheic Exchange on Water Temperatures in a Headwater Stream

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1615
Author(s):  
Christopher Surfleet ◽  
Justin Louen
Keyword(s):  
Water Temperature ◽  
Heat Budget ◽  
Stream Water ◽  
Temperature Response ◽  
Headwater Stream ◽  
Low Flow ◽  
Hyporheic Exchange ◽  
Maximum Temperature ◽  
Net Radiation ◽  
Heat Transfers

A headwater stream in coastal California was used to evaluate the temperature response of effective shade reduction. Spatial distribution of stream water temperatures for summer low-flow conditions (<0.006 m3 s−1) were highly correlated with net radiation and advective heat transfers from hyporheic exchange and subsequent streambed conduction. Using a heat budget model, mean maximum stream water temperatures were predicted to increase by 1.7 to 2.2 °C for 50% and 0% effective shade scenarios, respectively, at the downstream end of a 300 m treatment reach. Effects on mean maximum stream water temperature changes, as water flowed downstream through a 500 m shaded reach below the treatment reach, were reduced by 52 to 30% from the expected maximum temperature increases under the 50% and 0% effective shade scenarios, respectively. Maximum stream water temperature change predicted by net radiation heating alone was greater than measured and heat-budget-estimated temperatures. When the influence of hyporheic water exchange was combined with net radiation predictions, predicted temperatures were similar to measured and heat-budget-predicted temperatures. Results indicate that advective heat transfers associated with hyporheic exchange can promote downstream cooling following stream water temperature increases from shade reduction in a headwater stream with cascade, step-pool, and large woody debris forced-pool morphology.

Generation Lengths of Some Temperate Marine Copepods: Estimation, Prediction, and Implications

1978 ◽  
Vol 35 (10) ◽  
pp. 1330-1342 ◽  
Author(s):  
I. A. McLaren
Keyword(s):  
Community Dynamics ◽  
Laboratory Data ◽  
Temperature Response ◽  
Life Cycles ◽  
Calanus Finmarchicus ◽  
Published Data ◽  
Temperature Function ◽  
Oithona Similis ◽  
Single Temperature ◽  
Marine Copepods

Only copepodids should be used to trace synchronous cohorts from relative abundance of stages, and only long-lived adults correctly signal new generations from size changes. From extensive published data from Loch Striven, Scotland, life cycles are thus detailed for Pseudocalanus minutus, Microcalanus pygmaeus, Calanus finmarchicus, Centropages hamatus, Temora longicomis, Acartia clausi, and Oithona similis. Generation lengths are also estimated for all but M. pygmaeus from temperatures in nature and from laboratory data on food-satiated development. For stage durations (D) at various temperatures (T), Bělehrádek's temperature function D = a(T − α)−b is used. Temperature response can be about the same throughout a species range. With b fixed, α within a species can be the same for older stages as for embryonic duration, which can thus be used to estimate a for generation length even from a laboratory example at a single temperature. If food-satiated durations are available only for some stages, it can be assumed that other stages are similar (isochronal development). Food-satiated generation lengths predicted thus from the laboratory match those inferred from the Loch Striven samples. Trophic studies may be less revealing than further work on the "intrinsic" determinants of copepod performance. Competition for food should not be assumed in studies of niches and community dynamics of marine copepods. Key words: Copepoda, generation lengths, cohorts, body sizes, prediction, temperature, production, life cycles

Towards a Nitinol Actuator for an Active Surgical Needle

2012 ◽  
Author(s):  
Naresh V. Datla ◽  
Mohammad Honarvar ◽  
Tuan M. Nguyen ◽  
Bardia Konh ◽  
Kurosh Darvish ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Response Time ◽  
Joule Heating ◽  
Tissue Damage ◽  
Temperature Response ◽  
Maximum Temperature ◽  
Applied Current ◽  
Actuation Force ◽  
Nitinol Wire ◽  
Minimize Tissue Damage

Surgical needles, for safe and accurate percutaneaous interventions, need to be navigated accurately through the tissue and placed precisely at the targets. A novel active needle, using Nitinol wires as actuators, has been proposed to navigate the needle within the tissue. In this design, when temperature of Nitinol wire was increased by Joule heating, the material undergoes a phase transformation that produces relatively large actuating forces and strains. Using both experimental and numerical simulations, the force-temperature response of the Nitinol wires were characterized. The results indicate that increasing the applied current decreases the response time to reach maximum force, but increases the maximum temperature reached. Therefore, the chosen applied current should be high enough to produce sufficient actuation force and shorter response time, but not too high such that the lower actuator temperatures are maintained to minimize tissue damage.

scholarly journals Estimates of vertical eddy diffusivity in the upper mesosphere in the presence of a mesospheric inversion layer

2011 ◽  
Vol 29 (11) ◽  
pp. 2019-2029 ◽  
Author(s):  
R. L. Collins ◽  
G. A. Lehmacher ◽  
M. F. Larsen ◽  
K. Mizutani
Keyword(s):  
Diffusion Coefficient ◽  
Inversion Layer ◽  
Eddy Diffusion ◽  
Lapse Rate ◽  
The Arctic ◽  
Maximum Temperature ◽  
Lower Edge ◽  
Sodium Layer ◽  
Eddy Diffusion Coefficient ◽  
Lidar Observations

Abstract. Rayleigh and resonance lidar observations were made during the Turbopause experiment at Poker Flat Research Range, Chatanika Alaska (65° N, 147° W) over a 10 h period on the night of 17–18 February 2009. The lidar observations revealed the presence of a strong mesospheric inversion layer (MIL) at 74 km that formed during the observations and was present for over 6 h. The MIL had a maximum temperature of 251 K, amplitude of 27 ± 7 K, a depth of 3.0 km, and overlying lapse rate of 9.4 ± 0.3 K km−1. The MIL was located at the lower edge of the mesospheric sodium layer. During this coincidence the lower edge of the sodium layer was lowered by 2 km to 74 km and the bottomside scale height of the sodium increased from 1 km to 15 km. The structure of the MIL and sodium are analyzed in terms of vertical diffusive transport. The analysis yields a lower bound for the eddy diffusion coefficient of 430 m2 s−1 and the energy dissipation rate of 2.2 mW kg−1 at 76–77 km. This value of the eddy diffusion coefficient, determined from naturally occurring variations in mesospheric temperatures and the sodium layer, is significantly larger than those reported for mean winter values in the Arctic but similar to individual values reported in regions of convective instability by other techniques.

scholarly journals A 6-yr Climatology of Fronts Affecting Helsinki, Finland, and Their Boundary Layer Structure

2013 ◽  
Vol 52 (9) ◽  
pp. 2106-2124 ◽  
Author(s):  
Victoria A. Sinclair
Keyword(s):  
Boundary Layer ◽  
Temperature Change ◽  
Frontal Zone ◽  
Layer Structure ◽  
Time Of Day ◽  
Lapse Rate ◽  
Maximum Temperature ◽  
Synoptic Scale ◽  
Boundary Layer Structure ◽  
Cold Fronts

AbstractA 6-yr climatology of the frequency, characteristics, and boundary layer structure of synoptic-scale fronts in Helsinki, Finland, was created using significant weather charts and observations from a 327-m-tall mast and from the Station for Measuring Ecosystem–Atmosphere Relationships III. In total, 855 fronts (332 cold fronts, 236 warm fronts, and 287 occluded fronts) affected Helsinki during the 6-yr period, equating to one front every 2.6 days. Seasonal and diurnal cycles were observed, with frontal frequency peaking during the cold season and during daytime. Composites of warm and cold fronts were developed to provide observationally based conceptual models of the low-level structure of fronts at the end of the North Atlantic Ocean storm track. The composite warm front displays a temperature increase of 4.0°C; a broad, forward-tilting frontal zone; and prolonged, weak-to-moderate precipitation. The composite cold front is characterized by a temperature decrease of 4.4°C, a narrow and slightly rearward-tilting frontal zone, and moderate precipitation collocated with the surface front. Relationships between frontal characteristics and the direction from which fronts approached, the season, time of day, prefrontal boundary layer lapse rate, and the location of the wind shift relative to the thermal gradient were investigated. The prefrontal lapse rate was the single most important variable in determining the temperature change, the height of the maximum temperature change, and the near-surface tilt of both warm and cold fronts. This result demonstrates the interaction between boundary layer and synoptic-scale processes that must be captured by numerical weather prediction models to accurately forecast surface fronts.

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