Minimum Temperature Threshold Research Articles

Substantial increase in minimum lake surface temperatures under climate change

The annual minimum of lake surface water temperature influences ecological and biogeochemical processes, but variability and change in this extreme have not been investigated. Here, we analysed observational data from eight European lakes and investigated the changes in annual minimum surface water temperature. We found that between 1973 and 2014, the annual minimum lake surface temperature has increased at an average rate of + 0.35 °C decade−1, comparable to the rate of summer average lake surface temperature change during the same period (+ 0.32 °C decade−1). Coherent responses to climatic warming are observed between the increase in annual minimum lake surface temperature and the increase in winter air temperature variations. As a result of the rapid warming of annual minimum lake surface temperatures, some of the studied lakes no longer reach important minimum surface temperature thresholds that occur in winter, with complex and significant potential implications for lakes and the ecosystem services that they provide.

Synchronized generation of high-resolution gridded precipitation and temperature fields

In this study, synchronized gridded precipitation and temperature generators were developed and evaluated in terms of their ability to reconstruct the spatial structure and other statistical properties of high-resolution CaPA (Canadian Precipitation Analysis) precipitation and GEM (Global Environmental Multiscale Model) temperature products. The precipitation generator is an extension to the gridded multi-site occurrence-amount model. While the multi-site framework is not efficiently applicable to regions with limited precipitation information and sparse observation network, this paper provides the full mathematical description of estimating the model based on high-resolution gridded products. The temperature model, on the other hand, introduces the first gridded hourly generator in the literature in which cyclic temperature components are conditioned using wet and dry day status information. This was achieved using harmonic functions establishing the connection between the simulated daily precipitation occurrence time-series and the moments of the generated temperature data. One of the key features of the proposed gridded generators is the capacity to produce temporally coherent fields of precipitation and temperature; an essential prerequisite for hydrologic modeling applications. The generators were evaluated in terms of their ability to reproduce the standard, interannual, and extreme-value characteristics of observed gridded products. The gridded precipitation model can preserve key statistical and spatial properties of the gridded CaPA observations to an acceptable level, while similar to the original multi-site framework, it falls short to capture long dry spells and the interannual variability of monthly total precipitation. The temperature model, on the other hand, preserves the majority of key features of the gridded GEM temperature observations, including the first two moments of the hourly data and the cumulative frequency of maximum and minimum temperature thresholds. The only notable defect identified is the departure of the interannual variability of the generated maximum and minimum temperatures from those observed.

Towards a thermodynamic mechanistic model for the effect of temperature on arthropod vector competence for transmission of arboviruses

Arboviruses such as West Nile virus (WNV), bluetongue virus (BTV), dengue virus (DENV) and chikungunya virus (CHIKV) infect their arthropod vectors over a range of average temperatures depending on the ambient temperature. How the transmission efficiency of an arbovirus (i.e. vector competence) varies with temperature influences not only the short term risk of arbovirus outbreaks in humans and livestock but also the long term impact of climate change on the geographical range of the virus. The strength of the interaction between viral surface (glyco)protein (GP) and the host cell receptor (Cr) on binding of virus to host cell is defined by the thermodynamic dissociation constant Kd_receptor which is assumed to equal 10−3 M (at 37 °C) for binding of a sialic acid (SA) on the arthropod midgut epithelial cell surface to a SA-binding site on the surface of BTV, for example. Here virus binding affinity is modelled with increasing number of GP/Cr contacts at temperatures from 10 °C to 35 °C taking into account the change in entropy on immobilization of the whole virus on binding (ΔSa_immob). Based on published data, three thermodynamic GP/Cr binding scenarios, namely enthalpy-driven, entropy-assisted and entropy-driven, are shown to affect the temperature sensitivity of virus binding in different ways. Thus for enthalpy-driven GP/Cr binding, viruses bind host cells much more strongly at 10 °C than 35 °C. A mechanistic model is developed for the number of arthropod midgut cells with bound virus and by building in a kinetic component for the rate of arbovirus replication and subsequent spread to the arthropod salivary glands, a model for the effect of temperature on vector competence is developed. The model separates the opposing effects of temperature on midgut cell binding affinity from the kinetic component of virogenesis. It successfully accommodates both increases in vector competence with temperature as for DENV and WNV in mosquitoes and decreases as for the CHIKV 2010–1909 strain in various populations of Aedes albopictus mosquitoes. Enhanced cell binding at lower temperatures through enthalpy-driven GP/Cr binding compensates for the lower replication rate to some degree such that some transmission can still occur at lower temperatures. In contrast, the strength of entropy-driven GP/Cr binding diminishes at low temperatures although there is no minimum temperature threshold for transmission efficiency. The magnitude of ΔSa_immob is an important data gap. It is concluded that thermodynamic and kinetic data obtained at the molecular level will prove important in modelling vector competence with temperature.

Effects of extreme temperatures on cerebrovascular mortality in Lisbon: a distributed lag non-linear model.

Cerebrovascular diseases are the leading cause of mortality in Portugal, especially when related with extreme temperatures. This study highlights the impacts of the exposure-response relationship or lagged effect of low and high temperatures on cerebrovascular mortality, which can be important to reduce the health burden from cerebrovascular diseases. The purpose of this study was to assess the effects of weather on cerebrovascular mortality, measured by ambient temperature in the District of Lisbon, Portugal. A quasi-Poisson generalized additive model combined with a distributed lag non-linear model was applied to estimate the delayed effects of temperature on cerebrovascular mortality up to 30days. With reference to minimum mortality temperature threshold of 22°C, there was a severe risk (RR = 2.09, 95% CI 1.74, 2.51) of mortality for a 30-day-cumulative exposure to extreme cold temperatures of 7.3°C (1st percentile). Similarly, the cumulative effect of a 30-day exposure to an extreme hot temperature of 30°C (99th percentile) was 52% (RR = 1.65, 95% CI 1.37, 1.98) higher than same-day exposure. Over the 13years of study, non-linear effects of temperature on mortality were identified, and the probability of dying from cerebrovascular disease in Lisbon was 7% higher in the winter than in the summer. The findings of this study provide a baseline for future public health prevention programs on weather-related mortality.

Cold housing in mild-climate countries: A study of indoor environmental quality and comfort preferences in homes, Adelaide, Australia

International evidence suggests that cold housing – and its effects on health – is not just confined to countries with very cold winters. Rather, a small but increasing body of work is revealing that unacceptably low indoor temperatures are often experienced in housing in mild-climate countries. This paper presents the findings from a field study of wintertime thermal comfort conditions in metropolitan Adelaide, Australia. Participants were selected from a large random sample of 4500 Australian households in the Australian Housing Conditions Dataset (AHCD). Nineteen households who self-identified in the dataset as unable to keep warm in their homes in cold weather were included in the study. Each household was interviewed to assess their heating practices and attitudes, invited to complete a daily comfort survey, and had the temperature and humidity in their homes recorded. On average, internal temperatures in the sample houses were well below recommended minimum temperature thresholds and respondents reported low satisfaction with their indoor thermal environment. The majority of households had no plans to make changes to their house to improve wintertime indoor conditions; rather, participants demonstrated a wide variety of warmth practices mainly directed toward achieving comfort conditions in close proximity to their body instead of throughout the entire room. The results from this small, exploratory study of wintertime housing conditions suggest that cold housing is a real and immediate problem for many households, despite Australia's relatively mild climates.

Observations of Spring Hard Freeze Injury to C<sub>4</sub> Perennial Grasses Native to the Great Plains, USA

The native prairies of the Great Plains USA are dominated by perennial C4 grasses like switchgrass (Panicum virgatum) and big bluestem (Andropogon gerardii). Spring hard freeze injury to C4 perennial grasses is rare but information is lacking in the literature. Our objective was to document effects of spring hard freeze damage to C4 perennial grasses native to the Great Plains USA. On 2 May at 24:00 pm, air temperature near Mead, Nebraska was below freezing and remained below freezing until 8:00 am on 3 May, with a minimum air temperature of -2.8°C. Based on 50-year of weather data for this site, a minimum threshold temperature of 0°C on or after 3 May occurred 16 times, but a minimum threshold temperature of -2.8°C on or after 3 May occurred only twice. Grass tillers were visually evaluated to determine extent of freeze damage. The terminal 3- to 5-cm of the leaf lamina was blackened 4-d after freezing and had complete browning, rolling, and desiccation 14-d after freezing. Tiller survival was not negatively affected by the freezing temperatures in May 2004. As the growing season progressed, all agronomic and livestock responses were within normal ranges for these C4 grasses. This is the first field report of multiple C4 prairie grass species responses to a spring hard freeze following significant spring growth. Plant recovery to this late-spring hard freeze demonstrates the ecological resilience of these C4 prairie grasses. These rare spring hard freezes had short-term impacts on C4 grasses but did not negatively impact agronomic performance for forage or bioenergy later in the growing season.

Establishing Appropriate Hot Weather Alerting Criteria for British Columbia, Canada

A heat health warning system (HHWS) was developed for the greater Vancouver area of British Columbia (BC), Canada following an unprecedented extreme hot weather event that resulted in a 40% increase in weekly mortality. While the greater Vancouver HHWS has been operational since 2012, there are currently no HHWSs covering the remainder of the province. In collaboration with Environment and Climate Change Canada we established hot weather alerting criteria for four regions with broadly similar climates in BC.We used daily forecasted and observed minimum and maximum air temperatures and daily mortality counts for May through September during 2004 to 2016. For each date (dayt), we selected daytime forecast high temperatures for dayt and dayt+1 and the overnight forecast low temperature falling between dayt and dayt+1 from forecasts made in the afternoon of dayt-2. We tried a range of combinations of minimum and maximum temperature thresholds for each of four climatic areas. For each date, we assigned a hot weather warning category equal to the sum of the total degrees by which the daytime forecast highs fell under the maximum threshold and the overnight forecast low fell under the minimum threshold. We assessed associations between the categories and daily mortality using time-series models.We established the following minimum/maximum hot weather alerting criteria, to be adopted in the summer of 2018: 16°C/29°C in the Southwest; 18°C/35°C in the Southeast; 13°C/28°C in the Northwest; and 14°C/29°C in the Northeast. These values were established by balancing a number of considerations regarding the appropriateness of each threshold, including evidence-based associations with daily mortality and minimization of warning fatigue. These criteria identified the two province-wide extreme hot weather events that affected BC in 2009 and 2015.Hot weather alerting criteria covering all of BC can help public health authorities and citizens prepare for extreme hot weather events.

Hot and bright: Thermal and light environments for the culture of Oedogonium intermedium and the geographical limits for large-scale cultivation in Australia

The successful implementation of the intensive cultivation of freshwater macroalgae for bioremediation purposes relies on the consistent year-round uptake of nutrients, which is closely linked to the amount of biomass produced. This study examined how light and temperature influence the biomass productivity and photosynthetic efficiency of a tropical strain of the freshwater macroalga Oedogonium intermedium (Wittrock ex Hirn). We subsequently use this information to identify, at a coarse level, the locations within Australia that can provide a thermal and light environment that is conducive to the intensive year-round, production of this species. The optimal temperature range to cultivate O. intermedium is between 20 and 35 °C, and in general productivity increased with increasing photon flux within this temperature range. At temperatures outside of this optimal range O. intermedium still had positive growth when cultured at a constant temperature of as low as 15 °C and as high as 40 °C, but productivity was impaired, and these temperatures represent the minimum and maximum temperature thresholds for chronic exposure. At low temperatures, higher photon flux rates increased productivity, however, at higher temperatures (>35 °C) a higher photon flux decreased productivity. These experimental insights have enabled us to identify, at a coarse level, locations within Australia that provide a suitable thermal and light environment for the year-round cultivation of O. intermedium. In general, latitudes of ≤25° provide a thermal and light environment that can maintain a high rate of biomass productivity year-round. In contrast, most locations at latitudes higher than 25° provide a suitable environment only during the summer months. During winter the combination of low temperatures and low solar irradiances will prevent the successful cultivation of this tropical strain. In these cooler locations alternative species of locally adapted, freshwater macroalgae should be identified and domesticated to ensure bioremediation outcomes are maintained at these lower latitudes.

Effect of Temperature on the Release of Proterometra macrostoma (Trematoda: Digenea) Cercariae from Their Snail Intermediate Host, Pleurocera semicarinata (Gastropoda: Pleuroceridae) at North Elkhorn Creek, Kentucky

The effect of temperature on cercarial release has been well documented for several digenean species; however, there have been no prior studies assessing shedding of cercariae from snails infected with the azygiid, Proterometra macrostoma. Snails, Pleurocera semicarinata, were collected at the Lemon's Mill site on North Elkhorn Creek in Scott County, Kentucky during June and July 2016. Snails shedding cercariae (n = 453) were assigned to temperature treatments (10, 13, 15, 18, 20, 25, and 30°C) that were within the range of previously reported seasonal water temperatures at North Elkhorn Creek. Snails were acclimated to experimental temperatures for 3 d. Cercarial counts were then made at 0900 h daily over the next 7 d, and the average 7-d cercarial release was calculated for each snail. The minimum emergence threshold temperature for Pr. macrostoma cercarial release was determined to be approximately 13°C, whereas the minimum development threshold temperature was between 10 and 12°C. Notably, cercarial release increased with temperature up to 25°C, but declined at 30°C. Q10 values calculated from 10°C intervals were greatest at the lowest (13–23°C) temperature interval (Q10 = 16.1), and declined at the higher (15–25 and 20–30°C) intervals (Q10 = 4.3 and Q10 = 1.8, respectively). Snail survivorship within combined replicates ranged from 87.1 to 100% over the 10-d experiment, with the lowest survivorship observed at 30°C. These results are discussed with regard to climate change and global warming.

Phenology of Hemlock Woolly Adelgid (Hemiptera: Adelgidae) in the Central Appalachian Mountains, USA

The ability to predict key phenological stages of insect pests is of prime importance in sampling and management programs. Hemlock woolly adelgid, Adelges tsugae (Annand) (Hemiptera: Adelgidae), is a non-native invasive pest of eastern and Carolina hemlock that is currently expanding its range westward through the central Appalachian region. We conducted intensive sampling of A. tsugae across four sites in West Virginia and western Maryland from March 2013 to May 2014, and developed a degree-day model (minimum temperature threshold of 4°C) to predict the temporal distribution of progrediens eggs, progrediens egg hatch, newly hatched sistens, and settled first-instar sistens. We then linked degree-day predictions to recent weather data collected from our study region from 2012 to 2016 to provide a range of calendar days over which these key phenological events occur. The initial occurrence of progrediens eggs and progrediens egg hatch is predicted to occur at 209 (mean date of 19 April) and 346 (mean date of 8 May) degree days, respectively. The initial occurrence of newly hatched sistens and settled first-instar sistens is predicted to occur at 852 (mean date of 19 June) and 1010 (mean date of 30 June) degree days, respectively. Because our study region represents a region in which A. tsugae continues to spread, this information should be useful in optimizing sampling programs and the timing of control tactics in the central Appalachian region.

Ignition of Fuel Slurries Based on Waste Products of Coal Processing and Oil Refining

Results of an experimental study of conditions and characteristics of ignition of fuel slurries prepared on the basis of typical waste products of coal washing and oil refining are reported. The main attention is paid to analyzing the differences in the characteristics and conditions of ignition of organic coal–water slurries prepared on the basis of coal washing waste products (nonbaking, coking, low-caking, fat, gas, and flame coals are considered). The ignition delay time and the minimum (threshold) temperature of ignition of the examined slurries are estimated. Conclusions on the influence of the properties and concentrations of the slurry components on the combustion initiation characteristics are formulated.

Temperature-Dependent Growth and Virulence, and Mass Production Potential of Two Candidate Isolates ofMetarhizium anisopliae(Metschnikoff) Sorokin for ManagingMaruca vitrataFabricius (Lepidoptera: Crambidae) on Cowpea

Entomopathogenic fungi are increasingly gaining recognition as a viable alternative to synthetic insecticides for pest management; their efficacy is influenced by several biotic and abiotic factors. In this study, the effect of temperature on germination, growth and virulence of two isolates of Metarhizium anisopliae, ICIPE 18 and ICIPE 69, against first-instar larvae of Maruca vitrata at temperatures ranging from 15–35 °C, and mass-production potential of the isolates were assessed under laboratory conditions. Minimum, optimum and maximum threshold temperatures for efficacy of the best performing isolate, ICIPE 69, were estimated by the quadratic equation which emerged as the best model among the nonlinear mathematical expressions tested. Neither isolate germinated at 15 °C while germination was low at 35 °C for both. The optimum temperature for germination, radial growth and virulence of ICIPE 69 and ICIPE 18 ranged between 25–30 °C and 25–33 °C, respectively. Mortality of M. vitrata by both isolates ranged between 56.0 and 91.6�ross the different temperatures, with the highest mortality occurring at 25 and 30 °C for ICIPE 69 and ICIPE 18, respectively. The shortest LT50 values were 2.5 days for ICIPE 18 and 2.2 days for ICIPE 69 at 33 °C and 25 °C, respectively. The quadratic model predicted 25–30 °C as the optimum temperature range for maximum efficacy of M. anisopliae isolate ICIPE 69 against M. vitrata. Upper and lower threshold temperatures were predicted as 40 °C and 10 °C, respectively. Comparison of aerial conidia production on rice showed that ICIPE 69 yielded higher amounts of conidia (18.4 g conidia/kg rice) than ICIPE 18 (12.4 g conidia/kg rice). The results suggest that ICIPE 69 is a promising candidate for biocontrol of M. vitrata.

Climate Change and Pest Management: Unanticipated Consequences of Trophic Dislocation

The growth of plants and insects occurs only above a minimum temperature threshold. In insects, the growth rate depends on the temperature above the threshold up to a maximum. In plants the growth rate above the threshold generally depends on the availability of sunlight. Thus, the relative growth rates of crops and insect phytophages are expected to differ between temperature regimes. We should therefore expect insect pest pressure at a location to change with climate warming. In this study, we used actual and simulated climate data developed for the IPCC 4th Assessment Report to drive linked plant and insect growth models to examine likely changes in insect-crop interaction. Projections of insect-crop dynamics through the 21st century suggest increases in pest pressure over much of the American Midwest, which could result in substantial increases in pesticide use to maintain productivity. Thus, climate warming could cause an increase in agriculture’s carbon footprint.

Will future climate change increase the risk of violating minimum flow and maximum temperature thresholds below dams in the Pacific Northwest?

Detecting and avoiding environmental thresholds that lead to catastrophic change in ecological communities is an important goal, and one that is especially challenging to address over broad geographic extents. Here, we conducted a regional-scale climate vulnerability assessment (RCVA) to quantify the risk of violating thermal and minimum-flow thresholds below reservoirs. Our analysis used hybrid (process-based and empirical) models of tailwater temperature and flow driven by 4-km downscaled CMIP5 climate projections. Downscaling employed a combination of process-based models, quantile mapping, and a non-linear ‘reservoir’ transform function. RCVA can be applied at regional scales without proprietary and data-intensive physical models of reservoir systems or ecological models of species that comprise tailwater communities. Using RCVA, we produced ensemble projections of risk and duration of extreme high-temperature or low-flow events below federal reservoirs in the Pacific Northwest (PNW), USA. Bayesian modeling of simulated results allowed us to evaluate differences between risk under a future and baseline scenario relative to model uncertainties and to quantify uncertainty in modeled risks. Based on assumptions that historical patterns of reservoir dynamics and operation will continue, and that regulatory thresholds will not change, the risk of thermal exceedance was projected to increase by an average of 0.27 and extend into late-spring and fall (average change in duration of 10.3 d). For flow, RCVA projected an increase of 0.07 in the average risk below-thresholds flows, with an average increase in duration of 4.6 d. Both results raise concerns that cold-water salmonids of the PNW will be at increased risk under a future climate scenario.

Temperature and Tissue Type Impact Development of Lucilia cuprina (Diptera: Calliphoridae) in Sri Lanka.

Lucilia cuprina (Wiedemann; Diptera: Calliphoridae) is a facultative ecto-parasitic fly, distributed throughout the temperate and subtropical regions of the world. This blow fly species is of medical, veterinary, and forensic importance due to it being used in maggot debridement therapy (MDT), a causative agent of myiasis, and a decomposer of vertebrate carrion. The current study examined the combined effects of temperature and tissue type on the development of L. cuprina. Specimens were reared on three tissue types; swine muscle, swine liver, and bovine muscle at 20°C, 25°C, 27°C, and 38°C. The optimum condition for L. cuprina development was for immatures reared on bovine muscle (287.4 h) followed by those reared on swine muscle (288.0 h) and swine liver (288.4 h) at 27°C. The minimum temperature threshold of L. cuprina was deduced to be 14°C. No significant differences in larval width and length over time were determined for the tissue type.

Spatial analysis of frost risk to determine viticulture suitability in Tasmania, Australia

Background and Aims New sites for viticulture should be located in areas where damaging spring frosts are less frequent and/or severe in order to remain economically viable. The aim of this study was to spatially determine frost risk at a high resolution (80 m) and develop new rules catered to viticultural suitability with respect to frost sensitivity for vines after budburst in spring across the state of Tasmania, Australia. Methods and Results Frost risk was mapped for minimum temperature thresholds at −3, −2, −1, 0, 1 and 2°C using temperature values from 636 short-term recording sites and linked to 57 Australian Bureau of Meteorology climate stations. Frost risk was spatially determined using regression tree interpolation and assessed against historical winegrape frost damage records garnered from survey information. Analysis indicated that the frost risk surfaces were accurate in portraying risk at the mesoclimate level and aligned well with grower expectations for frost risk modelled at ≤−1°C. Conclusions Classifications of suitable, moderately suitable and unsuitable corresponding to <1 frost every 10 years (<10%), >1/10 to 1 frost every 2 years (10–50%) and 1 > frost every 2 years (>50%) for temperature values ≤−1°C was found to correlate well with viticulture suitability with regard to frost risk (after budburst) in Tasmania. Significance of the Study This study presents a methodology for producing high-resolution frost risk maps across large land areas that can accurately identify sites prone to damaging spring frosts and inform on new potential viticulture sites with suitability in mind.

Temperature-dependent models of development and survival of an insect pest of African tropical highlands, the coffee antestia bug Antestiopsis thunbergii (Hemiptera: Pentatomidae)

The antestia bug Antestiopsis thunbergii (Hemiptera: Pentatomidae) is a major pest of Arabica coffee in African tropical highlands. It feeds on coffee plant vegetative parts and berries leading to a direct reduction in coffee yield and quality. This study aimed to determine A. thunbergii thermal requirements, and to obtain new information on the pest demography as influenced by temperature. Temperature-dependent models were developed using the Insect Life Cycle Modelling software (ILCYM) through a complete life table study at seven constant temperatures in the range 18–32°C. Non-linear functions were fitted to A. thunbergii development, mortality, fecundity and senescence. Model parameters and demographic variables obtained from the models were given for each temperature and development stage. Life table parameters were estimated for nine constant temperatures, from 18°C to 26°C, using stochastic simulations. The minimum temperature threshold (Tmin) and the thermal constant (k) for the development from egg to adult were estimated from a linear function at 12.1°C and 666.67° days, respectively. The maximum temperature threshold (Tmax) was estimated at 33.9°C from a Logan model. The optimum temperature for immature stages’ survival was estimated to be between 22.4 and 24.7°C. The maximum fecundity was 147.7 eggs female−1 at 21.2°C. Simulated A. thunbergii life table parameters were affected by temperature, and the maximum value of intrinsic rate of increase (rm) was 0.029 at 22°C and 23°C. In general, the life cycle data, models and demographic parameters we obtained were in line with previous reports for antestia bugs or other stink bug species. The relationships between the pest thermal requirements and ecological preferences in highland coffee were discussed. Our results will contribute to risk prediction under climate change for this important coffee pest.

A spatially explicit crop planting initiation and progression model for the conterminous United States

Abstract The ability to accurately estimate crop planting date and planting progression has major implications in crop management, crop model applications, and in developing adaptation strategies for future climate change. The objectives of this study are: 1) identify major factors that determine planting initiation and progression of six major crops in the U.S. and 2) develop a spatially explicit planting initiation and progression model. The crops that were evaluated are maize ( Zea mays ), cotton ( Gossypium hirsutum ), rice ( Oryza sativa ), sorghum ( Sorghum bicolor ), soybean ( Glycine max ), and winter wheat ( Triticum aestivum ). County-level daily planting data from 2005 to 2015 for representative states were obtained from USDA Risk Management Agency. For the five summer crops, the earliest planting gradually shifts to later dates with increasing latitude and elevation. The trend is reversed for winter wheat, with planting initiation shifting to earlier dates from south to north and from low to high elevation. A minimum planting temperature threshold was established for the five summer crops, which decreases from south to north and from low to high elevation. A maximum planting temperature threshold was established for winter wheat, which decreases from south to north but increases from low to high elevation. A spatially explicit temperature model as a function of latitude, longitude and elevation was established to predict planting initiation, while a soil texture-based soil wetness index predicts planting delays due to excessive precipitation. The model was calibrated with 2005–2009 data and validated with 2010–2015 data; it provided sound goodness of fit for planting initiation and weekly planting progression. The spatially explicit model for planting initiation and progression could be used to guide crop production planning and to improve the planting date and progression algorithms in crop models for regional simulation analysis.

Temperature-dependent parasitism and development in Aenasius arizonensis Girault (Hymenoptera: Encyrtidae), a solitary endoparasitoid of Phenacoccus solenopsis (Hemiptera: Pseudococcidae)

ABSTRACTOphmella communa (Coleoptera: Chrysomelidae) is a biological control agent of Ambrosia artemisiifolia (Asterales: Asteraceae). To reveal its climate adaptation, the effect of temperature on life traits of Aenasius arizonensis, a parasitoid of Phenacoccus solenopsis was studied. The results showed that both the highest parasitism and emergence rates of A. arizonensis were observed at 31 °C. The parasitism and emergence rates of the parasitoid significantly increased with the increasing temperature from 19 °C to 31 °C, but dropped when the temperature exceeded 31 °C. Female ratio reached a higher value at 19, 22, 31, 34 or 37 °C. The minimum threshold temperatures for female and male parasitoids were 11.5 and 11.2 °C, respectively. The effective accumulative temperatures for the parasitoid to develop from eggs to both female and male adults were 222.2 day-degrees. Since the highest parasitism rate, the highest emergence rate and a higher female ratio were observed at 31 °C, we conclude that the optimum temperature for mass rearing of A. arizonensis is 31 °C in the insectary based on the results of our study.

Seasonal and diurnal patterns of activity in honeybees (Apis spp.) on the northern edge of the Asian tropics; their implications for the climate-change resilience of pollination

Apis honeybees are very important pollinators in tropical Asia but their diversity declines rapidly north of the tropics. This suggests that climate is a major control on their distributions and that climate change may influence the services they provide. Four Apis honeybees coexist in a flower-rich botanical garden in Yunnan, China, on the northern margin of the tropics (21o41′N): A. florea and A. andreniformis (small, open-nesting), A. cerana (medium, cavity-nesting), and A. dorsata (large, open-nesting). We made standardized observations of their diurnal and seasonal activity patterns and recorded temperature, humidity, and solar radiation at flowers being visited. A. dorsata comprised two-thirds of honeybee individuals observed, although this species was largely absent from July to November. A. cerana was active on each day that observations were made and tolerated temperatures of 7℃–41.5℃ (including observations from two other sites in Yunnan). The other species had higher minimum temperature thresholds for activity, but A. florea had a higher maximum temperature tolerance (46.5℃) and A. dorsata was sometimes active at night. Generalized linear models showed abundances of A. cerana and A. dorsata had positive relationships with numbers of flowers and negative ones with temperature. A. florea abundance had a positive relationship with temperature, while the presence of A. andreniformis was positively related to temperature and humidity. Apis bees visited 48.6% of the flower species observed. Impacts of projected warming over coming decades are expected to vary among species, but overall pollination services by honeybees at this site seem likely to be resilient.