Changes in Extremely Hot Summers over the Global Land Area under Various Warming Targets

Summer temperature extremes over the global land area were investigated by comparing 26 models of the fifth phase of the Coupled Model Intercomparison Project (CMIP5) with observations from the Goddard Institute for Space Studies (GISS) and the Climate Research Unit (CRU). Monthly data of the observations and models were averaged for each season, and statistics were calculated for individual models before averaging them to obtain ensemble means. The summers with temperature anomalies (relative to 1951–1980) exceeding 3σ (σ is based on the local internal variability) are defined as “extremely hot”. The models well reproduced the statistical characteristics evolution, and partly captured the spatial distributions of historical summer temperature extremes. If the global mean temperature increases 2°C relative to the pre-industrial level, “extremely hot” summers are projected to occur over nearly 40% of the land area (multi-model ensemble mean projection). Summers that exceed 5σ warming are projected to occur over approximately 10% of the global land area, which were rarely observed during the reference period. Scenarios reaching warming levels of 3°C to 5°C were also analyzed. After exceeding the 5°C warming target, “extremely hot” summers are projected to occur throughout the entire global land area, and summers that exceed 5σ warming would become common over 70% of the land area. In addition, the areas affected by “extremely hot” summers are expected to rapidly expand by more than 25%/°C as the global mean temperature increases by up to 3°C before slowing to less than 16%/°C as the temperature continues to increase by more than 3°C. The area that experiences summers with warming of 5σ or more above the warming target of 2°C is likely to maintain rapid expansion of greater than 17%/°C. To reduce the impacts and damage from severely hot summers, the global mean temperature increase should remain low.     

Potential Impacts of Future Warming and Land Use Changes on Intra-Urban Heat Exposure in Houston,Texas

Extreme heat events in the United States are projected to become more frequent and intense as a result of climate change. We investigated the individual and combined effects of land use and warming on the spatial and temporal distribution of daily minimum temperature (T_min) and daily maximum heat index (HI_max) during summer in Houston, Texas. Present-day (2010) and near-future (2040) parcel-level land use scenarios were embedded within 1-km resolution land surface model (LSM) simulations. For each land use scenario, LSM simulations were conducted for climatic scenarios representative of both the present-day and near-future periods. LSM simulations assuming present-day climate but 2040 land use patterns led to spatially heterogeneous temperature changes characterized by warmer conditions over most areas, with summer average increases of up to 1.5°C (T_min) and 7.3°C (HI_max) in some newly developed suburban areas compared to simulations using 2010 land use patterns. LSM simulations assuming present-day land use but a 1°C temperature increase above the urban canopy (consistent with warming projections for 2040) yielded more spatially homogeneous metropolitan-wide average increases of about 1°C (T_min) and 2.5°C (HI_max), respectively. LSM simulations assuming both land use and warming for 2040 led to summer average increases of up to 2.5°C (T_min) and 8.3°C (HI_max), with the largest increases in areas projected to be converted to residential, industrial and mixed-use types. Our results suggest that urbanization and climate change may significantly increase the average number of summer days that exceed current threshold temperatures for initiating a heat advisory for metropolitan Houston, potentially increasing population exposure to extreme heat.     

Climate Warming May Facilitate Invasion of the Exotic Shrub Lantana camara

Plant species show different responses to the elevated temperatures that are resulting from global climate change, depending on their ecological and physiological characteristics. The highly invasive shrub Lantana camara occurs between the latitudes of 35°N and 35°S. According to current and future climate scenarios predicted by the CLIMEX model, climatically suitable areas for L. camara are projected to contract globally, despite expansions in some areas. The objective of this study was to test those predictions, using a pot experiment in which branch cuttings were grown at three different temperatures (22°C, 26°C and 30°C). We hypothesized that warming would facilitate the invasiveness of L. camara. In response to rising temperatures, the total biomass of L. camara did increase. Plants allocated more biomass to stems and enlarged their leaves more at 26°C and 30°C, which promoted light capture and assimilation. They did not appear to be stressed by higher temperatures, in fact photosynthesis and assimilation were enhanced. Using lettuce (Lactuca sativa) as a receptor plant in a bioassay experiment, we also tested the phytotoxicity of L. camara leachate at different temperatures. All aqueous extracts from fresh leaves significantly inhibited the germination and seedling growth of lettuce, and the allelopathic effects became stronger with increasing temperature. Our results provide key evidence that elevated temperature led to significant increases in growth along with physiological and allelopathic effects, which together indicate that global warming facilitates the invasion of L. camara.     

Warming Amplification of Minimum and Maximum Temperatures over High-Elevation Regions across the Globe

An analysis of the annual mean temperature (T_MEAN) (1961–2010) has revealed that warming amplification (altitudinal amplification and regional amplification) is a common feature of major high-elevation regions across the globe against the background of global warming since the mid-20th century. In this study, the authors further examine whether this holds for annual mean minimum temperature (T_MIN) and annual mean maximum temperature (T_MAX) (1961–2010) on a global scale. The extraction method of warming component of altitude, and the paired region comparison method were used in this study. Results show that a significant altitudinal amplification trend in T_MIN (T_MAX) is detected in all (four) of the six high-elevation regions tested, and the average magnitude of altitudinal amplification trend for T_MIN (T_MAX) [0.306±0.086 °C km^-1(0.154±0.213 °C km^-1)] is substantially larger (smaller) than T_MEAN (0.230±0.073 °C km^-1) during the period 1961–2010. For the five paired high- and low-elevation regions available, regional amplification is detected in the four high-elevation regions for T_MIN and T_MAX (respectively or as a whole). Qualitatively, highly (largely) consistent results are observed for T_MIN (T_MAX) compared with those for T_MEAN.     

Potential Impacts of Climate Warming on Water Supply Reliability in the Tuolumne and Merced River Basins,California

We present an integrated hydrology/water operations simulation model of the Tuolumne and Merced River Basins, California, using the Water Evaluation and Planning (WEAP) platform. The model represents hydrology as well as water operations, which together influence water supplied for agricultural, urban, and environmental uses. The model is developed for impacts assessment using scenarios for climate change and other drivers of water system behavior. In this paper, we describe the model structure, its representation of historical streamflow, agricultural and urban water demands, and water operations. We describe projected impacts of climate change on hydrology and water supply to the major irrigation districts in the area, using uniform 2°C, 4°C, and 6°C increases applied to climate inputs from the calibration period. Consistent with other studies, we find that the timing of hydrology shifts earlier in the water year in response to temperature warming (5–21 days). The integrated agricultural model responds with increased water demands 2°C (1.4–2.0%), 4°C (2.8–3.9%), and 6°C (4.2–5.8%). In this sensitivity analysis, the combination of altered hydrology and increased demands results in decreased reliability of surface water supplied for agricultural purposes, with modeled quantity-based reliability metrics decreasing from a range of 0.84–0.90 under historical conditions to 0.75–0.79 under 6°C warming scenario.     

Heated Relations: Temperature-Mediated Shifts in Consumption across Trophic Levels

A rise in temperature will intensify the feeding links involving ectotherms in food webs. However, it is unclear how the effects will quantitatively differ between the plant-herbivore and herbivore-carnivore interface. To test how warming could differentially affect rates of herbivory and carnivory, we studied trophic interaction strength in a food chain comprised of green algae, herbivorous rotifers and carnivorous rotifers at 10, 15, 20 and 25°C. We found significant warming-induced changes in feeding by both herbivorous and carnivorous rotifers, but these responses occurred at different parts of the entire temperature gradient. The strongest response of the per capita herbivore''s ingestion rate occurred due to an increase in temperature from 15 to 20°C (1.9 fold: from 834 to 1611 algal cells per h⁻¹) and of the per capita carnivore''s ingestion rate from 20 to 25°C (1.6 fold: from 1.5 to 2.5 prey h⁻¹). Handling time, an important component of a consumer''s functional response, significantly decreased from 15 to 20°C in herbivorous rotifers. In contrast, it decreased from 20 to 25°C in carnivorous rotifers. Attack rates significantly and strongly increased from 10 to 25°C in the herbivorous animals, but not at all in the carnivores. Our results exemplify how the relative forces of top-down control exerted by herbivores and carnivores may strongly shift under global warming. But warming, and its magnitude, are not the only issue: If our results would prove to be representative, shifts in ectotherm interactions will quantitatively differ when a 5°C increase starts out from a low, intermediate or high initial temperature. This would imply that warming could have different effects on the relative forces of carnivory and herbivory in habitats differing in average temperature, as would exist at different altitudes and latitudes.     

Influence of Storage at Freezing and Subsequent Refrigeration Temperatures on β-Galactosidase Activity of Lactobacillus acidophilus

The ability of three strains of Lactobacillus acidophilus to survive and retain β-galactosidase activity during storage in liquid nitrogen at −196°C and during subsequent storage in milk at 5°C was tested. The level of β-galactosidase activity varied among the three strains (0.048 to 0.177 U/10⁷ organisms). Freezing and storage at −196°C had much less adverse influence on viability and activity of the enzyme than did storage in milk at 5°C. The strains varied in the extent of the losses of viability and β-galactosidase activity during both types of storage. There was not a significant interaction between storage at −196°C and subsequent storage at 5°C. The strains that exhibited the greatest losses of β-galactosidase activity during storage in milk at 5°C also exhibited the greatest losses in viability at 5°C. However, the losses in viability were of much greater magnitude than were the losses of enzymatic activity. This indicates that some cells of L. acidophilus which failed to form colonies on the enumeration medium still possessed β-galactosidase activity. Cultures of L. acidophilus to be used as dietary adjuncts to improve lactose utilization in humans should be carefully selected to ensure that adequate β-galactosidase activity is provided.     

Decomposition of Organic Carbon in Fine Soil Particles Is Likely More Sensitive to Warming than in Coarse Particles: An Incubation Study with Temperate Grassland and Forest Soils in Northern China

It is widely recognized that global warming promotes soil organic carbon (SOC) decomposition, and soils thus emit more CO₂ into the atmosphere because of the warming; however, the response of SOC decomposition to this warming in different soil textures is unclear. This lack of knowledge limits our projection of SOC turnover and CO₂ emission from soils after future warming. To investigate the CO₂ emission from soils with different textures, we conducted a 107-day incubation experiment. The soils were sampled from temperate forest and grassland in northern China. The incubation was conducted over three short-term cycles of changing temperature from 5°C to 30°C, with an interval of 5°C. Our results indicated that CO₂ emissions from sand (>50 µm), silt (2–50 µm), and clay (<2 µm) particles increased exponentially with increasing temperature. The sand fractions emitted more CO₂ (CO₂-C per unit fraction-C) than the silt and clay fractions in both forest and grassland soils. The temperature sensitivity of the CO₂ emission from soil particles, which is expressed as Q₁₀, decreased in the order clay>silt>sand. Our study also found that nitrogen availability in the soil facilitated the temperature dependence of SOC decomposition. A further analysis of the incubation data indicated a power-law decrease of Q₁₀ with increasing temperature. Our results suggested that the decomposition of organic carbon in fine-textured soils that are rich in clay or silt could be more sensitive to warming than those in coarse sandy soils and that SOC might be more vulnerable in boreal and temperate regions than in subtropical and tropical regions under future warming.     

Response of Two Dominant Boreal Freshwater Wetland Plants to Manipulated Warming and Altered Precipitation

This study characterized the morphological and photosynthetic responses of two wetland plant species when they were subject to 2–6°C fluctuations in growth temperature and ±50% of precipitation, in order to predict the evolution of natural wetlands in Sanjiang Plain of North-eastern China. We investigated the morphological and photosynthetic responses of two dominant and competitive boreal freshwater wetland plants in Northeastern China to manipulation of warming (ambient, +2.0°C, +4.0°C, +6.0°C) and altered precipitation (−50%, ambient, +50%) simultaneously by incubating the plants from seedling to senescence within climate-controlled environmental chambers. Post-harvest, secondary growth of C. angustifolia was observed to explore intergenerational effects. The results indicated that C. angustifolia demonstrated a greater acclimated capacity than G. spiculosa to respond to climate change due to higher resistance to temperature and precipitation manipulations. The accumulated effect on aboveground biomass of post-harvest secondary growth of C. angustifolia was significant. These results explain the expansion of C. angustifolia during last 40 years and indicate the further expansion in natural boreal wetlands under a warmer and wetter future. Stability of the natural surface water table is critical for the conservation and restoration of G. spiculosa populations reacting to encroachment stress from C. angustifolia expansion.     

Short‐term thermal acclimation modulates predator functional response

Phenotypic plastic responses to temperature can modulate the kinetic effects of temperature on biological rates and traits and thus play an important role for species adaptation to climate change. However, there is little information on how these plastic responses to temperature can influence trophic interactions. Here, we conducted an experiment using marbled crayfish and their water louse prey to investigate how short‐term thermal acclimation at two temperatures (16 and 24°C) modulates the predator functional response. We found that both functional response parameters (search rate and handling time) differed between the two experimental temperatures. However, the sign and magnitudes of these differences strongly depended on acclimation time. Acclimation to 16°C increased handling time and search rate whereas acclimation to 24°C leads to the opposite effects with shorter handling time and lower search rate for acclimated predators. Moreover, the strength of these effects increased with acclimation time so that the differences in search rate and handing time between the two temperatures were reversed between the treatment without acclimation and after 24 h of acclimation. Overall, we found that the magnitude of the acclimation effects can be as strong as the direct kinetic effects of temperature. Our study highlights the importance of taking into account short‐term thermal plasticity to improve our understanding of the potential consequences of global warming on species interactions.     

Attachment of and Biofilm Formation by Enterobacter sakazakii on Stainless Steel and Enteral Feeding Tubes

Enterobacter sakazakii has been reported to form biofilms, but environmental conditions affecting attachment to and biofilm formation on abiotic surfaces have not been described. We did a study to determine the effects of temperature and nutrient availability on attachment and biofilm formation by E. sakazakii on stainless steel and enteral feeding tubes. Five strains grown to stationary phase in tryptic soy broth (TSB), infant formula broth (IFB), or lettuce juice broth (LJB) at 12 and 25°C were examined for the extent to which they attach to these materials. Higher populations attached at 25°C than at 12°C. Stainless steel coupons and enteral feeding tubes were immersed for 24 h at 4°C in phosphate-buffered saline suspensions (7 log CFU/ml) to facilitate the attachment of 5.33 to 5.51 and 5.03 to 5.12 log CFU/cm², respectively, before they were immersed in TSB, IFB, or LJB, followed by incubation at 12 or 25°C for up to 10 days. Biofilms were not produced at 12°C. The number of cells of test strains increased by 1.42 to 1.67 log CFU/cm² and 1.16 to 1.31 log CFU/cm² in biofilms formed on stainless steel and feeding tubes, respectively, immersed in IFB at 25°C; biofilms were not formed on TSB and LJB at 25°C, indicating that nutrient availability plays a major role in processes leading to biofilm formation on the surfaces of these inert materials. These observations emphasize the importance of temperature control in reconstituted infant formula preparation and storage areas in preventing attachment and biofilm formation by E. sakazakii.     

Effects of Warming Temperatures on Winning Times in the Boston Marathon

It is not known whether global warming will affect winning times in endurance events, and counterbalance improvements in race performances that have occurred over the past century. We examined a time series (1933–2004) from the Boston Marathon to test for an effect of warming on winning times by men and women. We found that warmer temperatures and headwinds on the day of the race slow winning times. However, 1.6°C warming in annual temperatures in Boston between 1933 and 2004 did not consistently slow winning times because of high variability in temperatures on race day. Starting times for the race changed to earlier in the day beginning in 2006, making it difficult to anticipate effects of future warming on winning times. However, our models indicate that if race starting times had not changed and average race day temperatures had warmed by 0.058°C/yr, a high-end estimate, we would have had a 95% chance of detecting a consistent slowing of winning marathon times by 2100. If average race day temperatures had warmed by 0.028°C/yr, a mid-range estimate, we would have had a 64% chance of detecting a consistent slowing of winning times by 2100.     

Microclimatic Performance of a Free-Air Warming and CO2 Enrichment Experiment in Windy Wyoming,USA

In order to plan for global changing climate experiments are being conducted in many countries, but few have monitored the effects of the climate change treatments (warming, elevated CO₂) on the experimental plot microclimate. During three years of an eight year study with year-round feedback-controlled infra-red heater warming (1.5/3.0°C day/night) and growing season free-air CO₂ enrichment (600 ppm) in the mixed-grass prairie of Wyoming, USA, we monitored soil, leaf, canopy-air, above-canopy-air temperatures and relative humidity of control and treated experimental plots and evaluated ecologically important temperature differentials. Leaves were warmed somewhat less than the target settings (1.1 & 1.5°C day/night) but soil was warmed more creating an average that matched the target settings extremely well both during the day and night plus the summer and winter. The site typically has about 50% bare or litter covered soil, therefore soil heat transfer is more critical than in dense canopy ecosystems. The Wyoming site commonly has strong winds (5 ms^-1 average) and significant daily and seasonal temperature fluctuations (as much as 30°C daily) but the warming system was nearly always able to maintain the set temperatures regardless of abiotic variation. The within canopy-air was only slightly warmed and above canopy-air was not warmed by the system, therefore convective warming was minor. Elevated CO₂ had no direct effect nor interaction with the warming treatment on microclimate. Relative humidity within the plant canopy was only slightly reduced by warming. Soil water content was reduced by warming but increased by elevated CO₂. This study demonstrates the importance of monitoring the microclimate in manipulative field global change experiments so that critical physiological and ecological conclusions can be determined. Highly variable energy demand fluctuations showed that passive IR heater warming systems will not maintain desired warming for much of the time.     

Climatic Warming Increases Winter Wheat Yield but Reduces Grain Nitrogen Concentration in East China

Climatic warming is often predicted to reduce wheat yield and grain quality in China. However, direct evidence is still lacking. We conducted a three-year experiment with a Free Air Temperature Increase (FATI) facility to examine the responses of winter wheat growth and plant N accumulation to a moderate temperature increase of 1.5°C predicted to prevail by 2050 in East China. Three warming treatments (AW: all-day warming; DW: daytime warming; NW: nighttime warming) were applied for an entire growth period. Consistent warming effects on wheat plant were recorded across the experimental years. An increase of ca. 1.5°C in daily, daytime and nighttime mean temperatures shortened the length of pre-anthesis period averagely by 12.7, 8.3 and 10.7 d (P<0.05), respectively, but had no significant impact on the length of the post-anthesis period. Warming did not significantly alter the aboveground biomass production, but the grain yield was 16.3, 18.1 and 19.6% (P<0.05) higher in the AW, DW and NW plots than the non-warmed plot, respectively. Warming also significantly increased plant N uptake and total biomass N accumulation. However, warming significantly reduced grain N concentrations while increased N concentrations in the leaves and stems. Together, our results demonstrate differential impacts of warming on the depositions of grain starch and protein, highlighting the needs to further understand the mechanisms that underlie warming impacts on plant C and N metabolism in wheat.     

Spatio-Temporal Characteristics of Global Warming in the Tibetan Plateau during the Last 50 Years Based on a Generalised Temperature Zone - Elevation Model

Temperature is one of the primary factors influencing the climate and ecosystem, and examining its change and fluctuation could elucidate the formation of novel climate patterns and trends. In this study, we constructed a generalised temperature zone elevation model (GTEM) to assess the trends of climate change and temporal-spatial differences in the Tibetan Plateau (TP) using the annual and monthly mean temperatures from 1961–2010 at 144 meteorological stations in and near the TP. The results showed the following: (1) The TP has undergone robust warming over the study period, and the warming rate was 0.318°C/decade. The warming has accelerated during recent decades, especially in the last 20 years, and the warming has been most significant in the winter months, followed by the spring, autumn and summer seasons. (2) Spatially, the zones that became significantly smaller were the temperature zones of −6°C and −4°C, and these have decreased 499.44 and 454.26 thousand sq km from 1961 to 2010 at average rates of 25.1% and 11.7%, respectively, over every 5-year interval. These quickly shrinking zones were located in the northwestern and central TP. (3) The elevation dependency of climate warming existed in the TP during 1961–2010, but this tendency has gradually been weakening due to more rapid warming at lower elevations than in the middle and upper elevations of the TP during 1991–2010. The higher regions and some low altitude valleys of the TP were the most significantly warming regions under the same categorizing criteria. Experimental evidence shows that the GTEM is an effective method to analyse climate changes in high altitude mountainous regions.     

Ocean Warming,More than Acidification,Reduces Shell Strength in a Commercial Shellfish Species during Food Limitation

Ocean surface pH levels are predicted to fall by 0.3–0.4 pH units by the end of the century and are likely to coincide with an increase in sea surface temperature of 2–4°C. The combined effect of ocean acidification and warming on the functional properties of bivalve shells is largely unknown and of growing concern as the shell provides protection from mechanical and environmental challenges. We examined the effects of near-future pH (ambient pH –0.4 pH units) and warming (ambient temperature +4°C) on the shells of the commercially important bivalve, Mytilus edulis when fed for a limited period (4–6 h day⁻¹). After six months exposure, warming, but not acidification, significantly reduced shell strength determined as reductions in the maximum load endured by the shells. However, acidification resulted in a reduction in shell flex before failure. Reductions in shell strength with warming could not be explained by alterations in morphology, or shell composition but were accompanied by reductions in shell surface area, and by a fall in whole-body condition index. It appears that warming has an indirect effect on shell strength by re-allocating energy from shell formation to support temperature-related increases in maintenance costs, especially as food supply was limited and the mussels were probably relying on internal energy reserves. The maintenance of shell strength despite seawater acidification suggests that biomineralisation processes are unaffected by the associated changes in CaCO₃ saturation levels. We conclude that under near-future climate change conditions, ocean warming will pose a greater risk to shell integrity in M. edulis than ocean acidification when food availability is limited.     

Long-Term Conditioning to Elevated pCO2 and Warming Influences the Fatty and Amino Acid Composition of the Diatom Cylindrotheca fusiformis

The unabated rise in anthropogenic CO₂ emissions is predicted to strongly influence the ocean’s environment, increasing the mean sea-surface temperature by 4°C and causing a pH decline of 0.3 units by the year 2100. These changes are likely to affect the nutritional value of marine food sources since temperature and CO₂ can influence the fatty (FA) and amino acid (AA) composition of marine primary producers. Here, essential amino (EA) and polyunsaturated fatty (PUFA) acids are of particular importance due to their nutritional value to higher trophic levels. In order to determine the interactive effects of CO₂ and temperature on the nutritional quality of a primary producer, we analyzed the relative PUFA and EA composition of the diatom Cylindrotheca fusiformis cultured under a factorial matrix of 2 temperatures (14 and 19°C) and 3 partial pressures of CO₂ (180, 380, 750 μatm) for >250 generations. Our results show a decay of ~3% and ~6% in PUFA and EA content in algae kept at a pCO₂ of 750 μatm (high) compared to the 380 μatm (intermediate) CO₂ treatments at 14°C. Cultures kept at 19°C displayed a ~3% lower PUFA content under high compared to intermediate pCO₂, while EA did not show differences between treatments. Algae grown at a pCO₂ of 180 μatm (low) had a lower PUFA and AA content in relation to those at intermediate and high CO₂ levels at 14°C, but there were no differences in EA at 19°C for any CO₂ treatment. This study is the first to report adverse effects of warming and acidification on the EA of a primary producer, and corroborates previous observations of negative effects of these stressors on PUFA. Considering that only ~20% of essential biomolecules such as PUFA (and possibly EA) are incorporated into new biomass at the next trophic level, the potential impacts of adverse effects of ocean warming and acidification at the base of the food web may be amplified towards higher trophic levels, which rely on them as source of essential biomolecules.     

Artificial asymmetric warming reduces nectar yield in a Tibetan alpine species of Asteraceae

Background and Aims Asymmetric warming is one of the distinguishing features of global climate change, in which winter and night-time temperatures are predicted to increase more than summer and diurnal temperatures. Winter warming weakens vernalization and hence decreases the potential to flower for some perennial herbs, and night warming can reduce carbohydrate concentrations in storage organs. This study therefore hypothesized that asymmetric warming should act to reduce flower number and nectar production per flower in a perennial herb, Saussurea nigrescens, a key nectar plant for pollinators in Tibetan alpine meadows.Methods A long-term (6 years) warming experiment was conducted using open-top chambers placed in a natural meadow and manipulated to achieve asymmetric increases in temperature, as follows: a mean annual increase of 0·7 and 2·7 °C during the growing and non-growing seasons, respectively, combined with an increase of 1·6 and 2·8 °C in the daytime and night-time, respectively, from June to August. Measurements were taken of nectar volume and concentration (sucrose content), and also of leaf non-structural carbohydrate content and plant morphology.Key Results Six years of experimental warming resulted in reductions in nectar volume per floret (64·7 % of control), floret number per capitulum (8·7 %) and capitulum number per plant (32·5 %), whereas nectar concentration remained unchanged. Depletion of leaf non-structural carbohydrates was significantly higher in the warmed than in the ambient condition. Overall plant density was also reduced by warming, which, when combined with reductions in flower development and nectar volumes, led to a reduction of ∼90 % in nectar production per unit area.Conclusions The negative effect of asymmetric warming on nectar yields in S. nigrescens may be explained by a concomitant depletion of leaf non-structural carbohydrates. The results thus highlight a novel aspect of how climate change might affect plant–pollinator interactions and plant reproduction via induction of allocation shifts for plants growing in communities subject to asymmetric warming.     

Juveniles Are More Resistant to Warming than Adults in 4 Species of Antarctic Marine Invertebrates

Juvenile stages are often thought to be less resistant to thermal challenges than adults, yet few studies make direct comparisons using the same methods between different life history stages. We tested the resilience of juvenile stages compared to adults in 4 species of Antarctic marine invertebrate over 3 different rates of experimental warming. The species used represent 3 phyla and 4 classes, and were the soft-shelled clam Laternula elliptica, the sea cucumber Cucumaria georgiana, the sea urchin Sterechinus neumayeri, and the seastar Odontaster validus. All four species are widely distributed, locally abundant to very abundant and are amongst the most important in the ecosystem for their roles. At the slowest rate of warming used (1°C 3 days⁻¹) juveniles survived to higher temperatures than adults in all species studied. At the intermediate rate (1°C day⁻¹) juveniles performed better in 3 of the 4 species, with no difference in the 4^th, and at the fastest rate of warming (1°C h⁻¹) L. elliptica adults survived to higher temperatures than juveniles, but in C. georgiana juveniles survived to higher temperatures than adults and there were no differences in the other species. Oxygen limitation may explain the better performance of juveniles at the slower rates of warming, whereas the loss of difference between juveniles and adults at the fastest rate of warming suggests another mechanism sets the temperature limit here.     

Factors influencing range contraction of a rodent herbivore in a steppe grassland over the past decades

1. Climate warming and human disturbance are known to be key drivers in causing range contraction of many species, but quantitative assessment on their distinctive and interactive effects on local disappearance is still rare.
2. In this study, we examined the association of climate warming and human disturbance stressors with local disappearance probability of Brandt''s voles (Lasiopodomys brandtii) in a steppe grassland in northern China.
3. We used logistic generalized additive models to quantify the relationship between local disappearance probability of Brandt''s voles and environmental variables. The year following the last observation year was used to estimate the disappearance threshold of Brandt''s voles. We projected the distribution change of Brandt''s voles under future climate warming scenarios.
4. We found climate warming attributed to local disappearance and range contraction for southern populations of Brandt''s voles from 1971 to 2020. Human stressors and high vegetation coverage increased the probability of local disappearance of voles in years of abundant precipitation. The southern boundary retreated northward at a speed of 99.0 km per decade with the temperature rise of 0.36°C. The disappearance threshold of maximum air temperature of Brandt''s voles in the warmest month (27.50 ± 1.61°C) was similar to the lower critical temperature of its thermal neutral zone.
5. Our study suggests that the rapid climate change over the past decades contributed to the range contraction of its southern boundary of this keystone species in the steppe grassland of China. It is necessary to take actions to preserve the isolated populations of Brandt''s voles from the effects of accelerated climate change and human disturbance.