Increase In Winter Temperature Research Articles

Effects of drought stress on cold hardiness of non-acclimated viola ( Viola × wittrockiana ‘Iona Gold with Blotch’) in controlled conditions

Abstract Predicted increases in winter temperatures may negatively impact plant survival by preventing maximal cold acclimation prior to cold temperatures. Accordingly, research is needed to identify strategies that may help promote cold hardiness and increase freezing tolerance of cold season ornamental plants. Therefore, the objectives of this research were to study the effects of drought stress on freezing tolerance of Viola × wittrockiana Iona Gold with Blotch during cold season under non-cold acclimating (20 ± 1 °C) conditions and examine the physiological and biochemical changes in plants in response to freezing temperature. After being grown in the greenhouse, plants were first subjected to different levels of soil water availability including control (90%), 70% and 50% field capacity (FC). Then, some traits including proline, carbohydrate and chlorophyll were determined. Finally, plants were transferred to the Thermo Gradient Freezer with six freezing temperatures (0, −3, −6, −9, −12, and −15 °C), as well as 20 °C as the control treatment. Electrolyte leakage (EL) after temperature treatments, plant survival percentage (SU) and some traits related to regrowth after recovery period were determined. Result showed that drought stress increased some factors such as carbohydrate, proline and chlorophyll. Electrolyte leakage significantly increased by lowering temperature and increased by 46% at 15 °C compared to control. Plant survival was significantly affected by treatments so that lowering the temperature to −15 °C caused total mortality in all the plants of irrigation treatments. Plants under 70% FC at 0 °C had the highest increased reproductive component. Number of leaf and leaf area peaked under the moderate water deficit (70% FC) conditions at 0 °C. Plants under 70% FC at 0 °C had the highest increases (87, 134, 90 and 101%, respectively) in dry weights of vegetative, reproductive, root, and total dry weights compared to control. Drought stress can increase freezing tolerance of viola depending on temperature regime.

The amenity value of climate change across different regions in the United States

ABSTRACTThis article estimates the effect of climatic variables on house prices near ski resorts in different regions in the United States. We find that among the climate variables we test, average winter temperature has the most significant and robust effect where an increase in this climate variable increases house prices near ski resorts at a decreasing rate. At the mean average winter temperature levels, an increase in average winter temperature reduces housing prices for all regions except the Northeast. The consumer surplus from projected average winter temperature changes is negative across all regions and the largest negative effects are in the Midwest and Mountain regions.

Changes in snow cover alter nitrogen cycling and gaseous emissions in agricultural soils

Climate change-related increases in winter temperatures and precipitation, as predicted for eastern Canada, may alter snow cover, with consequences for soil temperature and moisture, nitrogen cycling, and greenhouse gas fluxes. To assess the effects of snow depth in a humid temperate agricultural ecosystem, we conducted a two-year field study with (1) snow removal, (2) passive snow accumulation (via snow fence), and (3) ambient snow treatments. We measured in situ N2O and CO2 fluxes and belowground soil gas concentration, and conducted denitrification and potential nitrification laboratory assays, from November through May. Snow manipulation significantly affected winter N2O dynamics. In the first winter, spring thaw N2O fluxes in snow removal plots were 31 and 48 times greater than from ambient snow and snow accumulation plots respectively. Mid-winter soil N2O concentration was also highest in snow removal plots. These effects may have been due to increased substrate availability due to greater soil frost, along with moderate gas diffusivities facilitating N2O production, in snow removal plots. In the second winter, spring thaw N2O fluxes and soil N2O concentration were greatest for ambient snow plots. Peak fluxes in ambient snow plots were 19 and 24 times greater than in snow accumulation and snow removal plots, respectively. Greater soil moisture in ambient snow plots overwinter could have facilitated denitrification both through decreased O2 availability and increased disruption of soil aggregates during freeze-thaw cycles. Overall, results suggest that effects of changing snow cover on N cycling and N2O fluxes were not solely a direct effect of snow depth; rather, effects were mediated by both soil water content and temperature. Furthermore, the fact that treatments with greatest mid-winter belowground N2O accumulation also had greatest spring thaw N2O fluxes in both years suggests the hypothesis that high spring thaw fluxes were due not only to spring soil conditions, but also to an effect of soil conditions in frozen soils that had facilitated N2O production throughout winter.

Sensitivity of winter tourism to temperature increases over the last decades

This paper provides new evidence on the impact of temperatures on tourism demand in the winter season. The analysis is based on time series data spanning from 1960 to 2015 for the South Tyrolean mountains in Italy. Since 1960, winter temperatures have increased by 0.4 degrees Celsius per decade, on average. A nonlinear autoregressive distributed lag (ARDL) model is employed for the estimations. This model allows two separate coefficients to impact tourism demand, following temperature changes (decreases or increases). Results reveal that an increase in winter temperatures by one degree Celsius leads to a decline in the number of accommodation guests (arrivals) by eight per cent, while temperature decreases have no effect on the number of arrivals. However, sensitivity to temperature increases has been declining since the early 1990s, probably due to the widespread usage of snowmaking facilities. The number of these facilities has increased by almost 10 per cent per year on average over the same period. In recent years (1986–2015), and as a consequence of these measures, temperature increases no longer have an effect on winter tourism demand. Conversely, decreases in temperatures lead to small increases in arrivals (by four per cent increase due to a one degree Celsius decrease).

Calculation of Long-Term Averages of Surface Air Temperature Based on Insolation Data

The solar radiation coming to the Earth’s ellipsoid is considered without taking into account the atmosphere on the basis of the astronomical ephemerides for the time interval from 3000 BC to 3000 AD. Using the regression equations between the Earth’s insolation and near-surface air temperature, the insolation annual and semiannual climatic norms of near-surface air temperature for the Earth as a whole and the hemispheres are calculated in intervals of 30 years for the period from 2930 BC to 2930 AD with 100 and 900- to 1000-year time steps. The analysis shows that the annual insolation rates of the near-surface air temperature of the Earth and the hemispheres decrease at all intervals. The semiannual insolation rates of the near-surface air temperature increase in winter and decrease in summer. This means that the seasonal difference decreases. The annual and semiannual rates of insolation near-surface air temperature of the Earth increase in the equatorial and decrease in the polar regions; the latitudinal contrast increases. The interlatitudinal gradient is higher in the Southern Hemisphere. It practically does not change in winter and increases in summer, most strongly in the Southern Hemisphere.

Winter warming effects on tundra shrub performance are species‐specific and dependent on spring conditions

Abstract Climate change‐driven increases in winter temperatures positively affect conditions for shrub growth in arctic tundra by decreasing plant frost damage and stimulation of nutrient availability. However, the extent to which shrubs may benefit from these conditions may be strongly dependent on the following spring climate. Species‐specific differences in phenology and spring frost sensitivity likely affect shrub growth responses to warming. Additionally, effects of changes in winter and spring climate may differ over small spatial scales, as shrub growth may be dependent on natural variation in snow cover, shrub density and cryoturbation. We investigated the effects of winter warming and altered spring climate on growing‐season performance of three common and widespread shrub species in cryoturbated non‐sorted circle arctic tundra. By insulating sparsely vegetated non‐sorted circles and parts of the surrounding heath with additional snow or gardening fleeces, we created two climate change scenarios: snow addition increased soil temperatures in autumn and winter and delayed snowmelt timing without increasing spring temperatures, whereas fleeces increased soil temperature similarly in autumn and winter, but created warmer spring conditions without altering snowmelt timing. Winter warming affected shrub performance, but the direction and magnitude were species‐specific and dependent on spring conditions. Spring warming advanced, and later snowmelt delayed canopy green‐up. The fleece treatment did not affect shoot growth and biomass in any shrub species despite decreasing leaf frost damage in Empetrum nigrum. Snow addition decreased frost damage and stimulated growth of Vaccinium vitis‐idaea by c. 50%, while decreasing Betula nana growth (p < .1). All of these effects were consistent the mostly barren circles and surrounding heath. Synthesis. In cryoturbated arctic tundra, growth of Vaccinium vitis‐idaea may substantially increase when a thicker snow cover delays snowmelt, whereas in longer term, warmer winters and springs may favour E. nigrum instead. This may affect shrub community composition and cover, with potentially far‐reaching effects on arctic ecosystem functioning via its effects on cryoturbation, carbon cycling and trophic cascading. Our results highlight the importance of disentangling effects of winter and spring climate change timing and nature, as spring conditions are a crucial factor in determining the impact of winter warming on plant performance.

Humans and climate change drove the Holocene decline of the brown bear

The current debate about megafaunal extinctions during the Quaternary focuses on the extent to which they were driven by humans, climate change, or both. These two factors may have interacted in a complex and unexpected manner, leaving the exact pathways to prehistoric extinctions unresolved. Here we quantify, with unprecedented detail, the contribution of humans and climate change to the Holocene decline of the largest living terrestrial carnivore, the brown bear (Ursus arctos), on a continental scale. We inform a spatially explicit metapopulation model for the species by combining life-history data and an extensive archaeofaunal record from excavations across Europe with reconstructed climate and land-use data reaching back 12,000 years. The model reveals that, despite the broad climatic niche of the brown bear, increasing winter temperatures contributed substantially to its Holocene decline — both directly by reducing the species’ reproductive rate and indirectly by facilitating human land use. The first local extinctions occurred during the Mid-Holocene warming period, but the rise of the Roman Empire 2,000 years ago marked the onset of large-scale extinctions, followed by increasingly rapid range loss and fragmentation. These findings strongly support the hypothesis that complex interactions between climate and humans may have accelerated megafaunal extinctions.

Plant age and ambient temperature: significant drivers for powdery mildew (Erysiphe cruciferarum) epidemics on oilseed rape (Brassica napus)

Powdery mildew (Erysiphe cruciferarum) is an important disease in oilseed rape crops worldwide, but of sporadic importance in most southern Australian crops. Six Brassica napus cultivars were exposed to E. cruciferarum simultaneously in four plant age cohorts. First symptoms of powdery mildew appeared 9 days after inoculation (dai) on the oldest plants [42 days after seeding (das)], but 44 dai in the youngest plants that were exposed to inoculum from sowing, although final disease severity did not differ with the plant age at exposure. The maximum level of pod peduncle infestation was unaffected by plant age (P = 0.37) or cultivar (P = 0.28). The effect of temperature was also investigated. The development of disease on plants was slower and final severity reduced at a day/night temperature 14/10 °C compared with 22/17 °C. In vitro, maximum growth of germ tubes from conidia of E. cruciferarum was at 15–20 °C and survival of conidia reduced by temperatures >30 °C. The results explain the sporadic nature of powdery mildew outbreaks in winter‐grown oilseed rape in Australia, where slow rates of infection occur when seasonal colder prevailing winter conditions coincide with the presence of younger plants, together curtailing rapid disease development until temperatures increase in late winter/early spring. These results explain why epidemics are most severe in the two warmer cropping regions, viz. the northern agricultural region of Western Australia and New South Wales. This study suggests that with increases in winter temperatures under future climate scenarios, earlier and more severe powdery mildew outbreaks in Australia will be favoured.

Demographics of <i>Eucalyptus grandis</i> and implications for invasion

Alien invasive species can have negative impacts on the functioning of ecosystems. Plantation species such as pines have become serious invaders in many parts of the world, but eucalypts have not been nearly as successful invaders. This is surprising considering that in their native habitat they dominate almost all vegetation types. Available theory on the qualities that characterise invasive species was used to assess the invasive potential of Eucalyptus grandis – a common plantation species globally. To determine rates of establishment of E. grandis outside plantations, we compared population demographics and reproductive traits at two locations in Mpumalanga, South Africa: one at higher elevation with more frost. Eucalyptus grandis has a short generation time. We found no evidence that establishment of E. grandis was limiting its spread into native grassland vegetation, but it does appear that recruitment is limited by frost and fire over much of its range in Mpumalanga. Populations at both study locations displayed characteristics of good recruitment. Size class distributions showed definite bottlenecks to recruitment which were more severe when exposed to frost at higher elevations. Generally, the rate of spread is low suggesting that the populations are on the establishing populations’ invasion stage. This research gives no indication that there are any factors that would prevent eucalyptus from becoming invasive in the future, and the projected increase in winter temperatures should be a cause for concern as frost is currently probably slowing recruitment of E. grandis across much of its planted range.Conservation implications: Eucalyptus plantations occur within indigenous grasslands that are of high conservation value. Frost and fire can slow recruitment where they occur, but there are no obvious factors that would prevent E. grandis from becoming invasive in the future, and monitoring of its rates of spread is recommended.

Dendroclimotological research of scots pine in stand of the Left-bank Forest-steppe of Ukraine

Purpose of this research was to detect influence of climatic change on pine radial increment in stand in the Left-bank Forest-steppe of Ukraine as example 100-years-old stand at State Enterprise 'Kharkiv forest scientific research station’. Methods. Dendrochronological. Method of correlation function and multiple regressions (response function) were used to analyze the influence of climatic factors on tree radial increment. For this purpose computer program RESPO was used. Results. Tree ring series were built and were used for correlation analysis between climatic factors and pine radial increment for two periods: 1960-1988 and 1988-2016.Years of minimum (1933, 1942, 1956, 1972, 1976, 1976, 1987, 1992, 2002, 2006 та 2012) and maximum (1933, 1942, 1956, 1972, 1975, 1976, 1979, 1979, 1979, 1987, 1992, 2002 та 2012) of radial increment were detected. Depressions of pine radial increment were as a result of negative weather conditions: low and high winter and early-spring temperature, droughts during vegetation period. Maximums of radial increments were depended on favorable weather conditions for pine radial growth. Correlation and Response analysis for two periods showed that increase of temperature and precipitation, excluding winter precipitation, changed response of forest ecosystems to climatic change: if in first period (1960-1988) radial increment limited by April temperature and together July temperature positively influenced on radial growth, in second period (1988-2016) June temperature negatively infuenced on radial increment. Slight increase precipitation during vegetation period could not soften impact if high temperature during vegetatation period on tree radial increment. Conclusions. At comparison 1960-1988 and 1988-2016 it was detected that during first period positive influence of summer temperature on radial growth was distinctive and for second period one started to limit increment (negative influence) were detected. Slight increase of precipitation for vegetation period in second period significantly didn’t influence on pine radial growth. In second period increase of winter temperature and number of thaws negatively influenced on soil moisture, decreased of tree ring widths.

Recent warming on Spitsbergen—Influence of atmospheric circulation and sea ice cover

AbstractSpitsbergen has experienced some of the most severe temperature changes in the Arctic during the last three decades. This study relates the recent warming to variations in large‐scale atmospheric circulation (AC), air mass characteristics, and sea ice concentration (SIC), both regionally around Spitsbergen and locally in three fjords. We find substantial warming for all AC patterns for all seasons, with greatest temperature increase in winter. A major part of the warming can be attributed to changes in air mass characteristics associated with situations of both cyclonic and anticyclonic air advection from north and east and situations with a nonadvectional anticyclonic ridge. In total, six specific AC types (out of 21), which occur on average 41% of days in a year, contribute approximately 80% of the recent warming. The relationship between the land‐based surface air temperature (SAT) and local and regional SIC was highly significant, particularly for the most contributing AC types. The high correlation between SAT and SIC for air masses from east and north of Spitsbergen suggests that a major part of the atmospheric warming observed in Spitsbergen is driven by heat exchange from the larger open water area in the Barents Sea and region north of Spitsbergen. Finally, our results show that changes in frequencies of AC play a minor role to the total recent surface warming. Thus, the strong warming in Spitsbergen in the latest decades is not driven by increased frequencies of “warm” AC types but rather from sea ice decline, higher sea surface temperatures, and a general background warming.

Winter warming effects on overwinter survival, energy use, and spring emergence ofCerotoma trifurcata(Coleoptera: Chrysomelidae)

Bean leaf beetle Cerotoma trifurcata (Forster) (Coleoptera: Chrysomelidae) is a pest of soybean in the U.S.A. and is becoming a concern in Canada. The projected increase in winter temperatures under climate change could affect overwinter survival, timing of spring emergence and, ultimately, the severity of this pest. We assessed the potential effects of warmer winters in field experiments performed in three consecutive years. Three warming levels were applied: (i) heated approximately 4 °C above ambient; (ii) unheated with snow cover left intact; and (iii) unheated with snow cover removed. Survival and date of emergence were assessed in all years, and beetle lipid content was analyzed in 1 year to determine rates of energy use. Overwinter survival was 6.5–14.5% among years. Winter warming inconsistently affected overwinter survival: increasing survival in one winter, decreasing survival in the warmest winter and having no effect in one winter. Beetles that received supplemental winter warming emerged approximately 2 weeks earlier in spring, and lipid content did not differ among treatment groups. Earlier spring emergence may allow for the production of an additional generation per year of C. trifurcata under future climate change. However, further experiments are required to establish the relationship between overwinter survival and subsequent beetle population growth to determine potential pest status and best management practices under future climate conditions.

Anomalous Increase in Winter Temperature and Decline in Forest Growth Associated with Severe Winter Smog in the Ulan Bator Basin

A dramatic increase in winter (December–February) temperature by 7.2 K (1.1 K per decade) since 1950 has occurred in the Ulan Bator basin, Mongolia. This increase in temperature strongly exceeds the global average of late twentieth century warming and even exceeds warming in most of the polar regions with pronounced increases in temperature. The exceptional warming is restricted to Ulan Bator within the Mongolian forest-steppe region and to wintertime. This suggests that the observed warming could result from radiative forcing by black carbon aerosols. In winter, Ulan Bator’s air is heavily polluted by particulate matter, including black carbon, originating from the combustion of low-quality fuel at low temperature. Winter smog has strongly increased in recent decades, concomitant to the increase in winter temperature, as the result of a strong increase in the city’s population. Exponential growth of Ulan Bator’s population started in the mid-twentieth century, but since 1990, altered socioeconomic frame conditions and a warming climate have driven more than 700,000 pastoralists from rural Mongolia to Ulan Bator where people live in provisional dwellings and cause Ulan Bator’s heavy air pollution. Tree-ring analysis from larch trees growing at the edge of the Ulan Bator basin shows negative correlation of stem increment with December temperature. This result suggests that milder winters promote herbivores and, thus, reduce the tree’s productivity. The negative impact of winter warming on the larch forests adds to adverse effects of summer drought and the impact of high sulfur dioxide emissions. Winter warming putatively associated with high atmospheric concentrations of black carbon aerosols in the Ulan Bator basin is an interesting example of a case where greenhouse gas-mediated climate warming in an area where people themselves hardly contribute to global greenhouse gas emissions affects both humans and ecosystems and causes additional local climate warming.

Chronic effects of temperature on mortality in the Southeastern USA using satellite-based exposure metrics.

Climate change may affect human health, particularly for elderly individuals who are vulnerable to temperature changes. While many studies have investigated the acute effects of heat, only a few have dealt with the chronic ones. We have examined the effects of seasonal temperatures on survival of the elderly in the Southeastern USA, where a large fraction of subpopulation resides. We found that both seasonal mean temperature and its standard deviation (SD) affected long-term survival among the 13 million Medicare beneficiaries (aged 65+) in this region during 2000–2013. A 1 °C increase in summer mean temperature corresponded to an increase of 2.5% in death rate. Whereas, 1 °C increase in winter mean temperature was associated with a decrease of 1.5%. Increases in seasonal temperature SD also influence mortality. We decomposed seasonal mean temperature and its temperature SD into long-term geographic contrasts between ZIP codes and annual anomalies within ZIP code. Effect modifications by different subgroups were also examined to find out whether certain individuals are more vulnerable. Our findings will be critical to future efforts assessing health risks related to the future climate change.

The Snow Must Go On: Ground Ice Encasement, Snow Compaction and Absence of Snow Differently Cause Soil Hypoxia, CO2 Accumulation and Tree Seedling Damage in Boreal Forest.

At high latitudes, the climate has warmed at twice the rate of the global average with most changes observed in autumn, winter and spring. Increasing winter temperatures and wide temperature fluctuations are leading to more frequent rain-on-snow events and freeze-thaw cycles causing snow compaction and formation of ice layers in the snowpack, thus creating ice encasement (IE). By decreasing the snowpack insulation capacity and restricting soil-atmosphere gas exchange, modification of the snow properties may lead to colder soil but also to hypoxia and accumulation of trace gases in the subnivean environment. To test the effects of these overwintering conditions changes on plant winter survival and growth, we established a snow manipulation experiment in a coniferous forest in Northern Finland with Norway spruce and Scots pine seedlings. In addition to ambient conditions and prevention of IE, we applied three snow manipulation levels: IE created by artificial rain-on-snow events, snow compaction and complete snow removal. Snow removal led to deeper soil frost during winter, but no clear effect of IE or snow compaction done in early winter was observed on soil temperature. Hypoxia and accumulation of CO2 were highest in the IE plots but, more importantly, the duration of CO2 concentration above 5% was 17 days in IE plots compared to 0 days in ambient plots. IE was the most damaging winter condition for both species, decreasing the proportion of healthy seedlings by 47% for spruce and 76% for pine compared to ambient conditions. Seedlings in all three treatments tended to grow less than seedlings in ambient conditions but only IE had a significant effect on spruce growth. Our results demonstrate a negative impact of winter climate change on boreal forest regeneration and productivity. Changing snow conditions may thus partially mitigate the positive effect of increasing growing season temperatures on boreal forest productivity.

Spatial and temporal variations of the chromosomal inversion frequencies across the range of malaria mosquito Anopheles messeae Fall. (Culicidae) during the 40-year monitoring period

The analysis of personal and published data on the frequency dynamics of chromosomal inversions within the range of Anopheles messeae obtained during the period from 1974 through 2014 is presented. The results showed that, in general, across the species range, during the 40 years of genetic monitoring, there was a steady (stationary) clinal distribution of inversions in the first decade (1974–1985). Then, over the period of five years (1986–1990), there was a considerable change in the inversion frequencies in favor of southwestern chromosomal variants (particularly strongly fixed in the Tomsk population), and from 1992 to the present time, these changes remained and were relatively stably reproduced in most parts of the range. It was noted that the jump in warming during the winter of 1981–1982 led to a correlated jump of the southwestern chromosomes in the Tomsk population. In connection with the general tendency toward the increase in average winter temperatures, a sharp decrease in the 2R1 chromosome frequency in the Siberian region and Syktyvkar in the period from 1992 to the present time was observed. There is reason to assume that, over the past decade, the northern boundary of the An. messeae range moved northward to the tundra zone.

Simulation of forest tree species' bud burst dates for different climate scenarios: chilling requirements and photo-period may limit bud burst advancement.

This study investigates whether the assumed increase of winter and spring temperatures is depicted by phenological models in correspondingly earlier bud burst (BB) dates. Some studies assume that rising temperatures lead to an earlier BB, but even later BB has been detected. The phenological model PIM (promoter-inhibitor-model) fitted to the extensive phenological database of the German Weather Service was driven by several climate scenarios. This model accounts for the complicated mechanistic interactions between chilling requirements, temperature and photo-period. It predicts BB with a r 2 between 0.41 and 0.62 and a RMSE of around 1 week, depending on species. Parameter sensitivities depict species dependent interactions between growth and chilling requirements as well as photo-period. A mean trend to earlier BB was revealed for the period 2002- 2100, varying between -0.05 and -0.11 days per year, depending on species. These trends are lower than for the period 1951- 2009. Within climate scenario period, trends are decreasing for beech and chestnut, stagnating for birch and increasing for oak. Results suggest that not fulfilled chilling requirements accompanied by an increasing dependency on photo-period potentially limit future BB advancement. The combination of a powerful phenological model, a large scale phenological database and several climate scenarios, offers new insights into the mechanistic comprehension of spring phenology.

Early Holocene hydrology and environments of the Ner River (Poland)

The Ner River valley (central Poland) underwent substantial transformation during the Weichselian–Holocene transition as a result of fluvial processes and climate changes, resulting in the establishment of its present shape in the Holocene. A multiproxy study based on organic deposits from a palaeochannel fill (Lutomiersk–Koziówki) shows that after the channel was cut off during the late glacial termination, it became a shallow oxbow, fed by local springs. In the Boreal period, the oxbow lake was also fed by precipitation and became a telmatic environment overgrown by rush and swamp vegetation. Finally, it was covered by overbank deposits. The first flooding phase (9900–9600cal. BP) was followed by the accumulation of overbank sediments (after 9500cal. BP) and flooding increased after ca. 9300–9000cal. BP. Pollen data provide information on the regional vegetation context for local and regional changes. In the Atlantic period, an increase in both summer and winter temperatures is inferred from the pollen data, corresponding to an expansion of thermophilous deciduous forests. While in general, flooding phases of the Early Holocene are poorly recognised in Eastern Europe, the Lutomiersk–Koziówki site may be considered as one of the reference points for this phenomenon in the region.

Charting trends in the evolution of the La Alhambra forest (Granada, Spain) through analysis of pollen-emission dynamics over time

Changing climate conditions are having an appreciable impact both on the adaptive response of the species growing in urban and peri-urban forests (UPF) and on their evolutionary dynamics. This study sought to chart the evolution and pollen dynamics of major species growing in the La Alhambra peri-urban forest (Granada, Spain) over the last 22 years, to examine correlations with weather-related parameters and to estimate potential trends in the event of future climate change. Findings showed that overall pollen levels have gradually increased over the study period, reflecting both plant species diversification and the ability of Mediterranean species—particularly Pinus and Quercus—to adapt to short-term water stress situations. Nevertheless, the climate conditions expected over the coming years in the Mediterranean region, with considerable increase in winter temperatures and a drop in precipitation by up to 24 % for summer rainfall, there is likely to be a reduction in the intensity of pollen emissions, at least from species with strict environmental requirements. The results confirm that pollen emission is a valuable biological indicator for estimating the adaptive response of various species and the resilience of the forest mass to climate-change events.

The effects of recent changes in air temperature on trends in airborne Alternaria, Epicoccum and Stemphylium spore seasons in Bratislava (Slovakia)

Over the period 2002–2014, air temperature significantly increased regionally for Bratislava. However, no significant shifts have been observed in other meteorological parameters examined. The aim of this study was to analyse the effect of significant temperature trends on timing, duration and intensity of Alternaria, Epicoccum and Stemphylium spore seasons. Aerobiological monitoring was conducted using a Burkard 7-day volumetric spore trap. Mann–Kendall tau test was used to determine trends in spore seasons characteristics, whereas Spearman’s correlation coefficients were calculated to establish the relationships between temperature and spore season time series. Spore seasons of analysed taxa changed throughout the years of study. Alternaria spore season now starts earlier, ends later and lasts longer. Start, end and peak dates as well as duration of Alternaria spore seasons were significantly correlated with recorded increases in winter temperatures. Despite significant lengthening of Alternaria spore seasons, the lack of rising trend in its spore season index has been registered. This phenomenon could be partly explained by the reduction in the source vegetation due to drop of agricultural land use areas in Bratislava. In contrast, the intensity of Stemphylium spore seasons significantly increased during the study period and was correlated with recorded increases in summer–autumn temperatures. Based on the results of this study, it could be concluded that changes in selected fungal spore season patterns in Bratislava (earlier start date, later end date and longer duration of Alternaria spore seasons and higher Stemphylium spore season indexes) might be caused by the recorded local change in air temperature.