Long-term temporal changes in central European tree phenology (1946-2010) confirm the recent extension of growing seasons

[Allergy and immunotoxicology in preventive and clinical medicine from theory to practice: Environmental factors in bronchial asthma]

BACKGROUND

According to the gene-environment interactions concept, the mechanism of health impairment can be explained by genetic factors, environmental factors, or their interaction. Physical and mental health effects resulting from environmental exposure may be classified either as toxicity, immune response, and allergic reaction. Moreover, despite the already established therapeutic approaches to bronchial asthma and decreasing mortality due to bronchial asthma, patients with difficult and severe asthma are increasing in number. This review outlines recent topics in the field of allergies, focusing on asthma.

RESULTS AND DISCUSSION

Living environment-derived pollutants and their involvement in the pathogenesis of asthma and its exacerbation, referred to here as an exposome concept, comprises the three domains of internal, specific external, and general external. Living environment-derived pollutants include exposure to pollutants in workplaces, climate change, air pollution, microplastics, tobacco smoke, biodiversity change and loss, changing dietary habits, and the microbiome. These are associated with the modernization, urbanization, and globalization of human society. Although many novel compounds are currently available, their harmful health effects, such as allergy, are not thoroughly understood. Hence, the means to mitigate these are unknown. Dietary changes from a traditional diet rich in fish to a Western-style diet are considered critical environmental factors and therefore, associated with an increased prevalence of allergies. Cytokines, including thymic stromal lymphopoietin, IL-25, and IL-33, released from the airway epithelium in response to various triggers (exposure to diverse environmental factors) are known as alarmins. Anti-alarmin antibodies are a promising therapeutic approach against severe and difficult allergic disorders. Collaboration between hospitals and clinics and occupational and clinical medicine is imperative for treating and managing severe asthma. In addition to avoiding environmental exposure, understanding the pathogenesis and exacerbation of asthma is essential for future research in the field of allergy and immunotoxicology.

Assessment of Phenological Dynamics of Different Vegetation Types and Their Environmental Drivers with Near-Surface Remote Sensing: A Case Study on the Loess Plateau of China

Plant phenology is an important indicator of the impact of climate change on ecosystems. We have continuously monitored vegetation phenology using near-surface remote sensing, i.e., the PhenoCam in a gully region of the Loess Plateau of China from March 2020 to November 2022. In each image, three regions of interest (ROIs) were selected to represent different types of vegetation (scrub, arbor, and grassland), and five vegetation indexes were calculated within each ROI. The results showed that the green chromatic coordinate (GCC), excess green index (ExG), and vegetation contrast index (VCI) all well-captured seasonal changes in vegetation greenness. The PhenoCam captured seasonal trajectories of different vegetation that reflect differences in vegetation growth. Such differences may be influenced by external abiotic environmental factors. We analyzed the nonlinear response of the GCC series to environmental variables with the generalized additive model (GAM). Our results suggested that soil temperature was an important driver affecting plant phenology in the Loess gully region, especially the scrub showed a significant nonlinear response to soil temperature change. Since in situ phenology monitoring experiments of the small-scale on the Loess Plateau are still relatively rare, our work provides a reference for further understanding of vegetation phenological variations and ecosystem functions on the Loess Plateau.

Skin, gut, and lung barrier: Physiological interface and target of intervention for preventing and treating allergic diseases

The epithelial barriers of the skin, gut, and respiratory tract are critical interfaces between the environment and the host, and they orchestrate both homeostatic and pathogenic immune responses. The mechanisms underlying epithelial barrier dysfunction in allergic and inflammatory conditions, such as atopic dermatitis, food allergy, eosinophilic oesophagitis, allergic rhinitis, chronic rhinosinusitis, and asthma, are complex and influenced by the exposome, microbiome, individual genetics, and epigenetics. Here, we review the role of the epithelial barriers of the skin, digestive tract, and airways in maintaining homeostasis, how they influence the occurrence and progression of allergic and inflammatory conditions, how current treatments target the epithelium to improve symptoms of these disorders, and what the unmet needs are in the identification and treatment of epithelial disorders.

Environmental influences on childhood asthma: Climate change

Climate change is a key environmental factor for allergic respiratory diseases, especially in childhood. This review describes the influences of climate change on childhood asthma considering the factors acting directly, indirectly and with their amplifying interactions. Recent findings on the direct effects of temperature and weather changes, as well as the influences of climate change on air pollution, allergens, biocontaminants and their interplays, are discussed herein. The review also focusses on the impact of climate change on biodiversity loss and on migration status as a model to study environmental effects on childhood asthma onset and progression. Adaptation and mitigation strategies are urgently needed to prevent further respiratory diseases and human health damage in general, especially in younger and future generations.

A century of climate warming results in growing season extension: Delayed autumn leaf phenology in north central North America

Shifts in the timing of key leaf phenological events including budburst, foliage coloration, and leaf fall have been observed worldwide and are consistent with climate warming. Quantifying changes in growing season length (GSL) because of shifts in both spring and autumn leaf phenology is crucial for modeling annual net ecosystem carbon uptake. However, a lack of long-term autumn phenology datasets has prevented assessment of these growing season level changes. We investigated shifts in growing season length, budburst, foliage coloration, and leaf fall over the past century in seven native hardwood species using a historic leaf phenology dataset collected in Wauseon, OH from 1883-1912 paired with contemporary observations. Using long-term meteorological data, we investigated temperature and precipitation trends over 130 years. Finally, we correlated spring and fall phenophases with monthly temperature and precipitation variables from the twelve months preceding that phenophase using historical meteorological data. We found significant extension of growing season length over the past century in five of the seven study species (ANOVA, p < 0.05) which resulted primarily from delayed foliage coloration rather than from earlier budburst in contrast to the few other studies assessing total GSL change. Our results suggest that most of the leaf phenological studies that investigate only budburst are disregarding crucial information about the end of the growing season that is essential for accurately predicting the effects of climate change in mixed-species temperate deciduous forests.

Assessment of Changing Agroclimatic Conditions in Poland Based on Selected Indicators

The change in the spatial distribution of agroclimatic conditions based on the sum of active temperatures (SAT), growing degree days (GDD), and latitude–temperature index (LTI) is discussed in this article. Data from 20 meteorological stations of IMGW-PIB (Institute of Meteorology and Water Management—National Research Institute) in Poland from the years 1966–2020 were used. The temporal and spatial diversity of mean air temperature and the chosen indices were analyzed for the period from April to October. Designating areas of diverse thermal conditions with respect to plant comfort on the basis of agroclimatic indices was attempted, together with mean air temperature and its temporal changes. The clustering, using the Ward’s method, yielded four regions with different thermal resources in Poland. The study period showed an increase in the values of all agroclimatic indices and air temperature during the growing season, suggesting an increase in the thermal resources in the territory of Poland.

Spring and Autumn Phenology in Sessile Oak (Quercus petraea) Near the Eastern Limit of Its Distribution Range

Due to the visible and predictable influence of climate change on species’ spatial distributions, the conservation of marginal peripheral populations has become topical in forestry research. This study aimed to assess the spring (budburst, leaf development, and flowering) and autumn (leaf senescence) phenology of sessile oak (Quercus petraea), a species widespread across European forests close to its ranges’ eastern limit. This study was performed in Romania between spring 2017 and 2020, and it included a transect with three low-altitude populations, a reference population from its inner range, and a sessile oak comparative trial. The temperature was recorded to relate changes to phenophase dynamics. We identified small variations between the reference and peripheral populations associated with climatic conditions. In the peripheral populations, budburst timing had day-of-year (DOY) values <100, suggesting that sessile oak may be more susceptible to late spring frost. Furthermore, we found spring phenophase timing to be more constant than autumn senescence. Moreover, budburst in the sessile oak comparative trial had obvious longitudinal tendencies, with an east to west delay of 0.5–1.4 days per degree. In addition, budburst timing influenced leaf development and flowering, but not the onset of leaf senescence. These findings improve our understanding of the relationship between spring and autumn phenophase dynamics and enhance conservation strategies regarding sessile oak genetic resources.

Consistent temperature-dependent patterns of leaf lifespan across spatial and temporal gradients for deciduous trees in Europe

Temperature affects leaf lifespan (LL) across either space or time, driving long-term adaptation and short-term thermal acclimation, respectively. However, a comprehensive understanding of the phenomenon and the underlying phenological mechanisms remain poorly understood. The present study investigated the relationship between LL and temperature in six common deciduous trees across both spatial and temporal gradients, then explained the LL variation patterns based on phenological shifts. Using long-term (1971-2000) phenological records of six deciduous tree species at 54 sites across central Europe, we analyzed spatial and temporal variations of LL and leaf phenology along temperature gradients. We assessed the relative contribution of phenological shifts to LL variations by comparing absolute changes in leaf-out and leaf fall. We reported positive LL-temperature relationships across all observations along both spatial (+3.32 days/°C) and temporal (+4.43 days/°C) gradients. The paired t-test of the six deciduous tree species showed no significant difference in regression slopes of LL- temperature between the two gradients (t = -1.50, df = 5, P = 0.194). Prolonged LL can be explained mainly by earlier leaf-out induced by warmer temperatures both spatially (-3.22 days/°C) and temporally (-4.08 days/°C). The converging temperature-dependent patterns of LL across time and space indicate that short-term thermal acclimation keeps pace with long-term genetic adaptation for deciduous trees in Europe. Earlier leaf-out is the key force shaping the LL-temperature relationship. These results provide insights for predicting future vegetation dynamics under global warming.

Impact of Climate Change on Norway Spruce Flowering in the Southern Part of the Western Carpathians

This work presents the impact of climate change on full flowering (BBCH 65) in Norway spruce [Picea abies (L.) Karst.] at 54 phenological stations over two 30-year-long periods, from 1961 to 1990 and from 1991 to 2020. The stations were located in 10 protected areas (protected landscape area, national park) at elevations from 390 to 1,400 m a.s.l. We analyzed the changes in average onset of full flowering, trends of the phase, phenological altitudinal gradient, and correlations of flowering to monthly climatological standard normals of air temperature and sum of precipitation. The impact of climate change was observed in the second period, when flowering started 4–8 days earlier. The phenophase was shortened by 4 days in comparison to the first period, and the shift of the significant trend occurred 7 days earlier. The phenological altitudinal gradient did not substantially change. The analysis of the temperature impact on flowering showed an effect of the cold period preceding the onset of the phenological phase on its delayed onset. The change in January temperatures between periods indicated warming by 1.24–1.34°C. The change also occurred in the evaluation of the 3-month period when the spring air temperature increased. The mean 3-month air temperature (January–March) increased by 0.82–1.1°C in the second period. It was more substantial at lower elevations. The most significant changes in precipitation conditions were observed by the increase in precipitation in March and by the decrease in precipitation between the observed periods in April. The results of all indicators for Norway spruce flowering in the second period indicated changes in climatic conditions in the region.

Epithelial barrier hypothesis: Effect of the external exposome on the microbiome and epithelial barriers in allergic disease

Environmental exposure plays a major role in the development of allergic diseases. The exposome can be classified into internal (e.g., aging, hormones, and metabolic processes), specific external (e.g., chemical pollutants or lifestyle factors), and general external (e.g., broader socioeconomic and psychological contexts) domains, all of which are interrelated. All the factors we are exposed to, from the moment of conception to death, are part of the external exposome. Several hundreds of thousands of new chemicals have been introduced in modern life without our having a full understanding of their toxic health effects and ways to mitigate these effects. Climate change, air pollution, microplastics, tobacco smoke, changes and loss of biodiversity, alterations in dietary habits, and the microbiome due to modernization, urbanization, and globalization constitute our surrounding environment and external exposome. Some of these factors disrupt the epithelial barriers of the skin and mucosal surfaces, and these disruptions have been linked in the last few decades to the increasing prevalence and severity of allergic and inflammatory diseases such as atopic dermatitis, food allergy, allergic rhinitis, chronic rhinosinusitis, eosinophilic esophagitis, and asthma. The epithelial barrier hypothesis provides a mechanistic explanation of how these factors can explain the rapid increase in allergic and autoimmune diseases. In this review, we discuss factors affecting the planet's health in the context of the 'epithelial barrier hypothesis,' including climate change, pollution, changes and loss of biodiversity, and emphasize the changes in the external exposome in the last few decades and their effects on allergic diseases. In addition, the roles of increased dietary fatty acid consumption and environmental substances (detergents, airborne pollen, ozone, microplastics, nanoparticles, and tobacco) affecting epithelial barriers are discussed. Considering the emerging data from recent studies, we suggest stringent governmental regulations, global policy adjustments, patient education, and the establishment of individualized control measures to mitigate environmental threats and decrease allergic disease.

Climate Warming-Induced Changes in Plant Phenology in the Most Important Agricultural Region of Romania

Changes in plant phenology are a direct indicator of climate change and can produce important consequences for agricultural and ecological systems. This study analyzes changes in plant phenology in the 1961–2010 period (for both the entire interval and in three successive multi-decades: 1961–1990, 1971–2000 and 1981–2010) in southern and southeastern Romania, the country’s most important agricultural region. The analysis is based on mean monthly air temperature values collected from 24 regional weather stations, which were used for extracting the length (number of days) of phenophases (growing season onset, budding–leafing, flowering, fruiting, maturing, dissemination of seeds, start of leaf loss, end of leaf loss) and of the overall climatic growing season (CGS, which includes all phenophases), by means of the histophenogram method. Using a number of reliable statistical tools (Mann–Kendall test, Sen’s slope estimator and the regression method) for exploring annual trends and net (total) changes in the length of the phenological periods, as well as for detecting the climate—growing season statistical relationships, our results revealed complex phenology changes and a strong response in phenological dynamics to climate warming. Essentially, a lengthening of all phenophases (maximal in the maturing period, in terms of statistical significance and magnitude of trends—on average 0.48 days/yr/24 days net change in the 1961–2010 period, or even 0.94 days/yr/28 days net change in the 1971–2000 sub-period) was noticed, except for the fruiting and dissemination phenophases, which were dominated by negative trends in the number of days, but partially statistically significant (at a confidence level threshold of at least 90%). The CGS exhibited overall increasing trends, with an average of 0.21 days/yr/11 days net change in the 1961–2010 interval, and even of 0.90 days/yr/27 days net change in the 1981–2010 sub-period. Moreover, based on the slope values obtained upon application of a linear regression to mean temperature and CGS, we discovered that a 1 °C increase in climate warming accounted for a remarkable lengthening of the CGS, on average of 14 days between 1961 and 2010, and of 16 days between 1981 and 2010. Our results can help improve the adaptation of agroecological systems to future climate change.

Phenological trends of multi-taxonomic groups in Latvia, 1970-2018

Phenology provides intimate insights into ongoing changes in nature and seasonality with respect to humans. In this study, the most complete volunteer observer phenological data set for the territory of Latvia from 1970 to 2018 was evaluated. The data set includes observations of 159 phases of eight taxonomical groups, as well as abiotic phenomena such as the first snow, last spring frost, and agrarian activities. With reducing dimensionality, a hierarchical cluster analysis was used to group the 66 phenological phases of most observations into 7 clusters. The largest changes were observed in the early spring phenological phases of the pioneer species such as the start of flowering of Corylus avellana (hazel), Alnus incana (grey alder) and Populus tremula (aspen), noted as -8 days/decade. The trend of the spring emergence of insects and spring migratory birds also showed a negative tendency. The phenology of crops and agrarian activities has not changed significantly. The trends of the autumn phases were heterogeneous-leaf colouration and fall for some species (Populus tremula) and (Acer platanoides, Norway maple) was recorded on average later; for other species, there was a slightly earlier trend (Betula pendula, silver birch; Tilia cordata, linden). Earlier onset of the spring phases affects the changes in the length of the growing season (for Acer platanoides + 7.7 days/decade; Betula pendula + 3.3 days/decade). Since 1990, it has been common that many phases have begun sooner (particularly spring phases), whilst abiotic autumn phases have been characterised by late years. This study has shown that significant seasonal changes have taken place across the Latvian landscape due to climate change.

Intra-annual dendrogeomorphic dating and climate linkages of flood events in headwaters of central Europe

Unlike large rivers, floods in headwaters have been poorly documented despite the fact that greater discharges are expected in such areas due to ongoing rainfall intensification. The purpose of this study is to carry out intra-annual dating of past floods combined with analysis of their climate linkages which may point on distribution and origin of floods. To this end, we applied dendrogeomorphic dating of impact scars on riparian vegetation to provide flood chronologies in twelve headwaters of eastern Czechia and determined their seasonal occurrences. Furthermore, we analyzed the precipitation indices and evaluated the flood events using reanalysis of pressure fields and the climate oscillation indices, particularly those representing the North Atlantic, Scandinavian, and East Atlantic/Western Russian patterns. Based on 434 dated trees, we identified 22-31 flood event years in each region over the last 70 years. The most frequent floods occurred from May to July. In addition, in ten event years it was possible to identify multiple flood events: for example May and July-August floods in 2010, 2014, and 2016. The monthly precipitation showed the strongest, but still weak, correlation with indices of Scandinavian climate oscillation during summer months (R_s = 0.23-0.42; p < 0.00), suggesting the influence of a blocking anticyclone over Scandinavia and wet air propagation to central Europe. This finding was also confirmed by the most frequent positions of low-pressure centers located east of the study sites except for the region with western orographic enhancement. In addition, timing shift of extreme precipitation to earlier period was identified at two out of three regions. We conclude that intra-annual dating of floods supported by analyses of climate extremes provides new data from sparsely gauged headwaters, thereby supplementing the information on possible changes in flood occurrences during ongoing climate change.

Long-term standardized forest phenology in Sweden: a climate change indicator

Because climate change alters patterns of vegetative growth, long-term phenological measurements and observations can provide important data for analyzing its impact. Phenological assessments are usually made as records of calendar dates when specific phase changes occur. Such assessments have benefits and are used in Citizen Science monitoring. However, these kinds of data often have low statistical precision when describing gradual changes. Frequent monitoring of the phenological traits of forest trees and berries as they undergo gradual change is needed to acquire good temporal resolution of transitions relative to other factors, such as susceptibility to frosts, insects, and fungi, and the use of berries as a food resource. Intensive weekly monitoring of the growth of apical and branch buds and the elongation of shoots and leaves on four tree species, and the abundance of flowers and berries of bilberry and lingonberry, has been performed in Sweden since 2006. Here, we present quantitative methods for interpolating such data, which detail the gradual changes between assessments in order to describe average rates of development and amount of interannual variation. Our analysis has shown the active growth period of trees to differ with latitude. We also observed a change in the timing of the maximum numbers of ripening berries and their successive decline. Data from tree phenology assessments can be used to recommend best forestry practice and to model tree growth, while berry data can be used to estimate when food resources for animals are most available.

Climate change has cascading effects on tree masting and the breeding performance of a forest songbird in a primeval forest

Forest habitats change significantly under the influence of global warming. It is important to predict the effects of these changes, especially in primeval forests which currently represent a small percentage of temperate forests. Such changes often manifest themselves in an acceleration of the frequency of mass seeding of trees, which causes cascading effects in various organisms. We evaluated changes in: tree masts (oak Quercus robur and hornbeam Carpinus betulus), rodent abundance (yellow-necked mouse Apodemus flavicollis), folivorous caterpillar abundance (winter moth Operophtera brumata), and the breeding success of a cavity-nesting songbird (collared flycatcher Ficedula albicollis) in over a 30-year period in the Białowieża Forest (E Poland). We also analysed temperature, precipitation and snow cover to determine the effects of weather on each trophic level. Previous studies have exposed the indirect effect of tree masting on songbirds breeding in open nests. Our study uniquely highlights the relationships between trees, rodents, caterpillars, and a cavity-nesting bird. Precipitation was positively correlated with the fructification of trees, abundance of caterpillars, and the breeding losses of flycatchers (in July, August, October in the previous year, in May in the current year, respectively). We found that along with the changing climate, the frequency of mast years of oak increased, which caused an increasing frequency of rodent outbreaks. The abundance of mice was positively correlated with the predation on flycatcher broods (current year) and negatively - with the abundance of caterpillars (following year). We predict that current global trends in climate change will have a negative impact on the flycatcher due to the cascading effects from the above species. Bearing in mind that F. albicollis is one of the most numerous bird species, it can be assumed that more frequent masting will result in substantial changes in the entire bird assemblage, and presumably also other groups of animals.

The rising of allergic respiratory diseases in a changing world: from climate change to migration

INTRODUCTION

The rising of allergic respiratory diseases (ARDs) suggests a decisive role of environmental factors, that have dramatically changed in the last decades.

AREAS COVERED

This review addresses various aspects of the external exposome acting on the development, progression, clinical presentation and severity of ARDs. Climate change, air pollution and biodiversity loss act directly and through their complex interactions on atopic risk: reacent foundings on these aspects are discussed herein. The review also focuses on migration studies, underling the possible role of migrant status as an experimental model to study environment effects on atopy onset and progression.

EXPERT OPINION

Future perspective on this topic include prevention and mitigation strategies in regard to pollution and climate change, improvement of environmental monitoring methods, implementation of public health policies, further advances in 'omics' research and knowledge, prospective and immunological research on migrant populations and new policies to face human mobility.

Possible Increase of Vegetation Exposure to Spring Frost under Climate Change in Switzerland

We assessed future changes in spring frost risk for the Aare river catchment that comprises the Swiss Plateau, the most important agricultural region of Switzerland. An ensemble of 15 bias-corrected regional climate model (RCM) simulations from the EXAR data set forced by the RCP 4.5 and RCP 8.5 concentration pathways were analysed for two future periods. Correlating actual meteorological observations and Swiss phenological spring index, we proposed and tested an RCM-compatible methodology (based on temperature data only) for estimating a start of spring and severity of frost events. In the historical climate, a significant advancement in start of spring was observed and frost events were more frequent in those years in which spring started sooner. In 2021–2050, spring is projected to start eight (twelve) days earlier, considering the RCP 4.5 (8.5) scenario. Substantial changes were simulated for the 2070–2099 period under RCP 8.5, when the total severity of frost events was projected to be increased by a factor of 2.1 compared to the historical climate. The study revealed the possible future increase of vegetation exposure to spring frost in Switzerland and that this phenomenon is noticeable even in the near future under the ‘low concentration’ RCP 4.5 scenario.

Climate change fingerprints in recent European plant phenology

A paper published in Global Change Biology in 2006 revealed that phenological responses in 1971-2000 matched the warming pattern in Europe, but a lack of chilling and adaptation in farming may have reversed these findings. Therefore, for 1951-2018 in a corresponding data set, we determined changes as linear trends and analysed their variation by plant traits/groups, across season and time as well as their attribution to warming following IPCC methodology. Although spring and summer phases in wild plants advanced less (maximum advances in 1978-2007), more (~90%) and more significant (~60%) negative trends were present, being stronger in early spring, at higher elevations, but smaller for nonwoody insect-pollinated species. These trends were strongly attributable to winter and spring warming. Findings for crop spring phases were similar, but were less pronounced. There were clearer and attributable signs for a delayed senescence in response to winter and spring warming. These changes resulted in a longer growing season, but a constant generative period in wild plants and a shortened one in agricultural crops. Phenology determined by farmers' decisions differed noticeably from the purely climatic driven phases with smaller percentages of advancing (~75%) trends, but farmers' spring activities were the only group with reinforced advancement, suggesting adaptation. Trends in farmers' spring and summer activities were very likely/likely associated with the warming pattern. In contrast, the advance in autumn farming phases was significantly associated with below average summer warming. Thus, under ongoing climate change with decreased chilling the advancing phenology in spring and summer is still attributable to warming; even the farmers' activities in these seasons mirror, to a lesser extent, the warming. Our findings point to adaptation to climate change in agriculture and reveal diverse implications for terrestrial ecosystems; the strong attribution supports the necessary mediation of warming impacts to the general public.

Vapor-pressure deficit and extreme climatic variables limit tree growth

Assessing the effect of global warming on forest growth requires a better understanding of species-specific responses to climate change conditions. Norway spruce and European beech are among the dominant tree species in Europe and are largely used by the timber industry. Their sensitivity to changes in climate and extreme climatic events, however, endangers their future sustainability. Identifying the key climatic factors limiting their growth and survival is therefore crucial for assessing the responses of these two species to ongoing climate change. We studied the vulnerability of beech and spruce to warmer and drier conditions by transplanting saplings from the top to the bottom of an elevational gradient in the Jura Mountains in Switzerland. We (1) demonstrated that a longer growing season due to warming could not fully account for the positive growth responses, and the positive effect on sapling productivity was species-dependent, (2) demonstrated that the contrasting growth responses of beech and spruce were mainly due to different sensitivities to elevated vapor-pressure deficits (VPD), (3) determined the species-specific limits to VPD above which growth rate began to decline, and (4) demonstrated that models incorporating extreme climatic events could account for the response of growth to warming better than models using only average values. These results support that the sustainability of forest trees in the coming decades will depend on how extreme climatic events will change, irrespective of the overall warming trend.

The effect of climate change on the duration of avian breeding seasons: a meta-analysis

Many bird species are advancing the timing of their egg-laying in response to a warming climate. Little is known, however, of whether this advancement affects the respective length of the breeding seasons. A meta-analysis of 65 long-term studies of 54 species from the Northern Hemisphere has revealed that within the last 45 years an average population has lengthened the season by 1.4 days per decade, which was independent from changes in mean laying dates. Multi-brooded birds have prolonged their seasons by 4 days per decade, while single-brooded have shortened by 2 days. Changes in season lengths covaried with local climate changes: warming was correlated with prolonged seasons in multi-brooded species, but not in single-brooders. This might be a result of higher ecological flexibility of multi-brooded birds, whereas single brooders may have problems with synchronizing their reproduction with the peak of food resources. Sedentary species and short-distance migrants prolonged their breeding seasons more than long-distance migrants, which probably cannot track conditions at their breeding grounds. We conclude that as long as climate warming continues without major changes in ecological conditions, multi-brooded or sedentary species will probably increase their reproductive output, while the opposite effect may occur in single-brooded or migratory birds.

The rise of phenology with climate change: an evaluation of IJB publications

In recent decades, phenology has become an important tool by which to measure both the impact of climate change on ecosystems and the feedback of ecosystems to the climate system. However, there has been little attempt to date to systematically quantify the increase in the number of scientific publications with a focus on phenology and climate change. In order to partially address this issue, we examined the number of articles (original papers, reviews and short communications) containing the terms 'phenology' and 'climate change' in the title, abstract or keywords, published in the International Journal of Biometeorology in the 60 years since its inception in 1957. We manually inspected all issues prior to 1987 for the search terms and subsequently used the search facility on the Web of Science online database. The overall number of articles published per decade remained relatively constant (255-378) but rose rapidly to 1053 in the most recent decade (2007-2016), accompanied by an increase (41-172) in the number of articles containing the search terms. A number of factors may have contributed to this rise, including the recognition of the value of phenology as an indicator of climate change and the initiation in 2010 of a series of conferences focusing on phenology which subsequently led to two special issues of the journal. The word 'phenology' was in use from the first issue, whereas 'climate change' only emerged in 1987 and peaked in 2014. New technologies such as satellite remote sensing and the internet led to an expansion of and greater access to a growing reservoir of phenological information. The application of phenological data included determining the impact of warming of phenophases, predicting wine quality and the pollen season, demonstrating the potential for mismatch to occur and both reconstructing and forecasting climate. Even though this analysis was limited to one journal, it is likely to be indicative of a similar trend across other scientific publications.

The dynamics of the Corylus, Alnus, and Betula pollen seasons in the context of climate change (SW Poland)

The changes in the main features of early spring tree or shrub pollen seasons are important due to the significant impact on the occurrence of pollen-related allergy symptoms. This study shows the results of pollen monitoring for a period of eleven years (2003-2013) using a Burkard volumetric spore trap. The main characteristics of the hazel, alder, and birch pollination season were studied in Wrocław (SW Poland). The statistical analyses do not show a significant trend of annual total pollen count or shift in timing of the pollen season in the period of analysis. The research confirms a great impact (at the statistically significant level of 0.05) of the heat resources on pollination season (the value of the correlation coefficient ranges from -0.63 up to -0.87). Meteorological variables (e.g. sum of temperature for selected period) were compiled to 5-year running means to examine trends. Changes in the pollination period features due to climate change including both timing and intensity of pollen productivity, would have important consequences for allergy sufferers.

Seventeen-year trends in spring and autumn phenophases of Betula pubescens in a boreal environment

Trends in the timing of spring and autumn phenophases of Betula pubescens were investigated in the southern, middle, and northern boreal zones in Finland. The field observations were carried out at 21 sites in the Finnish National Phenological Network in 1997-2013. The effective temperature sum of the thermal growth period, i.e. the sum of the positive differences between diurnal mean temperatures and 5 °C (ETS1), increased annually on average by 6-7 degree day units. Timing of bud burst remained constant in the southern and middle boreal zones but advanced annually by 0.5 day in the northern boreal zone. The effective temperature sum at bud burst (ETS2) showed no trend in the southern and middle boreal zones, whereas ETS2 increased on average from 20-30 to 50 degree day units in the northern boreal zone, almost to the same level as in the other zones. Increase in ETS2 indicates that the trees did not start their growth in very early spring despite warmer spring temperatures. The timing of leaf colouring and leaf fall remained almost constant in the southern boreal zones, whereas these advanced annually by 0.3 and 0.6 day in the middle boreal zone and by 0.6 and 0.4 day in the northern boreal zone, respectively. The duration of the growth period remained constant in all boreal zones. The results indicate high buffering capacity of B. pubescens against temperature changes. The study also shows the importance of the duration of phenological studies: some trends in spring phenophases had levelled out, while new trends in autumn phases had emerged after earlier studies in the same network for a shorter observation period.

The interaction between freezing tolerance and phenology in temperate deciduous trees

Temperate climates are defined by distinct temperature seasonality with large and often unpredictable weather during any of the four seasons. To thrive in such climates, trees have to withstand a cold winter and the stochastic occurrence of freeze events during any time of the year. The physiological mechanisms trees adopt to escape, avoid, and tolerate freezing temperatures include a cold acclimation in autumn, a dormancy period during winter (leafless in deciduous trees), and the maintenance of a certain freezing tolerance during dehardening in early spring. The change from one phase to the next is mediated by complex interactions between temperature and photoperiod. This review aims at providing an overview of the interplay between phenology of leaves and species-specific freezing resistance. First, we address the long-term evolutionary responses that enabled temperate trees to tolerate certain low temperature extremes. We provide evidence that short term acclimation of freezing resistance plays a crucial role both in dormant and active buds, including re-acclimation to cold conditions following warm spells. This ability declines to almost zero during leaf emergence. Second, we show that the risk that native temperate trees encounter freeze injuries is low and is confined to spring and underline that this risk might be altered by climate warming depending on species-specific phenological responses to environmental cues.