Earlier breeding,lower success: does the spatial scale of climatic conditions matter in a migratory passerine bird?

Following over 20 years of research on the climatic effects on biodiversity we now have strong evidence that climate change affects phenology, fitness, and distribution ranges of different taxa, including birds. Bird phenology likely responds to changes in local weather. It is also affected by climatic year‐to‐year variations on larger scales. Although such scale‐related effects are common in ecology, most studies analyzing the effects of climate change were accomplished using climatic information on a single spatial scale. In this study, we aimed at determining the scale‐dependent sensitivity of breeding phenology and success to climate change in a migratory passerine bird, the barn swallow (Hirundo rustica). For both annual broods, we investigated effects of local weather (local scale) and the North Atlantic Oscillation (NAO, large scale) on the timing of breeding and breeding success. Consistent with previous studies in migratory birds we found that barn swallows in Eastern Germany bred progressively earlier. At the same time, they showed reduced breeding success over time in response to recent climatic changes. Responses to climatic variation were observed on both local and large climatic scales, but they differed with respect to the ecological process considered. Specifically, we found that the timing of breeding was primarily influenced by large‐scale NAO variations and to a lesser extent by local weather on the breeding grounds. Conversely, climatic conditions on the local scale affected breeding success, exclusively. The observed decrease in breeding success over years is likely a consequence of scale‐related mismatches between climatic conditions during different breeding phases. This provides further evidence that a species' response of earlier breeding may not be enough to cope with climate change. Our results emphasize the importance of considering the response of ecological processes along different climatic scales in order to better understand the complexity of climate change effects on biodiversity.     

Climatic effects on the phenology of lake processes

Populations living in seasonal environments are exposed to systematic changes in physical conditions that restrict the growth and reproduction of many species to only a short time window of the annual cycle. Several studies have shown that climate changes over the latter part of the 20th century affected the phenology and population dynamics of single species. However, the key limitation to forecasting the effects of changing climate on ecosystems lies in understanding how it will affect interactions among species. We investigated the effects of climatic and biotic drivers on physical and biological lake processes, using a historical dataset of 40 years from Lake Washington, USA, and dynamic time‐series models to explain changes in the phenological patterns among physical and biological components of pelagic ecosystems. Long‐term climate warming and variability because of large‐scale climatic patterns like Pacific decadal oscillation (PDO) and El Niño–southern oscillation (ENSO) extended the duration of the stratification period by 25 days over the last 40 years. This change was due mainly to earlier spring stratification (16 days) and less to later stratification termination in fall (9 days). The phytoplankton spring bloom advanced roughly in parallel to stratification onset and in 2002 it occurred about 19 days earlier than it did in 1962, indicating the tight connection of spring phytoplankton growth to turbulent conditions. In contrast, the timing of the clear‐water phase showed high variability and was mainly driven by biotic factors. Among the zooplankton species, the timing of spring peaks in the rotifer Keratella advanced strongly, whereas Leptodiaptomus and Daphnia showed slight or no changes. These changes have generated a growing time lag between the spring phytoplankton peak and zooplankton peak, which can be especially critical for the cladoceran Daphnia. Water temperature, PDO, and food availability affected the timing of the spring peak in zooplankton. Overall, the impact of PDO on the phenological processes were stronger compared with ENSO. Our results highlight that climate affects physical and biological processes differently, which can interrupt energy flow among trophic levels, making ecosystem responses to climate change difficult to forecast.     

Timing of squid migration reflects North Atlantic climate variability.

The environmental and biotic conditions affecting fisheries for cephalopods are only partially understood. A problem central to this is how climate change may influence population movements by altering the availability of thermal resources. In this study we investigate the links between climate and sea-temperature changes and squid arrival time off southwestern England over a 20-year period. We show that veined squid (Loligo forbesi) migrate eastward in the English Channel earlier when water in the preceding months is warmer, and that higher temperatures and early arrival correspond with warm (positive) phases of the North Atlantic oscillation (NAO). The timing of squid peak abundance advanced by 120-150 days in the warmest years ('early' years) compared with the coldest ('late' years). Furthermore, sea-bottom temperature was closely linked to the extent of squid movement. Temperature increases over the five months prior to and during the month of peak squid abundance did not differ between early and late years, indicating squid responded to temperature changes independently of time of year. We conclude that the temporal variation in peak abundance of squid seen off Plymouth represents temperature-dependent movement, which is in turn mediated by climatic changes associated with the NAO. Such climate-mediated movement may be a widespread characteristic of cephalopod populations worldwide, and may have implications for future fisheries management because global warming may alter both the timing and location of peak population abundance.     

Effects of recent climate change on phytoplankton phenology in a temperate lake

1. A number of long-term studies have shown that spring biological events have advanced in recent decades and that this is a response to climate change. In lentic systems, changes in phytoplankton phenology have been attributed to various directly climate-related processes including changes in the onset and duration of thermal stratification, earlier ice-break up and increased water temperature. Both indirect climatic drivers and non-climate drivers such as elevated grazing pressure and nutrient enrichment can also affect phenology.
2. This study investigated whether phenological trends in phytoplankton could be detected in a relatively short time series in a shallow, ice-free, polymictic lake with a high annual discharge and whether any such trends could be causally explained.
3. It was found that the centre of gravity of the spring chlorophyll a bloom advanced significantly by 1.6 days per year over a 15-year period. This was accompanied by a significant increase in water temperature of 0.12 °C per year which is high compared to published rates of change over longer time series. No direct effects of ice cover, stratification or water discharge rates could be linked to the advancement of the spring bloom. Instead, the shift in timing was attributed to an advance in the timing of the dominant spring diatom, Aulacoseira spp., instigated by a temperature-driven increase in replication rate leading to an earlier onset of silica (SiO₂) limitation.     

Mushroom's spore size and time of fruiting are strongly related: is moisture important?

Most basidiomycete fungi produce annual short-lived sexual fruit bodies from which billions of microscopic spores are spread into the air during a short time period. However, little is known about the selective forces that have resulted in some species fruiting early and others later in the fruiting season. This study of relationships between morphological and ecological characteristics, climate factors and time of fruiting are based upon thorough statistical analyses of 66 520 mapped records from Norway, representing 271 species of autumnal fruiting mushroom species. We found a strong relationship between spore size and time of fruiting; on average, a doubling of spore size (volume) corresponded to 3 days earlier fruiting. Small-spored species dominate in the oceanic parts of Norway, whereas large-spored species are typical of more continental parts. In separate analyses, significant relationships were observed between spore size and climate factors. We hypothesize that these relationships are owing to water balance optimization, driven by water storage in spores as a critical factor for successful germination of primary mycelia in the drier micro-environments found earlier in the fruiting season and/or in continental climates.     

The onset of spring and timing of migration in two arctic nesting goose populations: the pink‐footed goose Anser bachyrhynchus and the barnacle goose Branta leucopsis

An earlier onset of spring has been recorded for many parts of Eurasia in recent decades. This has consequences for migratory species, both in changing the conditions encountered by individuals on reaching migratory sites and in affecting cues regulating the timing of migration where decisions to migrate are influenced by local environmental variables. Here we examine the timing of spring migration for two arctic goose populations, the pink‐footed goose Anser brachyrhynchus (during 1990–2003) and barnacle goose Branta leucopsis (during 1982–2003), which both breed on Svalbard. The satellite‐derived Normalised Difference Vegetation Index (NDVI) was used to express the onset of spring at their wintering and spring staging sites. Pink‐footed geese use several sites during spring migration, ranging from the southernmost wintering areas in Belgium to two spring staging areas in Norway, and distances between sites used along the flyway are relatively short. There was a positive correlation in the onset of spring between neighbouring sites, and the geese migrated earlier in early springs. Barnacle geese, on the other hand, have a long overseas crossing from their wintering grounds in Britain to spring staging areas in Norway. Although spring advanced in both regions, there was no corresponding correlation in the timing of onset of spring between their wintering and spring staging sites, and little evidence for barnacle geese migrating earlier over the whole study period. Hence, where geese can use spring conditions at one site as an indicator of the conditions they might encounter at the next, they have responded quickly to the advancement of spring, whereas in a situation where they cannot predict, they have not yet responded, despite the advancement of spring in the spring staging area.     

Flowering and fruiting phenology in the coastal shrublands of Doñana,south Spain

Flowering and fruiting phenological patterns at the individual-, population-, and community level were studied in a southern Spanish scrub community composed of 30 shrub species. Few individuals of any species produced a high number of flowers. Intrapopulation deviation in the peak time of flowering showed a strong and positive skewness. Relative flowering duration, however, displayed a virtually normal distribution. Generally, species flowering in spring have a short flowering time, while species flowering earlier or later in the year show significantly longer flowering periods. Species were in bloom throughout the year, but there was a major peak during spring and two lesser ones in autumn and early summer. Shallow rooting taxa in typically mediterranean genera displayed a strategy of spring flowering and summer fruiting. Summer and autumn flowering occurred among heath-like shrubs of relatively wet places, and forest-associated, vertebrate-dispersed species which commonly have underground storage organs. Species with ripe fruits presented two peaks, the major one during the summer including the majority of taxa with seeds dispersed by non-vertebrate agents. There was a minor fruiting peak in autumn dominated by taxa that rely on vertebrates for dispersal. The complex seasonal patterns observed are interpreted in relation to environmental conditions and physiological constraints on species living in a highly seasonal climate.     

Phenological asynchrony in plant–butterfly interactions associated with climate: a community‐wide perspective

Although much information has been accumulated on the effects of climate change on particular species worldwide, research aimed at assessing how such change influences biotic interactions from a community‐wide perspective is still in its infancy. We contribute to filling in this gap by analyzing a 17‐year (1996–2012) dataset that includes records of flower‐visitation interactions between 12 butterfly species and 17 plant species in a coastal wetland area in northeastern Iberian Peninsula. We assessed the extent to which temporal asynchronies between plants and adult butterflies are influenced by different climatic variables that affect both plant and insect phenologies. Temperature and degree of aridity at various monthly summaries were used as predictors of the plant–butterfly phenological asynchrony. We identified the seasonal window with the greatest effect on asynchronies for two butterfly generations (spring and summer), and assessed whether the magnitude of asynchrony is associated with the level of butterfly specialization. We used generalized linear mixed models considering a total of 39 plant–butterfly interactions. Average asynchrony was higher in the spring generation and dry conditions during winter lead to decreased temporal overlap with flowers in this butterfly generation, whereas dry conditions in the spring lead to decreased temporal overlap in the summer butterfly generation. The magnitude of the effect was consistently small at the community level (all interactions pooled). Moreover, no clear climatic trend over the study time frame was detected. Finally, specialized and generalized butterflies in their resource use as adults were similarly vulnerable to asynchronies, in contrast to previous predictions of greater mutualistic disruptions in species with narrower niches. We conclude that a least in the Mediterranean region, phenological asynchronies might be more affected by aridity level than by temperature itself, and thus the former can be a key climatic trait to make better predictions in this region.     

The commercial exploitation of the white rot fungus Lentinula edodes (shiitake)

The Japanese wood mushroom, Lentinula edodes, can be cultivated under UK climatic conditions using extensive cultivation systems adapted from traditional growing methods developed in Japan and Taiwan. As well as producing a desirable and high value food product, cultivation offers a viable alternative enterprise for farmers. The growing methods described could provide incentives for the management of broad-leaved woodland in Britain with consequent conservation benefits. Four different strains of Lentinula edodes were grown on oak logs under natural environmental conditions below the woodland canopy and fruited in polyethylene tunnels. Yields ranged from 0.5–0.9 kg wet weight shiitake per cordwood log per year over a three year fruiting period.     

Climatic influences on fire regimes along a rain forest-to-xeric woodland gradient in northern Patagonia, Argentina

ABSTRACT. Influences of annual climatic variation on fire occurrence were examined along a rainfall gradient from temperate rainforest to xeric woodlands in northern Patagonia, Argentina. Fire chronologies were derived from fire scars on trees and related to tree-ring proxy records of climate over the period 1820–1974. Similarly, fire records of four Patagonian national parks for the period 1940–1988 were compared to instrumental weather data. Finally, the influences of broad-scale synoptic weather patterns on fire occurrence in northern Patagonia were explored.
Fire in Nothofagus rainforests is highly dependent on drought during the spring and summer of the same year in which fires occur and is less strongly favoured by drought during the spring of the previous year. The occurrence of fire in dry vegetation types near the steppe ecotone is less dependent on drought because even during years of normal weather fuels are thoroughly desiccated during the dry summer. In xeric Austrocedrus woodlands, fire occurrence and spread are promoted by droughts during the fire season and also appear to be favoured by above-average moisture conditions during the preceding 1 to 2 growing seasons which enhances fuel production. Thus, in the xeric woodlands fire is not simply dependent on drought but is favoured by greater climatic variability over time scales of several years.
Fire activity in northern Patagonia is greatly influenced by the intensity and latitudinal position of the subtropical high pressure cell of the southeast Pacific. Greater fire activity is associated with a more intense and more southerly located high pressure cell which blocks the influx of Pacific moisture into the continent. Although long-term changes in fire occurrence along the rainforest-to-xeric woodland gradient have been greatly influenced by human activities, annual variation in fire frequency and extent is also strongly influenced by annual climatic variation.     

Seasonal Patterns of Flowering and Fruiting in a Dry Tropical Forest in Jamaica1

Tropical dry forests occupy more area and are more endangered than rainforests, yet their regeneration ecology has received less study and is consequently poorly understood. We recorded the flowering and fruiting phenology of a tropical dry forest in Jamaica over a period of 26 mo within ten 15 × 15‐m plots. Community‐wide recruitment reached a maximum in the wet season, whereas no recruitment occurred during the dry season. We observed a unimodal peak in rainfall and fruit production, and the periodicity and intensity of seed production were significantly correlated with rainfall seasonality (the optimal time for germination). Flowering at the community and system levels lagged behind a significant increase and subsequent decrease in rainfall by 7 and 3 mo, respectively, indicating that the dominant factor controlling flowering periodicity is the passage of the major (4‐mo long) rainy season and changes in soil moisture conditions. Fruiting lagged behind flowering by 2 mo and a significant increase in fruiting occurred 2 mo prior to a significant increase in rainfall. At the population level, a correspondence analysis identified a major dichotomy in the patterns of flowering and fruiting between species and indicated two broad species groups based on their time of peak fruiting and the number of times they were in fruit. These were either individuals which were usually in peak fruit 1–2 mo prior to the start of the major rainy season or those that were in fruit more or less continuously throughout the year with no peak fruiting time. This study supports the view that seasonal variation in rainfall and hence soil water availability constitutes both the proximate and the ultimate cause of flowering periodicity in tropical dry forests.     

Influence of organic matter and climatic factors on the harpacticoid copepod (Crustacea) population from the well sorted fine sands of Banyuls Bay

The authors investigated the development of the harpacticoid copepod population in relation to the variations in organic matter and meteorology. Sediment sampling was performed over a 2-year period in the shallow waters (3 m deep) of Banyuls Bay (Western Mediterranean). Each year presents two distinct periods: winter to early spring, and from late spring until fall. During the first period of the annual cycle, the organic carbon and nitrogen cycles are fairly dissociated; the quantity of copepods appears to be dependent upon the climatic and physical conditions. During the second period, the climatic conditions are very similar from year to year, without heavy rains or strong storms, and the values observed both for the organic matter and the copepod population are also similar. The hypothesis is proposed that organic matter can be considered a limiting factor to population increase.     

气候波动对西安39种木本植物展叶始期及其积温需求的影响

过去几十年来暖春等异常气候事件发生的频次和强度显著增加, 使植物春季物候期发生了明显变化。但异常气候事件对植物春季物候积温需求的影响仍不清楚, 限制了对未来物候变化预测精度的提升。该研究利用西安植物园1963-2018年39种木本植物的展叶始期和相应气象数据, 首先根据3-4月平均气温划分了偏冷年、正常年和偏暖年, 对比了冷暖年相对于正常年的展叶始期变化。其次, 利用3种积温算法计算了各植物逐年的展叶始期积温需求, 比较了积温需求在冷暖年和正常年的差异。最后, 评估了传统积温模型在模拟偏冷或偏暖年展叶始期时的误差。结果表明, 所有植物的展叶始期在偏暖年比正常年平均早8.6天, 而在偏冷年平均晚8.2天。在偏暖年, 大多数物种展叶始期的积温需求(以5 ℃为阈值, 平均257.5度日)显著高于正常年(平均195.1度日); 在偏冷年的积温需求(平均168.0度日)低于正常年, 但在统计上差异不显著。就不同类群而言, 古老类群相对于年轻类群在偏冷年的推迟天数更多, 积温需求变化较小, 但在偏暖年无显著差异。不同生活型间物候与积温需求变化也无显著差异。造成偏暖年积温需求增加的可能原因是偏暖年冬季气温较高, 导致植物受到的冷激程度减轻, 从而抑制了后续的展叶。在正常年, 积温模型模拟木本植物展叶始期的平均误差仅为0.4-1.9天。在偏暖年和偏冷年, 模拟值分别比观测值平均早4.1天和晚3.0天。因此在预测未来物候变化时, 需要考虑气候波动条件下的积温需求变化。     

Growing seasons of Nordic mountain birch in northernmost Europe as indicated by long-term field studies and analyses of satellite images

The phenophases first greening (bud burst) and yellowing of Nordic mountain birch (Betula pubescens ssp.tortuosa, also called B. p. ssp. czerepanovii) were observed at three sites on the Kola Peninsula in northernmost Europe during the period 1964–2003, and at two sites in the trans-boundary Pasvik-Enare region during 1994–2003. The field observations were compared with satellite images based on the GIMMS-NDVI dataset covering 1982–2002 at the start and end of the growing season. A trend for a delay of first greening was observed at only one of the sites (Kandalaksha) over the 40 year period. This fits well with the delayed onset of the growing season for that site based on satellite images. No significant changes in time of greening at the other sites were found with either field observations or satellite analyses throughout the study period. These results differ from the earlier spring generally observed in other parts of Europe in recent decades. In the coldest regions of Europe, e.g. in northern high mountains and the northernmost continental areas, increased precipitation associated with the generally positive North Atlantic Oscillation in the last few decades has often fallen as snow. Increased snow may delay the time of onset of the growing season, although increased temperature generally causes earlier spring phenophases. Autumn yellowing of birch leaves tends towards an earlier date at all sites. Due to both later birch greening and earlier yellowing at the Kandalaksha site, the growing season there has also become significantly shorter during the years observed. The sites showing the most advanced yellowing in the field throughout the study period fit well with areas showing an earlier end of the growing season from satellite images covering 1982–2002. The earlier yellowing is highly correlated with a trend at the sites in autumn for earlier decreasing air temperature over the study period, indicating that this environmental factor is important also for autumn phenophases.     

Altered geographic and temporal variability in phenology in response to climate change

Aim In response to recent climate warming, numerous studies have reported an earlier onset of spring and, to a lesser degree, a later onset of autumn, both determined from phenological observations. Here, we examine whether these reported changes have affected the synchronization of events on a regional level by examining temporal and spatial variability in phenology. In particular, we study whether years with earlier springs are associated with an altered spatial variability in phenology. Location Germany and the United Kingdom. Methods Plant phenological observations of 35 different phases (events such as flowering and leafing) collected by the German Weather Service (1951–2002) and butterfly phenological records of 29 species collected by the UK Butterfly Monitoring Scheme (1976–2003) are used. In these long‐term records, we examine the temporal (year‐to‐year) variability and the spatial (geographic or between site) variability with particular emphasis on how they vary with time of the year and with earliness or lateness of the phase. Results Early phenological events (i.e. spring) are more variable than later events, both in time and in space, although the pattern is clearer for plants than for butterflies. Confirming previous results, we find a clear relationship between the mean date of spring and summer phases and the degree to which they have become earlier. The spatial variability of spring events is greater in warmer years that have faster plant development. However, late spring and summer events do not show a consistent relationship. Autumn events are somewhat more spatially variable in years characterized by later seasons. Main conclusions This is the first examination of spatial variability of plant and animal phenological events at a multinational scale. Earlier spring events are likely to be associated with increased spatial variability in plants, although this is unlikely to also be true for summer events. If species experience differential changes in geographic variation this may disrupt interactions among them, e.g. in food webs. On the other hand, these may offer advantages for mobile species. Further research on linked species is recommended.     

Meteorological forcing of plankton dynamics in a large and deep continental European lake

The timing of various plankton successional events in Lake Constance was tightly coupled to a large-scale meteorological phenomenon, the North Atlantic Oscillation (NAO). A causal chain of meteorological, hydrological, and ecological processes connected the NAO as well as winter and early spring meteorological conditions to planktonic events in summer leading to a remarkable memory of climatic effects lasting over almost half a year. The response of Daphnia to meteorological forcing was most probably a direct effect of altered water temperatures on daphnid growth and was not mediated by changes in phytoplankton concentrations. High spring water temperatures during ”high-NAO years” enabled high population growth rates, resulting in a high daphnid biomass as early as May. Hence, a critical Daphnia biomass to suppress phytoplankton was reached earlier in high-NAO years yielding an early and longer-lasting clear-water phase. Finally, an earlier summer decline of Daphnia produced in a negative relationship between Daphnia biomass in July and the NAO. Meteorological forcing of the seasonal plankton dynamics in Lake Constance included simple temporal shifts of processes and successional events, but also complex changes in the relative importance of different mechanisms. Since Daphnia plays an important role in plankton succession, a thorough understanding of the regulation of its population dynamics provides the key for predictions of the response of freshwater planktonic food webs to global climate change. Received: 15 February 1999 / Accepted: 23 August 1999     

Landscape fragmentation affects responses of avian communities to climate change

Forecasting the consequences of climate change is contingent upon our understanding of the relationship between biodiversity patterns and climatic variability. While the impacts of climate change on individual species have been well‐documented, there is a paucity of studies on climate‐mediated changes in community dynamics. Our objectives were to investigate the relationship between temporal turnover in avian biodiversity and changes in climatic conditions and to assess the role of landscape fragmentation in affecting this relationship. We hypothesized that community turnover would be highest in regions experiencing the most pronounced changes in climate and that these patterns would be reduced in human‐dominated landscapes. To test this hypothesis, we quantified temporal turnover in avian communities over a 20‐year period using data from the New York State Breeding Atlases collected during 1980–1985 and 2000–2005. We applied Bayesian spatially varying intercept models to evaluate the relationship between temporal turnover and temporal trends in climatic conditions and landscape fragmentation. We found that models including interaction terms between climate change and landscape fragmentation were superior to models without the interaction terms, suggesting that the relationship between avian community turnover and changes in climatic conditions was affected by the level of landscape fragmentation. Specifically, we found weaker associations between temporal turnover and climatic change in regions with prevalent habitat fragmentation. We suggest that avian communities in fragmented landscapes are more robust to climate change than communities found in contiguous habitats because they are comprised of species with wider thermal niches and thus are less susceptible to shifts in climatic variability. We conclude that highly fragmented regions are likely to undergo less pronounced changes in composition and structure of faunal communities as a result of climate change, whereas those changes are likely to be greater in contiguous and unfragmented habitats.     

Dispersal and climate change: a case study of the Arctic tern Sterna paradisaea

Dispersal is an important evolutionary process that can affect admixture of populations and cause rapid responses to changing climatic conditions due to gene flow from populations at different altitudes or latitudes already experiencing these conditions. We investigated long-term patterns of natal and breeding dispersal in a coastal seabird, the Arctic tern Sterna paradisaea , that experiences specific climatic conditions in the northern temperate and Arctic climate zones during breeding and different climatic conditions in the Antarctic during winter. Long natal and breeding dispersal distances were costly as shown by their effects on delayed breeding. Dispersal distances varied significantly among years, with natal dispersal showing a strong temporal increase during the last 70 years. Annual differences in dispersal distance could be accounted for by climate conditions in the breeding grounds and the winter quarters. Natal dispersal was related to climate conditions in both the year of hatching and the year of breeding, whereas breeding dispersal was only related to climate conditions in the second year of the dispersal event. Only the north Atlantic oscillation (NAO) index for winter showed a consistent temporal trend, suggesting that the temporal trend in natal dispersal distance must be caused by changes in the NAO (or associated phenomena). These findings indicate that dispersal can change rapidly in response to changing climate conditions.