Increasing Spring Temperatures Research Articles

The time series of flowering and leaf bud burst of boreal trees (1846–2005) support the direct temperature observations of climatic warming

The timing of spring phenological events of boreal trees, such as flowering and leaf bud burst, is controlled to a great extent by the ambient air temperature, and these events are already showing an advancement that can be attributed to climatic warming. In this paper we utilised this phenomenon to verify direct observations of climatic warming. We constructed eight phenological time series using observations covering 160 years of the leaf bud burst of two species and of the flowering of six species of native deciduous trees growing in Finland. To eliminate the effect of urbanization on local temperature, we rejected the observations made in densely populated areas. When analyzing the trends in the timing of leaf bud burst and flowering we found an advancement of these phenological events ranging from 3.3 to 11.0 days per century. We then converted the observed phenological trends into temperature trends by using thermal time-type models that link the timing of bud burst and flowering to the temperature conditions during bud development. Warming estimates derived from the phenological trends suggested that the mean spring temperature increase in Finland has been 1.8 °C per century, which is very close to the value of 1.5 °C per century indicated by long-term temperature records.

The impact of climate change on long‐term population trends of birds in a central European country

AbstractNumerous studies have shown that climate changes associated with increasing global temperature affect bird species. For instance, long‐distance migrants are not able to respond adequately to rapid advances in spring phenology, and thus their populations decline due to lower breeding performance. Moreover, many species in the Northern Hemisphere have shifted their northern breeding range boundaries further north. However, studies focusing on bird populations at the scale of individual countries, which are responsible for creating environmental policies, are rather scarce. We hypothesized that bird species with different European latitudinal breeding distributions would have different long‐term population trends in the Czech Republic, a small central European country, as a result of range dynamics caused by increasing spring temperature. In accordance with this prediction, the results of an analysis based on large‐scale monitoring data (from 1982 to 2006) showed that species with more northern latitudinal distributions had more negative population trends in the Czech Republic. However, the strength of the relationship depended on the approach used for characterization of the species latitudinal distributions. When a phylogenetic regression was applied, the only significant explanatory variable was the latitudinal distribution expressed in categories defined by species range areas in different latitudinal bands. A more detailed analysis showed that southern and northern species groups have opposite population trajectories: the former increased and the latter declined throughout the study period. The effect of climate change remained significant when habitat association and the migratory strategy of each species were taken into account. However, it is difficult to determine whether climate change or habitat change is the more important driver of long‐term trends in bird populations as the effects of both factors are dependent on interspecific variability in levels of species specialization.

Influence of Subsurface Drainage on Soil Temperature in a Cold Climate

Soil temperature during springtime is an important factor for crop establishment and growth in poorly drained soils of northwest Minnesota. In this region, shallow water tables causing spring planting delays and excess water conditions during the growing season, may have contributed to significant unplanted cropland and yield reductions in recent years. Temperature is a regulating factor for many biological and chemical processes in the soil. One of the most commonly cited benefits of subsurface drainage on poorly drained soils is faster soil warm-up in the spring. Previous studies of this phenomenon do not provide definitive conclusions concerning the influence of soil drainage on soil temperature. The results of three site years of field observations of soil temperatures from drainage research plots at two locations in northwest Minnesota are presented herein. Replicated soil temperature and water table depths were measured continuously at five depths for two drain spacings and an undrained treatment. Subsurface drainage was found to significantly increase soil temperatures in both a coarser textured Vallers loam soil and a finer textured Hegne silty clay loam soil. Up to 4°C temperature increases occurred primarily between May and July with the greatest increases at 30-60 cm depths. Treatments with narrow drainage spacing showed a greater spring temperature increase than treatments with wider drainage spacings.

A phenology‐based reconstruction of interannual changes in past spring seasons

Plant phenological observations are accurately dated information of seasonal vegetation variability in midlatitude climates. In order to extend phenological records into the past and assess climate impacts on vegetation on long timescales, there is a need to make use of historical observations of plant phenology. Here we present a continuous, annually resolved reconstruction of a statistical ‘Spring plant’ defined as the weighted mean for the flowering of cherry and apple tree and budburst beech from plant phenological observations across a range of sites in Switzerland from 1702 to 2005. The reconstruction indicates a statistical reconstruction uncertainty (±3.4 days) at interannual timescale. The earliest and the latest year were observed in 1961 (14 April) and 1879 (13 May), respectively. In the context of the last 300 years, the recent three decades do not show a preponderance of very early years as expected from increased spring temperatures. Most of the years in the period after 1990, however, are earlier than the reconstruction mean (27 April). The 1940s, 1910s, 1890s and the early 18th century are periods with similarly early starts of spring season in comparison with the recent decades. Moving linear trend analysis shows unprecedented agreement towards earlier spring onsets in observed and temperature‐based, reconstructed plant phenological records in the late 20th/early 21st century. Our reconstructed ‘Spring plant’ provides long‐term evidence of vegetation variability for comparisons with temperature measurement and other spring onset indicators such as snow melt. The multicentennial long record offers a high potential for applications in long‐term climate impact studies and vegetation model validations.

Assessing ecological responses to environmental change using statistical models

SummaryThere is a clear need to improve our ability to assess the ecological consequences of environmental change. Because of the complexity of ecosystems and a need to disentangle the effects of multiple pressures, predictions are often reliant on models and expert opinion. These require validation with observed data; in this respect, long‐term data sets are particularly valuable.Innovative statistical methods (nonparametric regression and additive models) are presented for identifying nonparametric ecological trends and changes in seasonality in response to environmental change. These are illustrated through the example of Loch Leven, a shallow freshwater lake. Monitoring data for 35 years are examined, spanning periods of enrichment, ecological recovery and changing climate.Models are developed for phosphorus and nitrogen; temperature and rainfall;Daphniagrazers; and chlorophyll a, with the ecological objectives of examining trends in water quality and the corresponding trends in nutrient availability, grazer abundance and climate.The analysis highlighted a generally decreasing availability of P over the study period, and generally increasing nonparametric trends in nitrate concentration and rainfall. Increasing spring temperatures were also evident, as were significant nonparametric changes in density of summer grazers.Significant reductions are highlighted in spring and summer chlorophyll a, related to the return ofDaphniato the loch. However, no response in chorophyll ato the later declining trends in P is apparent, but seasonality has changed.Synthesis and applications.The analysis highlights the value of nonparametric statistical models for assessing complex ecological responses to environmental change. The models outlined can examine key ecological impacts of climate change, particularly effects on the timing of seasonal events and processes. The models are illustrated using long‐term water‐quality data from Loch Leven to explore patterns in key environmental drivers and ecological responses affecting freshwater ecosystems. Analysis of chlorophyll a, in particular, highlighted the value of examining the seasonal trends separately, with different trends evident for winter and spring and a changing seasonal pattern.

Introduction. The boreal forest and global change

The boreal forest is the second largest biome in the world containing 33% of the Earth's forest cover ([FAO 2001][1]) of which approximately 25% is natural. It is circumpolar and shares similar taxa across its range. It has approximately 20 300 identified species. Along with the tropics, the

Impact of climate change on migratory birds: community reassembly versus adaptation

ABSTRACTAim Species can respond to global climate change by range shifts or by phenotypic adaptation. At the community level, range shifts lead to a turnover of species, i.e. community reassembly. In contrast, phenotypic adaptation allows species to persist in situ, conserving community composition. So far, community reassembly and adaptation have mostly been studied separately. In nature, however, both processes take place simultaneously. In migratory birds, climate change has been shown to result in both exchange of species and adaptation of migratory behaviour. The aim of our study is to predict the impact of global climate change on migratory bird communities and to assess the extent to which reassembly and adaptation may contribute to alterations.Location Europe.Methods We analysed the relationship between current climate and the proportion of migratory species across bird assemblages in Europe. The magnitude of community reassembly was measured using spatial variation in the proportion of potentially migratory species. Adaptation was inferred from spatial variation in the proportion of potentially migratory species that actually migrate at a specific site. These spatial relationships were used to make temporal predictions of changes in migratory species under global climate change.Results According to our models, increasing winter temperature is expected to lead to declines in the proportion of migratory species, whereas increasing spring temperature and decreasing spring precipitation may lead to increases. Changes in winter and spring temperature are expected to cause mainly adaptation in migratory activity, while changes in spring precipitation may result in both changes in the proportion of potentially migratory species and adaptation of migratory activity.Main conclusions Under current climate change forecasts, changes in the proportion of migratory species will be modest and the communities of migratory birds in Europe are projected to be altered through adaptation of migratory activity rather than through exchange of species.

Climate changes in the Amur River basin in the last 115 years

Tendencies in climate change in the Amur River basin are generally synchronous to the global ones. During the last century, the annual mean temperature of surface air increased by 1.3°C, minimum warming being observed in the east part of the basin (0.6°C) and maximum one in the west part (1.7–2.5°C). The largest impact on the annual mean temperature growth comes from winter and spring temperature increase (2–4°C/100 years). During the last 30 years, the warming rate in the basin was 2–3 times higher than during the whole period of 1891–2004. Simultaneously with warming in the Amur River basin, annual and warm-season precipitation totals increased by 8 and 6%, respectively, during the 115-year period. The highest increase in precipitation totals occurs in cold season (29% during 115 years). During the last 30 years, together with intense warming in the Amur River basin, the annual precipitation totals are found to decrease by an average of 2.1%/10 years.

Spring temperature, clutch initiation date and duck nest success: a test of the mismatch hypothesis

1. Increases in average global temperature during the twentieth century have prompted calls for research on the effect of temperature variation on avian population dynamics. Particular attention has been paid to the hypothesis that increased temperatures may affect a species' ability to shift their breeding efforts to match the phenology of their prey, and thus result in reduced reproductive success (the 'mismatch hypothesis'). 2. We used data from a long-term study of breeding ducks to investigate how duck nest success varied with clutch initiation date, and to test whether spring temperature affected this relationship in a manner consistent with the mismatch hypothesis. We modelled five possible functional forms of how nest success might vary with clutch initiation date and spring temperature, and used an information-theoretic approach to determine which model best described the nesting outcomes of five dabbling duck species nesting in Saskatchewan, Canada. 3. Probability of nest success for the five species did not vary strongly with clutch initiation date, and we found evidence consistent with the mismatch hypothesis for one species, northern pintail Anas acuta, although weight of evidence was weak. 4. Overall nest success of all five species was positively associated with spring temperature. These results suggest that increasing spring temperature alone (within the range observed in this study) may not affect nest success in a manner that would result in lower populations of breeding ducks.

Climate change and timing of spring migration in the long-distance migrant Ficedula hypoleuca in central Europe: the role of spatially different temperature changes along migration routes

Coinciding with increasing spring temperatures in Europe, many migrants have advanced their arrival or passage times over the last decades. However, some species, namely long-distance migrants, could be constrained in their arrival dates due to their largely inherited migratory behaviour and thus a likely inflexibility in their response to exogenous factors. To examine this hypothesis for pied flycatchers (Ficedula hypoleuca), we tested the effects of the temperature regimes along their migration routes north of the Sahara on their arrival times in central Europe. To do so, we developed a site-independent large-scale approach based on temperature data available on the Internet. Temperature regimes along the migration routes of pied flycatchers within Europe convincingly correlate with their first arrival times. It can be concluded that the progression of spring migration in this species is strongly influenced by temperature en route. Because of the recent inconsistent climatic changes in various parts of Europe, we hypothesize that individuals migrating along different routes will be unequally affected by further climatic changes.

The effect of temperature on photoperiodically regulated gonadal maturation, regression and moult in starlings – potential consequences of climate change

Summary Birds use increasing photoperiod during spring as the major cue to time gonadal maturation and breeding so that nestlings are growing during peak food (normally invertebrate) abundance. Climate warming will advance invertebrate abundance, so birds relying entirely on photoperiod will breed too late. Can temperature modulate responses to photoperiod? Common Starlings, Sturnus vulgaris, were kept in two indoor aviaries, in which photoperiod tracked natural changes, but temperature was held at either 20 °C or 5 °C (year 1), or at 18 °C or 8 °C (year 2). Despite the large differences in temperature (15 °C and 10 °C), this had no effect on the rate or timing of testicular maturation. However, unexpectedly, testicular regression occurred significantly earlier at the higher temperatures. Post‐nuptial moult also started significantly earlier in both males and females. Therefore, the degree to which birds can advance the timing of egg‐laying in response to increasing spring temperature may be constrained. At the same time, increasing spring temperature will advance the end of the breeding season (fewer breeding attempts). The reported advances in median egg‐laying dates may, in part, be a consequence of this rather than an indication of successful adaptation. Adaptation to climate change may require evolutionary changes in the physiological responses to photoperiod.

Relating tree phenology with annual carbon fluxes at Tharandt forest

Within climate change research vegetation plays an important role in both indicating climate change by plant phenology and mitigating climate change by carbon sequestration. A 41-year study period of phenological observations at Tharandt International Phenological Garden and an 8-year study period of continuous flux measurements of carbon dioxide above Norway spruce (Picea abies L. [Karst.]) in the Tharandt forest were used to investigate long-term trends of phenological observations concurrent with climatic trends and to assess the importance of phenological changes for annual carbon gain of the forest. It could be shown that length of growing season determined from phenology was less variable than determined from temperature levels and significantly correlated with mean annual temperature. The slight increase in the length of growing season (LGS) (0.14 d/a) resulted from an earlier onset of spring (-0.32 d/a) and of autumn phases (-0.18 d/a). Obviously, this reflected regional climatic trends with significant temperature increase in spring and slight decrease in autumn. The pronounced effect in spring is also reflected by strongest correlation of annual carbon gain with the emergence of May shoot while the correlation with LGS was less significant. It was therefore concluded that earlier emergence of May shoot was more important for annual carbon gain (22.4 gC/m 2 /d gross uptake) than the increase in total LGS (17.1 gC/m 2 /d gross uptake). However, positive effects of premature phenological stages on carbon gain may be reduced by drought effects during summer as observed for the study year 2003.

Climate change and the effect of increasing spring temperatures on emergence dates of the butterfly Apatura iris (Lepidoptera: Nymphalidae)

Data on pupation and emergence dates for the nymphalid Purple Emperor butterfly Apatura iris have been collected at Basel, Switzerland, between 1982 and 2002. The butterfly has been shown to emerge on average 9 (males) to 12 (females) days ear- lier per decade, 19 and 24 days earlier respectively over the study period. Emergence dates relate strongly to spring temperatures, particularly with daily maximum temperatures for the months March to May. Temperatures for these months have increased signifi- cantly during this period (0.7°C to 1.8°C per decade). Three factors suggest that the strongest influence of the rise in spring tempera- tures has been on late larval instar growth and development: (i) May temperatures dominate emergence date models and larvae are feeding faster and for longer periods during this month, (ii) Salix caprea flowering date, a surrogate for bud burst, is excluded in stepwise regression models with temperatures and years suggesting that tree phenology may be less important than temperature effects on later development, and (iii) convergence of female and male emergence dates over time points to limits on earlier feeding in protandrous males. A negative consequence observed with earlier emergence dates is lethal extra broods.

Growing season changes in Fennoscandia and Kola peninsula during the period 1982 to 1999 - Implications for reindeer husbandry (In Norwegian with Summary in English)

Growing season changes in Fennoscandia and Kola peninsula during the period 1982 to 1999 - Implications for reindeer husbandry (In Norwegian with Summary in English)

Evolution in a Changing Environment: A Case Study with Great Tit Fledging Mass

Heritable phenotypic traits under significant and consistent directional selection often fail to show the expected evolutionary response. A potential explanation for this contradiction is that because environmental conditions change constantly, environmental change can mask an evolutionary response to selection. We combined an "animal model" analysis with 36 years of data from a long-term study of great tits (Parus major) to explore selection on and evolution of a morphological trait: body mass at fledging. We found significant heritability of this trait, but despite consistent positive directional selection on both the phenotypic and the additive genetic component of body mass, the population mean phenotypic value declined rather than increased over time. However, the mean breeding value for body mass at fledging increased over time, presumably in response to selection. We show that the divergence between the response to selection observed at the levels of genotype and phenotype can be explained by a change in environmental conditions over time, that is, related both to increased spring temperature before breeding and elevated population density. Our results support the suggestion that measuring phenotypes may not always give a reliable impression of evolutionary trajectories and that understanding patterns of phenotypic evolution in nature requires an understanding of how the environment has itself changed.

Onset of breeding among Swedish Starlings Sturnus vulgaris in relation to spring temperature in 1981—2003

Both spring temperature and date of the first Starling Sturnus vulgaris egg were highly correlated between different study sites and weather stations in the southern half of Sweden. In southern Sweden, but not in northern Sweden, onset of breeding correlated strongly with spring temperature, particularly during the last ten days of April, the period that happens to coincide with the start of breeding. The response was one to two days per degree. No response was found with periods relative to the start of egg-laying, indicating that in the latter part of April the general conditions for breeding are normally satisfied as soon as temperature reaches a certain level. Possible climatic trends were too weak to be detected in the noise of the annual fluctuations. The best current estimate of long-term spring temperature increase during the next one hundred years is four degrees, which would mean that the Starling will start egg-laying 4–8 days earlier at the end of the present than at the end of the previous century.

Rapid growth and early flowering in an invasive plant, purple loosestrife ( Lythrum salicaria L.) during an El Niño spring.

Phenological shifts may play a role in the success of invasive species, especially in association with climatic variability. We studied the response of a North American population of the invasive plant, Lythrum salicaria L., to changes in local climate associated with the El Niño/Southern Oscillation Event (ENSO) of 1997-1998. For L. salicaria plants at two wetland sites near North Bay, Ontario, Canada, we made weekly observations of flowering phenology and monthly measurements of aboveground biomass during the 1997 and 1998 growing seasons (April-October). Reproductive output was measured as cumulative length and biomass of inflorescences at the end of the growing season. Temperature and precipitation during the 1997 growing season were typical for the region and provided good baseline data for comparison to the full effects of the ENSO event in 1998, which increased spring temperatures and reduced precipitation in the study area. In response to these conditions, populations of L. salicaria began to flower 14 days earlier (Julian day = 181 +/- 10) in 1998 than in 1997 (Julian day = 195 +/- 12), and accumulated more aboveground biomass early in the growing season (P < 0.05). However, by the end of the growing season, there were no significant differences between years in aboveground biomass or total inflorescence lengths, and senescence of plants occurred at similar times for both growing seasons. Advances in spring phenology during ENSO events offer several potential advantages to L. salicaria, and could have a significant impact on biological control programs initiated for this species in North America.

Trends in Seasonal Sea Ice Duration in Southwestern Hudson Bay

The southwestern region of Hudson Bay is one of the last areas in the Hudson and James Bay lowlands region to become free of sea ice in the spring. This late breakup is due to the effects of winds and currents. By analyzing time series with three different statistical techniques, we found a statistically significant increase in the length of the ice-free season in this region from 1971 to 2003. Much of this increase was attributed to earlier breakup of the ice, which is consistent with increased spring temperatures in this region. The onset of breakup advanced by at least three days per decade over the study period.

Genetic and plastic responses of a northern mammal to climate change.

Climate change is predicted to be most severe in northern regions and there has been much interest in to what extent organisms can cope with these changes through phenotypic plasticity or microevolutionary processes. A red squirrel population in the southwest Yukon, Canada, faced with increasing spring temperatures and food supply has advanced the timing of breeding by 18 days over the last 10 years (6 days per generation). Longitudinal analysis of females breeding in multiple years suggests that much of this change in parturition date can be explained by a plastic response to increased food abundance (3.7 days per generation). Significant changes in breeding values (0.8 days per generation), were in concordance with predictions from the breeder's equation (0.6 days per generation), and indicated that an evolutionary response to strong selection favouring earlier breeders also contributed to the observed advancement of this heritable trait. The timing of breeding in this population of squirrels, therefore, has advanced as a result of both phenotypic changes within generations, and genetic changes among generations in response to a rapidly changing environment.

Historical Meadow Dynamics in Southwest British Columbia: a Multidisciplinary Analysis

Lepofsky, D., E. K. Heyerdahl, K. Lertzman, D. Schaepe and B. Mierendorf 2003. Historical Meadow Dynamics in Southwest British Columbia: a Multidisciplinary Analysis. Conservation Ecology 7(3):5. https://doi.org/10.5751/ES-00559-070305