Mean April Temperature Research Articles

Predicting the vessel lumen area tree-ring parameter of <i>Quercus robur</i> with linear and nonlinear machine learning algorithms

Climate-growth relationships in <i>Quercus robur</i> chronologies for vessel lumen area (VLA) from two oak stands (QURO-1 and QURO-2) showed a consistent temperature signal: VLA is highly correlated with mean April temperature and the temperature at the end of the previous growing season. QURO-1 showed significant negative correlations with winter sums of precipitation. Selected climate variables were used as predictors of VLA in a comparison of various linear and nonlinear machine learning methods: Artificial Neural Networks (ANN), Multiple Linear Regression (MLR), Model Trees (MT), Bagging of Model Trees (BMT) and Random Forests of Regression Trees (RF). ANN outperformed all the other regression algorithms at both sites. Good performance also characterised RF and BMT, while MLR, and especially MT, displayed weaker performance. Based on our results, advanced machine learning algorithms should be seriously considered in future climate reconstructions.

Sve raniji povratak kukavice (Cuculus canorus L.) sa zimovanja u šume sjeverozapadne Hrvatske

The Earth is getting warmer at its surface and this global warming can be linked to numerous different phenomena worldwide and it has great impact on ecosystems. Responses to climate change vary interspecies, intraspecies and among different area. Most of the birds in the temperate regions arrive earlier from their wintering places and it is believed that this is a response to the significantly higher spring temperatures. The main aim of this work is to describe changes in spring arrival dates of Common Cuckoo (Cuculus canorus) in the period between 1989 and 2016, and also, to identify relationship between dates of arrival and mean spring temperature in the researched period. The Common Cuckoo is an obligate brood parasite and common bird species in study area. In this research, mean April temperature is used as the mean spring temperature because April is the month when this bird species returns from wintering. First arrival date is the common type of data in investigation of connections between climate change and timing of migration. In research of the most bird species this is when the birds are observed for the first time that year, but in the Common Cuckoo, noting the first time hearing them sing is more usual method. Results of this study suggest that climate changes cause earlier arrival of the Common Cuckoo from the wintering place to the breeding area. Their first arrival date in northwestern Croatia has advanced (significantly) by seven days over the past 28 years. Correlation between first arrival date and average April temperature is also significant. Mean spring temperature increased significantly from 1989 to 2016. This result indicates that mean spring temperature has an influence on the date of the Common Cuckoo first arrival. For the Common Cuckoo, it is important that climate changes don’t cause significant differences in the timing of breeding between them and their host bird species.

Determining past leaf-out times of New England's deciduous forests from herbarium specimens.

• There is great interest in studying leaf-out times of temperate forests because of the importance of leaf-out in controlling ecosystem processes, especially in the face of a changing climate. Remote sensing and modeling, combined with weather records and field observations, are increasing our knowledge of factors affecting variation in leaf-out times. Herbarium specimens represent a potential new source of information to determine whether the variation in leaf-out times observed in recent decades is comparable to longer time frames over past centuries.• Here we introduce the use of herbarium specimens as a method for studying long-term changes in leaf-out times of deciduous trees. We collected historical leaf-out data for the years 1834-2008 from common deciduous trees in New England using 1599 dated herbarium specimens with young leaves.• We found that leaf-out dates are strongly affected by spring temperature, with trees leafing out 2.70 d earlier for each degree C increase in mean April temperature. For each degree C increase in local temperature, trees leafed out 2.06 d earlier. Additionally, the mean response of leaf-out dates across all species and sites over time was 0.4 d earlier per decade. Our results are of comparable magnitude to results from studies using remote sensing and direct field observations.• Across New England, mean leaf-out dates varied geographically in close correspondence with those observed in studies using satellite data. This study demonstrates that herbarium specimens can be a valuable source of data on past leaf-out times of deciduous trees.

Temperature Characteristics and Spring Frost Risk in the Sour Cherry (Prunus Cerasus L.) Blooming Period in 1985–2010

Abstract The aim of the paper is an attempt to present the relationships between sour cherry (Prunus cerasus L.) blooming time, climatic conditions and spring frost risk in western Poland (Great Poland Lowland). Air temperature indices from meteorological stations in Przybroda and Poznań for the period 1985-2010 representing contemporary climate warming were used. ‘English Morello’ sour cherry phenological records for the period 1985-2010 were collected at the Research Station of Poznań University of Life Sciences located in Przybroda. The earliest end of blooming was observed on 2nd of May 1999, and the latest one on 26th of May 1987. The average period of sour cherry blooming was between 30th April and 12th May. During 50% of the years the blooming period lasted from 11 to 15 days. Mean monthly temperature in Przybroda varied from -1.1°C in January to 19.6°C in July. A significant relationship between the beginning date of cherry blooming and the beginning of the thermal vegetation period was found. Variability of the index explained more than 50% of variability in the first dates of cherries blooming (coefficient of determination R2 = 0.505 is significant on the level p < 0.05). The beginning of blooming was also significantly (p < 0.05) correlated with mean April temperature, which could explain about 43% of variability in the dates of the first bloom. An increase in April temperature by 1.0°C caused earlier blooming by about 2.8 days. During the period of 1985-2010 a significant increase in April temperature was observed (in Poznań 0.79°C per decade). It had an effect on advanced dates of the beginning of sour cherry blooming of about 3 days per decade. In 26 of the years the last frost occurred 4 times (15% of seasons) during the blooming phenological phase or later in Przybroda. Frost occurred 10 days before blooming started and during blooming in 54% of the years.

Prolonged limitation of tree growth due to warmer spring in semi-arid mountain forests of Tianshan, northwest China

Based on radial tree growth measurements in nine plots of area 625 m2 (369 trees in total) and climate data, we explored the possibly changing effects of climate on regional tree growth in the temperate continental semi-arid mountain forests in the Tianshan Mountains in northwest China during 1933–2005. Tree growth in our study region is generally limited by the soil water content of pre- and early growing season (February–July). Remarkably, moving correlation functions identified a clear temporal change in the relationship between tree growth and mean April temperature. Tree growth showed a significant (p < 0.05) and negative relationship to mean April temperature since approximately the beginning of the 1970s, which indicated that the semi-arid mountain forests are suffering a prolonged growth limitation in recent years accompanying spring warming. This prolonged limitation of tree growth was attributed to the effects of soil water limitation in early spring (March–April) caused by the rapid spring warming. Warming-induced prolonged drought stress contributes, to a large part, to the marked reduction of regional basal area increment (BAI) in recent years and a much slower growth rate in young trees. Our results highlight that the increasing water limitation induced by spring warming on tree growth most likely aggravated the marked reduction in tree growth. This work provides a better understanding of the effects of spring warming on tree growth in temperate continental semi-arid forests.

Contrasting effects of climate change on the timing of reproduction and reproductive success of a temperate insectivorous bat

AbstractWe used long‐term datasets to analyse (1) the patterns of covariation between basic climatic variables (temperature and rainfall) and the timing of reproduction and reproductive success; and (2) long‐term trends in both reproductive parameters of a maternity colony of Daubenton's bats Myotis daubentonii in South Bohemia, Czech Republic. The mean April temperature was the best predictor of the timing of reproduction. The higher the April temperature, the earlier the first neonates appeared. The mean date of first parturition was June 4, but it advanced significantly by c. 11 days between 1970 and 2012. Similarly, the mean April temperature increased over the study period by c. 2.7°C. Between 1999 and 2012, the mean reproductive success (proportion of reproductive females) was 74%, but varied between 33% (2009) and 93% (2006). It was negatively related to May–July precipitation. Thus, reproductive success was lower in years with increased rainfall. Given the published evidence that advancement in parturition is positively related to survival of juvenile bats rising spring temperatures may have a beneficial influence on the population dynamics of Daubenton's bats. However, increased incidence of climatic extremes, such as excessive summer rainfall, may largely buffer this effect. Consequently, populations of temperate insectivorous bats may experience increasing environmental stress under continuing climate change.

A Blue Tit Cyanistes caeruleus population: its recent increase and breeding data

Before 1983, Blue Tits Cyanistes caeruleus never made up more than four pairs of the breeding population in a nestbox study carried out in South Central Sweden. From five breeding pairs in 1983, the population increased to 29 pairs in 2007 and remained high to the end of the study in 2011. Mean laying date was strongly correlated with mean April temperature, which increased during 1983–2011. During the same period mean laying date became nearly ten days earlier. Mean clutch size was 9.90 eggs but varied both within and between years and showed a negative relationship to population size. The mean number of fledglings varied strongly between years, partly because of predation but also due to nestling starvation.

Does climate influence phenological trends in social wasps (Hymenoptera: Vespinae) in Poland?

Responses of insects to recent climate change have been well documented in a number of taxa, but not in wasps. This study examined shifts in phenology of the two most important wasp species (Vespa crabro and Vespula germanica) in Poland over the last three decades. Both species showed similar temporal trends, advancing their phenology after the early 1980s, but this pattern was detected only for workers not for the appearance of queens. The appearance times for V. germanica were negatively related to mean April temperature, appearing earlier in years with warmer springs, and positively related to precipitation in April. The studied species advanced aspects of their phenology, but linking this to temperature was not achieved for V. crabro suggesting that we have to pay more attention to the life history traits of the study organisms.

Modelling the effect of climate on maple syrup production in Québec, Canada

Due to the exceptional sweetness of its sap, sugar maple ( Acer saccharum Marsh.) is economically exploited at a commercial scale for maple syrup production in northeastern North America. Approximately 80% of world production is realised in the province of Quebec, Canada, where it is economically important for rural communities. Despite important financial investments in industrial infrastructure over recent decades, the maple syrup yield (ml of sap/tap/year) has followed a general declining trend over the last 15 years, presumably because of unfavourable climatic conditions. In this study, the relationship between climate and maple syrup yield by tap for the whole province was investigated. A multiple regression model using four monthly climatic variables (mean January and April temperature and maximum temperature in February and March) explained 84% of the annual variation in yield between 1985 and 2006. This model was used to predict sugar maple syrup yield using a data set of future climatic scenarios issued from a large number of global climate models driven by different scenarios of CO 2 emissions. The results show that sap yield of sugar maple should decrease by 15 and 22% in 2050 and 2090, respectively, as compared to the 1985–2006 period. The increase in mean April temperature was responsible for most of the reduction in yield. Assuming that the variables included in the prediction model are expressing a pattern of successive climatic conditions that could be displaced in time, i.e., that may happen sooner in the season, the maple syrup yield could be maintained at its current level if the period of sap production can shift in time to occur 12 days and 19 days sooner in 2050 and 2090, respectively. Other potential effects of climate change on sugar maple range and health that could also affect the yield of maple syrup production in the future were not addressed in this study.

First arrival dates of the Nightingale (Luscinia megarhynchos) to Central Croatia in the early 20th century and at the turn of the 21st century

Abstract Global climate change has important impacts on animal life-cycles. One of the responses to global warming is an earlier arrival time of many migratory bird species. The first arrival date of the Nightingale (Luscinia megarhynchos) in Central Croatia was studied for the periods of 1901–1917 and 1991–2005. Data were derived from the first spring observations and first capture data. A statistically significant advance of 11 ± 1.4 days was recorded. The difference in the mean April temperature between two study periods was significant, while changes in NAO winter index were not significant. Adequate data from the beginning of the 20th century exist; however, recent studies were done on a relatively short-term basis. Therefore, the analysis of two discrete datasets may help to fill the gaps in the knowledge about the climate change response.

Breeding Biology of the Endangered Blue ChaffinchFringilla Teydea Polatzekiin Gran Canaria (Canary Islands)

The Blue Chaffinch is a passerine endemic to the Canary Islands and comprises two subspecies, one found on Tenerife (Fringilla teydea teydea) and the other on Gran Canaria (F. t. polatzeki). Even though the status of the Gran Canaria subspecies is endangered due to habitat loss and fragmentation, knowledge of its life history is anecdotal. We studied its breeding ecology during the years 1991–2004. New data are presented on breeding phenology, number of broods per year, egg biometrics, nest-site characteristics, breeding site fidelity and breeding success. In general, the breeding biology of the two subspecies were similar, with discrepancies in some previously reported traits, such as egg laying interval and frequency of second clutches. The Blue Chaffinch breeds earlier on Gran Canaria than on Tenerife: nests were begun mainly in the second fortnight of May. We did not find any relationship between the onset of egg laying and rainfall in March. However, the onset of the breeding period was negatively correlated with mean April temperature. The Blue Chaffinch showed preferences for a south-easterly nest orientation and for nest placement at the end of branches, where the nest is hidden by pine needles. Nests were located at various heights, from 5.5 to 23.8 m above the ground. 33% of females produced two broods a year. We found no differences in nest site characteristics between successful and unsuccessful nests, which suggests that other factors may be affecting the vulnerability of nests. The main cause of nesting failure (73.9%) was predation, due mostly to the Great Spotted Woodpecker.

Results of a first look into the Austrian animal phenological records

The year to year variability and trends of animal phenological phases (honey bee, cockchafer, 3 butterfly species, swallow and cuckoo) of the Austrian phenological observational network were related to each other and to mean monthly temperatures over the time period 1951-1998. Insect phases were well correlated with each other (r 2 = 0.4 to 0.6) and with temperature (r 2 = 0.25 to 0.55), whereas both bird phases were only well correlated with each other (r 2 = 0.57), but showed low common variance values with temperature and with other animal phases. The slope of the temperature-pheno regression, also termed as temperature sensitivity of the phenological phase, was high in the case of the insect phases (-3 to -5 days/°C), but low in the cases of both bird phases (about -1 days/°C). All animal phenological time series showed a trend towards later occurrence dates. The trends of the bird phases were even significant (p<0.1). There was a marked discrepancy between the trends of all animal phenological and temperature time series, especially between the insects and temperature: the mean temperature time series of February, March and April with the highest common variance with the insect phases showed a strongly increasing trend (0.027°C/year), whereas the first appearance dates of the insects tended to occur later (0.06 to 0.15 days/year). Both bird phases correlated weakly with the mean April temperature (r 2 about 0.1). The temperature trend of April was 0.0003°C/year, whereas the trend of the bird phases was 0.2 days/year for the cuckoo and 0.25 days/year for the swallow. From these observations we conclude that a strong temperature sensitivity of the phenological phase based on the year to year variability (in days/°C) does not necessarily result in corresponding trends of temperature and phenological phase. A strong trend of non-atmospheric factors such as population density influencing the animal phases is suspected. Factors other than local atmospheric temperature, like climatic conditions in the overwintering area and on the migration route, probably govern the arrival times of the migratory birds.

Climate as the dominant control on C3 and C4 plant abundance in the Loess Plateau: Organic carbon isotope evidence from the last glacial-interglacial loess-soil sequences

Abundance of C3 and C4 photosynthesis plants can be inferred relatively from stable carbon isotopic composition of organic matter in soils. The samples from five sequences of the last glacialinterglacial loesssoil in the Chinese Loess Plateau have been measured for organic carbon isotopic ratios (δ13 Corg). The organic carbon isotope data show that relative abundance (or biomass) of C4 plants was increased ca. 40% for each sampling site from the last glacial maximum (LGM) to Holocene optimum, and increased southeastward on the Loess Plateau during both periods of LGM and Holocene. Statistic analyses on the steady maximum δ13 Corg values of Holocene soils and modern climatic data from the Loess Plateau and Inner Mongolia indicate that the C4 plant abundance increases with increasing temperature and decreasing precipitation. The C4 plant abundance is related much closer with mean April temperature and precipitation than annual. These results lead us to deduce following conclusions. First, temperature is the major factor for control on variations in C4 plant abundance in the Loess Plateau from the last glacial to interglacial. In the absence of favorable temperature condition, both of low moisture and low atmospheric CO2 concentration are insufficient to drive an expansion of the C4 plants in the plateau. Second, δ13 Corg in the loess-paleosol sequences, as a proxy of the relative abundance of C4 plants in the Loess Plateau, could not be used as an indicator of changes in the summer monsoon intensity unless the temperature had changed without great amplitude. Since all C4 plants are grasses, finally, the increase of the C4 plants supports that forest has not been dominant in the ecosystem on the Loess Plateau during Holocene although precipitation and atmospheric CO2 were largely increased relative to those during LGM.

Climate change and breeding success: decline of the capercaillie in Scotland

Abstract The number of capercaillie in Scotland has fallen since the 1970s. Previous work showed that low breeding success, exacerbated by deaths of fully grown birds flying into forest fences, was the primary cause of the decline. The hypothesis that climate change caused the lower breeding success was investigated in this study. Temperature usually rose during April. There was no trend in mean April temperature during the study (1975–99) but there was a progressive cooling in mid‐April relative to the rest of the month, such that the normal April warming was increasingly delayed. Hens reared more chicks when the temperature rose more in early April. It is suggested that this stimulated timely plant growth, so improving the laying hens’ plane of nutrition and the viability of their chicks. Hens also reared more chicks when late May was warmer and early June was warmer and had fewer rain days. Young chicks may have foraged more successfully in warm dry conditions. However, neither temperature nor rain days in late May or early June showed any trend during the study. Increasingly protracted spring warming seems to have been a major cause of the decline of the capercaillie in Scotland.

Historical Analysis of Grasshopper (Orthoptera: Acrididae) Population Responses to Climate in Southern Idaho, 1950–1980

The relationships between grasshopper densities and climatic variables in southern Idaho were examined using historical grasshopper survey records from 1950 to 1980. Mean annual grasshopper densities were calculated from grasshopper counts made within a 20-km radius of each of 26 weather stations spanning the Snake River plains and adjacent areas. The mean annual densities for each location were averaged to yield 27-yr mean grasshopper densities. Maximum r 2 improvement regression techniques were used to select average weather factors that were correlated with grasshopper densities. The average November precipitation and mean April temperature proved to be the best indicators of the mean grasshopper density for a location, accounting for 92% of the variation in the 27-yr mean densities. The relationships of temperature and precipitation to annual grasshopper population fluctuations were analyzed at 15 locations. Most of the mean monthly temperature variables included in the regression equations were positively correlated with grasshopper densities, except for November, December, and January mean temperatures, which were negatively correlated with grasshopper densities in the following year. Precipitation variables included in the regression models were positively correlated with grasshopper densities at nearly all locations. Precipitation appears to be an important factor driving grasshopper population dynamics in southern Idaho, possibly by its effect on vegetation quality and quantity.

Influence of weather and nitrogen fertilization on white clover percentage of permanent grassland.

On humus sandy soil little affected by moisture deficiency, and on compact river clay with somewhat lower water-table (40-180 cm) and occurrence of water deficiency during the summer months, herbage sampling during 1960-1966 showed that the percentage of Trifolium repens present in any month was significantly correlated with temperature and total radiation for the previous month. The mean clover percentage for a single season correlated significantly with mean April temperature. At temperatures common in April, growth of clover is considerably more affected by a rise in temperature than is that of the competing grasses Loliuni perenne and Poa trivialis. The clover percentage was unfavourably affected by N application but unaffected by precipitation or potential evaporation. (Abstract retrieved from CAB Abstracts by CABI’s permission)