Leaf Data Research Articles

Shifts in Plant Phenology and Its Responses to Climate Warming in Three Temperate Cities of China during 1963–2020

The advance of spring phenology and the delay of autumn phenology caused by global warming have been documented by many studies. However, most research has focused on natural areas, with limited studies conducted on phenological observations in urban environments. Here, we selected the first flowering date (FFD), first leaf date (FLD), and leaf coloring date (LCD) at three sites (Beijing, Harbin, and Mudanjiang) from the China Phenological Observation Network. We analyzed the phenological changes of 84 species between 1963–1991 and 1992–2020 to examine their response to urban warming. We then quantified the correlations and regressions between phenological events and preseason temperature. The results show the following: (1) Among the three sites, the mean FFD and FLD were earliest in Beijing, while the mean LCD occurred earliest in Harbin and latest in Beijing. (2) FFD and FLD exhibited a significant trend towards earlier occurrences at all three sites, while LCD showed a significant delay trend except for the Mudanjiang site. Specifically, at the Beijing, Harbin, and Mudanjiang sites, the mean FFD advanced by 8.32 days, 6.11 days, and 2.60 days in the latter period (p < 0.05), whereas the mean FLD advanced by 11.30 days, 7.21 days, and 5.02 days (p < 0.05), respectively. (3) In Beijing, Harbin, and Mudanjiang, both FFD and FLD were significantly negatively correlated with preseason temperature. However, no consistent relationship was observed between LCD and preseason temperature. These results enhance our understanding of the response of plant phenology to urban warming.

A dataset of gridded phenology of woody plants in Europe from 1951 to 2021

Plant phenology records the timing of plant cyclic growth events, and stand as one of the most important indicators of climate change. The monitoring and research of plant phenology is of great significance for understanding the response of ecosystems to global changes and simulating the material and energy balance of terrestrial ecosystems. Based on the ground observation phenological data of six representative woody plants compiled by the Pan European Phenology Project (PEP725) in the past 70 years, this paper employed three phenology models (Unichill, Unified and TSC) to predict and upscale the phenology data on the continental scale, and prepared a dataset of gridded phenology of woody plants in Europe. This dataset contains the grid data of the first leaf date (FLD) and first flower date (FFD) of six woody plants in Europe (34°57′N-72°3′N，25°3′W-40°3′E) from 1951 to 2021, with a spatial resolution of 0.1 ° and a temporal resolution of one day. The quality assessment of the grid phenology data shows that the average error for FLD and FFD is 7.9 and 7.6 days respectively, which are close to simulation errors of spring phenology observed in other regional-scale studies, revealing the high accuracy of the data. This dataset can better characterize the temporal and spatial patterns of plant phenology at a continental scale in Europe, and provide an effective verification approach for plant phenology products from other sources. Furthermore, it can offer valuable data support for research on global change and terrestrial ecosystem simulation.

Feasibility of incorporating leaf date palm fibers in geopolymer composites made from mining waste

This study explores the potential of developing novel high performance geopolymer composite (GPC) materials utilizing mining waste (MW) as an aluminosilicate precursor for the geopolymer matrix and reinforcing it with leaf date palm fibers (LDPFs). Specifically, we examined the effects of incorporating varying amounts of LDPF fibers on the mechanical, physical, and morphological properties of the formulated GPC. The explored range of the incorporated fibers was from 0% to 4% (wt/wt). Mechanical properties were evaluated using modulus of rupture (MOR) and modulus of elasticity (MOE), while physical properties were assessed through water absorption (WA) and thickness swelling (TS). Additionally, X-ray diffraction (XRD), FTIR spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) were employed to visualize matrix phases and analyze the composition, elucidate changes in the structure, and examine the interfacial failure morphology, respectively. The results revealed that the MOR and MOE nearly doubled in the formulation reinforced with 2% (wt/wt) LDPF fibers compared to the geopolymer matrix, confirming the efficacy of these fibers as reinforcing element enhancing the strength and stiffness of the geopolymer matrix. The physical properties exhibited an increase with higher fiber loading, though they remained lower compared to those of other composites found in literature, confirming the suitability of LDPF fibers for geopolymer composite formulations. The structural and morphological analyses of the geopolymer composites indicated an acceptable degree of geopolymerisation and the fibers displayed good interfacial bonding with the geopolymer matrix, respectively. The research findings suggest that leaf date palm fibers are well-suited for reinforcing geopolymer matrix derived from mining waste, presenting a cost-effective option for construction materials.

Phylogenetic conservation in plant phenological traits varies between temperate and subtropical climates in China.

Phenological traits, such as leaf and flowering dates, are proven to be phylogenetically conserved. The relationship between phylogenetic conservation, plant phenology, and climatic factors remains unknown. Here, we assessed phenological features among flowering plants as evidence for phylogenetic conservatism, the tendency for closely related species to share similar ecological and biological attributes. We use spring phenological traits data from 1968-2018 of 65 trees and 49 shrubs in Xi'an (temperate climate) and Guiyang (subtropical climate) to understand plant phenological traits' relationship with phylogeny. Molecular datasets are employed in evolutionary models to test the phylogenetic conservatism in spring phenological characteristics in response to climate-sensitive phenological features. Significant phylogenetic conservation was found in the Xi'an plant's phenological traits, while there was a non-significant conservation in the Guiyang plant species. Phylogenetic generalized least squares (PGLS) models correlate with phenological features significantly in Xi'an while non-significantly in Guiyang. Based on the findings of molecular dating, it was suggested that the Guiyang species split off from their relatives around 46.0 mya during the middle Eocene of the Tertiary Cenozoic Era, while Xi'an species showed a long evolutionary history and diverged from their relatives around 95 mya during the late Cretaceous Mesozoic Era. First leaf dates (FLD) indicative of spring phenology, show that Xi'an adjourned the case later than Guiyang. Unlike FLD, first flower dates (FFD) yield different results as Guiyang flowers appear later than Xi'an's. Our research revealed that various factors, including phylogeny, growth form, and functional features, influenced the diversity of flowering phenology within species in conjunction with local climate circumstances. These results are conducive to understanding evolutionary conservation mechanisms in plant phenology concerning evolutionary processes in different geographical and climate zones.

Springing forward: Migrating songbirds catch up with the start of spring in North America.

In temperate regions, the annual pattern of spring onset can be envisioned as a 'green wave' of emerging vegetation that moves across continents from low to high latitudes, signifying increasing food availability for consumers. Many herbivorous migrants 'surf' such resource waves, timing their movements to exploit peak vegetation resources in early spring. Although less well studied at the individual level, secondary consumers such as insectivorous songbirds can track vegetation phenology during migration as well. We hypothesized that four species of ground-foraging songbirds in eastern North America-two warblers and two thrushes-time their spring migrations to coincide with later phases of vegetation phenology, corresponding to increased arthropod prey, and predicted they would match their migration rate to the green wave but trail behind it rather than surfing its leading edge. We further hypothesized that the rate at which spring onset progresses across the continent influences bird migration rates, such that individuals adjust migration timing within North America to phenological conditions they experience en route. To test our hypotheses, we used a continent-wide automated radio telemetry network to track individual songbirds on spring migration between the U.S. Gulf Coast region and northern locations closer to their breeding grounds. We measured vegetation phenology using two metrics of spring onset, the spring index first leaf date and the normalized difference vegetation index (NDVI), then calculated the rate and timing of spring onset relative to bird detections. All individuals arrived in the southeastern United States well after local spring onset. Counter to our expectations, we found that songbirds exhibited a 'catching up' pattern: Individuals migrated faster than the green wave of spring onset, effectively closing in on the start of spring as they approached breeding areas. While surfing of resource waves is a well-documented migration strategy for herbivorous waterfowl and ungulates, individual songbirds in our study migrated faster than the green wave and increasingly caught up to its leading edge en route. Consequently, songbirds experience a range of vegetation phenophases while migrating through North America, suggesting flexibility in their capacity to exploit variable resources in spring.

Selecting the superior late-leafing genotypes of Persian walnut (Juglans regia L.) using morphological and pomological evaluations

BackgroundLate-spring frost is one of the major factors limiting and reducing yield of Persian walnut (Juglans regia L.) in temperate regions, including Iran. Therefore, in the present study, seedling-originated genotypes of walnut were investigated to identify late-leafing genotypes with high-quality kernels for direct cultivation in orchards or as parents in breeding programs. In the first step, the variation of the selected trees was investigated in terms of traits related to phenology, vegetation, and fruit. In the second step, late-leafing trees were identified and their traits related to kernel quality were investigated to identify superior genotypes.ResultsStrong variabilities were exhibited among the studied genotypes based on the traits recorded. The genotypes showed high variation based on dates of leafing, full male flowering date, and full female flowering date, including very early, early, moderate, and late. After recording the leafing date, 21 late-leaf genotypes were identified and evaluated to select the superiors among them in terms of kernel quantity and quality. Among them, the values of nut-related traits ranged as follows: nut length: 30.12–49.74 mm, nut width: 29.31–37.17 mm, nut weight: 8.77–16.47 g, and shell thickness: 1.15–2.25 mm. The values of kernel-related traits ranged as follows: kernel length: 22.35–35.73 mm, kernel width: 21.79–29.03 mm, kernel weight: 3.22–8.17 g, and kernel percentage: 35.08–53.95%.ConclusionsAccording to the ideal values and situations of commercial characteristics of walnut, twelve promising late-leafing genotypes (No. 9, 13, 32, 33, 72, 77, 78, 82, 83, 86, 92, and 98) were identified and are recommended for cultivation in orchards.

A superior genetic source for late leafing in walnut 'Ahir Nut'

One of the main objectives of walnut crossbreeding programmes is to produce cultivars with late leafing dates. Sixteen years ago, a walnut crossbreeding programme was initiated by Prof. Mehmet Sütyemez, and now a new walnut genotype, namely ‘Ahir Nut’, has been generated with a leafing date that starts later than all commercially-famous walnut cultivars in the world. The present study describes this walnut genotype. For a detailed analysis, ‘Ahir Nut’ was compared with two French-origin walnut cultivars, i.e., ‘Franquette’ and ‘Ronde de Montignac’, which have had the latest leafing dates until now. In an experimental orchard in Turkey, the leafing date in ‘Ahir Nut’ was 14 May, whereas the leafing date in ‘Franquette’ and ‘Ronde de Montignac’ were 23 April and 25 April, respectively. This approximately 3-week difference between ‘Franquette’ and ‘Ronde de Montignac’ to ‘Ahir Nut’ reveals how valuable this genotype is for walnut breeding studies. The harvest dates for ‘Ahir Nut’, ‘Franquette’ and ‘Ronde de Montignac’ were 4 October, 3 October, and 7 October, respectively. The defoliation date for ‘Ahir Nut’ was 4 December. The nut weight and kernel percentage of ‘Ahir Nut’ were calculated as 11.61 g and 49.84%, respectively. Remarkable phenological traits were found in ‘Ahir Nut’, making it a promising option for future walnut cultivation. In the present study, the late leafing date of ‘Ahir Nut’ prompted further research into the molecular and walnut crossbreeding potentials. This new genotype has been conserved as an important genetic resource for future walnut breeding programmes around the world.

Seasonal variations of cold hardiness and dormancy depth in five temperate woody plants in China

Woody plant species in temperate regions must withstand a cold winter and freezing events through cold acclimation and dormancy in autumn and winter. However, how seasonal changes in dormancy depth and cold hardiness affect the frost risk of temperate species is unclear because few studies have assessed dormancy depth and cold hardiness simultaneously. In this study, an experiment was conducted to estimate the dormancy depth and cold hardiness of five common woody temperate plant species during the winter of 2018/2019 in Beijing, China. Twigs of each species were collected at different dates during winter and the timing of budburst was monitored under the same forcing conditions. The dormancy depth was quantified as growing degree day (GDD) requirements of spring events. Simultaneously, the cold hardiness of buds at each sampling date was determined based on the electrical conductivity of the holding solution. Two indices (chilling accumulation and cold hardiness index) were used to simulate the past dynamics of dormancy depth, spring phenology, and cold hardiness from 1952 to 2021. The maximum dormancy depth of the study species was observed between early October and early December, and thereafter decreased exponentially. The cold hardiness peaked in mid-winter (end of December) through cold acclimation and thereafter decreased in spring (deacclimation). During the past 70 years, the budburst date (first flowering date or first leaf date) of five species was estimated to have advanced significantly, and dormancy depth in early spring was predicted to have increased owing to the warming-associated decrease in chilling accumulation. However, cold hardiness has decreased because of weakened acclimation and accelerated deacclimation under a warming climate. The frost risk before and after budburst remained unchanged because of the reduction in occurrence and severity of low-temperature events and earlier late spring frosts. The present methods could be generalized to estimate and predict the seasonal changes in dormancy depth and cold hardiness of temperate species in the context of climate change.

Base Temperature Comparisons for Leafing Date, Pistillate Flower Receptivity, and Pollen Shedding in Persian Walnut

Leafing dates and the male and female bloom periods in Persian walnut (Juglans regia L.) vary with cultivars and years. Changes in phenological phases and the process of passing through the phenological stages could be explained by the growing degree days (GDD) if the minimum base temperature (Tb) were determined. In this study, the long-term phenological data of some walnut cultivars derived and/or grown in Hungary and Iran were used to determine the Tb values for leafing date (LD), pistillate flower receptivity start (PRS), pistillate flower receptivity end (PRE), and start and end of the pollen shedding period (PSS and PSE, respectively). The GDD were calculated (with 0.1 °C precision) for the LD and PSS with respect to the earliest cultivar as well as for PRS compared to LD and PRE. Furthermore, the GDD were reckoned for PSE based on PRS and PSS of the same cultivar in each year. The analysis of the data revealed that for the LD, PRS, and PRE, the Tb5.5 with the highest correlation was shown to be the most appropriate. For the PSS and PSE, the best correlation was observed at Tb0 in both countries. The strongest coefficients were observed (0.72 for Iranian and 0.8 for Hungarian conditions) between GDD with Tb of 5.5 °C for PRS and LD. The less correlation was observed between LD and PSS (0.5 for Iranian and 0.57 for Hungarian conditions). The correlation coefficients between GDD and leafing date were the same (0.52) in both countries. Cultivars involved in the trial required more GDD in Iran than in Hungary.

Resident bird species track inter-annual variation in spring phenology better than long-distance migrants in a subalpine habitat

The ability to track variation in climate is important for species to persist in a given environment. Lack of responses to both long-term changes and inter-annual variation in climate parameters can result in reduced fitness and population decline. Furthermore, migration strategy can influence the ability to track climatic variation due to the potential to use reliable environmental cues. Here, we studied the temporal relationship between birch leafing and onset of breeding for three bird species with contrasting migration strategies over a 20-year period in a subalpine habitat in Central Norway. We found no temporal change in birch leafing date or breeding onset for the three bird species over the study period. However, we found a statistically significant difference in the ability to track inter-annual variation in birch leafing date between the resident and two long-distance migratory species. The resident great tit Parus major was more capable of initiating egg laying in closer association to variation in birch leafing in early springs, than the long-distance migratory European pied flycatcher Ficedula hypoleuca and common redstart Phoenicurus phoenicurus. Long-distance migrants seem to have been constrained by arrival date or time from arrival to entering the breeding areas, in contrast to resident birds, which might be better able track early initiation of spring in breeding areas by adjusting egg laying date. Our findings highlight the importance of not solely studying directional long-term climatic change, but also pay attention to inter-annual variation.

Herbaria Reveal Herbivory and Pathogen Increases and Shifts in Senescence for Northeastern United States Maples Over 150 Years

Recent studies suggest climate-related delays in the timing of leaf coloration and abscission in maple trees but lack baseline data prior to the late 20th century. To better understand how autumn foliar phenology and late-season damage risks have changed for this genus over the past century, we evaluated 2,972 digitized herbaria specimens of red and sugar maple collected between 1826 and 2016 for the presence of leaves, autumn leaf coloration, and pathogen or herbivore damage. We found that the onset (first appearance) of colored leaves has shifted 0.26 days later each year, leading to a delay of more than a month in autumn phenology since 1880. We find that these shifts are related to precipitation regimes in both the fall and summer seasons and that more severe droughts are associated with higher probabilities of colored leaves. Moreover, we found that the probability of both herbivory and pathogen damage has increased significantly over the study period. In particular, we find a strong association between increasing summer drought conditions and increased probability of herbivory. Furthermore, the presence of foliar damage increased the probability of leaf coloration on herbaria specimens. However, the end-of-season abscission date (last appearance of leaves) was strongly associated with herbivory and climate in a contrary direction: Increasing yearly drought, higher fall temperatures, and the presence of herbivory were associated with earlier abscission. In fact, the last leaf dates for specimens with herbivory were nearly 2 weeks earlier than specimens without herbivore damage. Our study documents significant changes in maple senescence over the last 150 years and suggests that incorporating herbivory into models may improve our ability to predict forest responses to climate shifts.

State of theUKClimate 2020

INTRODUCTIONThis report provides a summary of the UK weather and climate through the calendar year 2020, alongside the historical context for a number of essential climate variables. This is the seventh in a series of annual ‘State of the UK climate’ publications and an update to the 2019 report (Kendonet al., 2020). It provides an accessible, authoritative and up‐to‐date assessment of UK climate trends, variations and extremes based on the most up to date observational datasets of climate quality.The majority of this report is based on observations of temperature, precipitation, sunshine and wind speed from the UK land weather station network as managed by the Met Office and a number of key partners and co‐operating volunteers. The observations are carefully managed such that they conform to current best practice observational standards as defined by the World Meteorological Organization (WMO). The observations also pass through a range of quality assurance procedures at the Met Office before application for climate monitoring. Time series of near‐coast sea‐surface temperature and sea‐level are also presented and in addition a short section on phenology which provides dates of first leaf and bare tree indicators for four common shrub or tree species.National and regional statistics in this report are from the HadUK‐Grid dataset which is the principal source of data (Holliset al., 2019). Temperature and rainfall series from this dataset extend back to 1884 and 1862, respectively. Details of the datasets used throughout this report and how the various series which are presented are derived are provided in the appendices.The report presents summary statistics for the most recent year 2020 against the most recent decade 2011–2020, the most recent 30‐year reference period (1981–2010) and the climate reference period 1961–1990. The full series provide longer‐term context, while a comparison is also made to centennial averages for the Central England Temperature series. The decade 2011–2020 is a non‐standard reference period, but it provides a 10‐year ‘snapshot’ of the most recent experience of the UK's climate and how that compares to historical records. This means differences between 2011 and 2020 and 30‐year reference periods may reflect shorter‐term decadal variations as well as long‐term trends.For this annual publication, the most recent decade (currently 2011–2020) changes every year, while the most recent 30‐year reference period (currently 1981–2010) changes every decade. For next year's report, the most recent 30‐year reference period will change from 1981–2010 to 1991–2020, while the climate reference period 1961–1990 will be retained. However, this report also includes a brief summary of key differences between preliminary 1991–2020 and 1981–2010 averages for temperature and rainfall.Throughout the report's text the terms “above normal” and “above average” and so on refer to the 1981–2010 baseline reference period unless otherwise stated. The majority of maps in this report show the year 2020 relative to the 1981–2010 reference period—that is, they are anomaly maps which show the spatial variation in this difference from average. Maps of actual values are in most cases not displayed because these are dominated by the underlying climatology, which for this report is of a lesser interest than the year‐to‐year variability. These data are presented to show what has happened in recent years, not necessarily what is expected to happen in a changing climate.Values quoted in tables throughout this report are rounded, but where the difference between two such values is quoted in the text (e.g., comparing the most recent decade with 1981–2010), this difference is calculated from the original unrounded values.Updates Compared to State of UK Climate 2019A chart showing global surface temperature has been added.The section on sea level rise has been revised.A section summarizing key differences between preliminary 1991–2010 and 1981–2010 averages has been added.FeedbackWe would welcome suggestions or recommendations for future annual publications of this report. Please send any feedback to the Met Office atncic@metoffice.gov.ukThis State of the UK Climate report was supported by the Met Office Hadley Centre Climate Programme funded by BEIS and Defra.

Crown Structure Explains the Discrepancy in Leaf Phenology Metrics Derived from Ground- and UAV-Based Observations in a Japanese Cool Temperate Deciduous Forest

Unmanned aerial vehicles (UAV) provide a new platform for monitoring crown-level leaf phenology due to the ability to cover a vast area while offering branch-level image resolution. However, below-crown vegetation, e.g., understory vegetation, subcanopy trees, and the branches of neighboring trees, along with the multi-layered structure of the target crown may significantly reduce the accuracy of UAV-based estimates of crown leaf phenology. To test this hypothesis, we compared UAV-derived crown leaf phenology results against those based on ground observations at the individual tree scale for 19 deciduous broad-leaved species (55 individuals in total) characterized by different crown structures. The mean crown-level green chromatic coordinate derived from UAV images poorly explained inter- and intra-species variations in spring leaf phenology, most probably due to the consistently early leaf emergence in the below-crown vegetation. The start dates for leaf expansion and end dates for leaf falling could be estimated with an accuracy of <1-week when the influence of below-crown vegetation was removed from the UAV images through visual interpretation. However, a large discrepancy between the phenological metrics derived from UAV images and ground observations was still found for the end date of leaf expansion (EOE) and start date of leaf falling (SOF). Bayesian modeling revealed that the discrepancy for EOE increased as crown length and volume increased. The crown structure was not found to contribute to the discrepancy in SOF value. Our study provides evidence that crown structure is a pivotal factor to consider when using UAV photography to reliably estimate crown leaf phenology at the individual tree-scale.

Spatiotemporal variations in leaf-out phenology of typical European tree species and their responses to climate change.

Over the past decades, global warming significantly affected the spring phenology of plants. Many studies have reported the temporal and spatial patterns of spring phenological changes in China, but relatively less is known for that in Europe, which is also located in the temperate area of the Northern Hemisphere. To facilitate the regional comparison of phenological change and understand its response to climate change, we used the data of first leaf date (FLD) in Europe (1980-2014) and the corresponding meteorological data to examine the spatiotemporal variations in leaf-out phenology of four typical tree species (Aesculus hippocastanum, Betula pendula, Fagus sylvatica, and Quercus robur), and to identify the major climatic factors driving such variations. The results showed that the FLD of the four species in the study area advanced by 3.3-7.5 d·10 a-1 during 1980-2014. The FLD was delayed at a rate of 2.03-3.19 d per degree of latitude from south to north, of 0.19-0.80 d per degree of longitude from west to East (except for Fagus sylvatica), of 2.25-3.44 d·100 m-1 from low to high elevation. The advances in the FLD were mainly attributed to the increases of temperature in spring and the increases of precipitation in spring and winter. The rise of temperature in autumn and winter would delay FLD.

Similarities of leafing and leaf fall date of 'Pedro' walnut variety with its progenies in breeding programs.

In this research, 'Pedro' walnut variety (maternal parent) was open pollinated. Offspring genotypes were compared with their maternal parent in terms of morphological and molecular features. Leafing and leaf fall dates were measured as two phenological traits. Genetic differences were identified by molecular fingerprinting using twelve Inter Simple Repetitive Sequence Polymorphism (ISSR) primers. In some progenies, leafing and leaf fall occurred later than the maternal parent ('Pedro'). Progenies were grouped according to their similarities with the maternal parent regarding leafing date. Specifically, 14.44% of the progenies were 'Very close' to the parent, 16.66% were 'Close', 30.00% 'Far' and 38.89% 'Very far'. Regarding the leaf fall date, 7.78% of the progenies were 'Very close' to the parent, 28.88% were 'Close', 36.66% 'Far' and 26.67% 'Very far'. A total of 43 bands were obtained in molecular analyses. These bands were largely polymorphic (95.34%). The average number of the alleles was 3.90, while the polymorphism information content varied between 0.14 and 0.91 among the genotypes. Genetic distances were tested according to the UPGMA (Unweighted Pair Group Method with Arithmetic Average) and by The Structure Analysis. The UPGMA dendrogram divided the genotypes into two main clusters and the similarity coefficient of the genotypes varied between 0.61 and 0.99. This study revealed that 'Pedro' can be used as an excellent parental variety in hybridization programs which prioritize late-leafing in walnut breeding. Furthermore, ISSR primers can be safely used for fingerprinting walnuts in general.

Phenological changes in herbaceous plants in China's grasslands and their responses to climate change: a meta-analysis.

Plant phenological events are sensitive indicators of climate change, and their change could markedly affect the structure and function of ecosystems. Previous studies have revealed the spatiotemporal variations in the phenological events of woody plants. However, limited studies have focused on the phenophases of herbaceous plants. In this study, by using a meta-analysis method, we extracted information about the phenological changes in herbaceous plants in China's grasslands from existing studies (including the period, station, species, phenophases, phenological trends, and climatic determinants) and analyzed the patterns manifested in the dataset. The results showed that the spring phenophases (e.g., first leaf date and first flowering date) of the herbaceous plants mainly advanced over the past 30years, but a large difference existed across grassland types. The spring phenophases of forages (species from the Cyperaceae, Gramineae, and Leguminosae families) became earlier in the desert steppe and alpine steppe but showed no apparent trends in the alpine meadow and even became later in the meadow steppe and typical steppe. In most cases, the increase in spring temperatures and precipitation promoted the greening up of herbaceous plants, while sunshine duration was positively correlated with the green-up date of herbaceous plants. For the autumn phenophases, the proportions of the earlier and later trends were very close, but the trends varied among the grassland types. The leaf coloring dates of the forages were delayed in the meadow steppe and alpine steppe but showed no distinct pattern in the typical steppe or alpine meadow and even became earlier in the desert steppe. In most cases, the increase in growing season temperature led to an earlier leaf coloring date of the herbaceous plants, but the increase in the preseason precipitation delayed the leaf coloring date. Our results suggested that the phenophases of herbaceous plants have complicated responses to multiple environmental factors, which makes predicting future phenological changes difficult.

State of the UK Climate 2019

INTRODUCTIONThis report provides a summary of the UK weather and climate through the calendar year 2019, alongside the historical context for a number of essential climate variables. This is the sixth in a series of annual ‘State of the UK Climate’ publications and an update to the 2018 report (Kendon et al., 2019). It provides an accessible, authoritative and up‐to‐date assessment of UK climate trends, variations and extremes based on the most up to date observational datasets of climate quality.The majority of this report is based on observations of temperature, precipitation, sunshine and wind speed from the UK land weather station network as managed by the Met Office and a number of key partners and co‐operating volunteers. The observations are carefully managed such that they conform to current best practice observational standards as defined by the World Meteorological Organization (WMO). The observations also pass through a range of quality assurance procedures at the Met Office before application for climate monitoring. Time series of near‐coast sea‐surface temperature (SST) and sea‐level are also presented and in addition a short section on phenology which provides dates of first leaf and bare tree indicators for four common shrub or tree species.National and regional statistics in this report are from the HadUK‐Grid dataset (Hollis et al., 2019). Temperature and rainfall series from this dataset extend back to 1884 and 1862, respectively. Details are provided in the relevant sections and appendices.The report presents summary statistics for the year 2019 and the most recent decade (2010–2019) relative to 1961–1990 and 1981–2010 averages. The period 2010–2019 is a non‐standard reference period, but it provides a 10‐year ‘snapshot’ of the most recent experience of the UK's climate and how that compares to historical records. This means differences between 2010 and 2019 and the baseline reference averages may reflect shorter‐term decadal variations as well as long‐term trends. These data are presented to show what has happened in recent years, not necessarily what is expected to happen in a changing climate.The majority of maps in this report show the year 2019 relative to the 1981–2010 baseline reference averaging period—that is, they are anomaly maps which show the spatial variation in this difference from average. Maps of actual values are in most cases not displayed because these are dominated by the underlying climatology, which for this report is of a lesser interest than the year‐to‐year variability.Throughout the report's text the terms ‘above normal’ and ‘above average’, and so on refer to the 1981–2010 baseline reference averaging period unless otherwise stated. Values quoted in tables throughout this report are rounded, but where the difference between two such values is quoted in the text (e.g., comparing the most recent decade with 1981–2010), this difference is calculated from the original unrounded values.Updates compared to State of UK Climate 2018 A section on phenology has been added The method used to calculate rainfall percentiles (fig. 31) has been revised Updated climate data to HadUK‐Grid version 1.0.2.0, including data rescue projects that have improved or extended early monthly sunshine and rainfall series. FeedbackWe would welcome suggestions or recommendations for future publications of this report. Please send any feedback to the Met Office at ncic@metoffice.gov.ukThis State of the UK Climate report was supported by the Met Office Hadley Centre Climate Programme funded by BEIS and Defra.

Exploring differences in spatial patterns and temporal trends of phenological models at continental scale using gridded temperature time-series

Phenological models are widely used to estimate the influence of weather and climate on plant development. The goodness of fit of phenological models often is assessed by considering the root-mean-square error (RMSE) between observed and predicted dates. However, the spatial patterns and temporal trends derived from models with similar RMSE may vary considerably. In this paper, we analyse and compare patterns and trends from a suite of temperature-based phenological models, namely extended spring indices, thermal time and photothermal time models. These models were first calibrated using lilac leaf onset observations for the period 1961–1994. Next, volunteered phenological observations and daily gridded temperature data were used to validate the models. After that, the two most accurate models were used to evaluate the patterns and trends of leaf onset for the conterminous US over the period 2000–2014. Our results show that the RMSEs of extended spring indices and thermal time models are similar and about 2 days lower than those produced by the other models. Yet the dates of leaf out produced by each of the models differ by up to 11 days, and the trends differ by up to a week per decade. The results from the histograms and difference maps show that the statistical significance of these trends strongly depends on the type of model applied. Therefore, further work should focus on the development of metrics that can quantify the difference between patterns and trends derived from spatially explicit phenological models. Such metrics could subsequently be used to validate phenological models in both space and time. Also, such metrics could be used to validate phenological models in both space and time.

Adaptation of oregano (Origanum vulgare L.) to cultivation in Elvas region, South Portugal

Origanum vulgare L. sustainable cultivation should be promoted in order to reduce genetic erosion risk caused by harvest in nature. The main goal of this study was to respond to the request of a farmer from Elvas region, focusing on the assessment of the adaptation to cultivation of six accessions, three spontaneous in Alto Alentejo (OV1, OV2, OV3) and three commercial (OVT1, OVT2, OVT3). Plant propagation was carried out from stem cuttings for the three spontaneous accessions and from seed for the three commercial accessions. Using material from OV2, a stem cutting vegetative propagation trial was carried out, using softwood (tip and intermediate) and semi-hardwood (basal) stem cuttings. Seed germination was tested using the 3 commercial seed accessions and the 3 spontaneous accessions (harvest in nature and after cultivation) at 20°C with 12-h photoperiod. The following descriptors were observed on the field characterization essay: flowering date, length, width and colour of the basal leaf, growth habit, width and height of the plant, length of the main stem, length and width of the terminal inflorescence, flowered portion of the stem length and width, plant biomass (fresh and dry). The softwood intermediate stem cuttings rooted better (83.8%) and rooting rate was significantly higher than basal semi-hardwood cuttings (56.8%). Seed germination varied from 69.5 to 92%, with significant differences between the commercial seeds and seeds of the spontaneous accessions after cultivation. On the characterization field essay, the flowering date was the only descriptor with significant differences between spontaneous accessions. The earliest-flowering accession was OV1 and the later-flowering accession was OV2. The difference between the flowering dates of these accessions was 13 days. The work provided useful information to the farmer for oregano growing, however, the study should be continued with a larger amount of accessions of broader geographical origin.

Effects of climate variation on the first leaf dates of 39 woody species and their thermal requirements in Xi’an, China

Effects of climate variation on the first leaf dates of 39 woody species and their thermal requirements in Xi’an, China