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Effects of urbanization on flowering phenology in the metropolitan Phoenix region of USA: Findings from herbarium records
Abstract
Phenological studies have become more prominent recently because of rising interests in understanding how plants, communities, and ecosystems respond to global climate change and urban climate modifications. Herbarium records of plants can be a particularly useful source of information for studying historical trends in phenology in areas where long-term phenological records do not exist. In this study, we used herbarium records to examine the historical patterns of flowering phenology of 87 shrubs and ephemerals in the Phoenix metropolitan region in the southwestern United States from 1902 through 2006. We found that 19% of plant species examined either advanced or delayed their flowering. Also, the flowering responses of 28% of the species examined showed significant differences between urban and non-urban areas: 24% advanced in urban areas and 5% delayed. Our study indicates that urbanization may have a significant effect on the flowering phenology of a small but substantial proportion of plants, which will likely affect native biological diversity and ecosystem services due to potential changes in population and community dynamics.
... In other words, specimens can allow us to examine the effects of urbanization across both space and time simultaneously. Indeed, herbarium specimens have been successfully used to uncover variation in plant phenological responses to climate across wide spatial scales (Park et al., 2019 and to study the effects of urbanization, albeit at much smaller spatial and taxonomic scales (Primack et al., 2004;Lavoie & Lachance, 2006;Neil et al., 2010). Such efforts have been greatly facilitated by increasing digitization and mobilization of natural history collections (Hedrick et al., 2020) and are examples of how the herbarium of the future and the 'global metaherbarium' are facilitating expansive and novel science (Davis, 2022). ...
... Thus, in warmer conditions, increased urbanization may result in extending the time necessary to fulfill these requirements, leading to delayed flowering and fruiting (Yu et al., 2010;Chen et al., 2017). It has also been suggested that urbanization affects plant phenology by raising minimum temperatures more than mean or maximum temperatures (Kalnay & Cai, 2003;Neil et al., 2010;Argüeso et al., 2014;Cai et al., 2017), and this effect is likely to be more pronounced during winter months. As temperatures vary across the landscape, urbanization effects on plant reproductive phenology can vary spatially across environmental gradients within species' ranges as well. ...
... The species we sampled and their phenological responses are neither random nor fully representative of assemblages across regions. However, previous studies have shown that phenological trends derived from herbarium specimens are unlikely to be systematically biased and are compatible with direct observations from the field (Primack et al., 2004;Davis et al., 2015); such data have been used successfully to test hypotheses regarding phenological responses to climate and urbanization (Neil et al., 2010;Park et al., 2019). Finally, our analyses cannot determine the ultimate causes of these patterns, and further research into how urbanization modifies environmental cues that trigger phenological events is necessary. ...
Urbanization can affect the timing of plant reproduction (i.e. flowering and fruiting) and associated ecosystem processes. However, our knowledge of how plant phenology responds to urbanization and its associated environmental changes is limited.
Herbaria represent an important, but underutilized source of data for investigating this question. We harnessed phenological data from herbarium specimens representing 200 plant species collected across 120 yr from the eastern US to investigate the spatiotemporal effects of urbanization on flowering and fruiting phenology and frost risk (i.e. time between the last frost date and flowering).
Effects of urbanization on plant reproductive phenology varied significantly in direction and magnitude across species ranges. Increased urbanization led to earlier flowering in colder and wetter regions and delayed fruiting in regions with wetter spring conditions. Frost risk was elevated with increased urbanization in regions with colder and wetter spring conditions.
Our study demonstrates that predictions of phenological change and its associated impacts must account for both climatic and human effects, which are context dependent and do not necessarily coincide. We must move beyond phenological models that only incorporate temperature variables and consider multiple environmental factors and their interactions when estimating plant phenology, especially at larger spatial and taxonomic scales.
... Previous studies showed that microclimatic variability related to urban structures directly affects plant phenology (Chmielewski and Rötzer 2002;Dallimer et al. 2016;Jochner and Menzel 2015;Zipper et al. 2016). Yet these studies have largely focused on tree species (Lu et al. 2006;Mimet et al. 2009;Roetzer et al. 2000) or tree-dominated ecosystems (Li et al. 2017;Liang et al. 2016, but see Cheptou et al. 2008;König et al. 2018;Lambrecht et al. 2016;Neil et al. 2010). In response to the UHI phenological changes such as advanced flowering phenology of urban trees (Lu et al. 2006;Mimet et al. 2009) and an advanced start and delayed end of growing season have been observed (Li et al. 2017). ...
... Phenology of herbaceous plants has been shown to be sensitive to changes in micro-climate (König et al. 2018). So far, phenological studies largely covered non-urban systems such as alpine grassland and prairies (Cornelius et al. 2011;Dunne et al. 2012;Bennie et al. 2018;Wilsey et al. 2018, but see Cheptou et al. 2008;König et al. 2018;Lambrecht et al. 2016;Neil et al. 2010 ), as well as Californian annual grasslands (Bart et al. 2017;Chiariello 1989;Yang and Leigh 2020). For instance, alpine meadow species advance their timing of flowering in response to experimental warming and snow-removal treatment in conjunction with warmer soil temperatures (Dunne et al. 2012). ...
... While there is some urban phenological research on the herb growth forms, such as a for the annual herb Crepis sancta (Cheptou et al. 2008;Lambrecht et al. 2016) or herbarium record studies on ephemeral plants (Neil et al. 2010), so far studies of phenology of multiple grassland species in response to urbanization and urban micro-climate are scarce. ...
Understanding phenological responses of plants to changing temperatures is important because of multiple associated ecological consequences. Cities with their urban heat island can be used as laboratories to study phenological adaptation to climate change. However, previous phenology studies focused on trees and did not disentangle the role of micro-climate and urban structures.
We studied reproductive phenology of dry grassland species in response to micro-climate and urbanization in Berlin, Germany. Phenological stages were recorded weekly at the individual plant level for five native grassland species across 30 dry grassland sites along an urbanization and temperature gradient. We estimated 50% onset probabilities for flowering and seed maturation of populations, and analysed variation in onset dates using regression models.
Early flowering species significantly advanced flowering phenology with increasing mean air temperature but were little influenced by urbanization. By contrast, late-flowering species showed significant phenological responses to both air temperature and urbanization, possibly because micro-climate was most affected by urbanization in late summer. Surprisingly, not all grassland species showed an advanced phenology with increasing intensity of urbanization.
This contradicts observed patterns for urban trees, indicating that phenological shifts in urban areas cannot be generalized from the observation of one growth form or taxonomic group. Growth form appears as a possible determinant of phenological responses. Results suggest that the phenology of dry grassland species may directly respond to the urban heat island, albeit with variable direction and magnitude. This has implications for ecosystem services, shifted allergy seasons, changes of biogeochemical cycles and potential ecological mismatches.
... Um Herbário possui nas suas instalações um vasto número de elementos taxonómicos (Tegelberg et al., 2014), onde estes elementos possuem um grande interesse científico para pessoas ligadas a esta área e até mesmo para pessoas sem ligação direta. Estes elementos permitem que sejam estudados a fim de perceber os impactos que o passar do tempo teve ou não sobre um espécime (Neil et al., 2010;Poulíčková et al., 2013). Assim estes elementos podem dar um contributo importante para estudos científicos ou meramente para enriquecimento pessoal de um individuo que se interesse pelo assunto. ...
... Isto é possível uma vez que a quando da recolha é identificado o local exato da recolha, podendo ser identificada a latitude e longitude. (Baker, 2011;Haston et al. 2012;Neil et al. 2010) De acordo com Neil et al. (2010) ...
... Isto é possível uma vez que a quando da recolha é identificado o local exato da recolha, podendo ser identificada a latitude e longitude. (Baker, 2011;Haston et al. 2012;Neil et al. 2010) De acordo com Neil et al. (2010) ...
... In order to detect changes in phenology and link it with recent climate change, it is necessary to take into consideration changes in the geographical distribution of plant species, their local geography (latitude and elevation) as well as changes in urbanised areas, as all this can influence temperature (Ahas et al. 2002;Parmesan 2007;Neil et al. 2010). Changes in a phenological cycle are one of the essential biodiversity responses to climate change, having an impact on ecosystem functioning and productivity (Menzel et al. 2006b; EEA 2012). ...
... For example, different types of data have been used to address changes in phenology or invasive species intrusions (e.g. herbarium records, photographs), where, for changes in geographic distribution, previous research mainly uses field-based surveys, field notes, and historical museum collections (Tsutsui and Suarez 2004;Elith and Leathwick 2007;Crawford and Hoagland 2009;Gallagher et al. 2009;Neil et al. 2010;Robbirt et al. 2011). Some studies have used 'database of herbarium records' but such databases already include geographical coordinates and do not need manual geo-referencing (Hijmans and Spooner 2001). ...
... Although phenological changes can clearly happen in response to natural variation or to non-climatic factors (e.g. genetic variation or plant to plant interaction, or plant-pollinator interaction), recent studies show that changes in the 20 th and 21 st century can be related to the post-industrial climate change(Walkovszky 1998;Hughes 2000;Badeck et al. 2004;Wolfe et al. 2005;Menzel et al. 2006a;Parmesan 2006;Elzinga et al. 2007;Kauserud et al. 2008;Miller-Rushing et al. 2008;Neil et al. 2010). ...
... Vegetation phenology refers to plant cycle events triggered by seasonal changes (Richardson et al. 2018;Neil, Landrum, and Wu 2010). It is an important indicator of vegetation growth (White et al. 2009) and climate change (Zhou et al. 2016). ...
... Results from satellite imagery indicate that the phenological changes caused by urbanization can promote the growth of vegetation, causing an earlier start of growing season (SOS) and significantly longer length of the growing season (LOS) in urbanized areas. For example, in USA (Neil, Landrum, and Wu 2010;White et al. 2002;Ziska et al. 2003), Europe (Rahman, Armson, and Ennos 2014;Roetzer et al. 2000), and China (Lu et al. 2006;Zhou et al. 2016), the SOS of plant species in urban areas takes place significantly earlier than in rural areas by several days to weeks. However, most previous urban phenology studies concentrate on the "urban-rural" binary classes, which is inadequate for systematically acquiring heterogeneous phenological characteristics across the entire metropolitan area. ...
Phenological changes caused by urbanization may provide evidence of how vegetation responds to global warming. However, the phenological characteristics of vegetation in metropolitan areas have been poorly studied, especially in terms of spatiotemporal variations. In this study, we explored the applicability of Local Climate Zones (LCZs) to investigate the spatiotemporal variations in urban vegetation phenology by linking MODIS-derived phenology metrics with LCZs in the Austin metropolitan area in Texas, USA. We extracted three vegetation phenology metrics from MODIS data between 2008 and 2018, including the start of growing season, end of growing season, and length of the growing season (i.e. SOS, EOS, and LOS, respectively). The results showed that during the study period, the EOS and SOS gradually advanced, while LOS showed no obvious change. Statistical analysis was conducted to examine the spatiotemporal variations of the phenology metrics among different LCZs and along “Urban-Rural Gradients” (URGs). There were 37.5%, 75.0%, and 74.3% pairs of LCZs, indicating statistically significant phenological differences in terms of SOS, EOS, and LOS in 2012, respectively. In contrast, most pairs of URGs showed almost no differences in phenological metrics, especially in EOS. Geographically, SOS showed a fluctuating change with an advancing tendency, whereas the EOS decreased very slowly with distance from the city center (i.e. along the URGs). LCZs can be used to help identify distinctive phenology metrics with statistically significant differences, especially in EOS and LOS. Compared to URGs, LCZs offer a unique analytical framework for studying urban ecosystem patterns, functions, and dynamics. Lastly, LCZs can enable the identification of sensitive areas for ecological protection in support of sustainable urban development and environmental stewardship.
... The '' x'' symbol represents studies that analyzed a difference in the mean flowering day between historic and current time period groups rather than using a type of regression analysis. (Primack et al., 2004;Lavoie & Lachance, 2006;Miller-Rushing et al., 2006;Primack & Miller-Rushing, 2009;Neil, Landrum & Wu, 2010;Panchen et al., 2012;Park, 2012;Primack & Miller-rushing, 2012;Searcy, 2012;Calinger, Queenborough & Curtis, 2013;Park, 2014;Park & Schwartz, 2015;Bertin, 2015;Davis et al., 2015). Although studies by Borchert (1996) and Zalamea et al. (2016) analyzed flowering periodicity in tropical plants using herbarium specimens, we found no study to date that has used herbarium specimens to analyze effects of recent climate change in a tropical region. ...
... Park & Schwartz (2015) eliminated species with records that spanned less than three years. Neil, Landrum & Wu (2010) organized species into functional groups (spring ephemerals, spring shrubs, fall ephemerals, winter-spring ephemerals, and winter-spring shrubs) in order to overcome the problem of low sample sizes for each species but found that responses of individual species varied greatly within functional groups. Several studies found sample size had a greater influence on first-flowering estimates than on mean flowering estimates. ...
Studies in plant phenology have provided some of the best evidence for large-scale responses to recent climate change. Over the last decade, more than thirty studies have used herbarium specimens to analyze changes in flowering phenology over time, although studies from tropical environments are thus far generally lacking. In this review, we summarize the approaches and applications used to date. Reproductive plant phenology has primarily been analyzed using two summary statistics, the mean flowering day of year and first-flowering day of year, but mean flowering day has proven to be a more robust statistic. Two types of regression models have been applied to test for associations between flowering, temperature and time: flowering day regressed on year and flowering day regressed on temperature. Most studies analyzed the effect of temperature by averaging temperatures from three months prior to the date of flowering. On average, published studies have used 55 herbarium specimens per species to characterize changes in phenology over time, but in many cases fewer specimens were used. Geospatial grid data are increasingly being used for determining average temperatures at herbarium specimen collection locations, allowing testing for finer scale correspondence between phenology and climate. Multiple studies have shown that inferences from herbarium specimen data are comparable to findings from systematically collected field observations. Understanding phenological responses to climate change is a crucial step towards recognizing implications for higher trophic levels and large-scale ecosystem processes. As herbaria are increasingly being digitized worldwide, more data are becoming available for future studies. As temperatures continue to rise globally, herbarium specimens are expected to become an increasingly important resource for analyzing plant responses to climate change.
... Land use may also act as an additional driver of phenological advancement and may further exacerbate the impacts associated with phenological changes (Neil et al., 2010). For example, urbanization may create warmer microclimates resulting in further advancement of phenology (Neil et al., 2010). ...
... Land use may also act as an additional driver of phenological advancement and may further exacerbate the impacts associated with phenological changes (Neil et al., 2010). For example, urbanization may create warmer microclimates resulting in further advancement of phenology (Neil et al., 2010). Together, land-use change and climate change also lead to increases in the prevalence of invasive species and diseases, further challenging floral and faunal communities (Crowl et al., 2008;Patz et al., 2008). ...
Addressing the impacts of climate change on terrestrial species requires knowledge of how climates will change, how species will respond, and what is the scope of actions that can be taken to help species and systems adapt. There is a rapidly growing understanding of how species will respond to projected climatic changes with changes in their phenologies, distributions, population dynamics, interspecific interactions, and disease dynamics. Many management strategies have been proposed for addressing these changes, including general principles such as fostering resilience, practicing adaptive management, and expanding the scale of management as well as more specific recommendations such as increasing landscape connectivity and increasing the extent of reserve networks.
... Herbarium-based phenological studies are invaluable for understanding the effects of climate change on plant species [1][2][3][4][5][6][7][8]. These studies leverage the extensive historical records provided by herbarium specimens, which have shown congruence with ield observations, effectively assessing patterns and mechanisms of plant phenological responses [6,9]. ...
... Herbarium-based phenological studies are invaluable for understanding the effects of climate change on plant species [1][2][3][4][5][6][7][8]. These studies leverage the extensive historical records provided by herbarium specimens, which have shown congruence with ield observations, effectively assessing patterns and mechanisms of plant phenological responses [6,9]. ...
Herbarium records provide a valuable historical database for assessing plant phenology shifts in the context of global climate change. The herbarium specimens, collected from diverse locations and periods, offer comprehensive data illustrating how many plants are altering their blooming times in response to global climate change. The appropriate use and analysis of long-term herbarium records offer an additional dimension for the study of plant phenology through the application of advanced experimental methodologies such as bioinformatics and satellite imagery, statistics, and Artificial Intelligence (AI) which, coupled with field observations, will improve ecosystems evaluation. These efforts can significantly contribute to conservation strategies and climate change mitigation and further support the synchronization of scientific inputs for evaluating the impacts of climate change and its ecological implications.
... Most current knowledge of this interaction is based on remote sensing data, which has broad spatial coverage but a short time span. Longer-term herbarium data have also been used to study the impact of urbanization on phenology, but these studies were limited to local scales (Neil et al., 2010). The work of Park et al. (2023) adds broader-scale evidence to support the previous finding of urbanization advancing plant phenology in colder regions (Li et al., 2019), and additionally further highlights the role of both temperature and precipitation as key components of the climatic background. ...
This article is a Commentary on Park et al. (2023), 239: 2153–2165.
... In contrast, temporal studies can provide an understanding of how different selective pressures have acted on organisms and can highlight the evolutionary processes [30]. By comparing historical and contemporary specimens, studies have demonstrated how urbanization can affect behaviour [31,32], morphology [33,34] and life cycles [35]. The effectiveness of such studies is dependent on the consistency of specimen collection over space and time. ...
Simple Summary: Museums play an important role in research by providing specimens of animals collected across time and space. Traditionally, these collections were used mainly for taxonomy. A contemporary use is to investigate temporal changes in the presence of species during urbanization. We used a study area in Perth, Western Australia, to test whether museum collections of 13 common reptile species were adequate to assess how urbanization in Perth had affected the presence of reptile species. We found that sampling was not adequate to answer this question, with 91% of our study region considered poorly sampled. We encourage a renewed focus on building the collections of museums. Abstract: It has been increasingly popular to use natural history specimens to examine environmental changes. As the current functionality of museum specimens has extended beyond their traditional taxonomic role, there has been a renewed focus on the completeness of biological collections to provide data for current and future research. We used the collections of the Western Australian Museum to answer questions about the change in occurrence of five common reptile species due to the rapid urbanization of Perth. We recorded a significant decline in collection effort from the year 2000 onwards (F = 7.65, p < 0.01) compared to the period 1990-1999. Spatial analysis revealed that only 0.5% of our study region was well sampled, 8.5% were moderately sampled and the majority of the regions (91%) were poorly sampled. By analysing the trend of specimen acquisition from 1950 to 2010, we discovered a significant inconsistency in specimen sampling effort for 13 common reptile species across time and space. A large proportion of past specimens lacked information including the place and time of collection. An increase in investment to museums and an increase in geographically and temporally systematic collecting is advocated to ensure that collections can answer questions about environmental change.
... There is a strong relationship between changes in the timing of natural events, such as leaf unfolding, flowering, fruit ripening, or leaf coloring and fall and changes in regional temperatures . Studies at a spatial scale detected advanced and more extended phenological events (Cochard et al., 2019;Davis et al., 2016;Fisogni et al., 2020;Kondratyeva et (Fitchett and Raik, 2021;Lee, 2017;Lindh et al., 2018;Neil et al., 2010;van Vliet et al., 2014;Xingyuan et al., 2016), as well as those that combined both temporal and spatial analyses also detected earlier phenology events (Comber and Brunsdon, 2015;Jeong et al., 2011;Li et al., 2017;Qiu et al., 2017). Analyzes involving a large time scale associated with data between urban and non-urban populations can be useful for comparing the period in which there were changes in phenology and the events of expansion of urbanization in cities. ...
The urban landscape is becoming the environment most familiar to most of humanity, which has consequences for society, the environment, and biodiversity. Here, we present a systematic review of current research integrating several areas of urban ecology to evaluate how plants are responding to urbanization. We found that most studies were conducted in Europe and North America. The most represented biome was that of Temperate Broadleaf and Mixed Forests. The majority of studies reported negative consequences of urbanization. The Urban Drivers most commonly cited as responsible for changes in plant species and communities were Land Cover Change and Biotic Invasion. In general, urbanization reduces the richness of plant species and pollinators' availability. It also homogenizes the environment, promotes the invasion of non-native species, causes changes in phenological events, and presents difficulties for plant growth. However, some species show evidence of adaptation to these adversities through their phenotypic plasticity and the evolution of traits that make individuals resilient to the urban environment. Although it has been established that urbanization imposes novel selective pressures resulting in unique adaptations to city life, patterns of changes in biodiversity in response to urbanization can vary by region, biomes, city history, and the taxa studied. The Urban Drivers responsible for floristic responses work simultaneously by modifying the environment. Therefore, it is challenging to predict response patterns of plants under urban growth. It is necessary to outline strategies for continuous monitoring to document the progress of species in perpetuating themselves in the face of urbanization.
... Dochází k transportu pylových zrn z městských sídel do venkovských oblastí a naopak (Jochner et al., 2011). V mikroklimatu měst dochází k prodlužování vegetačního období (Han et al., 2013) a k dřívějšímu nástupu vegetace (Fischer et al., 2006;Beaubien, 2013;Neil et al., 2010). V rámci ČR existuje pylová informační služba, která je provozována a garantována Českou iniciativou pro astma, ve spolupráci s Ministerstvem zdravotnictví. ...
... How urbanization affects plant phenology in autumn (e.g., leaf senescence), and thus growing season length (GSL), across large spatial scales is still relatively unexplored (Jochner & Menzel, 2015). Most studies, focusing on temperate and boreal regions, have observed earlier spring plant phenology in urban areas than in rural areas, with evidence from field observations (Gazal et al., 2008), herbarium records (Neil et al., 2010), and satellite images (White et al., 2002). ...
Aim
Urbanization is becoming one of the most important drivers of global environmental change as human population and economic development rapidly increase. However, the effects of urbanization on plant phenology are still poorly understood, especially for leaf senescence and growing season length across large spatial scales. We aimed to fill this knowledge gap by combining in situ observations and remote sensing phenological data.
Location
The United States and Europe.
Time period
2009–2018.
Major taxa studied
Vascular plants.
Methods
We divided the United States and Europe into 10 km by 10 km grid cells. We estimated leaf senescence dates for 93 species, and growing season length for a subset of 54 of these species, for grid cells with enough data using a database with >22 million in situ phenology observations. We also estimated growing season lengths at the community level for the Eastern Temperate Forest ecoregion in the US using remote sensing data. We then investigated effects of urbanization (using human population density as a proxy), temperature, and their interactions on leaf senescence and growing season lengths using linear mixed models.
Results
Urbanization and warmer regional temperature both delayed plant leaf senescence. In addition, the effects of urbanization on leaf senescence and growing season lengths depended on climate context: urbanization delayed leaf senescence and extended growing season length in cold regions; however, urbanization advanced leaf senescence and shortened growing season length in warm regions, implying the positive effects of urbanization on growing season length in cold regions may be weaker in a warmer future.
Main conclusions
Our study provides strong empirical evidence that the influence of urbanization on plant phenology and growing season length varies with regional temperature. Our results have important implications for predicting plant phenology and growing season length in a warmer and more urbanized future.
... In stickleback fish and minnows, anthropogenic change to aquatic habitats resulted in varied phenotypic changes in body morphology (Cureton & Broughton, 2014;Kern & Langerhans, 2018;Kitano et al., 2008;Pease, Grabowski, Pease, & Bean, 2018). In urban-living non-native plants, changes in phenology, notably early onset of flowering, were linked to the influences of urban heat islands (Lavoie & Lachance, 2006;Neil, Landrum, & Wu, 2010). ...
... Numerous observational studies have reported urban-rural phenological differences in Africa (Gazal et al., 2008), Europe (Comber & Brunsdon 2015;Gazal et al., 2008;Jochner et al., 2012;Menzel & Fabian 1999;Roetzer et al., 2000), Asia (Gazal et al., 2008;Jeong et al., 2011;Omoto & Aono 1990), and North America (Gazal et al., 2008;Neil et al. 2010;Primack et al., 2004). ...
Urban land cover contributes to higher temperatures in urban areas compared to adjacent rural
areas, which can cause an earlier start of the growing season for urban vegetation. Variations in plant
community characteristics between urban and rural areas also produce intra-urban differences in
vegetation phenophases, although few studies have investigated differences in phenology between plant
functional types in multiple urban environments. In this study I used an exploratory analysis based on the
Landsat Phenology Algorithm and weather station data to quantify differences in leaf-onset dates for
different plant functional types in the New York City Metropolitan Area. The results demonstrate that
Landsat can be used to identify urban-rural variations in leaf-onset for different plant functional types,
and that these variations are driven by different climate variables depending on plant functional type.
Furthermore, results from such analyses suggest that long-term changes in leaf onset vary across different
plant functional types—i.e., grasslands may be advancing at a slower rate than forests.
Keywords: urban heat island; vegetation phenology; Landsat
... Over the past decade, herbarium records have become a popular source of historical plant phenology data for global change research (Primack et al. 2004, Miller-Rushing et al. 2006, Lavoie and Lachance 2006, Gallagher et al. 2009, Neil et al. 2010, Robbirt et al. 2011, Calinger et al. 2013, Everill et al. 2014, Hart et al. 2014. Herbarium specimens include dates and collection locations, are found among natural history collections all over the globe, and have been collected over long time scales (more than a century in North America and multiple centuries in Europe, for example). ...
A rapidly changing climate and human disturbance patterns have accelerated the spread
of invasive plants species in Alaska. Non-native plant invasions can disrupt pollinator services to native plants and have the potential to impact the pollination and fruit set in berry species important for subsistence harvest. My dissertation aims to address the dual need for greater understanding of the impacts of invasive plants on pollination of berry species in boreal ecosystems and the need for research on education strategies that best prepare Alaskans to respond to the issue. I integrate an ecological field experiment, a citizen science program where data is used to validate phenology models derived from heraium data, and an invasive plants education experiment testing the effects of a metacognitive learning intervention to provide multiple perspectives that inform the management of invasive plants in Alaska. The ecological field experiment found that invasive Melilotus albus acts as a magnet species for pollinators, which increased seed production in Vaccinium vitis-idaea, slightly decreased pollination in Rhododendron groenlandicum, and had no detectable interactions with Vaccinium uliginosum. The impact M. albus had on R. groenlandicum changed with distance from the invasive plant patch, but the impact on V. vitis-idaea did not. Using data from a statewide citizen science program monitoring the phenology of these species, I found that herbarium-based phenology models were valid for assessing relative shifts in phenology of these species across Alaska. Employing the research on M. albus and the berry species as a test case, I found that students who received the metacognitive learning intervention show long-term improvement in metacognitive skills compared to students in the control group, but that the groups did not differ in their ability to apply resilience thinking skills to the environmental problem-solving. I
synthesized social-ecological resilience and education research to investigate how citizen science and metacognitive learning could contribute to the capacity of Alaskans to respond to socialecological change. Together, the ecology and education research presented here provide diverse perspectives on how to best manage and build the human capacity to manage M. albus near subsistence plant species.
... The differences in plant phenology between rural and urban areas are the subject of research conducted all over the world, both in Europe [10,21,29,30,33,34] and in North America [12,[33][34][35][36] South America [30], Asia [33,[37][38][39] or Africa [33]. However, these studies, which are mainly based on the observations of one or several species, do not aim to capture the variability within cities [21,40]. ...
The differences in plant phenology between rural and urban areas are the subject of research conducted all over the world. There are few studies aimed at assessing the impact of the urban heat island on plant vegetation only in urban areas. The aim of this study is to assess the impact of the distance from the city center and the form of land cover on the phenological development of trees using the example of the horse chestnut (Aesculus hippocastanum L.). The research area covered the entire city of Wrocław. In order to best capture the impact of the distance from the city center on the rate of changes of individual phenophases, 3 areas were designated-at a distance of 1 km, 2 km and 5 km. The study assessed the average duration of individual phenological phases along with the variability characteristics for leafing, flowering and fruiting in relation to the designated zones and classified forms of land cover based on mean value (̅) and standard deviation (± SD) in individual weeks of the year. For the leafing and flowering phases, the frequency of the occurrence of phases in individual weeks of the year was analyzed in relation to the designated zones and classified land use methods. The results obtained on the basis of phenological observations carried out in 2017 in Wrocław confirmed the extension of the period of vegetation in the city center in relation to its peripheries. Trees growing in road lanes entered the vegetation period later and defoliated faster, which confirms the negative impact of street conditions on the development of trees in urban space. Thus, the growing season in road lanes is shorter and due to the 1-year observation period, it is justified to conduct further observations.
... However, the environment of the city is extremely aggressive for plants. The impact of a complex of abiotic and biotic factors leads to a decrease in decorative properties, often the death of plants [11][12][13]. The selection of the assortment requires an integrated approach based on the formation of high-quality, healthy planting material, in order to maximize the potential of ornamental plants adapted to growing conditions of the particular area [14,15]. ...
A strategically important task of nursery in the modern realities of urban development, perspectivization and greening of landscape design of urban ecosystems, is the cultivation of high-quality planting material of ornamental crops in an optimally short time. Researches on improving seedling production technology have actual and practical importance in solving these problems. Scientifically-based measures, including optimization of soil conditions by applying vermicompost obtained from sewage sludge, buckwheat husk and ash using earthworms from the family Lumbricidae , in combination with buckwheat husk ash, as well as treatment with immunomodulating bioactive substances “Mival-agro”, “Gumi”, “Lignohumate”, allowed to increase plant survival, improve biometric indicators and obtain seedlings of the 1st commercial grade with the possibility of using them for special landings (solitaire, mixborder).
... Such herbarium-based phenological studies provide an improved understanding of the impacts of climate change warming over broad time periods. These are two major types: i) based on the assessment of a group of species (Primack et al., 2004;Bolmgren and Lonnberg, 2005;Miller-Rushing et al., 2006) and ii) involves patterns of the individual species (Gallagher et al., 2009;Neil et al., 2010;Robbirt et al., 2011;Gaira et al., 2014;Davis et al., 2015). However, herbarium records are critical to analyzing the sequence of phenological change, since different botanists introduced selection biases inherent to collected specimens under non-experimental conditions. ...
Regarding the effects of warming on phenology, essentially that climate warming is advancing vegetation phenology around the globe, and case studies of specific species/regions work to gauge this impact. Thus, we attempted to demonstrate phenological patterns of selected 4 alpine/sub-alpine and 4 temperate medicinal herbs based on higher medicinal value of Indian Himalayan Region (IHR) using total 654 herbarium records and applied Generalized Additive Model (GAM) as non-normal and non-linear application. The GAMs demonstrated an advancement in the flowering time for alpine/sub-alpine species (Arnebia benthamii, Meconopsis aculeate, Podophyllum hexandrum) and temperate species (Delphinium denudatum and Dioscorea deltoidea), while delayed flowering for Swertia cordata (p < 0.001). Combining the herbarium records, the model significantly projected advancement in flowering time (21–25 days) over the last 100 years only for alpine/sub-alpine species (p < 0.0001). However, the relationship between flowering time and warming winter temperature was predicted advancement in flowering time for alpine/sub-alpine species (6–10 days per 1 °C) and temperate species (8–11 days per 1 °C). The results reveal that long-term herbarium records may be considered as a useful tool for predicting the possible impact of climate change on plant phenology in the IHR using GAM approach.
... Urban habitat characteristics can also impact the phenology of plant-pollinator interactions. Concerning plants, the warmer urban climate (through the presence of an urban heat island, hereafter UHI) may either advance or delay (Jochner & Menzel, 2015;Neil, Landrum, & Wu, 2010) plant flowering phenology. Moreover, the year-round presence of ornamental plants in urban green spaces may extend the availability of floral resources for pollinating insects (Tasker, Reid, Young, Threlfall, & Latty, 2020). ...
Urban habitat characteristics create environmental filtering of pollinator communities.
They also impact pollinating insect phenology through the presence of an
urban heat island and the year-round availability of floral resources provided by
ornamental plants.
Here, we monitored the phenology and composition of pollinating insect communities
visiting replicates of an experimental plant assemblage comprising two
species, with contrasting floral traits: Sinapis alba and Lotus corniculatus, whose
flowering periods were artificially extended. Plant assemblage replicates were set
up over two consecutive years in two different habitats: rural and densely urbanized,
within the same biogeographical region (Ile-de-France region, France).
The phenology of pollination activity, recorded from the beginning (early March)
to the end (early November) of the season, differed between these two habitats.
Several pollinator morphogroups (small wild bees, bumblebees, honeybees) were
significantly more active on our plant sets in the urban habitat compared to the
rural one, especially in early spring and autumn. This resulted in different overall
reproductive success of the plant assemblage between the two habitats. Over
the course of the season, reproductive success of S. alba was always significantly
higher in the urban habitat, while reproductive success of L. corniculatus was significantly
higher in the urban habitat only during early flowering.
These findings suggest different phenological adaptations to the urban habitat
for different groups of pollinators. Overall, results indicate that the broadened
activity period of pollinating insects recorded in the urban environment could enhance
the pollination function and the reproductive success of plant communities
in cities.
... In stickleback fish and minnows, anthropogenic change to aquatic habitats resulted in varied phenotypic changes in body morphology (Cureton & Broughton, 2014;Kern & Langerhans, 2018;Kitano et al., 2008;Pease, Grabowski, Pease, & Bean, 2018). In urban-living non-native plants, changes in phenology, notably early onset of flowering, were linked to the influences of urban heat islands (Lavoie & Lachance, 2006;Neil, Landrum, & Wu, 2010). ...
Urban environments are among the fastest changing habitats on the planet, and this change has evolutionary implications for the organisms inhabiting them. Herein, we demonstrate that natural history collections are critical resources for urban evolution studies. The specimens housed in these collections provide great potential for diverse types of urban evolution research, and strategic deposition of specimens and other materials from contemporary studies will determine the resources and research questions available to future urban evolutionary biologists. As natural history collections are windows into the past, they provide a crucial historical timescale for urban evolution research. While the importance of museum collections for research is generally appreciated, their utility in the study of urban evolution has not been explicitly evaluated. Here, we: A) demonstrate that museum collections can greatly enhance urban evolution studies, B) review patterns of specimen use and deposition in the urban evolution literature, C) analyze how urban vs. rural and native vs. nonnative vertebrate species are being deposited in museum collections, and D) make recommendations to researchers, museum professionals, scientific journal editors, funding agencies, permitting agencies, and professional societies to improve archiving policies. Our analyses of recent urban evolution studies reveal that museum specimens can be used for diverse research questions, but they are used infrequently. Further, although nearly all studies we analyzed generated resources that could be deposited in natural history collections (e.g. collected specimens), a minority (12%) of studies actually did so. Depositing such resources in collections is crucial to allow the scientific community to verify, replicate, and/or re‐visit prior research. Therefore, to ensure that adequate museum resources are available for future urban evolutionary biology research, the research community–– from practicing biologists to funding agencies and professional societies must make adjustments that prioritize the collection and deposition of urban specimens.
... The urban environment has a great impact on plant phenology. Since 1950, the flowering period of urban garden plants has moved 1~3 days ahead in Europe (Menzel, 2002), and from 1902 to 2006, the flowing period for the shrub species in nearly 1/4 of North America also came much earlier (Neil, 2010). In China, the spring phenological period of most plants in urban areas has moved to an earlier date, and the autumn phenological period was delayed (Caruso, 2004). ...
... Numerous studies have observed earlier flowering in urban areas relative to that in rural areas. Field observations and herbarium records have documented that leaves tend to emerge 4 to 17 d earlier on urban trees than on rural trees for the same species in the United States, Europe, and China (11)(12)(13). However, these studies were restricted to a limited numbers of sites or to simple urban−rural comparisons and thus did not capture much of the interurban variation in phenological change. ...
Urbanization has caused environmental changes, such as urban heat islands (UHIs), that affect terrestrial ecosystems. However, how and to what extent urbanization affects plant phenology remains relatively unexplored. Here, we investigated the changes in the satellite-derived start of season (SOS) and the covariation between SOS and temperature (R
T
) in 85 large cities across the conterminous United States for the period 2001-2014. We found that 1) the SOS came significantly earlier (6.1 ± 6.3 d) in 74 cities and R
T
was significantly weaker (0.03 ± 0.07) in 43 cities when compared with their surrounding rural areas (P < 0.05); 2) the decreased magnitude in R
T
mainly occurred in cities in relatively cold regions with an annual mean temperature <17.3 °C (e.g., Minnesota, Michigan, and Pennsylvania); and 3) the magnitude of urban-rural difference in both SOS and R
T
was primarily correlated with the intensity of UHI. Simulations of two phenology models further suggested that more and faster heat accumulation contributed to the earlier SOS, while a decrease in required chilling led to a decline in R
T
magnitude in urban areas. These findings provide observational evidence of a reduced covariation between temperature and SOS in major US cities, implying the response of spring phenology to warming conditions in nonurban environments may decline in the warming future.
... Many studies have shown that plants tend to flower earlier in warmer conditions (Fitter & Fitter, 2002;Franks, Sim, & Weis, 2007;Roetzer, Wittenzeller, Haeckel, & Nekovar, 2000). Consistently, Neil, Landrum, and Wu (2010) showed that there was a higher proportion of plant species with advanced flowering in (warmer) urban areas compared with the proportion of species with delayed flowering. ...
Abstract Anthropogenic activities in urban ecosystems induce a myriad of environmental changes compared with adjacent rural areas. These environmental changes can be seen as series of abiotic and biotic selection filters affecting the distribution of plant species. What are the attributes of plant species that compose urban communities, compared with rural communities, as related to their ecological affinities (e.g., to temperature, humidity), and reproductive traits (e.g., entomophily, autogamy, floral morphology)? Using a floristic dataset from a citizen science project recording plant species growing spontaneously in the streets, we analyzed the distribution of species according to their ecological requirements and reproductive traits along an urbanization gradient in the Parisian region. We developed an original floral and pollinator typology composed of five floral and four pollinator morphotypes. The proportion of impervious areas, used as a proxy of urbanization, was measured at different spatial scales, to reveal at which spatial scales urbanization is selecting plant traits. We found significant differences in plant communities along the urbanization gradient. As expected with the warmer and drier conditions of urban areas, species with higher affinities to higher temperature, light and nutrient soil content, and lower atmospheric moisture were over‐represented in urban plant communities. Interestingly, all of the significant changes in plant abiotical affinities were the most pronounced at the largest scale of analysis (1,000 m buffer radius), probably because the specific urban conditions are more pronounced when they occur on a large surface. The proportion of autogamous, self‐compatible, and nonentomophilous species was significantly higher in urban plant communities, strongly suggesting a lower abundance or efficiency of the pollinating fauna in urban environments. Last, among insect‐pollinated species, those with relatively long and narrow tubular corollas were disadvantaged in urban areas, possibly resulting from a reduction in pollinator abundance particularly affecting specialized plant–pollinator interactions.
... There have also been some unintended benefits of urbanisation on life history characteristics of urban residents. In temperate regions, some plants now have longer growing seasons in urban areas due to increased temperature and the heat island effects of cities (White et al. 2002;Lu et al. 2006;Neil et al. 2010). Thus, it is important to consider the natural life history conditions of existing wildlife in urbanised landscapes to design specific conservation management programmes, such that life stage-specific habitats which are required for completion of life cycle for several organisms are not degraded. ...
The objective of this book is to review the current state of knowledge on the impact of
climate change on Indian biodiversity. The chapters - contributed by leading ecologists, ecosystem scientists, hydrologists and conservation biologists - cover the threats posed by climate change to ecosystem functions and services, phenology, pollinators, forest dynamics, marine and coastal ecosystems, the Himalayas, freshwater ecosystems, urban ecosystems and wildlife-human conflict.
... Thus, if herbarium specimens strongly emphasise certain locations in Nunavut, the phenology recorded on the herbarium specimens may not be representative of the phenology on a broader scale across the Territory. For example, the more accessible communities or coastal regions may experience warmer climates and/or warmer urban microhabitats that could lead to earlier phenology than more remote or inland areas (Edlund and Alt, 1989;Hertzman, 1997;Woo and Ohmura, 1997;Atkinson and Gajewski, 2002;Przybylak, 2003;Neil et al., 2010). ...
Premise of the Study
Herbarium specimens are increasingly used in phenological studies. However, natural history collections can have biases that influence the analysis of phenological events. Arctic environments, where remoteness and cold climate govern collection logistics, may give rise to unique or pronounced biases.
Methods
We assessed the presence of biases in time, space, phenological events, collectors, taxonomy, and plant traits across Nunavut using herbarium specimens accessioned at the National Herbarium of Canada (CAN).
Results
We found periods of high and low collection that corresponded to societal and institutional events; greater collection density close to common points of air and sea access; and preferences to collect plants at the flowering phase and in peak flower, and to collect particular taxa, flower colours, growth forms, and plant heights. One‐quarter of collectors contributed 90% of the collection.
Discussion
Collections influenced by temporal and spatial biases have the potential to misrepresent phenology across space and time, whereas those shaped by the interests of collectors or the tendency to favour particular phenological stages, taxa, and plant traits could give rise to imbalanced phenological comparisons. Underlying collection patterns may vary among regions and institutions. To guide phenological analyses, we recommend routine assessment of any herbarium data set prior to its use.
... One potential way to overcome the constraints of long-term field observational data on phenophases is by using historical records in herbaria and museums (Davis et al., 2015;Meineke et al., 2018aMeineke et al., , 2019. Although such records have not necessarily been collected expressly for phenological investigations, and therefore present their own biases (Daru et al., 2018;Panchen et al., 2019), a significant body of literature now exists in which historical records have potential for investigating climaterelated phenological trends across plant species (Primack et al., 2004;Bolmgren and Lonnberg, 2005;Coleman and Brawley, 2005;Lavoie and Lachance, 2006;Miller-Rushing et al., 2006;Bowers, 2007;Houle, 2007;Kauserud et al., 2008;Gallagher et al., 2009;Neil et al., 2010;Park and Mazer, 2018). Like observational studies, however, most herbarium-based studies on plant phenology are based on collections from temperate parts of the northern and southern hemispheres (see Willis et al., 2017 and references therein). ...
Premise of the Study
Herbarium specimens are increasingly used as records of plant flowering phenology. However, most herbarium‐based studies on plant phenology focus on taxa from temperate regions. Here, we explore flowering phenologic responses to climate in the subtropical plant genus Protea (Proteaceae), an iconic group of plants that flower year‐round and are endemic to subtropical Africa.
Methods
We present a novel, circular sliding window approach to investigate phenological patterns developed for species with year‐round flowering. We employ our method to evaluate the extent to which site‐to‐site and year‐to‐year variation in temperature and precipitation affect flowering dates using a database of 1727 herbarium records of 25 Protea species. We also explore phylogenetic conservatism in flowering phenology.
Results
We show that herbarium data combined with our sliding window approach successfully captured independently reported flowering phenology patterns (r = 0.93). Both warmer sites and warmer years were associated with earlier flowering of 3–5 days/°C, whereas precipitation variation had no significant effect on flowering phenology. Although species vary widely in phenological responsiveness, responses are phylogenetically conserved, with closely related species tending to shift flowering similarly with increasing temperature.
Discussion
Our results point to climate‐responsive phenology for this important plant genus and indicate that the subtropical, aseasonally flowering genus Protea has temperature‐driven flowering responses that are remarkably similar to those of better‐studied northern temperate plant species, suggesting a generality across biomes that has not been described elsewhere.
... contains supplementary material, which is available to authorized users. efforts have focused on Mediterranean climates in Spain (Gordo and Sanz 2010) and California (Cleland et al. 2006), subtropical China and India (Hart et al. 2014;Gaira et al. 2014;Chen et al. 2017), coastal Australia (Rumpff et al. 2010), and xeric regions in the western USA (Neil et al. 2010;Munson and Long 2016). This study examines plant phenological sensitivity to temperature and precipitation change in the US Southeastern Coastal Plain (SECP; Fig. 1). ...
Plant phenological shifts (e.g., earlier flowering dates) are known consequences of climate change that may alter ecosystem functioning, productivity, and ecological interactions across trophic levels. Temperate, subalpine, and alpine regions have largely experienced advancement of spring phenology with climate warming, but the effects of climate change in warm, humid regions and on autumn phenology are less well understood. In this study, nearly 10,000 digitized herbarium specimen records were used to examine the phenological sensitivities of fall- and spring-flowering asteraceous plants to temperature and precipitation in the U.S. Southeastern Coastal Plain. Climate data reveal warming trends in this already warm climate, and spring- and fall-flowering species responded differently to this change. Spring-flowering species flowered earlier at a rate of 1.8-2.3 days per 1°C increase in spring temperature, showing remarkable congruence with studies of northern temperate species. Fall-flowering species flowered slightly earlier with warmer spring temperatures, but flowering was significantly later with warmer summer temperatures at a rate of 0.8-1.2 days per 1°C. Spring-flowering species exhibited slightly later flowering times with increased spring precipitation. Fall phenology was less clearly influenced by precipitation. These results suggest that even warm, humid regions may experience phenological shifts and thus be susceptible to potentially detrimental effects such as plant-pollinator asynchrony.
... Several studies found phenology shifts in plant species across different biomes such as tropical (Borchert and Rivera 2001;Boulter et al. 2006), subtropical (Pei et al. 2015), temperate (Menzel et al. 2006), and alpine ecosystems (Hart et al. 2014). Although there are a few phenological studies in desert biomes where rainfall is less than 100 mm per year (Bowers 2005(Bowers , 2007Neil et al. 2010), there have been no similar studies for semi-arid regions. Therefore, this study addresses this gap in knowledge to climate change by assessing the changes in plant phenology responses occurring in a semi-arid region. ...
Climate change has been significantly changing ecosystems. Regarding angiosperms, elevated temperature has affected the flowering time of plants across habitats, where earlier flowering was induced. The impacts of climate change on vegetation are expected to be more pronounced in dry regions because of the high irregularity in precipitation and temperature. Assessment of the effects of the long-term climate change on plants is recently possible due to the increased digitization of historical herbarium specimens. For instance, these herbarium specimens can be used to detect changes in flowering time. In this study, the shifts in flowering time of plant species collected from a semi-arid region in the western USA (the Trans-Pecos ecoregion, Texas, USA) was analyzed using a herbarium database. A total of 7,163 herbarium records from 172 species were examined. Statistically significant shifts were detected in the flowering day for the early flowering stage of 19 species in the semi-arid region from 1900 to 2017. According to t-test results, 9 species delayed flowering ranging between 17 and 50 days, whereas 10 species flowering started flowering ranging from 31 to 55 days earlier (p≤ 0.05). Overall, these results contribute to a better understanding of the expression of plant reproductive strategies by revealing the plant responses to warming, and the ability of plants to respond climate change.
... Numerous studies examined phenological responses of plants using herbarium specimens from several biomes: temperate (Rumpff et al. 2010;Park and Schwartz 2015), tropical (Boulter et al. 2006;Zalamea et al. 2011), desert (Bowers 2007;Neil et al. 2010), alpine (Gallagher et al. 2009Mohandass et al. 2015), and Arctic (Panchen and Gorelick 2017). However, there are no herbarium studies in the subarctic biome (e.g., Alaska) where is predicted to be one of the most affected areas under global climate change (IPCC 2013;Chapin et al. 2014;Baruah et al. 2017). ...
Climate change has been affecting plants over the last century and caused changes in life history features such as the flowering time. Herbarium specimens provide a snapshot of the past environmental conditions during their collection. The collection date in a herbarium specimen is a good proxy to determine the flowering period (phenology). In this study, phenological data from subarctic plant specimens collected over 100 years were gathered by using one of the largest herbarium databases in the World. The collection dates of 7146 herbarium specimens were analyzed and significant shifts in the phenology of subarctic plants were detected. In this study, most of the analyzed 142 species in a subarctic biogeographic region tended to flower earlier in the 1950-2018 period compared to the 1900-1949 as a possible result of the climate change. Flowering time shifted from 8 to 26 days in some species. Changes in flowering time may alter species interactions, community composition, and species distribution in a region. Therefore, results of this study may shed light on the possible shifts in phenology and plant responses under the climate change.
... Herbarium specimens, pressed plants often collected in flower or fruit, provide a reliable historical record of flowering and fruiting phenology for use in phenology-climate change studies (Davis, Willis, Connolly, Kelly, & Ellison, 2015). Many herbarium specimen studies from temperate regions have been used to study flowering time responses to contemporary climate change (Davis et al., 2015;Diskin, Proctor, Jebb, Sparks, & Donnelly, 2012;Gallagher et al., 2009;Hart, Salick, Ranjitkar, & Xu, 2014;Lavoie & Lachance, 2006;MacGillivray, Hudson, & Lowe, 2010;Munson & Sher, 2015;Neil, Landrum, & Wu, 2010;Panchen et al., 2012;Park & Schwartz, 2015;Primack, Imbres, Primack, Miller-Rushing, & Del Tredici, 2004;Robbirt, Davy, Hutchings, & Roberts, 2010). There are, however, few studies on the effects of climate change on the timing of fruiting events (Gallinat, Primack, & Wagner, 2015) and, to our knowledge, no studies that have used herbarium specimens to assess the impacts of climate change on timing of seed dispersal nor on flowering and seed dispersal times of Arctic plants. ...
The pace of climate change in the Arctic is dramatic, with temperatures rising at a rate double the global average. The timing of flowering and fruiting (phenology) is often temperature dependent and tends to advance as the climate warms. Herbarium specimens, photographs, and field observations can provide historical phenology records and have been used, on a localised scale, to predict species’ phenological sensitivity to climate change. Conducting similar localised studies in the Canadian Arctic, however, poses a challenge where the collection of herbarium specimens, photographs, and field observations have been temporally and spatially sporadic. We used flowering and seed dispersal times of 23 Arctic species from herbarium specimens, photographs, and field observations collected from across the 2.1 million km2 area of Nunavut, Canada, to determine (1) which monthly temperatures influence flowering and seed dispersal times; (2) species’ phenological sensitivity to temperature; and (3) whether flowering or seed dispersal times have advanced over the past 120 years. We tested this at different spatial scales and compared the sensitivity in different regions of Nunavut. Broadly speaking, this research serves as a proof of concept to assess whether phenology–climate change studies using historic data can be conducted at large spatial scales. Flowering times and seed dispersal time were most strongly correlated with June and July temperatures, respectively. Seed dispersal times have advanced at double the rate of flowering times over the past 120 years, reflecting greater late-summer temperature rises in Nunavut. There is great diversity in the flowering time sensitivity to temperature of Arctic plant species, suggesting climate change implications for Arctic ecological communities, including altered community composition, competition, and pollinator interactions. Intraspecific temperature sensitivity and warming trends varied markedly across Nunavut and could result in greater changes in some parts of Nunavut than in others.
... Spatial and temporal patterns of floral resources are affected by human modification of the surrounding landscape (Ford et al. 2000;Foley et al. 2005;Tscharntke et al. 2005;Knapp et al. 2012). Increased anthropogenic influence is associated with increases in non-native flora (Kuhman et al. 2010), declines in phylogenetic diversity (Knapp et al. 2012), and advanced onset of flowering (Neil et al. 2010) while changes in forest cover and structure are associated with shifts in understory plant communities including reduced species richness, cover and abundance of native herbs and increased cover of non-native species (Bellemare et al. 2002;Vellend 2005;Kuhman et al. 2011). ...
ContextCultural ecosystem services, many of which depend on biodiversity, are recognized as important but seldom quantified biophysically across landscapes. Furthermore, many ecosystem service models are static, and the supply of cultural ecosystem services may be misrepresented if seasonal shifts in biotic communities are ignored. Objectives
We modeled landscape dynamics of wildflower blooms in a temperate montane landscape to determine (1) how floral resources (wildflower species richness, abundance, timing, and presence of charismatic species) changed over the growing season, (2) how projected wildflower viewing hotspots varied over space and time, and (3) how spatial shifts in floral resources affected potential public access to wildflower viewing. Methods
Data were collected at 63 sites across a rural-to-urban gradient in the Southern Appalachian Mountains (USA). Generalized linear models were used to identify factors affecting floral resources at two temporal scales. Floral resources were projected across the landscape and hotspots of wildflower viewing were quantified using overlay analysis. ResultsFloral resources were affected by topoedaphic conditions, climate, and surrounding building density and changed seasonally. Seasonal models revealed locational shifts in ecosystem service hotspots, which changed the proportion of hotspots accessible to the public and identified wildflower-viewing opportunities unnoticed by static models. Conclusion
Relationships between landscape gradients, biodiversity, and ecosystem service supply varied seasonally, and our models identified cultural ecosystem service hotspots otherwise obscured by simple proxies. Landscape models of biodiversity-based cultural ecosystem services should include seasonal dynamics of biotic communities to avoid under- or over-emphasizing the importance of particular locations in ecosystem service assessments.
... Numerous observational studies have reported urban-rural phenological differences in Africa (Gazal et al 2008), Europe (Menzel and Fabian 1999, Roetzer et al 2000, Gazal et al 2008, Jochner et al 2012, Comber and Brunsdon 2015, Asia (Omoto and Aono 1990, Gazal et al 2008, Jeong et al 2011, and North America (Primack et al 2004, Gazal et al 2008, Neil et al 2010. These studies primarily select one or several species to monitor phenology at discrete points and are not designed to capture variability within urban areas (Mimet et al 2009, Fotiou et al 2011, Comber and Brunsdon 2015. ...
Despite documented intra-urban heterogeneity in the urban heat island (UHI) effect, little is known about spatial or temporal variability in plant response to the UHI. Using an automated temperature sensor network in conjunction with Landsat-derived remotely sensed estimates of start/end of the growing season, we investigate the impacts of the UHI on plant phenology in the city of Madison WI (USA) for the 2012–2014 growing seasons. Median urban growing season length (GSL) estimated from temperature sensors is ~5 d longer than surrounding rural areas, and UHI impacts on GSL are relatively consistent from year-to-year. Parks within urban areas experience a subdued expression of GSL lengthening resulting from interactions between the UHI and a park cool island effect. Across all growing seasons, impervious cover in the area surrounding each temperature sensor explains >50% of observed variability in phenology. Comparisons between long-term estimates of annual mean phenological timing, derived from remote sensing, and temperature-based estimates of individual growing seasons show no relationship at the individual sensor level. The magnitude of disagreement between temperature-based and remotely sensed phenology is a function of impervious and grass cover surrounding the sensor, suggesting that realized GSL is controlled by both local land cover and micrometeorological conditions.
... The urban climate, notably, the urban heat island, solar radiation (in terms of the amount of diffuse versus direct radiation), irrigation, enhanced levels of CO2 and atmospheric deposition of nitrogen, affects the biological processes of photosynthesis and respiration in urban canopies. The phenology of urban vegetation (i.e., time of leaf growth and leaf-fall), which is different to rural surroundings (Gazal et al. 2008, Neil et al. 2010) and the enhanced size of urban vegetation because of elevated CO2 concentrations (documented in Baltimore by George et al. 2009), affect net CO2 sequestration. ...
... However, the presented research has shown that local plants could have released these ragweed pollen grains. If these plants are located in large urban areas, then increased temperatures due to the heat island effect can advance flowering [34], and other environmental variables, e.g. air pollution, can enhance pollen production [35,36] and allergenicity [37]. ...
Introduction
[b][/b][b]Background. [/b][i][/b]Ambrosia artemisiifolia[/i] L. is a noxious invasive alien species in Europe. It is an important aeroallergen and millions of people are exposed to its pollen.
Objective
The main aim of this study is to show that atmospheric concentrations of [i]Ambrosia[/i] pollen recorded in Denmark can be derived from local or more distant sources.
Methods
This was achieved by using a combination of pollen measurements, air mass trajectory calculations using the HYPLIT model and mapping all known Ambrosia locations in Denmark and relating them to land cover types.
Results
The annual pollen index recorded in Copenhagen during a 15-year period varied from a few pollen grains to more than 100. Since 2005, small quantities of Ambrosia pollen has been observed in the air every year. We have demonstrated, through a combination of Lagrangian back-trajectory calculations and atmospheric pollen measurements, that pollen arrived in Denmark via long-distance transport from centres of Ambrosia infection, such as the Pannonian Plain and Ukraine.
Combining observations with results from a local scale dispersion model show that it is possible that Ambrosia pollen could be derived from local sources identified within Denmark.
Conclusions
The high allergenic capacity of Ambrosia pollen means that only small amounts of pollen are relevant for allergy sufferers, and just a few plants will be sufficient to produce enough pollen to affect pollen allergy sufferers within a short distance from the source. It is necessary to adopt control measures to restrict Ambrosia numbers. Recommendations for the removal of all Ambrosia plants can effectively reduce the amount of local pollen, as long as the population of Ambrosia plants is small.
In agriculture crop ecosystems, pollination is the foremost fundamental activity performed by fascinating creatures like bees, butterflies, hoverflies, birds, and bats, ensuring reproductive success in angiosperms. Currently, most pollinators appear in red data books as their population and abundance deplete in the ecosystems. Threats like habitat loss, climate change, urbanization, use of chemical pesticides, pests, and diseases drove their extinction. The decline in the pollinator population may considerably decrease global food production and productivity. Effective and efficient conservation strategies are the key elements to mitigate the threats faced by pollinators in the promotion of pollinator resilience. Here, we explored various conservation strategies that restore the pollinator habitat by following sustainable agricultural practices and some policy interventions. Public awareness and collaborative efforts among governments, NGOs, and the private sector are crucial for successfully implementing and adapting these conservation strategies. By acclimatizing an integrated, collaborative, and convincing approach to pollinator conservation, we can assure and predict ecosystem sustainability and productivity, which eventually supports biodiversity and food security
The research studies on herbarium specimens have unraveled the mysteries hidden in historical treasured specimens, which could not have been possible with the living plants. A plethora of research studies have been carried out on herbarium specimens. The specimens have been instrumental in advancing our comprehension of diverse scientific phenomena, including but not limited to climate change, the impact of the ozone hole, phenological variations, indicators of effective pollination, interactions in pollination processes, antibiotic activity, biodiversity assessments, and the development of evolving conservation strategies. Additionally, they have facilitated investigations into coevolution within plant–insect relationships, allowed for noninvasive anatomical studies, led to the discovery of phytochemicals with commercial significance, provided insights into the migration patterns of plant pathogens, aided our current understanding of the origin of invasive herbivores, and supported research in molecular systematics and evolution. Furthermore, herbarium specimens have been instrumental in addressing issues related to patent claims, among other scientific inquiries. The observations on the trend of research studies on herbarium specimens indicate that several new understandings are likely to emerge in times to come since the specimens are dynamically contributing to the enhancement of the knowledge base. The current review comprehensively covers the fascinating research studies on herbarium specimens, as evidenced by appropriate examples.
Understanding phenological responses of plants to changing temperatures is important because of multiple associated ecological consequences. Cities with their urban heat island can be used as laboratories to study phenological adaptation to climate change. However, previous phenology studies focused on trees and did not disentangle the role of micro-climate and urban structures.
We studied reproductive phenology of dry grassland species in response to micro-climate and urbanization in Berlin, Germany. Phenological stages were recorded weekly at the individual plant level for five native grassland species across 30 dry grassland sites along an urbanization and temperature gradient. We estimated 50% onset probabilities for flowering and seed maturation of populations, and analysed variation in onset dates using regression models.
Early flowering species significantly advanced flowering phenology with increasing mean air temperature but were little influenced by urbanization. By contrast, late-flowering species showed significant phenological responses to both air temperature and urbanization, possibly because micro-climate was most affected by urbanization in late summer. Surprisingly, not all grassland species showed an advanced phenology with increasing intensity of urbanization.
This contradicts observed patterns for urban trees, indicating that phenological shifts in urban areas cannot be generalized from the observation of one growth form or taxonomic group. Growth form appears as a possible determinant of phenological responses. Results suggest that the phenology of dry grassland species may directly respond to the urban heat island, albeit with variable direction and magnitude. This has implications for ecosystem services, shifted allergy seasons, changes of biogeochemical cycles and potential ecological mismatches.
Extensive growth in human population, rapid urbanisation, and climate change mediated extreme weather conditions are the three major challenges the world is facing today. Among these challenges, rapid urbanisation can be seen as playing catalytic role in land‐use changes and waste generation mediating the processes responsible for the global climate change. Rapid conversion of pervious lands to impervious surfaces during the process of urbanisation is deteriorating the inherent ecosystem services of the natural ecosystems provided to the humankind. Moreover, pseudo‐adaptation technologies based on extensive energy consumption and natural resource exploration are further adding to the causes for the happening of the climate change phenomenon. Now the scientific communities and even the common people have developed an understanding of the protection and maintenance of the natural vegetation to mitigate the climate change‐related extreme weather conditions. The concept of urban ecology is getting wider attention in the recent years. Green infrastructure, green space development, and water‐resource maintenance can be seen as the major policy measures for the recent urban developments. In addition, preservation of local floral and faunal diversity by the government and urban inhabitants has also been observed in the recent studies. In this chapter, we will provide a brief understanding of the urbanisation‐climate change nexus. Further, elaboration of the emergent climate change adaptation and mitigation measures to be considered in the urban ecosystems has been done in the latter part of the chapter. A bibliometric analysis was performed for collating the studies related to the urban ecology‐climate change nexus published during the past two decades. Overall, this chapter will be briefly introducing the problems associated with rapid urbanisation in the climate change scenario and the possible nature‐based mitigation strategies with respect to the urban ecology principles.
District Jhelum is located in the extremely diverse province of Punjab, Pakistan, and flowering event in plants is always influenced by the environment. This study was conducted during 2018 to 2020 to investigate the climatic effects on flowering cycle of plants. The main focus of the study was to find out the particular association between flowering phenology of plants and climatic variables. Month-wise phenological response of plants was recorded during frequent field visits at multiple representative microhabitats. The response data is saved as binary data matrix, and mean monthly climatic data is obtained through remote sensing, and analysed by using multivariate analyses like canonical correspondence analysis, hierarchical classification and pseudo-canonical correlation. CCA and Hierarchical classification were applied to assess the importance climatic variations towards the flowering phenological response and potential groups respectively. A total of 404 plant species of 223 genera belonging to 75 plant families were examined. Majority of plant species were found in flowering during the month of March (174 spp.) followed by April (159 spp.) and August (158 spp.), similarly, Summer was the leading season (208 spp.) followed by Monsoon (203 spp.), Spring (181 spp.) and Autumn (157 spp.). CCA results depicted that total variations in the flowering phenology response data were 3.45084, and about 45.6% were explained by the explanatory climatic variables. Wind speed, mean monthly maximum temperature and soil moisture were detected as most influential drivers of flowering phenology in the study area. The current study will be useful for researchers as a major source of knowledge for the conservation of valuable species. Such type of attempts will be supportive to explore the phenological response of plants in various habitats such as forest, hilly, riverine, desert and range lands flora in their future projects.
Studies in plant phenology have provided some of the best evidence for large-scale responses to recent climate change. Over the last decade, more than thirty studies have used herbarium specimens to analyze changes in flowering phenology over time. In this review, we summarize the approaches and applications used to date. Reproductive plant phenology has primarily been analyzed using two summary statistics, the mean flowering day of year and first flowering day of year, but mean flowering day has proven to be a more robust statistic. Three types of regression models have been applied to test for changes in phenology; flowering day regressed on year, flowering day regressed on temperature, and temperature regressed on year. Most studies analyzed the effect of temperature by averaging temperatures from three months prior to the date of flowering, but other approaches may be suitable in some cases. On average, published studies have used 55 herbarium specimens per species to characterize changes in phenology over time, but in many cases fewer specimens were used. Geospatial grid data is increasingly being used for determining average temperatures at herbarium specimen collection locations, allowing testing for finer scale correspondence between phenology and climate. Multiple studies have shown that inferences from herbarium specimen data are comparable to findings from systematically collected field observations. Herbarium specimens are expected to become an increasingly important resource for analyzing plant responses to climate change. As temperatures continue to rise globally, there is a need to understand phenological rates of change in response to warming and implications of these changes, especially in tropical environments where phenological studies are thus far generally lacking.
Urban dry grasslands have a huge importance as providers of ecosystem services to urban inhabitants and are ecosystems which occur spontaneously along the urban-rural gradient. Plant species of different growth forms have been shown to alter their ecological processes as a reaction to urban exposure. One of these reactions is a modification of phenology. Since phenological shift are not only a cause of climate change but also of the urban environment, the study of intra-urban phenology may elucidate mechanisms and implications of future plant trait variation.
In this paper, the influence of the urban environment in terms of micro-climate and urban structure variables on the reproductive phenology of five native grassland species is observed, with a focus on intra-annual variability and species-specificity of impacts. Phenological data was obtained during an observation campaign in 2017 in Berlin, during which five grassland species (perennial and annual herbs/grasses) were observed weekly at the individual level on 30 sites. Moreover, micro- climate was recorded via on-site loggers and different urban structure variables around the sites were extracted in GIS. Phenology data was converted to 50% onset-probabilities and correlated to micro-climate and urban structure.
Main findings are that early flowering species react significantly to air temperature averages of the precedent week but are not influenced by urban structures at all (see graphical abstract). On the other hand, species flowering in late summer are influenced by both, air temperature and urban structure since micro-climate is strongly driven by urban structure in summer.
The results suggest that grassland species directly react to the urban heat island, which is stronger apparent in summer than in spring. The discussion centres around controversies due to delays of phenology for perennial grasses and tries to provide an overview about the entire urban-phenology mechanism. Since grasslands can be easily observed in-situ on the species and individual level, results are precise and certain species can well serve as indicators for urban micro-climate and the UHI.
Phenology is an important ecological indicator for understanding the feedback of plants to climate changes, but observation of plant phenology is not a trivial task, particularly for the large-scale areas of interest. Urban plant phenology monitoring is such a typical case, since massive residents do not necessarily mean enough eligible phenology observers. To handle this traditional challenge, this study attempted those surveillance cameras (SCs) widespread almost in any city all over the world. The schematic plan is to install an automatic software module, which has the function of plant phenology monitoring, as a plug-in into any central unit that wire-controls RGB SCs. The kernel of the module is a general-purposed algorithm capable of deriving the starting and ending dates of the key phenological events of different plants that stand in the field of view of each telecontrolled SC. The kernels of the algorithm comprise deriving phenological indices from the digital number (DN) records by a SC from all of its RGB channels and, then, modeling of plant dynamics based on the proposed novel phase-limited multi-Gaussian model for curve-fitting of phenological phases. In the case of determining the key phenological dates regarding flowering and foliation in this study, tests suggested that the proposed scheme and phenological indices and the programmed software plug-in all worked well. Overall, the feasibility of using the widespread SCs for urban plant phenology monitoring was validated, and the scheme can be further extended to composing phenology observation networks at local or global scales. The solution is of implications for more understanding the interannual rhythms of terrestrial ecosystems as well as the inherent mechanisms of vegetation-climate interactions.
Plant and fungal specimens in herbaria are becoming primary resources for investigating how plant phenology and geographic distributions shift with climate change, greatly expanding inferences across spatial, temporal, and phylogenetic dimensions. However, these specimens contain a wealth of additional data—including nutrients, defensive compounds, herbivore damage, disease lesions, and signatures of physiological processes—that capture ecological and evolutionary responses to the Anthropocene but which are less frequently utilized. Here, we outline the diversity of herbarium data, global change topics to which they have been applied, and new hypotheses they could inform. We find that herbarium data have been used extensively to study impacts of climate change and invasive species, but that such data are less commonly used to address other drivers of biodiversity loss, including habitat conversion, pollution, and overexploitation. In addition, we note that fungal specimens are under‐explored relative to vascular plants. To facilitate broader application of plant and fungal specimens in global change research, we consider the limitations of these data and modern sampling and statistical tools that may be applied to surmount challenges they present. Using a case study of insect herbivory, we illustrate how novel herbarium data may be employed to test hypotheses for which few data exist. With the goal of positioning herbaria as hubs for global change research, we suggest future research directions and curation priorities. This article is protected by copyright. All rights reserved.
Studies in plant phenology have provided some of the best evidence for large-scale responses to recent climate change. Over the last decade, more than thirty studies have used herbarium specimens to analyze changes in flowering phenology over time. In this review, we summarize the approaches and applications used to date. Reproductive plant phenology has primarily been analyzed using two summary statistics, the mean flowering day of year and first flowering day of year, but mean flowering day has proven to be a more robust statistic. Three types of regression models have been applied to test for changes in phenology; flowering day regressed on year, flowering day regressed on temperature, and temperature regressed on year. Most studies analyzed the effect of temperature by averaging temperatures from three months prior to the date of flowering, but other approaches may be suitable in some cases. On average, published studies have used 55 herbarium specimens per species to characterize changes in phenology over time, but in many cases fewer specimens were used. Geospatial grid data is increasingly being used for determining average temperatures at herbarium specimen collection locations, allowing testing for finer scale correspondence between phenology and climate. Multiple studies have shown that inferences from herbarium specimen data are comparable to findings from systematically collected field observations. Herbarium specimens are expected to become an increasingly important resource for analyzing plant responses to climate change. As temperatures continue to rise globally, there is a need to understand phenological rates of change in response to warming and implications of these changes, especially in tropical environments where phenological studies are thus far generally lacking. PeerJ Preprints | https://doi.org/10.7287/peerj.preprints.3425v1 | CC BY 4.0 Open Access | rec
The timing of phenological events, such as leaf-out and flowering, strongly influence plant success and their study is vital to understanding how plants will respond to climate change. Phenological research, however, is often limited by the temporal, geographic, or phylogenetic scope of available data. Hundreds of millions of plant specimens in herbaria worldwide offer a potential solution to this problem, especially as digitization efforts drastically improve access to collections. Herbarium specimens represent snapshots of phenological events and have been reliably used to characterize phenological responses to climate. We review the current state of herbarium-based phenological research, identify potential biases and limitations in the collection, digitization, and interpretation of specimen data, and discuss future opportunities for phenological investigations using herbarium specimens.
Plant phenology is an indicator of climate change. Both global warming and extreme climate lead to a critical change in plant phenological characteristics. It is of great importance to elucidate the evolution and mechanism of plant phenology in response to climate change. Natural plant phenological system contains the most direct and effective ecophysiological evidences as a product of global environmental change, which acts as an important complement to instrumental records. Plant phenological performance is extensively considered as a series of life history strategies for plants in a changing environment, which is in general closely related to reproduction of plant population and maintenance of biological diversity. It is highly sensitive to climate change and displays fine adaptability to the change as well. The combination of current phenological database with historical phenological records provides a facility to reveal the coupling relationship between climate change and plant phenological cycle. Previous studies showed that long-term located observation and relevant integrated analysis on plant phenological performance would help reveal the ecological adaptive characteristics of plant phonology, and assess the positive and negative feedbacks between plant phenology and climate change. With the rise of global change ecology in recent years, great efforts have been made on quantitatively assessing material production and carbon cycle in ecosystem in field of plant phenology, particularly underlying that interaction between plant phenological cycle and carbon cycle in ecosystem has become a hot issue. This paper summarizes major progresses in plant phenology under global change and proposes a few domestic and international hot issues in this field. The research interest of plant phenology has gradually shifted the focus from previous field observations and preliminary statistical analysis to current environmental outcome assessement and regulatory mechanism investigation of phenological cycle. The methodology of plant phenology has been upgraded from the superficial description on the response of plant phenological cycle to climate change to the coupling exploration on plant phenology at the multi-scale and multi-element scales. With the development of interdisciplinary research, plant phenology has been extended to a systematic evaluation on the impacts of phenological changes on ecosystems, climatic change, agricultural production and even human health. With these transitions, a few key issues has been raised accordingly, such as the differentiate contribution of atmospheric temperature and photoperiod to plant phenological cycle in different temperature belts, the nonlinear characteristics of the change in plant phenology versus climate change, the complexity of plant phenology at the community level, as well as the importance of crop phenology in agricultural ecosystems. It can be argued that the initiative of plant phenology would play a critical role in practical fields such as agricultural production, human health and landscape design, but also significantly boosts the progress in interdisciplinary research involved in ecology, climatology and geography. Finally, a few recommendations are proposed in terms to the construction of phenological observation network, the exploitation and application of new technologies and the integration of relevant research programs.
CAP LTER focuses on an arid-land ecosystem profoundly influenced, even defined, by the presence and activities of humans and is one of only two LTER sites that specifically studies the ecology of an urban system. In this large-scale project, biological, physical, and social scientists are working together to study the structure and function of the urban ecosystem, to assess the effects of urban development on surrounding agricultural and desert lands, and to study the relationship and feedbacks between human decisions and ecological processes.
Our interdisciplinary investigations into the relationship between land-use decisions and ecological consequences in the rapidly growing urban environment of Phoenix are of broad relevance for the study of social ecological systems and cites in particular. Refinements in our conceptual model of social ecological systems focuses our attention on recognizing the scales and periodicities of ecological and human phenomena, understanding the means and impacts of human control of variability in space and time, and finally an evaluation of the resilience of various aspects of socio-ecological systems especially their vulnerabilities and their potential for adaptive learning.
Human activities dramatically change the abundance, diversity, and composition of species. However, little is known about
how the most intense human activity, urbanization, alters food webs and trophic structure in biological communities. Studies
of the Phoenix area, situated amid the Sonoran Desert, reveal some surprising alterations in the control of trophic dynamics.
Species composition is radically altered, and resource subsidies increase and stabilize productivity. Changes in productivity
dampen seasonal and yearly fluctuations in species diversity, elevate abundances, and alter feeding behaviors of some key
urban species. In urban systems—in contrast to the trophic systems in outlying deserts, which are dominated by limiting resources—predation
by birds becomes the dominant force controlling arthropods on plants. Reduced predation risk elevates the abundance of urban
birds and alters their foraging behavior such that they exert increased top-down effects on arthropods. Shifts in control
of food web dynamics are probably common in urban ecosystems, and are influenced by complex human social processes and feedbacks.
Because of rapid growth and urbanization of Atlanta, Georgia, over the past few decades, the city has developed a pronounced urban heat island (UHI) that has been shown to enhance and possibly to initiate thunderstorms. This study attempts to find patterns and causes of Atlanta's induced precipitation that might not have been initiated otherwise. Land use maps, radar reflectivity, surface meteorological data, upper-air soundings, and airmass classification (spatial synoptic classification) types are all used to determine when, where, and why precipitation is initiated by Atlanta. Findings illustrate significant spatial and temporal patterns based on a 5-yr climatological description of events. July had the most events, with a diurnal peak just after local midnight. Low-level moisture, rather than UHI intensity, appears to be the most important factor for UHI-induced precipitation. However, UHI intensity also plays an important role. Events tended to occur under atmospheric conditions that were more unstable than those on rain-free days but not unstable enough to produce widespread convection.
Two Long-Term Ecological Research (LTER) sites now include urban areas (Baltimore, Maryland and Phoenix, Arizona). A goal of LTER in these cities is to blend physical and social science investigations to better understand urban ecological change. Research monitoring programs are underway to investigate the effects of urbanization on ecosystems. Climate changes in these urban areas reflect the expanding population and associated land surface modifications. Long-term urban climate effects are detectable from an analysis of the GHCN (Global Historical Climate Network) database and a comparison of urban versus rural temperature changes with decadal population data. The relation of the urban versus rural minimum temperatures (Delta Tmin(u-r)) to population changes is pronounced and non-linear over time for both cities. The Delta Tmax(u-r) data show no well-defined temporal trends.
We developed two sets of regression models for flowering and fruiting of arid zone trees and shrubs, based on (i) rainfall in the current and preceding seasons and (ii) soil moisture lagged over varying time periods combined with mean maximum temperature and daylength in the month prior to phenological observations. Using up to 4 years of flowering and fruiting records, we found that both approaches identified responses matching those reported in two other long-term data sets or in the literature, for some species but not for all. The second approach appeared to provide better correlations than the first but we were unable to predict flowering and fruiting effectively. Flowering and fruiting of central Australian trees and shrubs were least in late summer, creating potential limitations on animal populations dependent on them for food. With better predictive capabilities, there is some scope for managing the trees and shrubs for particular purposes. However, very long-term phenological records are needed to improve predictions.
Presents a series of hypotheses which examine possible evolutionary causes and consequences of different phenological patterns. Evidence is also summarised regarding the environmental and genetic controls of timing, since these are the proximate factors that can influence the evolution of such patterns, followed by discussion of the relationships of these three elements to the whle life cycle of the plant, considered in terms of ecological and evolutionary constraints (eg the effects of resource limitation, contraints of morphology, phenological correlations, and genetic correlations).-P.J.Jarvis
This article explores the possibility of urbanization- and irrigation-induced increases in summer precipitation totals in central Arizona. Maximum precipitation impacts are hypothesized to occur downwind of the Phoenix area in the Lower Verde basin. Results from statistical tests indicate that summer precipitation totals in the Lower Verde basin are greater than totals in nearby basins. Precipitation totals in the basin also appear to be equivalent to totals at more monsoon-impacted stations in eastern Arizona. While this research is preliminary, the results do provide encouraging evidence of the existence of anthropogenically enhanced summer precipitation in central Arizona.
Studies of flowering and leafing phenology have dramatically increased during the last few decades because changes in plant
phenology can be indicative of possible effects of climate change at multiple scales. This article reviews the available literature
focusing on the effects of urbanization on flowering phenology. The literature of flowering phenology in urban environments
suggests that spring-blooming plants in a variety of ecosystems in North America, Europe, and China tend to bloom earlier
in the city than in the surrounding un-urbanized habitat. Moreover, ephemerals, early spring bloomers, and insect-pollinated
plants in these environments tend to be more sensitive than perennials, mid- or late-spring bloomers, and wind-pollinated
plants. Researchers attribute advanced flowering in urban environments to the Heat Island Effect. The potential ecological
consequences of changes in flowering phenology in urbanized areas are not well understood or explicitly studied. However,
studies in global biology have suggested that climate change may result in a series of important ecological consequences as
well as human-related problems such as earlier and extended allergy seasons. More field-based studies are needed to elucidate
this issue.
To understand how urbanization has transformed the desert landscape in the central Arizona – Phoenix region of the United States, we conducted a series of spatial analyses of the land-use pattern from 1912–1995. The results of the spatial analysis show that the extent of urban area has increased exponentially for the past 83 years, and this urban expansion is correlated with the increase in population size for the same period of time. The accelerating urbanization process has increased the degree of fragmentation and structural complexity of the desert landscape. To simulate land-use change we developed a Markov-cellular automata model. Model parameters and neighborhood rules were obtained both empirically and with a modified genetic algorithm. Land-use maps for 1975 and 1995 were used to implement the model at two distinct spatial scales with a time step of one year. Model performance was evaluated using Monte-Carlo confidence interval estimation for selected landscape pattern indices. The coarse-scale model simulated the statistical patterns of the landscape at a higher accuracy than the fine-scale model. The empirically derived parameter set poorly simulated land-use change as compared to the optimized parameter set. In summary, our results showed that landscape pattern metrics (patch density, edge density, fractal dimension, contagion) together were able to effectively capture the trend in land-use associated with urbanization for this region. The Markov-cellular automata parameterized by a modified genetic algorithm reasonably replicated the change in land-use pattern.
Urbanization is arguably the most dramatic form of land transformation that profoundly influences biological diversity and
human life. Quantifying landscape pattern and its change is essential for the monitoring and assessment of ecological consequences
of urbanization. Combining gradient analysis with landscape metrics, we attempted to quantify the spatial pattern of urbanization
in the Phoenix metropolitan area, Arizona, USA. Several landscape metrics were computed along a 165 km long and 15 km wide
transect with a moving window. The research was designed to address four research questions: How do different land use types
change with distance away from the urban center? Do different land use types have their own unique spatial signatures? Can
urbanization gradients be detected using landscape pattern analysis? How do the urban gradients differ among landscape metrics?
The answers to these questions were generally affirmative and informative. The results showed that the spatial pattern of
urbanization could be reliably quantified using landscape metrics with a gradient analysis approach, and the location of the
urbanization center could be identified precisely and consistently with multiple indices. Different land use types exhibited
distinctive, but not necessarily unique, spatial signatures that were dependent on specific landscape metrics. The changes
in landscape pattern along the transect have important ecological implications, and quantifying the urbanization gradient,
as illustrated in this paper, is an important first step to linking pattern with processes in urban ecological studies.
Global climate change is likely to alter the phenological patterns of plants due to the controlling effects of climate on plant ontogeny, especially in an urbanized environment. We studied relationships between various phenophases (i.e., seasonal biological events) and interannual variations of air temperature in three woody plant species (Prunus davidiana, Hibiscus syriacus, and Cercis chinensis) in the Beijing Metropolis, China, based on phenological data for the period 1962–2004 and meteorological data for the period 1951–2004. Analysis of phenology and climate data indicated significant changes in spring and autumn phenophases and temperatures. Changes in phenophases were observed for all the three species, consistent with patterns of rising air temperatures in the Beijing Metropolis. The changing phenology in the three plant species was reflected mainly as advances of the spring phenophases and delays in the autumn phenophases, but with strong variations among species and phenophases in response to different temperature indices. Most phenophases (both spring and autumn phenophases) had significant relationships with temperatures of the preceding
months. There existed large inter- and intra-specific variations, however, in the responses of phenology to climate change. It is clear that the urban heat island effect from 1978 onwards is a dominant cause of the observed phenological changes. Differences in phenological responses to climate change may cause uncertain ecological consequences, with implications for ecosystem stability and function in urban environments.
Previous studies have found that urbanization often decreases net primary production (NPP), an important integrative measure of ecosystem functioning. In arid environments, however, urbanization may boost productivity by introducing highly productive plant communities and weakening the coupling of plant growth to naturally occurring cycles of water and nutrients. We tested these ideas by comparing NPP estimated for natural and anthropogenic land covers in the Phoenix metropolitan region of USA using MODIS NDVI data and a simplified parametric NPP model. Most anthropogenic land covers exhibited higher production than the natural desert. Consequently, the combined urban and agricultural areas contributed more to the regional primary production than the natural desert did in normal and dry years, whereas this pattern was reversed in wet years. Primary production of this urban landscape was only weakly correlated with rainfall, but strongly with socio-economic variables. Our productivity estimates agreed well with NPP predicted by a process-based ecosystem model for the area. Significant uncertainties, however, remain due to extremely high heterogeneity of urban vegetation. Nevertheless, our results clearly show that urbanization may not only increase regional NPP and disrupt the coupling between vegetation and precipitation, but also increase spatial heterogeneity of NPP in this arid region.
Museum specimens collected in the past may be a valuable source of information on the response of species to climate change. This idea was tested by comparing the flowering times during the year 2003 of 229 living plants growing at the Arnold Arboretum in Boston, Massachusetts, USA, with 372 records of flowering times from 1885 to 2002 using herbarium specimens of the same individual plants. During this period, Boston experienced a 1.5°C increase in mean annual temperature. Flowering times became progressively earlier; plants flowered 8 d earlier from 1980 to 2002 than they did from 1900 to 1920. Most of this shift toward earlier flowering times is explained by the influence of temperature, especially temperatures in the months of February, March, April, and May, on flowering time. Plants with a long flowering duration appear to be as useful for detecting responses to changing temperatures as plants with a short flowering duration. Additional studies using herbarium specimens to detect responses to climate change could examine specimens from specific, intensively collected localities, such as mountain peaks, islands, and unique habitats.
Global warming is affecting natural systems across the world. Of the biological responses to warming, changes in the timing of phenological events such as flowering are among the most sensitive. Despite the recognized importance of phenological changes, the limited number of long-term records of phenological events has restricted research on the topic in most areas of the world. In a previous study in Boston (American Journal of Botany 91: 1260-1264), we used herbarium specimens and one season of field observations to show that plants flowered earlier as the climate warmed over the past 100 yr. In our new study, we found that two extra years of data did not strengthen the explanatory power of the analysis. Analysis of herbarium specimens without any field data yielded results similar to analyses that included field observations. In addition, we found that photographs of cultivated and wild plants in Massachusetts, data similar to that contained in herbarium specimens, show changes in flowering times that closely match independent data on the same species in the same locations. Dated photographs of plants in flower represent a new resource to extend the range of species and localities addressed in global-warming research.
Urban areas are hot spots that drive environmental change at multiple scales. Material demands of production and human consumption alter land use and cover, biodiversity, and hydrosystems locally to regionally, and urban waste discharge affects local to global biogeochemical cycles and climate. For urbanites, however, global environmental changes are swamped by dramatic changes in the local environment. Urban ecology integrates natural and social sciences to study these radically altered local environments and their regional and global effects. Cities themselves present both the problems and solutions to sustainability challenges of an increasingly urbanized world.
Temporal patterns of flower production and the level of fruit set were determined for 20 individuals each of six shrub species (four families) in a semi-deciduous lowland forest in Panama. The species were: Hybanthus prunifolius, Turnera panamensis, Rinorea sylvatica, Psychotria horizontalis. Erythrina costaricensis var. panamensis, and Pentagonia macrophylla. There were two objectives of the study: 1) to compare among species the relation between the individual's flowering pattern and the population's flowering synchrony; and 2) to compare within species the relative influence of the individual's and the population's flowering phenology on the individual's fruit set. The six species differed in number of flowers per individual (mean values for species ranged from 98-2995), how long the individual produced flowers (mean values ranged from 3.5-59.0 days), and synchrony of the individual with its conspecifics (mean values ranged from 0.48-0.95, where value of 1.0 = perfect synchrony). Among the six species, population synchrony increased as the mean duration of an individual's flowering decreased. Population synchrony of the first day, peak (median) day, and the entire flowering period were highly correlated. When comparing individuals within each species, the individual's flower number was the best predictor of fruit set. Neither the individual's length of flower production nor its synchrony with conspecifics added significantly in explaining the variance in fruit set. A regression including the individual's number of flowers, length of flower production, and synchrony with conspecifics as independent variables and the proportion fruit set (and its arcsin transformation) as the dependent variable yielded no significant regressions. The consequences of these widely varying phenological patterns are discussed. Comparisons are made with the temporal patterns observed in other tropical forests.
Climatic and flowering data from a site in the northern Sonoran Desert of southern Arizona were used to define flowering triggers and developmental requirements for 6 woody plants. These formulations were then used to predict flowering dates at a second northern Sonoran Desert site. It was determined that flowering is triggered by rain in Larrea tridentata (DC.) Cov., Fouquieria splendens Engelm., Encelia farinosa A. Gray, Ambrosia deltoidea (A. Gray) Payne and Acacia constricta Benth., and that flowering is triggered by photoperiod in Cercidium microphyllum (Torr.) Rose & Johnst. The base temperature for floral development in L. tridentata, F. splendens, E. farinosa, A. deltoidea and C. microphyllum is about 10⚬C. Their mean degree-day requirements range from 414 to 719. Acacia constricta requires 522 degree-days above 15⚬C. Minimum rainfall triggers varied from 9 mm for Ambrosia to 20 mm for Encelia. Flowering time in C. microphyllum may reflect phylogenetic constraints, while flowering time in F. splendens may be strongly influenced by pollinator availability. Flowering times of the remaining species seem constrained more by climate than by biotic considerations such as phylogeny, seed germination and competition for pollinators.
relative humidity frequency distributions from 43 eastern U.S. locations are examined to derive empirical predictive relationships for the upper end of the scale, as a function of local environmental conditions. Such predictions are needed in order to estimate the fraction of time that certain surfaces may be wet from condensation and thus more susceptible to atmospheric corrosion. For example, SO2 is known to deposit more readily on wet surfaces. The additional constraint of ambient temperature above freezing is imposed, since both SO2 deposition and corrosion are expected to be minimal on frozen surfaces. Factors that influence the frequency of high relative humidity (>80%) in the eastern U.S. were found to include degree of urbanization, latitude, and location near large bodies of water and near airports.
Measurements of vapour pressure, taken four times a day over a 3-year period, were used to investigate the urban influence on diurnal and annual patterns of vapour pressure differences. The examined settlement is a medium-sized city without significant relief in the Great Hungarian Plain. Its regional climate is continental with a long warm season. On the basis of the results, the air in the city centre is more humid than in the rural area both by day and at night for the duration of the whole year. The diurnal pattern shows that the urban excess has its minimum at 01:00 h and its maximum at 19:00 h in the summer months, but similar regular diurnal variation does not exist during the rest of the year. The annual patterns show that the excess increases from January-February to August and then decreases until November-December at each observation time. The differences and variations of urban humidity excess can be explained by different moisture sources and by different energy balances in the urban and rural environments. Unambiguous relationships exist between the variations of urban humidity excess and a regional aridity index, between the variations of humidity excess and the water temperature of the River Tisza crossing the city, as well as between the variations of humidity excess and maximum heat island intensity. The role of combustion processes is also significant, especially in the colder half of the year.
Con el calentamiento de la tierra, la floración en muchos lugares ha cambiado hacia fechas más tempranas. En el norte del Desierto Sonorensis del suroeste de los EEUU suroestes y del noroeste de México, un incremento constante en la temperatura promedia anual desde los ultimos años de la década de 1890 hace floración avanzada en éste lugar más probable. En ésta investigación, modelos fenologícos fureon usado para predecir la fecha anual del la floración del la primavera en el norte del Desierto Sonorensis desde 1894 hasta 2004. Después, ejemplares del herbario fueron examinado como pruebas objetivas del campio predicho en el tiempo de floración. Los modelos fenologícos fueron basado en requistos conocidos de la floración (estímulos climáticos y sumas de calor) del arbustos del Desierto Sonorensis. Según los modelos, la floración pudiera ser avanzada 20–41 días desde 1894 hasta 2004. El análsis de los ejemplares del herbario colecciónados durante el siglo vigésimo sustentó los predicciónes de los modelos. Con tiempo fueron un incremento significativo en la proporción del los ejemplares de arbustos colecciónada con flores en marzo y un diminución significativa en la proporción colecciónada en mayo. Por lo tanto la curva de floración, la proporción de plantas con flores en cada mes, cambió hacia el principio del año entre 1900 y 1999. Éste cambio no podía ser explicado por la actividad de los coleccionistas, quiénes no demostraban una tendencia a estar ni más activos más temprano en el año ni menos activos más tarde en la primavera en los décadas recientes. Con el tiempo la floración más temprana podría tener impactos importantes en los comunidades de las plantas y los animales del Desierto Sonorensis, particularmente con los picaflores migratorios y las dinámicas de las poblaciónes de los arbustos.
Summary • Climatic warming produces significant gradual alterations in the timing of life- cycle events , and here we study the phenological effects of rainfall-pattern changes. •W e conducted ecosystem field experiments that partially excluded rain and runoff during the growing season in a Mediterranean forest and in a mediterranean shrub- land. Studies of time-series of leaf-unfolding, flowering and fruiting over the last 50 yr in central Catalonia were carried out, and greenup onset in the Iberian Peninsula was monitored by satellite images. • Experimental, historical and geographical changes in rainfall produced significant, complex and strongly species-specific, as well as spatially and temporally variable, phenological effects. Among these changes, it was found that in the Iberian Penin- sula, greenup onset changes from spring (triggered by rising temperatures) in the northern cool-wet regions to autumn (triggered by the arrival of autumn rainfalls) in the southern warm-dry regions. Even in the mesic Mediterranean central Catalo- nia (NE of the peninsula) rainfall had a stronger relative influence than temperature on fruiting phenology. • The results show that changes in rainfall and water availability, an important driver of climate change, can cause complex phenological changes with likely far-reaching consequences for ecosystem and biosphere functioning and structure. The seasonal shift in the Iberian Peninsula further highlights this importance and indicates that vegetation may respond to climate change not only with gradual, but also with abrupt temporal and spatial, changes in the timing of greenup onset.
The influence of vegetation on the urban climate was studied in the subtropical city Gaborone, the rapidly expanding capital of Botswana with approximately 200 000 inhabitants. Temperature records from an urban and a rural station were analysed for the period 1985–96. In an attempt to explain possible seasonal change in vegetation, NOAA satellite normalized difference vegetation index imagery was analysed. The present urban influence was investigated with temperature loggers at selected urban and rural sites. In addition, mobile measurements revealed spatial patterns in temperature and humidity for different land uses.
Seasonal patterns of urban–rural differences in minimum temperatures emerge during the period 1994–96, especially during the winter when the heat island effect is largest. It is shown that differences in urban and rural vegetation over the year partly explain this variation. Mobile measurements reveal a weak nocturnal heat island of 2–3 °C during clear and calm nights. There are intra-urban temperature differences that are in the same range as the urban–rural relationship due to the role of vegetation. Evapotranspiration lowers the temperature, which was detected by high humidity in areas of lush vegetation. This becomes apparent at midday, when densely vegetated areas were up to 2 °C cooler than rural sites. An oasis effect, therefore, only exists on a highly local basis. In contrast, parts of the city with sparse vegetation are warmer than the countryside.
There is an apparent opposed effect of rural and urban vegetation, whereby the former is hindering the temperature from falling and the latter is cooling the environment through evapotranspiration. This can be explained by the overwhelming amounts of imported water in the city promoting evaporative cooling. Copyright
Global climate change impacts can already be tracked in many physical and biological systems; in particular, terrestrial ecosystems provide a consistent picture of observed changes. One of the preferred indicators is phenology, the science of natural recurring events, as their recorded dates provide a high-temporal resolution of ongoing changes. Thus, numerous analyses have demonstrated an earlier onset of spring events for mid and higher latitudes and a lengthening of the growing season. However, published single-site or single-species studies are particularly open to suspicion of being biased towards predominantly reporting climate change-induced impacts. No comprehensive study or meta-analysis has so far examined the possible lack of evidence for changes or shifts at sites where no temperature change is observed. We used an enormous systematic phenological network data set of more than 125 000 observational series of 542 plant and 19 animal species in 21 European countries (1971–2000). Our results showed that 78% of all leafing, flowering and fruiting records advanced (30% significantly) and only 3% were significantly delayed, whereas the signal of leaf colouring/fall is ambiguous. We conclude that previously published results of phenological changes were not biased by reporting or publication predisposition: the average advance of spring/summer was 2.5 days decade−1 in Europe. Our analysis of 254 mean national time series undoubtedly demonstrates that species' phenology is responsive to temperature of the preceding months (mean advance of spring/summer by 2.5 days°C−1, delay of leaf colouring and fall by 1.0 day°C−1). The pattern of observed change in spring efficiently matches measured national warming across 19 European countries (correlation coefficient r=−0.69, P<0.001).
Graphical analysis of first-flowering dates of selected garden plants 1946–2002 shows an earlier trend, which appears to be linked to temperature and global warming. Some species, however, seem to buck this trend, which may be linked to photoperiodic response. Combined graphs of species selected at intervals throughout the calendar year reveal a rhythm or wave of several years in Leeds 1946–1962 and a less marked rhythm in Richmond 1961–2002.
Urbanization has profoundly transformed many landscapes throughout the world, and the ecological consequences of this transformation are yet to be fully understood. To understand the ecology of urban systems, it is necessary to quantify the spatial and temporal patterns of urbanization, which often requires dynamic modeling and spatial analysis. In this paper, we describe an urban growth model, the Phoenix Urban Growth Model (PHX-UGM), illustrate a series of model calibration and evaluation methods, and present scenario-based simulation analyses of the future development patterns of the Phoenix metropolitan region. PHX-UGM is a spatially explicit urban landscape model and is a modified version of the Human-Induced Land Transformations (HILT) model originally developed for the San Francisco Bay Area. Using land use and other data collected for the Phoenix area, existing growth rules were selectively modified and new rules were added to help examine key ecological and social factors. We used multiple methods and a multi-scale approach for model calibration and evaluation. The results of the different evaluation methods showed that the model performed reasonably well at a certain range of spatial resolutions (120–480 m). When fine-scale data are available and when landscape structural details are desirable, the 120-m grain size should be used. However, at finer levels the noise and uncertainty in input data and the exponentially increased computational requirements would considerably reduce the usefulness and accuracy of the model. At the other extreme, model projections with too coarse a spatial resolution would be of little use at the local and regional scales. A series of scenario analyses suggest that the Metropolitan Phoenix area will soon be densely populated demographically and highly fragmented ecologically unless dramatic actions are to be taken soon to significantly slow down the population growth. Also, there will be an urban morphological threshold over which drastic changes in certain aspects of landscape pattern occur. Specifically, the scenarios indicate that, as large patches of open lands (including protected lands, parks and available desert lands) begin to break up, patch diversity declines due partly to the loss of agricultural lands, and the overall landscape shape complexity also decreases because of the predominance of urban lands. It seems that reaching such a threshold can be delayed, but not avoided, if the population in the Phoenix metropolitan region continues to grow. PHX-UGM can be used as a tool for exploring the outcome of different urban planning strategies, and the methods illustrated in this paper can be used for evaluating other urban models.
An increase in temperature due to greenhouse effects is manifest in the changes in diurnal, annual and inter-annual patterns, which may alter phenological events in plants. Flowering dates of four tree species, Prunus davidina, Prunus armeniaca, Robinia pseudoacacia and Syringa oblata, were significantly advanced in response to temperature increase over the years 1950–2004 in Beijing, China, due to the impact of urban climate warming. Because both climate warming and the urban heat island effect in winter and early-spring were more rapid than in late-spring and early summer, the dates in early flowering species advanced more quickly than in late flowering species. The early flowering species, P. davidina, advanced by 2.9 days/decade, while the other species advanced by 1.5–2.0 days/decade during 1950–2004. Therefore, the intervals between flowering dates of different species were expanded. P. davidina, flowering in early-spring, was much more sensitive to minimum and average temperatures (2.88–2.96 days/°C), but less sensitive to maximum temperature (2.46 days/°C). R. pseudoacacia, flowering late in the warmer season, was more sensitive to average and maximum temperatures (2.45–2.89 days/°C), but less sensitive to minimum temperature (1.91 days/°C). Statistical analysis showed that, in Beijing, plant flowering is most sensitive to average temperature over 30 days before average blossom date. On the basis of the temperature response curve, the goodness of fitting demonstrates that spring flowering dates can be predicted from the period when temperature is over 0 °C.
The study employs a 108-year precipitation historical data record, global climate observing network observations and satellite data to identify possible anomalies in rainfall in and around two major arid urban areas, Phoenix, Arizona and Riyadh, Saudi Arabia. The analysis reveals that during the monsoon season, locations in northeastern suburbs and exurbs of the Phoenix metropolitan area have experienced statistically significant increases in mean precipitation of 12–14% from a pre-urban (1895–1949) to post-urban (1950–2003) period. Further analysis of satellite-based rainfall rates suggests the existence of the anomaly region (AR) over a 7-year period. The anomaly cannot simply be attributed to maximum topographic relief and is hypothesized to be related to urban-topographic interactions and possibly irrigation moisture. Temperature records suggest that Riyadh has experienced an adjustment in mean temperature in response to the growth of urban surfaces (e.g. the so-called urban heat island effect). While ground-based precipitation records also indicate an upward trend in mean and total precipitation in and around Riyadh in the last 10–15 years, it is difficult to attribute the increase to urbanization because other less urbanized stations in Saudi Arabia also show a similar increase. Recent satellite-based precipitation estimates indicate an AR 50–100 km north of Riyadh, but this study is not robust enough to conclusively link it to urbanization although certain climate-regime attributes suggests that it might be.
Climatic and flowering data from a site in the northern Sonoran Desert of southern Arizona were used to define flowering triggers and developmental requirements for 6 woody plants. These formulations were then used to predict flowering dates at a second northern Sonoran Desert site. It was determined that flowering is triggered by rain in Larrea tridentata (DC.) Cov., Fouquieria splendens Engelm., Encelia farinosa A. Gray, Ambrosia deltoidea (A. Gray) Payne and Acacia constricta Benth., and that flowering is triggered by photoperiod in Cercidium microphyllum (Torr.) Rose & Johnst. The base temperature for floral development in L. tridentata, F. splendens, E. farinosa, A. deltoidea and C. microphyllum is about 10-degrees-C. Their mean degree-day requirements range from 414 to 719. Acacia constricta requires 522 degree-days above 15-degrees-C. Minimum rainfall triggers varied from 9 mm for Ambrosia to 20 mm for Encelia. Flowering time in C. microphyllum may reflect phylogenetic constraints, while flowering time in F. splendens may be strongly influenced by pollinator availability. Flowering times of the remaining species seem constrained more by climate than by biotic considerations such as phylogeny, seed germination and competition for pollinators.
Phenological data have recently emerged as particularly effective tools for studying the impact of climate change on plants, but long phenological records are rare. The lack of phenological observations can nevertheless be filled by herbarium specimens as long as some correction procedures are applied to take into account the different climatic conditions associated with sampling locations. In this study, we propose a new herbarium-based method for reconstructing the flowering dates of plant species that have been collected across large areas. Coltsfoot (Tussilago farfara L.) specimens from southern Quebec were used to test the method. Flowering dates for coltsfoot herbarium specimens were adjusted according to the date of disappearance of snow cover in the region where they were collected and compared using a reference point (the date of earliest snowmelt). In southern Quebec, coltsfoot blooms earlier at present (15-31 d) than during the first part of the 20th century. This phenomenon is likely associated with the climate warming trends recorded in this region in the last century, especially during the last three decades when the month of April became warmer, thereby favoring very early-flowering cases. The earlier flowering of coltsfoot is, however, only noticeable in large urban areas (Montreal, Quebec City), suggesting a strong urban heat island effect on the flowering of this plant. Herbarium specimens are useful phenological indicators; however, the databases should be carefully examined prior to analysis to detect biases or trends associated with sampling locations.
The average first flowering date of 385 British plant species has advanced by 4.5 days during the past decade compared with the previous four decades: 16% of species flowered significantly earlier in the 1990s than previously, with an average advancement of 15 days in a decade. Ten species (3%) flowered significantly later in the 1990s than previously. These data reveal the strongest biological signal yet of climatic change. Flowering is especially sensitive to the temperature in the previous month, and spring-flowering species are most responsive. However, large interspecific differences in this response will affect both the structure of plant communities and gene flow between species as climate warms. Annuals are more likely to flower early than congeneric perennials, and insect-pollinated species more than wind-pollinated ones.
Although controlled laboratory experiments have been conducted to demonstrate the sensitivity of allergenic pollen production to future climatic change (ie, increased CO(2) and temperature), no in situ data are available.
The purpose of this investigation was to assess, under realistic conditions, the impact of climatic change on pollen production of common ragweed, a ubiquitous weed occurring in disturbed sites and the principal source of pollen associated with seasonal allergenic rhinitis.
We used an existing temperature/CO(2) gradient between urban and rural areas to examine the quantitative and qualitative aspects of ragweed growth and pollen production.
For 2000 and 2001, average daily (24-hour) values of CO(2) concentration and air temperature within an urban environment were 30% to 31% and 1.8 degrees to 2.0 degrees C (3.4 degrees to 3.6 degrees F) higher than those at a rural site. This result is consistent with most global change scenarios. Ragweed grew faster, flowered earlier, and produced significantly greater above-ground biomass and ragweed pollen at urban locations than at rural locations.
Here we show that 2 aspects of future global environmental change, air temperature and atmospheric CO(2), are already significantly higher in urban relative to rural areas. In general, we show that regional urbanization-induced temperature/CO(2) increases similar to those associated with projected global climatic change might already have public health consequences; we suggest that urbanization, per se, might provide a low-cost alternative to current experimental methods evaluating plant responses to climate change.
The tale of two climates – Baltimore and Phoenix urban LTER sites Urbanization alters spatiotemporal patterns of ecosystem primary production: A case study of the Phoenix Metropolitan region, USA
- A Brazel
- N Selover
- R Vose
- G K L Heisler
- Neil
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- J Unger
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Urbanization alters spatiotemporal patterns of ecosystem primary production: A case study of the Phoenix Metropolitan region
- K L Neil
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The tale of two climates -Baltimore and Phoenix urban LTER sites
- A Brazel
- N Selover
- R Vose
- G Heisler
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