Species that require long-day conditions to flower are not advancing their flowering phenology as fast as species without photoperiod requirements

BACKGROUND AND AIMS

Over the last few decades, many plant species have shown changes in phenology, such as the date on which they germinate, bud or flower. However, some species are changing more slowly than others, potentially owing to daylength (photoperiod) requirements.

METHODS

We combined data on flowering-time advancement with published records of photoperiod sensitivity to try to predict which species are advancing their flowering time. Data availability limited us to the Northern Hemisphere.

KEY RESULTS

Cross-species analyses showed that short-day plants advanced their flowering time by 1.4 days per decade and day-neutral plants by 0.9 days per decade, but long-day plants delayed their flowering by 0.2 days per decade. However, photoperiod-sensitivity status exhibited moderate phylogenetic conservation, and the differences in flowering-time advancement were not significant after phylogeny was accounted for. Both annual and perennial herbs were more likely to have long-day photoperiod cues than woody species, which were more likely to have short-day photoperiod cues.

CONCLUSIONS

Short-day plants are keeping up with plants that do not have photoperiod requirements, suggesting that daylength requirements do not hinder changes in phenology. However, long-day plants are not changing their phenology and might risk falling behind as competitors and pollinators adapt to climate change.

Seasonal and vertical patterns of water availability and variability determine plant reproductive phenology

BACKGROUND AND AIMS

Changing precipitation regimes can influence terrestrial plants and ecosystems. However, plant phenological responses to changing temporal patterns of precipitation and the underlying mechanisms are largely unclear. This study was conducted to explore the effects of seasonal precipitation redistribution on plant reproductive phenology in a temperate steppe.

METHODS

A field experiment was undertaken with control (C), advanced (AP) and delayed (DP) growing-season precipitation peaks and the combination of AP and DP (ADP). Seven dominant plant species were selected and divided into two functional groups (early- vs. middle-flowering species, shallow- vs. deep-rooted species) to monitor reproductive phenology, including budding, flowering and fruiting dates and the reproductive duration for four growing seasons, 2015-2017 and 2022.

KEY RESULTS

The AP, but not DP treatment advanced the phenological (i.e. budding, flowering and fruiting) dates and lengthened the reproductive duration across the four growing seasons and seven monitored species. In addition, the phenological responses showed divergent patterns among different plant functional groups, which could be attributed to shifts in soil moisture and its variability in different months and soil depths. Moreover, species with lengthened reproductive duration increased phenological overlap with other species, which could have a negative impact on their dominance under the AP treatment.

CONCLUSIONS

Our findings reveal that changing precipitation seasonality could have considerable impacts on plant phenology by affecting soil water availability and variability. Incorporating these two factors simultaneously in the phenology models will help us to understand the response of plant phenology under intensified changing precipitation scenarios. In addition, the observations of decreased dominance for the species with lengthened reproductive duration suggest that changing reproductive phenology can have a potential to affect community composition in grasslands under global change.

Natural and anthropogenic factors influence flowering synchrony and reproduction of a dominant plant in an inter-Andean scrub

PREMISE

Agriculture expansion, livestock, and global change have transformed biological communities and altered, through aerosols and direct deposition, N:P balance in soils of inter-Andean valleys, potentially affecting flowering phenology of many species and thereby flowering synchrony and plant reproduction.

METHODS

We evaluated the influence of variation in temperature and moisture along the local elevational gradient and treatments with the addition of N and P and grazing on flowering synchrony and reproduction of Croton, a dominant shrub of the inter-Andean dry scrub. Along the elevational gradient (300 m difference between the lowest and highest site), we set up plots with and without grazing nested with four nutrient treatments: control and addition of N or P alone or combined N + P. We recorded the number of female and male flowers in bloom monthly from September 2017 to August 2019 to calculate flowering synchrony. We assessed fruiting, seed mass, and pre-dispersal seed predation.

RESULTS

Higher growing-season soil temperatures, which were negatively associated with local elevation and higher nitrogen availability promoted flowering synchrony of Croton, particularly among larger plants. Greater flowering synchrony, high soil temperatures, and addition of N + P resulted in production of more fruits of Croton, but also intensified pre-dispersal seed predation.

CONCLUSIONS

Temperature, availability of moisture throughout the elevational gradient, and nutrient manipulation affected flowering synchrony, which subsequently affected production of fruits in Croton. These results emphasize the critical role of current anthropogenic changes in climate and nutrient availability on flowering synchrony and reproduction of Croton, a dominant plant of the inter-Andean scrub.

Precipitation and temperature timings underlying bioclimatic variables rearrange under climate change globally

Modeling how climate change may affect the potential distribution of species and communities typically utilizes bioclimatic variables. Distribution predictions rely on the values of the bioclimatic variable (e.g., precipitation of the wettest quarter). However, the ecological meaning of most of these variables depends strongly on the within-year position of a specific climate period (SCP), for example, the wettest quarter of the year, which is often overlooked. Our aim was to determine how the within-year position of the SCPs would shift (SCP shift) in reaction to climate change in a global context. We calculated the deviations of the future within-year position of the SCPs relative to the reference period. We used four future time periods, four scenarios, and four CMIP6 global climate models (GCMs) to provide an ensemble of expectations regarding SCP shifts and locate the spatial hotspots of the shifts. Also, the size and frequency of the SCP shifts were subjected to linear models to evaluate the importance of the impact modeler's decision on time period, scenario, and GCM. We found ample examples of SCP shifts exceeding 2 months, with 6-month shifts being predicted as well. Many areas in the tropics are expected to experience both temperature and precipitation-related shifts, but precipitation-related shifts are abundantly predicted for the temperate and arctic zones as well. The combined shifts at the Equator reinforce the likelihood of the emergence of no-analogue climates there. The shifts become more pronounced as time and scenario progress, while GCMs could not be ranked in a clear order in this respect. For most SCPs, the modeler's decision on the GCM was the least important, while the choice of time period was typically more important than the choice of scenario. Future predictive distribution models should account for SCP shifts and incorporate the phenomenon in the modeling efforts.

Complex climate-mediated effects of urbanization on plant reproductive phenology and frost risk

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.

Effects of intra-annual precipitation patterns on grassland productivity moderated by the dominant species phenology

Phenology and productivity are important functional indicators of grassland ecosystems. However, our understanding of how intra-annual precipitation patterns affect plant phenology and productivity in grasslands is still limited. Here, we conducted a two-year precipitation manipulation experiment to explore the responses of plant phenology and productivity to intra-annual precipitation patterns at the community and dominant species levels in a temperate grassland. We found that increased early growing season precipitation enhanced the above-ground biomass of the dominant rhizome grass, Leymus chinensis, by advancing its flowering date, while increased late growing season precipitation increased the above-ground biomass of the dominant bunchgrass, Stipa grandis, by delaying senescence. The complementary effects in phenology and biomass of the dominant species, L. chinensis and S. grandis, maintained stable dynamics of the community above-ground biomass under intra-annual precipitation pattern variations. Our results highlight the critical role that intra-annual precipitation and soil moisture patterns play in the phenology of temperate grasslands. By understanding the response of phenology to intra-annual precipitation patterns, we can more accurately predict the productivity of temperate grasslands under future climate change.

Testing the chilling- before drought-tolerance hypothesis in Pooideae grasses

Temperate Pooideae are a large clade of economically important grasses distributed in some of the Earth's coldest and driest terrestrial environments. Previous studies have inferred that Pooideae diversified from their tropical ancestors in a cold montane habitat, suggesting that above-freezing cold (chilling) tolerance evolved early in the subfamily. By contrast, drought tolerance is hypothesized to have evolved multiple times independently in response to global aridification that occurred after the split of Pooideae tribes. To independently test predictions of the chilling-before-drought hypothesis in Pooideae, we assessed conservation of whole plant and gene expression traits in response to chilling vs. drought. We demonstrated that both trait responses are more similar across tribes in cold as compared to drought, suggesting that chilling responses evolved before, and drought responses after, tribe diversification. Moreover, we found significantly more overlap between drought and chilling responsive genes within a species than between drought responsive genes across species, providing evidence that chilling tolerance genes acted as precursors for the novel acquisition of increased drought tolerance multiple times independently, partially through the cooption of chilling responsive genes.

Effects of drought on grassland phenology depend on functional types

Shifts in flowering phenology are important indicators of climate change. However, the role of precipitation in driving phenology is far less understood compared with other environmental cues, such as temperature. We use a precipitation reduction gradient to test the direction and magnitude of effects on reproductive phenology and reproduction across 11 plant species in a temperate grassland, a moisture-limited ecosystem. Our experiment was conducted in a single, relatively wet year. We examine the effects of precipitation for species, functional types, and the community. Our results provide evidence that reduced precipitation shifts phenology, alters flower and fruit production, and that the magnitude and direction of the responses depend on functional type and species. For example, early-blooming species shift toward earlier flowering, whereas later-blooming species shift toward later flowering. Because of opposing species-level shifts, there is no overall shift in community-level phenology. This study provides experimental evidence that changes in rainfall can drive phenological shifts. Our results additionally highlight the importance of understanding how plant functional types govern responses to changing climate conditions, which is relevant for forecasting phenology and community-level changes. Specifically, the implications of divergent phenological shifts between early- and late-flowering species include resource scarcity for pollinators and seed dispersers and new temporal windows for invasion.

Flowering time advances since the 1970s in a sagebrush steppe community: Implications for management and restoration

Climate change is widely known to affect plant phenology, but little is known about how these impacts manifest in the widespread sagebrush ecosystem of the Western United States, which supports a number of wildlife species of concern. Shifts in plant phenology can trigger consequences for the plants themselves as well as the communities of consumers that depend upon them. We assembled historical observations of first-flowering dates for 51 species collected in the 1970s and 1980s in a montane sagebrush community in the Greater Yellowstone Ecosystem and compared these to contemporary phenological observations targeting the same species and locations (2016-2019). We also assembled regional climate data (average spring temperature, day of spring snowmelt, and growing degree days) and tested the relationship between first-flowering time and these variables for each species. We observed the largest change in phenology in early-spring flowers, which, as a group, bloomed on average 17 days earlier, and as much as 36 days earlier, in the contemporary data set. Mid-summer flowers bloomed on average 10 days earlier, nonnative species 15 days earlier, and berry-producing shrubs 5 days earlier, while late summer flowering plants did not shift. The greatest correlates of early-spring and mid-summer flowering were average spring temperature and day of snowmelt, which was 21 days earlier, on average, in 2016-2019 relative to the 1973-1978 observations. The shifts in flowering phenology that we observed could indicate developing asynchronies or novel synchronies of these plant resources and wildlife species of conservation concern, including Greater Sage-grouse, whose nesting success is tied to availability of spring forbs; grizzly bears, which rely heavily on berries for their fall diet; and pollinators. This underscores the importance of maintaining a diverse portfolio of native plants in terms of species composition, genetics, phenological responsiveness to climatic cues, and ecological importance to key wildlife and pollinator species. Redundancy within ecological niches may also be important considering that species roles in the community may shift as climate change affects them differently. These considerations are particularly relevant to restoration and habitat-enhancement projects in sagebrush communities across western North America.

Can trees buffer the impact of climate change on pasture production and digestibility of Mediterranean dehesas?

Sustainability and functioning of silvopastoral ecosystems are being threatened by the forecasted warmer and drier environments in the Mediterranean region. Scattered trees of these ecosystems could potentially mitigate the impact of climate change on herbaceous plant community but this issue has not yet tested experimentally. We carried out a field manipulative experiment of increased temperature (+2-3 °C) using Open Top Chambers and rainfall reduction (30%) through rain-exclusion shelters to evaluate how net primary productivity and digestibility respond to climate change over three consecutive years, and to test whether scattered trees could buffer the effects of higher aridity in Mediterranean dehesas. First, we observed that herbaceous communities located beneath tree canopy were less productive (351 g/m²) than in open grassland (493 g/m²) but had a higher digestibility (44% and 41%, respectively), likely promoted by tree shade and the higher soil fertility of this habitat. Second, both habitats responded similarly to climate change in terms of net primary productivity, with a 33% increase under warming and a 13% decrease under reduced rainfall. In contrast, biomass digestibility decreased under increased temperatures (-7.5%), since warming enhanced the fiber and lignin content and decreased the crude protein content of aerial biomass. This warming-induced effect on biomass digestibility only occurred in open grasslands, suggesting a buffering role of trees in mitigating the impact of climate change. Third, warming did not only affect these ecosystem processes in a direct way but also indirectly via changes in plant functional composition. Our findings suggest that climate change will alter both the quantity and quality of pasture production, with expected warmer conditions increasing net primary productivity but at the expense of reducing digestibility. This negative effect of warming on digestibility might be mitigated by scattered trees, highlighting the importance of implementing strategies and suitable management to control tree density in these ecosystems.

Influence of Climatic Factors on the Phenology of Chokeberry Cultivars Planted in the Pedoclimatic Conditions of Southern Romania

This paper aimed to study the adaptation of a crop to the specific climatic conditions of southern Romania, Pitești-Mărăcineni, Romania, in terms of the phenology of two chokeberry (Aronia melanocarpa) cultivars (‘Melrom’ and ‘Nero’). The BBCH (Biologische Bundesantalt, Bundessortenamt and Chemische Industrie) scale was used for phenological observations. The recorded data were statistically processed, calculating the average onset time and duration of fruiting phenophases and dormancy duration, average air temperatures, total solar radiation, and the cold and heat accumulation. Bud swelling was registered between 28 January and 8 February, budburst occurred starting on 3 March, while flowering began in stages, between 15 April and 1 May, and was completed between 27 April and 14 May. During the 154 days of 53–87 BBCH, the average air temperature, 16.1 °C, ranged between the extremes of −6.1 and 36.8 °C. The onset data and spring–summer phenophases were mainly related to the minimum air-temperature oscillations. The flowering timing shortened as the maximum temperature and total solar radiation increased. The relation between the environmental factors and the flowering strategy indicates the A. melanocarpa as a species adapted to the temperate continental climate of southern Romania.

Reproductive Biology of Rheum webbianum Royle, a Vulnerable Medicinal Herb From Alpines of North-Western Himalaya

Information on reproductive biology and pollination ecology studies of threatened plants are essential to develop strategies for their sustainable utilization and effective conservation. As such, these studies were conducted on Rheum webbianum, a high-value "vulnerable" medicinal herb of the north-western Himalaya. This species presents a unique mode of reproductive behavior through the involvement of different floral events, including the movement of reproductive organs. The plants survive extremely cold conditions through underground perennating rhizomes that sprout into juvenile shoots with the onset of the favorable climatic conditions. The peduncle arises from the axils of the radical leaves, bearing a globular collection of densely arranged hermaphrodite flowers with temporally separated male and female phases; the male phase precedes the female phase (protandry). Anther dehiscence and stigma receptivity is post-anthesis. Anthers dehisce longitudinally along margins, liberating a large mass of spherical and tricolpate pollen with spinulose exine. Pollen viability decreased to < 10% on day 9. Pistil is tristylous, with each style terminating into a fan-shaped stigma lobe. The pollen receptive surface of each stigmatic lobe remains incurved at an angle of 360° and shows upward movement after anthesis, forming a funnel-like structure at an angle of 180° with respect to the ovary. Pollination syndrome is ambophilous. Spontaneous autogamy or geitonogamy to a certain extent is achieved in this species due to the arrangement of flowers in the inflorescence and overlapping of male and female reproductive phases among them. Incurved stigmatic lobes and outward movement of stamens too facilitate outcrossing. Pollen/ovule ratio estimates, results of pollination experiments on breeding behavior, outcrossing, and self-compatibility indices demonstrated that plants are self-compatible and cross-fertile.

Effect of Selected Meteorological Variables on Full Flowering of Some Forest Herbs in the Western Carpathians

At present, temperate forest ecosystems are endangered by both abiotic and biotic factors. The effects of abiotic components, e.g., meteorological variables, are constantly studied. However, the detailed mechanisms affecting the phenology of plants are still unknown. Two meteorological variables (air temperature and cumulative precipitation) were analysed for the period from 1995 to 2020 in order to determine which factor which has a more significant effect on onset of the full-flowering (FF) phenophase. A set of nine forest herbs, representing different phenological groups from the viewpoint of flowering, was examined (early spring: Petasites albus and Pulmonaria officinalis; mid-spring: Carex pilosa and Dentaria bulbifera; late spring: Fragaria visa and Galium odoratum; early summer: Veronica officinalis; mid-summer: Mycelis muralis; and late summer: Campanula trachelium). Temperature-sum requirements and temporal trends in the onset of FF were also studied. The research conducted at the Ecological Experimental Station in the Kremnické vrchy Mountains (central Slovakia) at an altitude of 500 m asl. Our results show that the air temperature correlated more significantly with the date of onset of FF (r > 0.6, p < 0.001) than with precipitation. On average, the air-temperature sums, calculated for the threshold temperatures of 0 °C and 5 °C, increased from 142.9 °C (Petasites albus) to 1732.9 °C (Campanula trachelium) and from 223.4 °C (Petasites albus) to 1820.8 °C (Campanula trachelium), respectively. Temporal trends in the onset of FF over the last 26 years confirm shifts to earlier dates for most species (excepting early spring Petasites albus). In spring flowering species, shifts ranged from 2 days (0.07 day/year) for Pulmonaria officinalis to 8 days (0.30 day/year) for Carex pilosa. As for summer species, the onset of flowering shifted more significantly to earlier dates—from 7 days (0.27 day/year) for Campanula trachelium to 12 days (0.46 day/year) for Veronica officinalis. The observed trends were statistically significant (p < 0.05) for five examined species (Carex pilosa, Dentaria bulbifera, Fragaria vesca, Veronica officinalis and Mycelis muralis).

A Mechanistic Framework for Understanding the Effects of Climate Change on the Link Between Flowering and Fruiting Phenology

Phenological shifts are a widely studied consequence of climate change. Little is known, however, about certain critical phenological events, nor about mechanistic links between shifts in different life-history stages of the same organism. Among angiosperms, flowering times have been observed to advance with climate change, but, whether fruiting times shift as a direct consequence of shifting flowering times, or respond differently or not at all to climate change, is poorly understood. Yet, shifts in fruiting could alter species interactions, including by disrupting seed dispersal mutualisms. In the absence of long-term data on fruiting phenology, but given extensive data on flowering, we argue that an understanding of whether flowering and fruiting are tightly linked or respond independently to environmental change can significantly advance our understanding of how fruiting phenologies will respond to warming climates. Through a case study of biotically and abiotically dispersed plants, we present evidence for a potential functional link between the timing of flowering and fruiting. We then propose general mechanisms for how flowering and fruiting life history stages could be functionally linked or independently driven by external factors, and we use our case study species and phenological responses to distinguish among proposed mechanisms in a real-world framework. Finally, we identify research directions that could elucidate which of these mechanisms drive the timing between subsequent life stages. Understanding how fruiting phenology is altered by climate change is essential for all plant species but is particularly critical to sustaining the large numbers of plant species that rely on animal-mediated dispersal, as well as the animals that rely on fruit for sustenance.

Substantial shifts in flowering phenology of Sternbergia vernalis in the Himalaya: Supplementing decadal field records with historical and experimental evidences

In an age of anthropocene, shifting plant phenology is one of the most striking biological indicators of global environmental change. Majority of the studies reporting shifts in plant phenology are available from the North America and Europe and largely scarce from the developing world, including the Himalaya; and studies integrating multiple methodological approaches to investigate the climate-driven phenological shifts are too rare. Here, we report the shifts in spring flowering phenology of model plant species, Sternbergia vernalis in response to the changing climate in Kashmir Himalaya, by integrating decadal field observational records with long-term herbarium and dated-photograph data, and supported with experimental evidences. Our results revealed a significant increasing trend of 0.038, 0.016 and 0.023 °C/year in the annual mean maximum temperature (T_max), mean minimum temperature (T_min) and diurnal temperature range (DTR) respectively; but an insignificant decreasing trend in annual precipitation of -1.24 mm/year over the last four decades (1980-2019) in this Himalayan region. The flowering phenology of S. vernalis has significantly advanced by 11.8 days/°C and 27.8 days/°C increase in T_max and T_min respectively, indicating that the climate warming has led to substantial shifts in flowering phenology of the model plant species. We also observed a strong association of seasonal T_max (December-February) and DTR on the early onset of spring flowering, however precipitation had no significant effect on the timing of flowering. The greenhouse experiment results further supported a significant effect of temperature in triggering the phenological shifts, wherein the model plant grown under different temperature treatments flowered 9-20 days earlier compared to the control. Our study showcases the integrated use of multiple methodological approaches for unravelling the long-term phenological shifts in response to climate change, and contributes in filling the knowledge gaps in the phenological research from the developing world in general and the Himalaya in particular.

Spatial and Ecological Drivers of Genetic Structure in Greek Populations of Alkanna tinctoria (Boraginaceae), a Polyploid Medicinal Herb

Background and Aims: Quantifying genetic variation is fundamental to understand a species' demographic trajectory and its ability to adapt to future changes. In comparison with diploids, however, genetic variation and factors fostering genetic divergence remain poorly studied in polyploids due to analytical challenges. Here, by employing a ploidy-aware framework, we investigated the genetic structure and its determinants in polyploid Alkanna tinctoria (Boraginaceae), an ancient medicinal herb that is the source of bioactive compounds known as alkannin and shikonin (A/S). From a practical perspective, such investigation can inform biodiversity management strategies. Methods: We collected 14 populations of A. tinctoria within its main distribution range in Greece and genotyped them using restriction site-associated DNA sequencing. In addition, we included two populations of A. sieberi. By using a ploidy-aware genotype calling based on likelihoods, we generated a dataset of 16,107 high-quality SNPs. Classical and model-based analysis was done to characterize the genetic structure within and between the sampled populations, complemented by genome size measurements and chromosomal counts. Finally, to reveal the drivers of genetic structure, we searched for associations between allele frequencies and spatial and climatic variables. Key Results: We found support for a marked regional structure in A. tinctoria along a latitudinal gradient in line with phytogeographic divisions. Several analyses identified interspecific admixture affecting both mainland and island populations. Modeling of spatial and climatic variables further demonstrated a larger contribution of neutral processes and a lesser albeit significant role of selection in shaping the observed genetic structure in A. tinctoria. Conclusion: Current findings provide evidence of strong genetic structure in A. tinctoria mainly driven by neutral processes. The revealed natural genomic variation in Greek Alkanna can be used to further predict variation in A/S production, whereas our bioinformatics approach should prove useful for the study of other non-model polyploid species.

Epigenetic responses of hare barley (Hordeum murinum subsp. leporinum) to climate change: an experimental, trait-based approach

The impact of reduced rainfall and increased temperatures forecasted by climate change models on plant communities will depend on the capacity of plant species to acclimate and adapt to new environmental conditions. The acclimation process is mainly driven by epigenetic regulation, including structural and chemical modifications on the genome that do not affect the nucleotide sequence. In plants, one of the best-known epigenetic mechanisms is cytosine-methylation. We evaluated the impact of 30% reduced rainfall (hereafter "drought" treatment; D), 3 °C increased air temperature ("warming"; W), and the combination of D and W (WD) on the phenotypic and epigenetic variability of Hordeum murinum subsp. leporinum L., a grass species of high relevance in Mediterranean agroforestry systems. A full factorial experiment was set up in a savannah-like ecosystem located in southwestern Spain. H. murinum exhibited a large phenotypic plasticity in response to climatic conditions. Plants subjected to warmer conditions (i.e., W and WD treatments) flowered earlier, and those subjected to combined stress (WD) showed a higher investment in leaf area per unit of leaf mass (i.e., higher SLA) and produced heavier seeds. Our results also indicated that both the level and patterns of methylation varied substantially with the climatic treatments, with the combination of D and W inducing a clearly different epigenetic response compared to that promoted by D and W separately. The main conclusion achieved in this work suggests a potential role of epigenetic regulation of gene expression for the maintenance of homoeostasis and functional stability under future climate change scenarios.

Predicting effects of warming requires a whole-of-life cycle perspective: a case study in the alpine herb Oreomyrrhis eriopoda

Global warming is affecting plant phenology, growth and reproduction in complex ways and is particularly apparent in vulnerable alpine environments. Warming affects reproductive and vegetative traits, as well as phenology, but seldom do studies assess these traits in concert and across the whole of a plant's life cycle, particularly in wild species. Thus, it is difficult to extrapolate from such effects to predictions about the persistence of species or their conservation and management. We assessed trait variation in response to warming in Oreomyrrhis eriopoda, an Australian native montane herb, in which populations vary in germination strategy (degree of dormancy) and growth characteristics as a function of ecological factors. Warming accelerated growth in the early stages of development, particularly for populations with non-dormant seed. The differences in growth disappeared at the transition to reproduction, when an accelerating effect on phenology emerged, to varying degrees depending on germination strategy. Overall, warming reduced flower and seed production and increased mortality, indicating a reduction in reproductive opportunities, particularly for populations with dormant seed. Developmental condition affected germination strategy of the next generation seed, leading to increased degree of dormancy and slowed germination rate. But there were no whole-scale shifts in strategy or total germination percent. Following through the life cycle reveals that warming will have some potentially positive effects (early growth rates) and some negative effects (reduced reproductive output). Ultimately, warming impacts will depend on how those effects play out in the field: early establishment and an accelerated trajectory to seed maturity may offset the tradeoff with overall seed production. Small differences among germination strategies likewise may cascade to larger effects, with important implications for persistence of species in the alpine landscape. Thus, to understand and manage the response of wild species to warming takes a whole-of-life perspective and attention to ecologically significant patterns of within-species variation.

Conservation of Micromeria browiczii (Lamiaceae), Endemic to Zakynthos Island (Ionian Islands, Greece)

The massive decline in biodiversity due to anthropogenic threats has led to the emergence of conservation as one of the central goals in modern biology. Conservation strategies are urgently needed for addressing the ongoing loss of plant diversity. The Mediterranean basin, and especially the Mediterranean islands, host numerous rare and threatened plants in need of urgent conservation actions. In this study, we assess the current conservation status of Micromeria browiczii, a local endemic to Zakynthos Island (Ionian Islands, Greece), and estimate its future risk of extinction by compiling and assessing scientific information on geographical distribution, population dynamics and reproductive biology. The population size and the geographical distribution of the species were monitored for five years. The current population of the species consists of 15 subpopulations. Considerable annual fluctuation of population size was detected. The species is assessed as Endangered according to the International Union for Conservation of Nature threat categories. According to population viability analysis results, its extinction risk was estimated to be 5.6% over the next 50 years, when six of the fifteen subpopulations (40%) might become extinct. The investigation of certain aspects of the species’ biology yielded important data necessary to identify critical aspects for its survival and to propose conservation measures.

Review: Plant eco-evolutionary responses to climate change: Emerging directions

Contemporary climate change is exposing plant populations to novel combinations of temperatures, drought stress, [CO₂] and other abiotic and biotic conditions. These changes are rapidly disrupting the evolutionary dynamics of plants. Despite the multifactorial nature of climate change, most studies typically manipulate only one climatic factor. In this opinion piece, we explore how climate change factors interact with each other and with biotic pressures to alter evolutionary processes. We evaluate the ramifications of climate change across life history stages,and examine how mating system variation influences population persistence under rapid environmental change. Furthermore, we discuss how spatial and temporal mismatches between plants and their mutualists and antagonists could affect adaptive responses to climate change. For example, plant-virus interactions vary from highly pathogenic to mildly facilitative, and are partly mediated by temperature, moisture availability and [CO₂]. Will host plants exposed to novel, stressful abiotic conditions be more susceptible to viral pathogens? Finally, we propose novel experimental approaches that could illuminate how plants will cope with unprecedented global change, such as resurrection studies combined with experimental evolution, genomics or epigenetics.

Prediction of Plant Phenological Shift under Climate Change in South Korea

Information on the phenological shift of plants can be used to detect climate change and predict changes in the ecosystem. In this study, the changes in first flowering dates (FFDs) of the plum tree (Prunus mume), Korean forsythia (Forsythia koreana), Korean rosebay (Rhododendron mucronulatum), cherry tree (Prunus yedoensis), and peach tree (Prunus persica) in Korea during 1920–2019 were investigated. In addition, the changes in the climatic factors (temperature and precipitation) and their relationship with the FFDs were analyzed. The changes in the temperature and precipitation during the January–February–March period and the phenological shifts of all research species during 1920–2019 indicate that warm and dry spring weather advances the FFDs. Moreover, the temperature has a greater impact on this phenological shift than precipitation. Earlier flowering species are more likely to advance their FFDs than later flowering species. Hence, the temporal asynchrony among plant species will become worse with climate change. In addition, the FFDs in 2100 were predicted based on representative concentration pathway (RCP) scenarios. The difference between the predicted FFDs of the RCP 4.5 and RCP 6.0 for 2100 was significant; the effectiveness of greenhouse gas policies will presumably determine the degree of the plant phenological shift in the future. Furthermore, we presented the predicted FFDs for 2100.

Invertebrate Decline Leads to Shifts in Plant Species Abundance and Phenology

Climate and land-use change lead to decreasing invertebrate biomass and alter invertebrate communities. These biotic changes may affect plant species abundance and phenology. Using 24 controlled experimental units in the iDiv Ecotron, we assessed the effects of invertebrate decline on an artificial grassland community formed by 12 herbaceous plant species. More specifically, we used Malaise traps and sweep nets to collect invertebrates from a local tall oatgrass meadow and included them in our Ecotron units at two different invertebrate densities: 100% (no invertebrate decline) and 25% (invertebrate decline of 75%). Another eight EcoUnits received no fauna and served as a control. Plant species abundance and flowering phenology was observed weekly over a period of 18 weeks. Our results showed that invertebrate densities affected the abundance and phenology of plant species. We observed a distinct species abundance shift with respect to the invertebrate treatment. Notably, this shift included a reduction in the abundance of the dominant plant species, Trifolium pratense, when invertebrates were present. Additionally, we found that the species shifted their flowering phenology as a response to the different invertebrate treatments, e.g. with decreasing invertebrate biomass Lotus corniculatus showed a later peak flowering time. We demonstrated that in addition to already well-studied abiotic drivers, biotic components may also drive phenological changes in plant communities. This study clearly suggests that invertebrate decline may contribute to already observed mismatches between plants and animals, with potential negative consequences for ecosystem services like food provision and pollination success. This deterioration of ecosystem function could enhance the loss of insects and plant biodiversity.

Hierarchical Canonical Correlation Analysis Reveals Phenotype, Genotype, and Geoclimate Associations in Plants

The local environment of the geographical origin of plants shaped their genetic variations through environmental adaptation. While the characteristics of the local environment correlate with the genotypes and other genomic features of the plants, they can also be indicative of genotype-phenotype associations providing additional information relevant to environmental dependence. In this study, we investigate how the geoclimatic features from the geographical origin of the Arabidopsis thaliana accessions can be integrated with genomic features for phenotype prediction and association analysis using advanced canonical correlation analysis (CCA). In particular, we propose a novel method called hierarchical canonical correlation analysis (HCCA) to combine mutations, gene expressions, and DNA methylations with geoclimatic features for informative coprojections of the features. HCCA uses a condition number of the cross-covariance between pairs of datasets to infer a hierarchical structure for applying CCA to combine the data. In the experiments on Arabidopsis thaliana data from 1001 Genomes and 1001 Epigenomes projects and climatic, atmospheric, and soil environmental variables combined by CLIMtools, HCCA provided a joint representation of the genomic data and geoclimate data for better prediction of the special flowering time at 10°C (FT10) of Arabidopsis thaliana. We also extended HCCA with information from a protein-protein interaction (PPI) network to guide the feature learning by imposing network modules onto the genomic features, which are shown to be useful for identifying genes with more coherent functions correlated with the geoclimatic features. The findings in this study suggest that environmental data comprise an important component in plant phenotype analysis. HCCA is a useful data integration technique for phenotype prediction, and a better understanding of the interactions between gene functions and environment as more useful functional information is introduced by coprojections of multiple genomic datasets.

Identification of suites of traits that explains drought resistance and phenological patterns of plants in a semi-arid grassland community

Grassland ecosystems are comprised of plants that occupy a wide array of phenological niches and vary considerably in their ability to resist the stress of seasonal soil-water deficits. Yet, the link between plant drought resistance and phenology remains unclear in perennial grassland ecosystems. To evaluate the role of soil water availability and plant drought tolerance in driving phenology, we measured leaf hydraulic conductance (K_sat), resistance to hydraulic failure (P₅₀), leaf gas exchange, plant and soil water stable isotope ratios (δ¹⁸O), and several phenology metrics on ten perennial herbaceous species in mixed-grass prairie. The interaction between P₅₀ and δ¹⁸O of xylem water explained 67% of differences in phenology, with lower P₅₀ values associated with later season activity, but only among shallow-rooted species. In addition, stomatal control and high water-use efficiency also contributed to the late flowering and late senescence strategies of plants that had low P₅₀ values and relied upon shallow soil water. Alternatively, plants with deeper roots did not possess drought-tolerant leaves, but had high hydraulic efficiency, contributing to their ability to efficiently move water longer distances while maintaining leaf water potential at relatively high values. The suites of traits that characterize these contrasting strategies provide a mechanistic link between phenology and plant-water relations; thus, these traits could help predict grassland community responses to changes in water availability, both temporally and vertically within the soil profile.

An examination of climate-driven flowering-time shifts at large spatial scales over 153 years in a common weedy annual

PREMISE

Understanding species' responses to climate change is a critical challenge facing biologists today. Though many species are widespread, few studies of climate-driven shifts in flowering time have examined large continuous spatial scales for individual species. And even fewer studies have examined these shifts at time scales greater than a few decades.

METHODS

We used digitized herbarium specimens and PRISM climate data to produce the spatially and temporally broadest-scale study of flowering time in a single species to date, spanning the contiguous United States and 153 years (1863-2016) for a widespread weedy annual, Triodanis perfoliata (Campanulaceae). We examined factors driving phenological shifts as well as the roles of geographic and temporal scale in understanding these trends.

RESULTS

Year was a significant factor in both geospatial and climatic analyses, revealing that flowering time has advanced by ~9 days over the past ~150 years. We found that temperature as well as vapor pressure deficit, an understudied climatic parameter associated with evapotranspiration and water stress, were strongly associated with peak flowering. We also examined how sampling at different spatiotemporal scales influences the power to detect flowering-time shifts, finding that relatively large spatial and temporal scales are ideal for detecting flowering-time shifts in this widespread species.

CONCLUSIONS

Our results emphasize the importance of understanding the interplay of geospatial factors at different scales to examine how species respond to climate change.

Plant growth and aboveground production respond differently to late-season deluges in a semi-arid grassland

Semi-arid ecosystems are strongly water-limited and typically quite responsive to changes in precipitation amount and event size. In the C₄-dominated shortgrass steppe of the Central US, previous experiments suggest that large rain events more effectively stimulate plant growth and aboveground net primary production (ANPP) than an equal amount of precipitation from smaller events. Responses to naturally occurring large events have generally been consistent with experimental results, with the exception of large events occurring later in the growing season (e.g., August). These have been reported as less effective at increasing net C uptake, despite temperatures optimal for C₄ plant growth. Since atmospheric warming is increasing the frequency of statistically extreme rain events (deluges) throughout the growing season, how late-season deluges affect semi-arid ecosystems remains to be resolved. We applied deluges in August of three sizes (1.0-2.5 times average August precipitation) to assess the potential for late-season deluges to stimulate plant growth and ANPP. These late-season deluges led to significant "green-up" of this grassland, with new leaf production, and an increase in flowering of the dominant grass species. Further, these responses increased as deluge size increased, suggesting that larger or multiple deluges may lead to even greater growth responses. However, despite strong plant-level responses, no increase in ANPP was measured. Our results confirm that aboveground plant growth in the C₄-dominated shortgrass steppe does respond to late-season deluges; however, if there is an increase in plant biomass, net accumulation aboveground is minimal at this time of year.

Phylogeny, host use, and diversification in the moth family Momphidae (Lepidoptera: Gelechioidea)

Insect herbivores and their hostplants constitute much of Earth's described biological diversity, but how these often-specialized associations diversify is not fully understood. We combined detailed hostplant data and comparative phylogenetic analyses of the lepidopteran family Momphidae to explore how shifts in the use of hostplant resources, not just hostplant taxon, contribute to the diversification of a phytophagous insect lineage. We inferred two phylogenetic hypotheses emphasizing relationships among species in the nominate genus, Mompha Hübner. A six-gene phylogeny was constructed with reared exemplars and collections from hostplants in the family Onagraceae from western and southwestern USA, and a cytochrome c oxidase subunit 1 (COI) phylogeny was inferred from collections and publicly available accessions in the Barcode of Life Data System. Species delimitation analyses combined with morphological data revealed ca. 56 undescribed species-level taxa, many of which are hostplant specialists on Onagraceae in the southwestern USA. Our phylogenetic reconstructions divided Momphidae into six major clades: 1) an Onagraceae flower- and fruit-boring clade, 2) a Melastomataceae-galling clade, 3) a leafmining clade A, 4) a leafmining clade B, 5) a Zapyrastra Meyrick clade, and 6) a monobasic lineage represented by Mompha eloisella (Clemens). Ancestral trait reconstructions using the COI phylogeny identified leafmining on Onagraceae as the ancestral state for Momphidae. Our study finds that shifts along three hostplant resource axes (plant taxon, plant tissue type, and larval feeding mode) have contributed to the evolutionary success and diversification of momphids.

Estimation of the Allergenic Potential of Urban Trees and Urban Parks: Towards the Healthy Design of Urban Green Spaces of the Future

The impact of allergens emitted by urban green spaces on health is one of the main disservices of ecosystems. The objective of this work is to establish the potential allergenic value of some tree species in urban environments, so that the allergenicity of green spaces can be estimated through application of the Index of Urban Green Zones Allergenicity (IUGZA). Multiple types of green spaces in Mediterranean cities were selected for the estimation of IUGZ. The results show that some of the ornamental species native to the Mediterranean are among the main causative agents of allergy in the population; in particular, Oleaceae, Cupressaceae, Fagaceae, and Platanus hispanica. Variables of the strongest impact on IUGZA were the bioclimatic characteristics of the territory and design aspects, such as the density of trees and the number of species. We concluded that the methodology to assess the allergenicity associated with urban trees and urban areas presented in this work opens new perspectives in the design and planning of urban green spaces, pointing out the need to consider the potential allergenicity of a species when selecting plant material to be used in cities. Only then can urban green areas be inclusive spaces, in terms of public health.

Aboveground net primary productivity not CO2 exchange remain stable under three timing of extreme drought in a semi-arid steppe

Precipitation patterns are expected to change in the semi-arid region within the next decades, with projected increasing in extreme drought events. Meanwhile, the timing of extreme drought also shows great uncertainty, suggesting that the timing of drought, especially during growing season, may subsequently impose stronger stress on ecosystem functions than drought itself. However, how the timing of extreme drought will impact on community productivity and carbon cycle is still not clear. In this study, three timing of extreme drought (a consecutive 30-day period without precipitation event) experiments were set up separately in early-, mid- and late-growing season in a temperate steppe in Inner Mongolia since 2013. The data, including soil water content (SWC), soil temperature (ST) chlorophyll fluorescence parameter (Fv/Fm), ecosystem respiration (Re), gross primary productivity (GPP), net ecosystem carbon absorption (NEE) and aboveground net primary productivity (ANPP) were collected in growing season (from May to September) of 2016. In this study, extreme drought significantly decreased SWC during the drought treatment but not for the whole growing season. Extreme drought decreased maximum quantum efficiency of plant photosystem II (Fv/Fm) under "optimum" value (0.75~0.85) of two dominant species (Leymus chinensis and Stipa grandis). While ANPP kept stable under extreme drought treatments due to the different responses of two dominant species, which brought a compensating effect in relative abundance and biomass. In addition, only early-growing season drought significantly decreased the average Re (P < 0.01) and GPP (P < 0.01) and depressed net CO2 uptake (P < 0.01) than mid- and late-growing season drought. ST and SWC influenced the changes of GPP directly and indirectly through photosynthetic ability of the dominant species by path analysis. Our results indicated that the timing of drought should be considered in carbon cycle models to accurately estimate carbon exchange and productivity of semi-arid grasslands in the context of changing climate.

Prairie plant phenology driven more by temperature than moisture in climate manipulations across a latitudinal gradient in the Pacific Northwest, USA

Plant phenology will likely shift with climate change, but how temperature and/or moisture regimes will control phenological responses is not well understood. This is particularly true in Mediterranean climate ecosystems where the warmest temperatures and greatest moisture availability are seasonally asynchronous. We examined plant phenological responses at both the population and community levels to four climate treatments (control, warming, drought, and warming plus additional precipitation) embedded within three prairies across a 520 km latitudinal Mediterranean climate gradient within the Pacific Northwest, USA. At the population level, we monitored flowering and abundances in spring 2017 of eight range-restricted focal species planted both within and north of their current ranges. At the community level, we used normalized difference vegetation index (NDVI) measured from fall 2016 to summer 2018 to estimate peak live biomass, senescence, seasonal patterns, and growing season length. We found that warming exerted a stronger control than our moisture manipulations on phenology at both the population and community levels. Warming advanced flowering regardless of whether a species was within or beyond its current range. Importantly, many of our focal species had low abundances, particularly in the south, suggesting that establishment, in addition to phenological shifts, may be a strong constraint on their future viability. At the community level, warming advanced the date of peak biomass regardless of site or year. The date of senescence advanced regardless of year for the southern and central sites but only in 2018 for the northern site. Growing season length contracted due to warming at the southern and central sites (~3 weeks) but was unaffected at the northern site. Our results emphasize that future temperature changes may exert strong influence on the timing of a variety of plant phenological events, especially those events that occur when temperature is most limiting, even in seasonally water-limited Mediterranean ecosystems.

Phenological responses to multiple environmental drivers under climate change: insights from a long-term observational study and a manipulative field experiment

Climate change has induced pronounced shifts in the reproductive phenology of plants, yet we know little about which environmental factors contribute to interspecific variation in responses and their effects on fitness. We integrate data from a 43 yr record of first flowering for six species in subalpine Colorado meadows with a 3 yr snow manipulation experiment on the perennial forb Boechera stricta (Brassicaceae) from the same site. We analyze shifts in the onset of flowering in relation to environmental drivers known to influence phenology: the timing of snowmelt, the accumulation of growing degree days, and photoperiod. Variation in responses to climate change depended on the sequence in which species flowered, with early-flowering species reproducing faster, at a lower heat sum, and under increasingly disparate photoperiods relative to later-flowering species. Early snow-removal treatments confirm that the timing of snowmelt governs observed trends in flowering phenology of B. stricta and that climate change can reduce the probability of flowering, thereby depressing fitness. Our findings suggest that climate change is decoupling historical combinations of photoperiod and temperature and outpacing phenological changes for our focal species. Accurate predictions of biological responses to climate change require a thorough understanding of the factors driving shifts in phenology.