Plant Phenology Research Articles

Global change aggravates drought, with consequences for plant reproduction.

The frequency and intensity of droughts are expected to increase under global change, driven by anthropogenic climate change and water diversion. Precipitation is expected to become more episodic under climate change, with longer and warmer dry spells, although some areas might become wetter. Diversion of freshwater from lakes and rivers and groundwater pumping for irrigation of agricultural fields are lowering water availability to wild plant populations, increasing the frequency and intensity of drought. Given the importance of seasonal changes and extremes in soil moisture to influence plant reproduction, and because the majority of plants are flowering plants and most of them depend on pollinators for seed production, this review focuses on the consequences of drought on different aspects of reproduction in animal-pollinated angiosperms, emphasizing interactions among drought, flowering and pollination. Visual and olfactory traits play crucial roles in attracting pollinators. Drought-induced floral changes can influence pollinator attraction and visitation, together with pollinator networks and flowering phenology, with subsequent effects on plant reproduction. Here, we review how drought influences these different aspects of plant reproduction. We identify knowledge gaps and highlight areas that would benefit from additional research. Visual and olfactory traits are affected by drought, but their phenotypic responses can vary with floral sex, plant sex, population and species. Ample phenotypic plasticity to drought exists for these traits, providing an ability for a rapid response to a change in drought frequency and intensity engendered by global change. The impact of these drought-induced changes in floral traits on pollinator attraction, pollen deposition and plant reproductive success does not show a clear pattern. Drought affects the structure of plant-pollinator networks and can modify plant phenology. The impact of drought on plant reproduction is not always negative, and we need to identify plant characteristics associated with these more positive responses.

A Google Trends analysis of people's sense of seasons in Hokkaido

Accurate evaluation of the spatiotemporal variability of people's interest in seasons (i.e., their “sense of seasons”) is required to deeply understand temporal changes in the relationship between people and landscape under climate and societal changes. To this end, it is useful to analyze the time series of relative search volume (RSV) for relevant search terms extracted from Google Trends (GT) for any target period and target area. We examined the presence and absence of 12-month seasonality of the time series of RSV for about 300 representative search terms for Hokkaido in Japan, which has vast natural resources and is visited year-round by many tourists from Japan and abroad. In the case of searchers in both all of Japan and Hokkaido alone, search terms categorized into the foods, leisure, natural scenic spots, and seafood fields showed a strong trend toward 12-month seasonality of the time series of RSV, whereas those categorized into the Ainu (indigenous people) and people fields had weak trends for 12-month seasonality. People's sense of seasons in all of Japan or Hokkaido alone was likely associated with tourism (search terms in the animals, festivals, foods, leisure, natural scenic spots, seafood, tourist spots, and vegetation fields), as well as with animal and plant phenology (terms in the animals and vegetation fields), provisioning ecosystem services (terms in the foods and seafood fields), climate (terms in the climate field), and cultural ecosystem services (terms in the animals, festival, foods, leisure, natural scenic spots, seafoods, and vegetation fields). However, search terms with no 12-month seasonality were included in the tourist spots fields: they included many tourist spots visited by tourists all year around. Despite the need to appropriately select a huge number of representative search terms to reduce the effect of GT limitations and the uncertainty caused by unexpected and rapid temporal changes in RSV, the GT analysis allowed us to evaluate the spatiotemporal variability of people's sense of seasons regarding various objects in the landscape, including those related to tourism, under climate and societal changes.

Herbivory resistance in dwarf shrubs combines with simulated warming to shift phenology and decrease reproduction

Abstract Research focus on the phenology of plants has accompanied current trends in climate warming, because the two are inextricably linked. Warmer temperatures have led to advanced plant phenology in a range of systems, although some responses are species specific. However, other stressors, such as herbivory, can delay or advance plant phenology, and few studies have addressed the combined impact of these drivers. We experimentally warmed plots with open top chambers (OTCs) and simulated herbivory resistance to insect outbreaks with methyl jasmonate (MeJA), along an elevational climatic gradient. We then recorded vegetative and reproductive phenology in two functionally important dwarf shrubs, the deciduous Vaccinium myrtillus (bilberry) and the evergreen V. vitis‐idaea (lingonberry), to test the responses to the combined treatments. Based on earlier findings, we expected larger phenological responses at higher elevations and for bilberry. We found that in the year after MeJA application, both bilberry and lingonberry delayed vegetative and reproductive phenology, although responses were stronger in bilberry. Warming with OTCs weakly advanced phenology in both species, but combined effects were not consistent. We further examined the consequences of this altered phenology on reproductive output with multigroup piecewise structural equation modelling and found that herbivory resistance driven changes to phenology had a strong mediating effect on berry numbers, particularly under warmed conditions and mainly in the year after MeJA application. Synthesis. These results demonstrate the need to consider combined pressures in understanding the impacts of global change on plants and highlight that multiple drivers may have unidentified synergetic effects on species phenology and reproduction.

Microclimatic variation regulates seed germination phenology in alpine plant communities

Abstract For most terrestrial plants, regeneration depends on the ability of seeds to germinate in the most favourable climatic conditions. Understanding seed germination phenology is thus crucial for predicting plant responses to environmental changes. However, a substantial gap persists regarding how microclimatic conditions influence germination in seasonal ecosystems. Here, we investigate the germination phenology of alpine plants in snow‐related microclimates as a tool for predicting the resilience of plant communities to climate change. We conducted a continuous seasonal experiment with fresh seeds to investigate germination phenology in 54 co‐occurring species from temperate and Mediterranean alpine communities. Using long‐term field microclimatic data series, we precisely mimicked two contrasting microclimatic regimes in growth chambers: (1) windy exposed edges with a snow‐free period in winter and warmer temperatures in summer (‘fellfield’) and (2) sheltered areas with lengthy snow cover and cooler temperatures (‘snowbed’). We validated the laboratory results with field sowing experiments to provide a complete picture of germination phenology. The analysis of phenology traits demonstrated that both communities displayed similar responses to microclimatic variation. Small microclimatic differences of 2–3°C a week, accumulated across a whole year in the laboratory, resulted in a quantifiable germination phenology delay in snowbed regime, with an average of 60 and 45 days for temperate and Mediterranean alpine respectively. The results from climatic chambers under realistic microclimatic regimes were consistent with the germination phenology registered from field experiments. We also observed macroclimatic effects manifested as reduced dormancy and increased autumn germination in Mediterranean alpine species. Synthesis. This study combines novel laboratory and field experimentation to tackle the understudied topic of germination phenology in habitats with sharp microclimatic gradients. Specifically, our findings suggest a predictable phenological shift in the germination of alpine plants along microclimatic gradients. In warmer conditions with reduced snow cover, alpine species are expected to advance germination 52 days on average, with potential disrupting effects on cold‐adapted species with strict germination requirements. This highlights the role of germination phenology to determine plant‐environmental relationships in mid‐latitude ecosystems, with strong impact on plant establishment and extinction risks under local microclimatic gradients.

Neonatal antipredator tactics shape female movement patterns in large herbivores.

Caring for newborn offspring hampers resource acquisition of mammalian females, curbing their ability to meet the high energy expenditure of early lactation. Newborns are particularly vulnerable, and, among the large herbivores, ungulates have evolved a continuum of neonatal antipredator tactics, ranging from immobile hider (such as roe deer fawns or impala calves) to highly mobile follower offspring (such as reindeer calves or chamois kids). How these tactics constrain female movements around parturition is unknown, particularly within the current context of increasing habitat fragmentation and earlier plant phenology caused by global warming. Here, using a comparative analysis across 54 populations of 23 species of large herbivores from 5 ungulate families (Bovidae, Cervidae, Equidae, Antilocapridae and Giraffidae), we show that mothers adjust their movements to variation in resource productivity and heterogeneity according to their offspring's neonatal tactic. Mothers with hider offspring are unable to exploit environments where the variability of resources occurs at a broad scale, which might alter resource allocation compared with mothers with follower offspring. Our findings reveal that the overlooked neonatal tactic plays a key role for predicting how species are coping with environmental variation.

1997–2016, Twenty Years of Pollen Monitoring Activity in Rome Tor Vergata (Rome South-East): Trends Analysis

Global environmental change is rapidly altering the dynamics of terrestrial vegetation, with consequences for the functioning of the Earth system. Recent studies show that climate change is influencing the phenology and distribution of plants. Airborne pollen reflects the flowering period of the plant, which is influenced by meteorological variables such as temperature and rainfall. The analysis of pollen trends is a very useful tool for understanding the effects of climate change on vegetation. In fact, it is accepted that the onset and peak abundance of certain pollen types should be used as possible bioindicators of climate change. The aim of the work is to analyze the presence of various pollen in Rome—from their release from the anthers to their permanence in the atmosphere, the trends of phenological (start, length, and end of the pollen season) and production (pollen abundance and pollen peaks) pollen indicators, the trends of the meteorological variables mainly involved (temperature and precipitation), and any relationships between pollen and meteorological variables, also based on the variation in vegetation. In the period considered, the analysis of the pollen spectra shows an increasing trend in herbaceous taxa, probably attributed to a gradual abandonment of farming practices in the neighboring area, which in recent years has been the subject of intense new construction activity and to a progressive deterioration in the maintenance of green areas.

Assessment of local plant materials for the management of nematode (Nematoda) infestation in tomato (Lycompersicum esculentus) production

Tomato (Lycopersicum esculentus) is an important global vegetable crop that contributes to nutrient security. Production of this crop is constrained by many factors of which nematode (Nematoda) infestation is observed to be quite threatening. The efficacy of three local plant materials namely: Neem (Azadirachta indica), Siam weed (Chromolaena odorata) and African marigold (Tagetes erecta) were assessed to suppress soil infested nematode for management strategy. This was achieved by conducting field trials at Lower Nursery, Njala campus through establishment of experimental plots of tomato host plant in a factorially Randomized Complete Block Design (RCBD) with three replicates in each treatment, repeated twice in 2022 and 2023. Data were collected on percentage survival rate, morphological parameters, phenology and yield parameters of tomato host plant respectively. The Data collected were analyzed using Statistical Analysis System (SAS). Differences between mean values of the various parameters were determined by two-way ANOVA analysis while significantly different means were separated using the Student-Newman-Keuls (SNK) test at p ≤ 0.05 level of significance. Azadirachta indica and Chromolaena odorata treatments proved to be highly effective in managing nematode in tomato production. Azadirachta indica and Chromolaena odorata treatments were the most efficient in managing nematodes among the options tested, as they recorded the highest percentage survival rates, agronomic parameters and shorter durations for both flowering and fruit setting compared to other treatments. Moneymaker and Mongal tomato varieties generally showed better survival rates, growth parameters and higher yields to Roma tomato variety. The neem treatment showed its extraordinary effectiveness with the highest survival rate as a percentage. This therapy is the most effective at suppressing nematodes among all those studied. With a higher percentage survival rate, the greatest fruit number and weight, and an effective treatment, Siam weeds have been demonstrated to be a viable substitute for neem. The neem and Siam weed therapy proved to be more beneficial than the marigold therapy, despite its mediocre success.

Host plant phenology drives risky larval dispersal in an outbreaking insect defoliator

Abstract Dispersal away from natal sites allows individuals to find suitable foraging sites to complete their development and successfully reproduce. Drivers of risky dispersal behaviour in forest landscapes by young larvae of outbreaking defoliators are not well understood. We assessed dispersal behaviour of young spruce budworm larvae in relation to spring budburst phenology of primary and secondary hosts, balsam fir and black spruce, respectively. We tested whether tree species and presence of suitable feeding sites influenced dispersal away from source branches and subsequent redistribution of insects. Laboratory experiments showed that dispersal is an active behaviour during which larvae disperse away from source trees without open buds, regardless of species. Establishment on sink branches was highest when they possessed open buds and the source did not. In the field, larval dispersal was higher from black spruce than from balsam fir and larval establishment was more persistent on balsam fir. The decision to disperse occurs before budburst of either host species. Larvae disperse preferentially away from black spruce whose old needles are too tough for larval mining, compared to balsam fir that can be mined for sustenance and refuge while larvae await budburst. While black spruce is a suitable host species after its buds expand, phenological defences drive larval dispersal away from this host plant. These findings are the first to show how risky dispersal behaviour in larval Lepidoptera is facultative and is determined by local food availability.

Maternal environmental control of progeny seed physiology: a review of concepts, evidence and mechanism

Abstract The environment experienced by a plant before and after reproduction can have a profound effect on the behaviour of the progeny after shedding. Maternal environmental effects on seeds are important for phenology and fitness in plants, especially for bet-hedging reproductive strategies. Maternal tissues that disperse with seeds are important for dormancy in many species, particularly those with coat-imposed dormancy and those that disperse in indehiscent fruits. Maternal nitrogen status, temperature and photoperiod modify maternal tissues and also influence the developing zygote. During seed development on the mother, the progeny may acquire environmental information directly, but there is also evidence for maternal–filial signalling and the epigenetic inheritance of environmental information through the germline.

An adaptive spatiotemporal tensor reconstruction method for GIMMS-3g+ NDVI

Satellite-derived normalized difference vegetation index (NDVI) is inevitably contaminated by clouds and aerosols, causing large uncertainties in depicting the seasonal and interannual variations of terrestrial ecosystems, and potentially misrepresents their responses to climate change and climate extremes. Although various methods have been developed to reconstruct NDVI time series using the similarity in time, space or their combination, they typically require known and accurate data quality information. It is still challenging to effectively reconstruct high-quality NDVI from Global Inventory Modeling and Mapping Studies-3rd Generation V1.2 (GIMMS-3g+), which is one of the longest observation records but lacks reliable data quality information. This study introduces an adaptive spatiotemporal tensor reconstruction algorithm that leverages the spatial and temporal patterns of vegetation to produce high-quality long-term NDVI datasets without the need of data quality information. The reconstruction process employs two different tensor completion models to satisfy the low-rank constraints. These two models can effectively remove the high-frequency noises originating from atmospheric contamination, while preserving the abrupt or low-frequency changes attributable to disturbances such as drought, even in the absence of data quality information. The resultant NDVI shows good consistency with observations from geostationary satellites. Regions that show a strong correlation (r > 0.7) with geostationary satellite NDVI increased from 46.7 % (original GIMMS-3g+) to 62.2 % and 62.3 % (two reconstructions results) for East Asia, and from 41.4 % to 58.0 % and 59.0 % for Amazon. Our method also demonstrates superior performance to traditional methods such as Whittaker, HANTS, SG-filter, and comparable performance with the state-of-the-art ST-Tensor method when the fraction of contaminated observations is low. The proposed method can also be applied to other datasets such as EVI, LAI, etc., without additional data quality inputs. The resultant vegetation index dataset has the potential to improve plant phenology retrievals and evaluation of ecosystem responses to extremes.

Definition of reproductive structures in Eucalyptus for phenological data collection.

In an era where global climate change is shifting plant phenology, global meta-analyses of multiple species are required more than ever. Common language or references for enhanced data compatibility are key for such analyses. Although the Plant Phenology Ontology (PPO) addresses this challenge, it does not capture several relevant reproductive structures that are critical in species with long reproductive cycles, like many Eucalyptus species. We reviewed the terminology and concepts that describe reproductive structures in eucalypts and compared them with the existing classes of the PPO to explore the PPO's potential for harmonizing disparate eucalypt datasets. We identified incongruencies within and between eucalypt terminology and the PPO. We tested the sensitivity of the PPO for capturing key eucalypt phenological structures and found it sensitive to classification of certain structures. To address these limitations, we developed the Eucalyptus Phenology Ontology (EPO), a new ontology that builds on the PPO and captures key reproductive structures using a more refined classification. The EPO integrates the relationships between reproductive structures, phenological stages, and phenological traits. The vocabulary is species-neutral so it can be applied to other taxa but specifies the synonyms and descriptions required to capture the complexity of eucalypt phenology.

Clockwork precision: egg-laying-induced rise of body temperature is seasonally programmed in a wild bird.

There is long time interest about the phenology of plants and animals living in seasonal environments as research in that field would help to understand the coping mechanisms leading to a higher fitness. For instance, it has been shown several decades ago that birds prepare themselves 2-4 months before the actual start of the breeding season by slowly growing reproductive organs. In parallel, the resting metabolic rate increase during reproduction in various vertebrates including mammals, reptiles, and birds. Recently, it has been reported that body temperature of a marine bird species was reaching an annual peak during egg-laying, raising the question about the seasonal dynamic of this important physiological feature. Using data loggers implanted in the abdominal cavity of female Common Eiders (Somateria mollissima mollissima) for a full year, we show here that daily body temperature (T b.daily) is slowly increasing first and then accelerating at the approach of the laying period. Because the rise of T b.daily is tightly associated with egg-laying in this species, we also analysed the influence of ambient temperature (water and air) and photoperiod on this seasonal dynamic. Based on the various mechanisms at work and a parsimonious interpretation of the data, we conclude that photoperiod is the main cue driving the seasonal breeding program of eiders. Although the laying dates of the instrumented females were highly clustered over a period of 4 years, we speculated that the remaining variation observed was the result of eco-physiological challenges occurring over the years.

Internal physiological drivers of leaf development in trees: Understanding the relationship between non‐structural carbohydrates and leaf phenology

Abstract Plant phenology is crucial for understanding plant growth and climate feedback. It affects canopy structure, surface albedo, and carbon and water fluxes. While the influence of environmental factors on phenology is well‐documented, the role of plant intrinsic factors, particularly internal physiological processes and their interaction with external conditions, has received less attention. Non‐structural carbohydrates (NSC), which include sugars and starch essential for growth, metabolism and osmotic regulation, serve as indicators of carbon availability in plants. NSC levels reflect the carbon balance between photosynthesis (source activity) and the demands of growth and respiration (sink activity), making them key physiological traits that potentially influence phenology during critical periods such as spring leaf‐out and autumn leaf senescence. However, the connections between NSC concentrations in various organs and phenological events are poorly understood. This review synthesizes current research on the relationship between leaf phenology and NSC dynamics. We qualitatively delineate seasonal NSC variations in deciduous and evergreen trees and propose testable hypotheses about how NSC may interact with phenological stages such as bud break and leaf senescence. We also discuss how seasonal variations in NSC levels, align with existing conceptual models of carbon allocation. Accurate characterization and simulation of NSC dynamics are crucial and should be incorporated into carbon allocation models. By comparing and reviewing the development of carbon allocation models, we highlight the shortcomings in current methodologies and recommend directions to address these gaps in future research. Understanding the relationship between NSC, source–sink relationships, and leaf phenology poses challenges due to the difficulty of characterizing NSC dynamics with high temporal resolution. We advocate for a multi‐scale approach that combines various methods, which include deepening our mechanistic understanding through manipulative experiments, integrating carbon sink and source data from multiple observational networks with carbon allocation models to better characterize the NSC dynamics, and quantifying the spatial pattern and temporal trends of the NSC‐phenology relationship using remote sensing and modelling. This will enhance our comprehension of how NSC dynamics impact leaf phenology across different scales and environments. Read the free Plain Language Summary for this article on the Journal blog.

Phenophases of Species of the Salix Genus in the Conditions of Osh City

The study of the phenology of urban trees and shrubs has increased dramatically worldwide in recent years, as changes in plant phenology may indicate the impacts of climate change at different scales. The aim of the study is to determine the patterns of the seasonal rhythm of individual species belonging to the Salixgenus in Osh. The studies were conducted in the period 2019-2023 at the Department of Biology, Chemistry and Nature Management of Osh State Pedagogical University. The subject of the study is 4 species of the genus Salix: Salix babylonica L., Salix turanica Nasarow, Salix wilhelmsiana M. Bieb. and Salix tenuijulis Ledeb. Phenological observations were carried out for 5 years using generally accepted phenological methods. The results of phenological observations in 2019-2023 show that the duration of the growing season in urban conditions is 240-245 days, and this indicator varies depending on climatic conditions. The observed species have differences in the flowering sequence, the beginning and duration of flowering. The total duration of flowering in the studied species is 25-35 days. The seasonal type of growth and phenological development of plants of the genus Salix is characterized by an early onset and late end of vegetation, stability of average phenological terms. Such a phenological rhythm of the studied species of the genus Salix makes it possible to consider cultivation for decorative and environmental purposes in urban conditions promising.

Plant phenology predicts the stability of primary production in three ecosystems of the northern Chihuahuan Desert

Abstract The temporal stability of plant productivity affects species' access to resources, exposure to stressors and strength of interactions with other species in the community, including support to the food web. The magnitude of temporal stability depends on how a species allocates resources among tissues and across phenological stages, such as vegetative growth versus reproduction. Understanding how plant phenological traits correlate with the long‐term stability of plant biomass is particularly important in highly variable ecosystems, such as drylands. We evaluated whether phenological traits predict the temporal stability of plant species productivity by correlating 18 years of monthly phenology observations with biannual estimates of above‐ground plant biomass for 98 plant species from semi‐arid drylands. We then paired these phenological traits with potential climate drivers to identify abiotic contexts that favour specific phenological strategies among plant species. Phenological traits predicted the stability of plant species above‐ground biomass. Plant species with longer vegetative phenophases not only had more stable biomass production over time but also failed to fruit in a greater proportion of years, indicating a growth–reproduction trade‐off. Earlier leaf‐out dates, longer fruiting duration and longer time lags between leaf and fruit production also predicted greater temporal stability. Species with stability‐promoting traits began greening in drier conditions than their unstable counterparts and experienced unexpectedly greater exposure to climate stress, indicated by the wider range of temperatures and precipitation experienced during biologically active periods. Our results suggest that bet‐hedging strategies that spread resource acquisition and reproduction over long time periods help to stabilize plant species productivity in variable environments, such as drylands. Read the free Plain Language Summary for this article on the Journal blog.

The Phenology of Coffea arabica var. Esperanza L4A5 Under Different Agroforestry Associations and Fertilization Conditions in the Caribbean Region of Costa Rica

This study focused on the phenology of Coffea arabica var. Esperanza L4A5, an F1 interspecific hybrid obtained by crossing commercial varieties with wild genotypes from Ethiopia and Sudan. Most phenological studies on C. arabica have been conducted in traditional high-altitude regions, leaving a gap in the understanding of its behavior in non-traditional areas such as the Caribbean region of Costa Rica. To establish a baseline on the phenological behavior of the Esperanza L4A5 hybrid in this region, we conducted a four-year study examining the effects of different agroforestry associations: (1) Albizia saman; (2) Hymenaea courbaril and Erythrina poeppigiana; (3) Anacardium excelsum and Erythrina poeppigiana; and coffee plots under full sun. Additionally, the phenology of the coffee plants was evaluated under differentiated fertilizations (physical, chemical, and without fertilization), considering meteorological factors such as temperature, humidity, and rainfall. The observed variables included the development of floral nodes, pre-anthesis, anthesis, and fruiting stages. To analyze the relationships between environmental factors, tree cover, fertilization, and the phenological stages, we employed multiple linear regression (MLR), which revealed that both tree cover and physical and chemical fertilizations had significant effects on the presence of developed floral nodes and, consequently, on fruit production. Furthermore, the random forest (RF) model was applied to capture complex interactions between variables and to rank the importance of meteorological factors, tree cover, and fertilization practices. These analyses demonstrated that the Esperanza L4A5 hybrid exhibited viable phenological development under the atypical conditions of the Caribbean region of Costa Rica, suggesting its potential to adapt and thrive in non-traditional coffee-growing areas.

The Global Forest Fire Emissions Prediction System version 1.0

Abstract. The Global Forest Fire Emissions Prediction System (GFFEPS) is a model that estimates biomass burning in near-real time for global air quality forecasting. The model uses a bottom-up approach, based on remotely sensed hotspot locations, and global databases linking burned area per hotspot to ecosystem-type classification at a 1 km resolution. Unlike other global fire emissions models, GFFEPS provides dynamic estimates of fuel consumption, fire behaviour and fire growth based on the Canadian Forest Fire Danger Rating System, plant phenology as calculated from daily global weather and burned-area estimates using near-real-time Visible Infrared Imaging Radiometer Suite (VIIRS) satellite-detected hotspots and historical burned-area statistics. Combining forecasts of daily fire weather and hourly meteorological conditions with a global land classification, GFFEPS produces fuel consumption and emission predictions in 3 h time steps (in contrast to non-dynamic models that use fixed consumption rates and require a collection of burned area to make post-burn estimates of emissions). GFFEPS has been designed for use in operational forecasting applications as well as historical simulations for which data are available. A study was conducted showing GFFEPS predictions through a 6-year period (2015–2020). Regional annual total smoke emissions, burned area and total fuel consumption per unit area as predicted by GFFEPS were generated to assess model performance over multiple years and regions. The model's fuel consumption per unit area results clearly distinguished regions dominated by grassland (Africa) from those dominated by forests (boreal regions) and showed high variability in regions affected by El Niño and deforestation. GFFEPS carbon emissions and burned area were then compared to other global wildfire emissions models, including the Global Fire Assimilation System (GFAS), the Global Fire Emissions Database (GFED4.1s) and the Fire INventory from NCAR (FINN 1.5 and 2.5). GFFEPS estimated values lower than GFAS and GFED (80 % and 74 %) and had values similar to FINN 1.5 (97 %). This was largely due to the impact of fuel moisture on consumption rates as captured by the dynamic weather modelling. Model evaluation efforts to date are described – an ongoing effort is underway to further validate the model, with further developments and improvements expected in the future.

Growing-degree-days (GDDs) in a uniform phenology scale (BBCH) for two walnut (Juglans regia L.) cultivars

ABSTRACT Descriptors are widely used for monitoring the phenology and pomology of plants. Among them, the BBCH (Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie) scale is the most important. We evaluated the growth of ‘Chandler’ and ‘Persia’ walnut cultivars to create a BBCH descriptor for the crop, and estimate the growing-degree days (GDDs) of different growth stages. The GDDs (°C-days) were measured using 0°C as a base temperature (Tb) for male flowering and 5.5°C for other phenological stages in both cultivars. Growth stages were divided into eight principal stages, each with multiple substages. Stage 0 includes the bud sprouting, while stage 9 occurs when the leaves develop and the tree enters the dormancy. Both cultivars had a similar heat unit requirement at the bud quiescent stage (84 and 71°C-days for ‘Chandler’ and ‘Persia’, respectively); however, ‘Chandler’ needs higher GDDs accumulation to reach the harvest (3876°C-days compared to 3539°C-days for ‘Persia’). The results suggest that ‘Persia’ can be cultivated in colder areas at higher altitudes or latitudes compared with ‘Chandler’.

Shifts in Plant Phenology Significantly Affect the Carbon Allocation in Different Plant Organs.

Earlier start of the growing season (SGS) and delayed end of the growing season (EGS) affect plant carbon uptake. However, the effects of phenological changes on carbon allocation to different plant organs remain unclear. Here, we examined the effects and potential mechanisms of phenological changes on carbon allocation to different organs over the northern hemisphere (> 30° N). We found the earlier SGS facilitated allocating carbon to roots in warm areas, and delayed EGS benefited allocating carbon to roots in dry areas. Moreover, the effects of SGS and EGS on carbon accumulation in different organs significantly enhanced over time. Path analyses indicated that phenological changes contributed to root-stem ratio mainly by regulating the growing season length. Our findings further highlight that phenological changes alter plants' investment strategies in carbon allocation for above- and below-ground parts, and considering this role is critical for accurately estimating the carbon budget in terrestrial ecosystems.

Large herbivores link plant phenology and abundance in Arctic tundra.

Plant phenological dynamics have been well studied in relation to abiotic conditions and climate change, but comparatively poorly studied in relation to herbivory. In contrast, plant abundance dynamics have been well studied in relation to abiotic conditions and herbivory, but poorly studied in relation to phenology. Consequently, the contribution of herbivory to plant phenological dynamics and therefrom to plant abundance dynamics remains obscure. We conducted a 9-year herbivore exclusion experiment to investigate whether herbivory might link plant phenological and abundance dynamics in arctic tundra. From 2009 to 2017, we monitored annual green-up timing and abundance of nine plant taxa, including deciduous shrubs, forbs, and graminoids, on plots that were either grazed or experimentally exclosed from herbivory by caribou (Rangifer tarandus) and muskoxen (Ovibos moschatus). In 62% of cases, green-up occurred earlier under herbivory, and in 75% of cases abundance was greater under herbivory, compared to green-up and abundance under herbivore exclusion. Moreover, taxa that responded to herbivory with earlier green-up also had comparatively greater abundance later in the growing season. Conversely, taxa that responded to herbivory with delayed green-up exhibited comparatively lower abundance later in the growing season. Hence, well-documented influences of large herbivores on plant abundance and community composition in arctic tundra may relate, at least to some extent, to influences of herbivory on plant phenology. We recommend that ongoing and future assessments of the contribution of herbivores to plant abundance and community responses to climate change, especially in the Arctic, should also consider impacts of herbivores on plant phenology.