Risk Of Frost Damage Research Articles

Characterisation of the vertical temperature gradient in the canopy reveals increased trunk height to be a potential adaptation to climate change

Given the important role of temperature in vine development and grape composition, climate change has already impacted wine production. Adaptation strategies are needed in order to sustain the production of wines and maintain their typicity. Several levers of adaptation are possible, including the use of more heat and drought tolerant plant material, relocating the vineyard and adaptations in the cellar. The training system is also a potential lever for adaptation that is relatively easy to implement. Taking that avenue, a study of the vertical thermal gradient in the vine canopy was carried out in order to determine whether trunk height could be an adaptation strategy for manipulating micro-climate in the bunch zone. Temperature was measured at four different heights from the soil (30, 60, 90 and 120 cm) in two adjacent vineyard parcels. One parcel was managed with cover crop and the other by tilling the soil. The results of this study show that increased trunk height is not likely to significantly delay ripeness, but it could minimise the potential damages of both frost and heat wave events. Type of parcel management was found to have an effect: close to the ground, the cover crop parcel generally had lower minimum temperatures and higher maximum temperatures in comparison to the tilled parcel, exposing the vines to an increased risk of both frost and heat wave damage. When investigating the factors driving the vertical thermal gradient, soil moisture and weather type were found to have an impact. Some of these factors, like mean temperature and soil moisture, may exacerbate the vertical temperature gradient of maximum temperature in a climate change context and increase the risk of damages due to extreme temperatures.

Evaluation of the Spatial and Temporal Variations of Condensation and Desublimation over the Qinghai–Tibet Plateau Based on Penman Model Using Hourly ERA5-Land and ERA5 Reanalysis Datasets

Condensation and desublimation are important processes of nocturnal land–atmosphere interactions, energy transfer, and the water cycle, and have important ecological and hydrological roles in mitigating physiological water deficits caused by low temperatures and reducing the risk of frost damage to plants, animals, and microorganisms near the surface in the Alpine Region. The aim of the present study is to evaluate the spatial and temporal variations of condensation and desublimation from 1950 to 2020 based on Penman model using hourly ERA5-Land and ERA5 reanalysis datasets on the Qinghai–Tibet Plateau (QTP), where condensation and desublimation occur frequently but lack quantitative evaluation. The results showed that: (1) Condensation showed a decreasing trend from southeast to northwest, with annual mean condensation ranging from 0 mm to 72.8 mm, while desublimation showed regional enrichment rather than zonal variation, with the annual mean desublimation ranging from 0 mm to 23.6 mm; (2) At 95% confidence level, condensation showed a significant increasing trend in the central and western QTP, while desublimation showed a significant decreasing trend in most regions of the QTP, and the decreasing trend of desublimation was more obvious than the increasing trend of condensation; (3) Both condensation and desublimation showed significant seasonal characteristics; the maximum monthly condensation was 2.37 mm and the monthly mean condensation was 0.70 mm, while the maximum monthly desublimation was 1.45 mm and the monthly mean desublimation was 0.95 mm; (4) The annual mean condensation was 8.45 mm, with an increasing trend of 0.24 mm/10a, the annual mean desublimation was 11.45 mm, with a decreasing trend of −0.26 mm/10a, and the total annual mean condensation and desublimation was 19.89 mm, with a weak decreasing trend on the QTP; (5) The increase in condensation is most associated with the increase in precipitation, while the decrease in desublimation is most associated with the increase in air temperature on the QTP.

The effect of climate change on spring frosts and flowering of Crataegus laevigata – The indicator of the validity of the weather lore about “The Ice Saints”

The onset and duration of phenological events are key indicators of the ecological impact of climate change on vegetation. During the flowering time in spring, late frosts are one of the most dangerous meteorological phenomena leading to damage to crops. During 1987–2016, we analyzed the occurrence and intensity of frosts during the period around the weather lore “Frost on the Ice Saints burns all the flowers” in short, “The Ice Saints” and their effects on the flowering phenology of hawthorn (Crataegus laevigata (Poir.) DC.). The late frosts were identified at 0.05 m and2.0 m above ground from temperature measurement data at five phenological stations located from 160 m to 700 m a.s.l. in Slovakia. Results indicate that recent climate change caused the beginning of flowering (BBCH60) for Crataegus laevigata to start significantly earlier by 4.2, 5.0, 6.2 and 3.6 days per decade at 160, 300, 400 and 500 m a.s.l., respectively. Thus, the risk of late frost damage to flowers during “The Ice Saints” is getting highly probable, particularly at 160, 300 and 500 m a.s.l., where the flowering and frosts occur simultaneously. Decreased risk of frost damage during “The Ice Saints” was found at 400 and 700 m a.s.l. It was because of the rare frost occurrence at 400 m a.s.l. in the last decade (2007–2016) of the studied period, and due to the flowering onset dated mostly after “The Ice Saints” at 700 m a.s.l. in the same period.

The early bud gets the cold: Diverging spring phenology drives exposure to late frost in a Picea mariana [(Mill.) BSP] common garden.

Under climate change, the increasing occurrence of late frost combined with advancing spring phenology can increase the risk of frost damage in trees. In this study, we tested the link between intra-specific variability in bud phenology and frost exposure and damages. We analysed the effects of the 2021 late frost event in a black spruce (Picea mariana (Mill.) BSP) common garden in Québec, Canada. We hypothesised that the timing of budbreak drives the exposure of vulnerable tissues and explains differences in frost damage. Budbreak was monitored from 2015 to 2021 in 371 trees from five provenances originating between 48° and 53° N and planted in a common garden at 48° N. Frost damages were assessed on the same trees through the proportion of damaged buds per tree and related to the phenological phases by ordinal regressions. After an unusually warm spring, minimum temperatures fell to -1.9°C on May 28 and 29, 2021. At this moment, trees from the northern provenances were more advanced in their phenology and showed more frost damage. Provenances with earlier budbreak had a higher probability of damage occurrence according to ordinal regression. Our study highlights the importance of intra-specific variability of phenological traits on the risk of frost exposure. We provide evidence that the timings of bud phenology affect sensitivity to frost, leading to damages at temperatures of -1.9°C. Under the same conditions, the earlier growth reactivation observed in the northern provenances increases the risks of late frost damage on the developing buds.

Epigenetics for crop adaptation to climate change

Epigenetics for crop adaptation to climate change

Development of an Integrated Solution to Prevent Spring Frost Damage Using an Aqueous-based Insulating Foam

In recent years, agricultural crops experience unusually early onset of vegetation due to global warming, which can cause major frost damage with devastating effects on crop yields. To mitigate the risk of frost damage, an integrated solution was developed, consisting of an aqueous-based biocompatible foam and a portable foam applicator enabling wine cultivators to treat up to 1000 m2 of vineyards with one filling containing 10 L of foam. The foam is biocompatible, stable for several days and easily removed by rain. Foam application yielded an insulation efficiency of up to 1.5°C during spring frost nights for the buds covered by the foam when combined with an electrically heated wire. Moreover, it was observed that the foam also created a 'mini greenhouse' effect at positive temperatures during the days, which might be a positive side effect helping the plants to grow at this early stage of the year.

Late frost as a driver of ecotypic differentiation in sugar maple: Implications for assisted migration

Global warming advances bud break, mismatches plant phenology from the local climate, and exposes the developing leaves to higher risks of frost damage. Bud break of sugar maple [Acer saccharum (Marsh.)], a species included in recent programs of assisted migration, is sensitive to nighttime spring temperatures. This suggests a link between frost events and leaf development. In this study, we raise the hypothesis that late frost is an evolutionary driver of growth reactivation in sugar maple provenances. We investigated the ecotypic variation of bud phenology in 30 provenances planted in two common gardens within and at the northern limit of the species range, in the Province of Quebec, Canada. Eight phases of bud break were assessed twice a week during 2020 on 252 and 272 seedlings in southern and northern sites, respectively. In the southern site, bud break occurred in May, starting on average 12 days earlier and ending 3 days earlier compared to the northern site. Logistic regression was used to estimate the probability of late frost and the results showed that regions located in the north, at higher elevations, and along the northeastern coast of the native maple range showed the latest occurrences of frost events in spring. This pattern mirrored the timing of bud break. When planted in the same common garden, provenances originating from sites with later spring frosts leafed out earlier. Such differences were maintained across the eight bud phenological phases and between the two common gardens, which indicates a similar response of the provenances to changing growing conditions. To avoid frost damage to sugar maple plantations, assisted migration should account for phenotypic traits in bud phenology, ensuring that the frost regime at the origin of the provenances is compatible with that of plantations.

Empirical modeling of pore size distribution for rock materials with its impact on pore water freezing

The phase transition of pore water in porous rock is closely related to the pore size distribution (PSD) based on thermodynamic equilibrium, and the ice formation is further affected by the internal hydraulic pressure and external confinement. This study quantitively assesses the risk of frost damage for rocks with/without surrounding pressures through a thermodynamic approach. First, an empirical PSD model is established and compared with experimental results, which is further adopted to calculate water saturation and ice volume under different humidity and temperature conditions. Then the depression of freezing point is discussed under undrained condition by dividing these rocks into three typical groups in terms of porosity and strength. Moreover, confinement by the high surrounding stress is considered for underground structures to study its influence on the ice formation process. Finally, correlation is found between the lowest bearable temperature and the expression of the porosity and strength of rocks, enabling a convenient assessment of frost damage risk for the rocks.

Genetic solutions through breeding counteract climate change and secure barley production in Australia

Climate changes threaten global sustainable food supply by reducing crop yield. Estimates of future crop production under climate change have rarely considered the capacity of genetic improvement in breeding high-yielding and stress-tolerant crop varieties. We believe that technological advancements and developing climate-resilient crop varieties may offset the adverse effects of climate change. In this study, we examined the historical record of barley breeding and yield, and the trends of climate changes over the past 70 years in Australia. We related the selection of fast development varieties to yield improvement, and revealed the genetic connections of fast development and yield potential through genome-wide association studies. Historical records show that Australia's barley yield has experienced a steady growth despite that the seasonal production window has been shortened due to increased risk of frost damage at flowering stage and terminal heat during maturity since the 1970s. The increase in yield is largely the result of higher yield capacity of the more recently developed varieties that develop faster to counteract the impact of increased terminal heat. We also show that the changing temperature may soon reach a critical point that dramatically changes the barley flowering behaviour to impact yield by pushing its growth beyond the seasonal production window to face increasing frost damage. For the first time, we provide evidence that the effects of climate change on crop production might be less severe than what is currently believed because the advancement of technologies and development of climate-resilient crop varieties may mitigate the adverse effect of climate change to some extent. The greater use of genetic techniques in crop breeding will play a vital role in sustainable global food production in the era of climate change. • The increase in barley production in Australia over the last 70 years is related to the improved yield of varieties. • The newer varieties are flowering earlier to counteract the increased terminal heat/drought stress in the maturity stage. • Crop genetic improvement is a powerful solution to counteract the adverse impact of climate change. • Modelling crop production under climate change should consider the capacity to breed stress-tolerant varieties.

Insight into Carbohydrate Metabolism and Signaling in Grapevine Buds during Dormancy Progression.

Perennial fruit crops enter dormancy to ensure bud tissue survival during winter. However, a faster phenological advancement caused by global warming exposes bud tissue to a higher risk of spring frost damage. Tissue dehydration and soluble sugars accumulation are connected to freezing tolerance, but non-structural carbohydrates also act as metabolic substrates and signaling molecules. A deepened understanding of sugar metabolism in the context of winter freezing resistance is required to gain insight into adaptive possibilities to cope with climate changes. In this study, the soluble sugar content was measured in a cold-tolerant grapevine hybrid throughout the winter season. Moreover, the expression of drought-responsive hexose transporters VvHT1 and VvHT5, raffinose synthase VvRS and grapevine ABA-, Stress- and Ripening protein VvMSA was analyzed. The general increase in sugars in December and January suggests that they can participate in protecting bud tissues against low temperatures. The modulation of VvHT5, VvINV and VvRS appeared consistent with the availability of the different sugar species; challenging results were obtained for VvHT1 and VvMSA, suggesting interesting hypotheses about their role in the sugar–hormone crosstalk. The multifaceted role of sugars on the intricate phenomenon, which is the response of dormant buds to changing temperature, is discussed.

Delayed autumnal leaf senescence following nutrient fertilization results in altered nitrogen resorption.

Increased atmospheric nitrogen (N) deposition could create an imbalance between N and phosphorus (P), which may substantially impact ecosystem functioning. Changes in autumnal phenology (i.e., leaf senescence) and associated leaf nutrient resorption may profoundly impact plant fitness and productivity. However, we know little about how and to what extent nutrient addition affects leaf senescence in tree species, or how changes in senescence may influence resorption. We thus investigated the impacts of N and P addition on leaf senescence and leaf N resorption in 2-year-old larch (Larix principisrupprechtii) seedlings in northern China. Results showed that nutrient addition (i.e., N, P or N+P addition) significantly delayed autumnal leaf senescence, and decreased leaf N resorption efficiency (NRE) and proficiency (NRP), particularly in the N and N+P treatments. Improved leaf N concentrations were correlated with delayed leaf senescence, as indicated by the positive relationship between mature leaf N concentrations and the timing of leaf senescence. Following nutrient addition, larch seedlings shifted toward delayed onset, but more rapid, leaf senescence. Additionally, we observed an initial negative correlation between the timing of leaf senescence and NRE and NRP, followed by a positive correlation, indicating delayed and less efficient remobilization during the early stages of senescence, followed by accelerated resorption in the later stages. However, the latter effect was potentially impaired by the increased risk of early autumn frost damage, thus failed to fully compensate for the negative effects observed during the early stages of senescence. Improved soil P availability increased leaf N resorption and thus weakened the negative impact of delayed leaf senescence on leaf N resorption, so P addition had no significant impact on leaf N resorption. Overall, our findings clarify the relationship between nutrient addition-resorption and the linkage with leaf senescence, and would have important implications for plant nutrient conservation strategy and nutrient cycling.

To plant or not to plant? A soil temperature climatology for the Northern and Central Plains

Sufficient soil temperatures at the time of planting are essential for a well-established stand in both large-scale agriculture and recreational home gardening. Planting too early in the season increases the risk for frost damage and slow seedling growth while planting too late risks not reaching the required growing degree days (GDD) for plant maturity. In this study, a climatology of the date in which soils reach critical temperature thresholds for crops was developed for the Northern and Central Plains. At least 15 years of soil temperature data from 155 automated stations from six different networks were utilized in this study. Results showed that Minnesota consistently reached each soil temperature threshold last, while south-central Colorado reached each threshold first, with differences in air temperature and soil moisture likely playing a role. These results were incorporated into an online tool that both professional and recreational agriculturists can use to determine when soil temperatures are best for planting. It will also help put soil temperatures into context based on a climatological average.

Hygrothermal performance of an internally insulated masonry wall: Experimentations without a vapour barrier in a historic Italian Palazzo

This paper presents the newly developed study, methodology and assessment of the hygrothermal performance of a historic building wall retrofitted with three different internal insulation technologies, without a vapour barrier. It aims at assessing any possible condensation problems at the most critical point of the tested stratigraphy (namely, in between the wall and the insulation material) and to limit the modification of the original hygrothermal behaviour of the original wall’s materials with the addition of a vapour layer, as would commonly be used. This evaluation was performed through in situ measurements and dynamic software simulations. In situ data was used for calibrating the 2D simulation model conducted with Delphinsoftware 6.0.20.Under the climatic conditions in Ferrara (Italy), the results of both the in-situ monitoring and simulation evidenced no risk of frost damage to the building’s original wall. With regards to the risk of interstitial condensation, simulations showed no high risk even in the absence of a water vapour barrier. Additionally, the amount of water vapour collected during the winter season dried out during the spring/summer period.

Laurentian Great Lakes warming threatens northern fruit belt refugia.

Climate refugia are anomalous "pockets" of spatially or temporally disjunct environmental conditions that buffer distinct flora and fauna against prevailing climatic conditions. Physiographic landscape features, such as large water bodies, can create these micro-to-macro-scale terrestrial habitats, such as the prevailing westerly winds across the Laurentian Great Lakes that create relatively cooler leeward conditions in spring and relatively warmer leeward conditions in autumn. The leeward Great Lakes climate effects create refugia (popularly known as a "fruit belt") favorable for fruit-bearing trees and shrubs. These fruit belt refugia owe their existence to seasonal inversions whereby spring cooling prevents early flower budding that leaves fruit trees susceptible to late spring killing frosts, and autumn warming prevents early killing frosts. With global climate change, however, warmer summers and milder winters, and corresponding warmer waters, might erode the leeward delaying effect on spring flowering, creating a paradoxical situation in which warming increases the risk of frost damage to plants. We evaluated the success of regional agriculture in the Great Lakes fruit belt to test our hypothesis that warmer spring climate (and concomitant warmer lake waters) correspond with degraded fruit production. We also examined long-term trends in Great Lakes climate conditions. We found that the cold-sensitive fruit tree (apple, grape, peach, and cherry) refugia were destabilized by relatively warmer springs. Moreover, we found several indicators that lake waters are warming across the Great Lakes, which portends negative consequences for agricultural and natural plant communities in the Great Lakes region and in similar "fruit belt" refugia worldwide.

Spatiotemporal evolution characteristics of the late frost damage risk to shrubby tea trees in tea region, southwest China from 1971 to 2020.

Understanding the spatiotemporal evolution characteristics of the risk of late frost damage has scientific guiding significance for optimizing the regional agricultural production layout and varie-ty tuning. Based on the daily meteorological data of 65 weather stations in the southwest China tea region from 1971 to 2020, we analyzed variation characteristics of the last frost date (LFD), tea bud open date (BOD), and their relationships, constructed frost damage probability index and frost damage severity index of spring shoots of shrubby tea trees, and analyzed the spatiotemporal evolution chara-cteristics of the late frost damage risk of shrub tea trees in the southwest tea region. The results showed that both the BOD and LFD had a significant ahead of trend from 1971 to 2020 and the early rate of the LFD was relatively faster than that of the BOD in the southwest tea region. The number of days that the tea buds were exposed to late frost damage after germination showed an non-significant declining trend. The risk of late frost damage of shrubby tea trees in most parts of the southwest tea region showed a declining trend, but Guizhou tea planting region showed an insignificant increasing trend. The risk of late frost damage to shrubby tea trees was high in the western marginal mountai-nous areas of Sichuan tea region, and the junction of Guizhou and Yunnan tea region. The risk of late frost damage was at low level in Sichuan Basin, southern Yunnan tea region, and southern Guizhou tea region. The risk of late frost damage to shrubby tea trees in the northern and central-eastern parts of Yunnan tea region showed an obvious decreasing trend, but increased significantly in the central and eastern parts of Guizhou tea region.

A Conceptual Design of LoRa based Weather Monitoring System for Smart Farming

Internet of Things (IoT) based smart farming applications opens up new opportunities for monitoring the agricultural fields. There are different communication protocols can be used in practice to connect the IoT-enabled devices. Among them, the low-power, wide area network (LPWAN) based protocols are well suited to the specific needs of agricultural applications due to their energy-efficient transmission of small data packets over long distances. This study presents the conceptual design of LoRa based weather monitoring system that can be used to warn the farmers about possible crop damages due to harsh weather conditions. The hardware design of a low-cost weather station has been explained in details. Also, the estimated coverage area of the application to be carried out in order to reduce the risk of apple flowering frost damage risk in Karaman Province, Turkey was evaluated using the Xirio Online radio planning tool. The obtained results have verified the feasibility of proposed weather monitoring system.

Tree Mortality Risks Under Climate Change in Europe: Assessment of Silviculture Practices and Genetic Conservation Networks

General Context: Climate change can positively or negatively affect abiotic and biotic drivers of tree mortality. Process-based models integrating these climatic effects are only seldom used at species distribution scale.Objective: The main objective of this study was to investigate the multi-causal mortality risk of five major European forest tree species across their distribution range from an ecophysiological perspective, to quantify the impact of forest management practices on this risk and to identify threats on the genetic conservation network.Methods: We used the process-based ecophysiological model CASTANEA to simulate the mortality risk of Fagus sylvatica, Quercus petraea, Pinus sylvestris, Pinus pinaster, and Picea abies under current and future climate conditions, while considering local silviculture practices. The mortality risk was assessed by a composite risk index (CRIM) integrating the risks of carbon starvation, hydraulic failure and frost damage. We took into account extreme climatic events with the CRIMmax, computed as the maximum annual value of the CRIM.Results: The physiological processes' contributions to CRIM differed among species: it was mainly driven by hydraulic failure for P. sylvestris and Q. petraea, by frost damage for P. abies, by carbon starvation for P. pinaster, and by a combination of hydraulic failure and frost damage for F. sylvatica. Under future climate, projections showed an increase of CRIM for P. pinaster but a decrease for P. abies, Q. petraea, and F. sylvatica, and little variation for P. sylvestris. Under the harshest future climatic scenario, forest management decreased the mean CRIM of P. sylvestris, increased it for P. abies and P. pinaster and had no major impact for the two broadleaved species. By the year 2100, 38–90% of the European network of gene conservation units are at extinction risk (CRIMmax=1), depending on the species.Conclusions: Using a process-based ecophysiological model allowed us to disentangle the multiple drivers of tree mortality under current and future climates. Taking into account the positive effect of increased CO2 on fertilization and water use efficiency, average mortality risk may increase or decrease in the future depending on species and sites. However, under extreme climatic events, our process-based projections are as pessimistic as those obtained using bioclimatic niche models.

Deacclimation and reacclimation of apple (Malus × domestica Borkh.), blackcurrant (Ribes nigrum L.) and raspberry (Rubus idaeus L.) shoots and buds under controlled conditions

In the future climate scenario the transient warm spells during winter are predicted to become more frequent and potentially increase the risk of frost damage in perennial horticultural crops. The aim of our study was to examine, whether apple (Malus × domestica Borkh.), blackcurrant (Ribes nigrum L.), and raspberry (Rubus idaeus L.) cultivars differing in winter hardiness have a different susceptibility to deacclimation during a warm spell and the ability to reacclimate in response to a subsequent cold period. Shoot samples were collected from commercial orchards in Finland on Feb. 6, 2019. Samples were subjected to a deacclimation treatment (+5°C, 4 d) followed by a reacclimation treatment (-7°C, 7 d). Controlled freezing tests were conducted immediately after sampling, and at the end of deacclimation and reacclimation treatments to determine frost hardiness (FH). FH was most stable in those cultivars that are known to be hardy in the Finnish climate conditions, i.e. ‘Pirja’ apple, ‘Mikael’ and ‘Öjebyn’ blackcurrants, and ‘Maurin Makea’ raspberry. Buds were consistently less hardy than shoots, the difference being largest in blackcurrant, 25°C. The buds of all cultivars, except ‘Pirja’ apple, deacclimated during four days at +5°C, but only ‘Ben Tron’ blackcurrant buds were able to reacclimate. The depth of dormancy was determined by forcing the shoot samples in a greenhouse to examine the relationship of the FH stability to the dormancy status in the cultivars. Sixty to 95 % of apple, 98 to 100 % of blackcurrant, and 55 to 67 % of raspberry buds broke during five weeks in forcing. Only the apple cultivars exhibited cultivar differences in the dormancy status in the beginning of February. ‘Pirja’ despite having the most stable FH of the apple cultivars, showed the most complete and fastest bud break in forcing. Consequently, the susceptibility to deacclimation during a warm spell and the ability to reacclimate at subsequent low temperatures were not related to the status of dormancy in these cultivars.

Model analysis of temperature impact on the Norway spruce provenance specific bud burst and associated risk of frost damage

The annual growth cycle of boreal trees is synchronized with seasonal changes in photoperiod and temperature. A warmer climate can lead to an earlier bud burst and increased risk of frost damage caused by temperature backlashes. In this study we analysed site- and provenance specific responses to interannual variation in temperature, using data from 18 Swedish and East-European provenances of Norway spruce (Picea abies), grown in three different sites in southern Sweden. The temperature sum requirements for bud burst, estimated from the provenance trials, were correlated with the provenance specific place of origin, in terms of latitudinal and longitudinal gradients. Frost damage had a significant effect on tree height development. Earlier timing of bud burst was linked to a higher risk of frost damage, with one of the sites being more prone to spring frost than the other two. The estimated provenance specific temperature sum requirements for bud burst were used to parametrize a temperature sum model of bud burst timing, which was then used together with the ensemble of gridded climate model data (RCP8.5) to assess the climate change impact on bud burst and associated risk of frost damage. In this respect, the simulated timing of bud burst and occurrence of frost events for the periods 2021–2050 and 2071–2100 were compared with 1989–2018. In response to a warmer climate, the total number of frost events in southern Sweden will decrease, while the number of frost events after bud burst will increase due to earlier bud burst timing. The provenance specific assessments of frost risk under climate change can be used for a selection of seed sources in Swedish forestry. In terms of selecting suitable provenances, knowledge on local climate conditions is of importance, as the gridded climate data may differ from local temperature conditions. A comparison with temperature logger data from ten different sites indicated that the gridded temperature data were a good proxy for the daily mean temperatures, but the gridded daily minimum temperatures tended to underestimate the local risk of frost events, in particular at the measurements 0.5 m above ground representing the height of newly established seedlings.

Habitat-specific effects of flowering advance on fruit-set success of alpine plants: a long-term record of flowering phenology and fruit-set success of Rhododendron aureum

Global warming tends to accelerate flowering phenology of alpine plants, and it may cause a decrease in fruit production due to lower pollinator activity and/or higher risk of frost damage earlier in the season. Because flowering period of alpine plants varies highly depending on snowmelt conditions, the effects of phenological variation on fruit-set success may vary among local populations. I observed the relationship between flowering time and fruit-set success in four populations of a bee-pollinated dwarf shrub, Rhododendron aureum, located in fellfield and snowbed habitats in northern Japan, for 12 or 13 years over the 25 years from 1995 to 2019. Flowering of the fellfield populations usually occurred in June, and flowering of the snowbed populations commonly started after mid-July, although there was considerable yearly variation in actual flowering time within individual populations. Generally, the fruit-set rates of the fellfield populations were low, with large yearly fluctuations, whereas those of the snowbed populations were stable and high. There was a clear trend toward a decrease in fruit-set rates with earlier flowering in the fellfield populations due to pollen limitation and occasional frost damage. The risk of frost damage increased with earlier flowering in the fellfield habitat. These results indicate that the effects of climate change on fruit-set success of alpine plants are strongly site-specific and are greatest early in the growing season.