Frost Risk Research Articles

Asymmetric temperature effect on leaf senescence and its control on ecosystem productivity.

Widespread autumn cooling occurred in the northern hemisphere (NH) during the period 2004-2018, primarily due to the strengthening of the Pacific Decadal Oscillation and Siberian High. Yet, while there has been considerable focus on the warming impacts, the effects of natural cooling on autumn leaf senescence and plant productivity have been largely overlooked. This gap in knowledge hinders our understanding of how vegetation adapts and acclimates to complex climate change. In this study, we utilize over 36,000 in situ phenological time series from 11,138 European sites dating back to the 1950s, and 30 years of satellite greenness data (1989-2018), to demonstrate that leaf senescence dates (LSD) in northern forests responded more strongly to warming than to cooling in autumn. Specifically, a 1 °C increase in temperature caused 7.5 ± 0.2 days' delay in LSD, whereas a 1 °C decrease led to an advance of LSD with 3.3 ± 0.1 days (P < 0.001). This asymmetry in temperature effects on LSD is attributed to greater preoverwintering plant-resource acquisition requirements, lower frost risk, and greater water availability under warming than cooling conditions. These differential LSD responses highlight the nonlinear impact of temperature on autumn plant productivity, which current process-oriented models fail to accurately capture. Our findings emphasize the need to account for the asymmetric effects of warming and cooling on leaf senescence in model projections and in understanding vegetation-climate feedback mechanisms.

Crop Coefficients and Irrigation Demand in Response to Climate-Change-Induced Alterations in Phenology and Growing Season of Vegetable Crops

This study investigates the effects of climate change on the irrigation demand of vegetable crops caused by alteration of climate parameters affecting evapotranspiration (ET), plant development, and growing periods in Central Europe. Utilizing a model framework comprising two varying climate scenarios (RCP 2.6 and RCP 8.5) and two regional climate models (COSMO C-CLM and WETTREG 2013), we calculate the daily crop water balance (CWBc) as a measure for irrigation demand based on reference ET and the temperature-driven duration of crop coefficients until 2100. Our findings for onion show that rising temperatures may shorten cultivation periods by 5 to 17 days; however, the irrigation demand may increase by 5 to 71 mm due to higher ET. By reaching the base temperatures for onion growth earlier in the year, cultivation start can be advanced by up to 30 days. Greater utilization of winter soil moisture reduces the irrigation demand by up to 21 mm, though earlier cultivation is restricted by frost risks. The cultivation of thermophilic crops, however, cannot be advanced to the same extent, as shown for bush beans, and plants will transpire more strongly due to longer dry periods simulated for summer. The results underscore the need for adaptive crop and water management strategies to counteract the simulated changes in phenology and irrigation demand of vegetable crops. Therefore, special consideration must be given to the regional-specific and model- and scenario-dependent simulation results.

Identification of the best viticultural areas by spatial optimisation. Application in New Zealand South Island in the context of climate change

The global winegrowing sector is under pressure due to the effects of global climate change. This is particularly true for New Zealand, where the wine industry is limited to a few regions. This study focuses on the South Island of New Zealand. It uses the Multi-objective Optimisation for Agrosystems (MOA) model to (i) investigate how potential exposure to climate risks and phenological stages will evolve under climate change, (ii) assess the suitability of current vineyards for viticulture in the future, and (iii) investigate potential emerging areas favourable for viticulture.The results show that a significant shift in the phenological stages of veraison and ripeness can be expected in the future due to the warming of the South Island of New Zealand. The projected phenological stages advancement is around one week in the near term for both Shared-Socioeconomic Pathways studied (SSP2-4.5 and SSP5-8.5) and is more than three weeks and one month in long-term for SSP2–4.5 and SSP5-8.5 respectively. A regional to local increase in frost risk (Canterbury, Otago, and Southland) and a slight increase in disease risk (especially on the coast) are also projected in the future, while the South Island of New Zealand is not expected to be affected by heatwaves. The results show that Marlborough, New Zealand's most important winegrowing region, will continue to be one of the best areas for viticulture in the 21st century. On the other hand, new winegrowing opportunities are expected to emerge inland and southwards.Overall, this study contributes to the understanding of the impact of climate change on the New Zealand wine industry and emphasises the need to adapt to changing climate conditions. It also provides insights into the future suitability of vineyards and identifies potential expansion areas for the New Zealand viticulture sector.

Leaf functional traits predict timing of nutrient resorption and carbon depletion in deciduous subarctic plants

Abstract Resorption of key elements promotes their conservation in plants in nutrient‐poor ecosystems. In seasonal environments, the timing of resorption is expected to influence resorption efficiency and plant fitness due to the trade‐off between maximizing photosynthetic carbon gain by late resorption and minimizing frost risks and nutrient loss by early resorption. Here, we hypothesize that (1) these alternative strategies with respect to the timing of element resorption both occur among summergreen species; (2) deciduous woody plants favour delayed resorption while herbaceous species benefit from gradual, early onset resorption; (3) this pattern is part of a more general relationship in which species with conservative resource economic traits have more delayed resorption. We measured nitrogen (N), phosphorus (P) and carbon (C) contents of mature, senescing and senesced leaves of 22 predominant plant species across four types of ecosystems in a subarctic region. We then calculated timing of resorption as the Julian calendar day of 50% of element resorption (T50), and examined its relationship with plant functional types and leaf resource economic traits (leaf mass per area [LMA], leaf C, N and P contents). The timing of N resorption in subarctic plants ranged from day 213 to 254, while the timing of P resorption ranged from day 211 to 261 and of C from day 214 to 260 across species. On average, the resorption of N and P and depletion of C were 13, 12 and 19 days respectively earlier in herbaceous plants than in woody ones. For all the three elements, T50 of plants decreased significantly with increasing acquisitive economic traits. Synthesis: As hypothesized, we found that (1) both “steady‐and‐slow” and “late‐and‐fast” strategies of resorption timing co‐occurred in a subarctic flora; consistent with these two strategies, herbaceous plants resorbed nutrients and carbon earlier than deciduous woody species; (2) relevant functional traits representing resource conservation were positively and linearly related to the timing of nutrient resorption and carbon depletion. These findings for element resorption timing have important implications for functional changes in the vegetation composition of seasonal regions in response to temperature fluctuations in a changing climate.

Mapping frost risk in fruit trees using GIS-based analysis: a case study in the province of Alicante (Spain)

Mapping frost risk in fruit trees using GIS-based analysis: a case study in the province of Alicante (Spain)

Higher risk of spring frost under future climate change across China's apple planting regions

Spring frost is one of major agro-meteorological disasters impacting apple production. Previous studies focused on the impacts of spring frost during the flowering period on apples, however, the frost events occurring at both pre- and post-flowering phases have significant impacts on apples. Our study employed four phenology models (parallel model, M1 model, sequential model, and growing degree hour model), along with their ensemble model driven by five global climate models (GCMs) to predict the key spring phenphases of apple across China’s apple planting regions under two emission scenarios (SSP245 and SSP585) during the 2050 s (2040–2069) and 2080 s (2070–2099). A new spring frost assessment index (FI) combining frequency and intensity of spring frost was developed to evaluate the impacts of climate change on spring frost risk of apple. The results showed a large spatial variation in projected spring phenophases across China’s apple planting regions. Projected budbreak (BBCH 09), initial flowering (BBCH 60), and final flowering (BBCH 69) would advance 5.6–15.9 days, 5.7–14.8 days, and 5.6–14.5 days, respectively, in regions I, II, and V of northern China apple planting regions. However, in regions III and IV of southern China apple planting regions, projected budbreak, initial flowering, and final flowering would delay –9.2–21.5 days, –7.5–20.6 days, and –6.8–20.8 days in the future climate scenarios, compared with the baseline (1980–2009). Projected last spring frost date considering the entire spring phenphases would advance 3.7–11.8 d in the future climate scenarios, compared with the baseline. Projected spring frost risk would increase in all the three growth stages including budbreak to initial flowering, flowering period, and final flowering to the last spring frost date across all the China's apple plating regions in future climate scenarios except southward China's apple plating region under the SSP585 in the 2080 s. Our study provides an important reference for early warning, prevention and mitigation of spring frost disasters, and the layout of the apple industry.

Parametric influence and optimization of the dehumidification performance of a variable-frequency dehumidifier

This paper optimizes a variable-frequency dehumidification system (VFDS) based on the principle of vapor compression refrigeration (VCR), wherein the compressor frequency and fan speed can be changed. The effect of the compressor frequency and fan speed on the operating parameters of the VFDS, including the evaporating temperature (T e), condensing temperature (T c), superheating (ΔT sh), and subcooling (ΔT sc), is studied experimentally under three operating conditions. The effect of variable-frequency on the dehumidification performance is analyzed at the mechanistic level through two dehumidification performance indicators, namely, the dehumidification capacity (DC) and dehumidification energy efficiency (DEE). ΔT sh is primarily controlled by the capillary throttling effect, which always starts to cross the “0” point when the fan speed is 600 rpm under different conditions. An increase in the compressor frequency leads to the opposite trend for DC and DEE, but their corresponding optimal fan speeds are relatively close. At 27 °C/60%, the optimal fan speed intervals with DC and DEE as single optimization objectives are both [600 rpm, 700 rpm]. However, at 30 °C/80%, the overall difference between the optimal fan speed intervals with DC and DEE as optimization objectives is 50–100 rpm. Importantly, the risk of frost at 18.3 °C/60% can lead to a significant extension of the optimal fan speed interval, which is [500 rpm, 900 rpm], making it more difficult to control. The concept of the dehumidification operating temperature difference (ΔT) is proposed to comprehensively evaluate the dehumidification capacity and as a control index for variable frequencies. The relationships among the optimal ΔT and the ambient dew point temperature (Td ) and compressor frequency are established through response surface methodology (RSM) with a maximum deviation of 5.97%. This work can provide an optimized variable-frequency solution for the VFDS and some guidance for the control logic development of the VFDS.

Differential phenological responses to temperature among various stages of spring vegetation green-up

Abstract Vegetation green-up is occurring earlier due to climate warming across the Northern Hemisphere, with substantial influences on ecosystems. However, it is unclear whether temperature responses differ among various green-up stages. Using high-temporal-resolution satellite data of vegetation greenness and averaging over northern vegetation (30–75° N), we found the negative interannual partial correlation between the middle green-up stage timing (50% greenness increase in spring–summer) and temperature (RP = −0.73) was stronger than those for the onset (15% increase, RP = −0.65) and end (90% increase, RP = −0.52) of green-up during 2000–2022. Spatially, at high latitudes, the middle green-up stage showed stronger temperature responses than the onset, associated with greater low-temperature constraints and stronger control of snowmelt on green-up onset as well as greater spring frost risk. At middle latitudes, correlations with temperature were similar between the onset and middle stages of green-up, except for grasslands of the Mongolian Plateau and interior western USA, where correlations with temperature were weaker for the middle stage due to water limitation. In contrast, the end of the green-up showed weaker temperature responses than the middle due to insufficient water and high climatic temperature during the end of the green-up in most of the study region, except for cold regions in the interior western USA, western Russia and the Tibetan Plateau, where temperature was still a main driver during end of green-up. Our findings underscore the differences in temperature responses among green-up stages, which alters the temporal alignment between plants and environmental resources.

When common recommendations for cultivating in cold soils inadvertently thaw permafrost

When common recommendations for cultivating in cold soils inadvertently thaw permafrost Melissa Ward Jones, details when common recommendations for cultivating in cold soils inadvertently thaw permafrost, starting with the challenges of cultivating at high latitudes. Cultivating crops within cold soils at high latitudes can be challenging. The growing season is short, with the risk of frosts at each seasonal margin, and overall, both air and soil temperatures limit crop options that can be grown. A common recommendation in cultivating cold soils is the use of seasonal extension techniques, such as greenhouses, high tunnels, low tunnels and various mulches (such as plastic and biodegradable like straw and compost) to artificially heat the soil, and depending on the technique used, the air temperature as well (Stevenson et al., 2014).

The Observed Changes in Climate Characteristics in the Trebinje Vineyard Area (Bosnia and Herzegovina)

The productivity and quality of grapes and wine are significantly influenced by changing climate conditions in vineyard regions worldwide. This study assesses changes in temperature, precipitation, and viticultural indices between the periods of 1971–1990 and 2000–2019 in Trebinje, a vineyard area located in the Herzegovina region of Bosnia and Herzegovina. Between the two periods, mean annual temperature increased by 2 °C and mean vegetational temperature by 2.4 °C, while mean precipitation remained within the range of climatological variability, with annual values increasing by 6% and vegetational values decreasing by 4.6%. Warming resulted in a longer duration of the vegetation season by 23.7 days, a reduced risk of late spring frosts, and an increased risk of very high temperatures during summer. These changes led to the reclassification of Trebinje vineyards’ climate from Region III to Region V, based on the Winkler index values, from a “temperate warm” to a “warm” category, based on the Huglin heliothermic index, and from “cool nights” to “temperate nights” based on the cool nights index. The category of the dryness index remained unchanged between the two periods. The findings emphasize the necessity for a renewal of the viticultural zoning and the development of climate change-adaptation plans for this region.

Multi-model ensemble of frost risks across East Asia (1850–2100)

Frost events can cause the deterioration of a wide range of heritage materials, including stone, brick and earth. In a warming world, the frequency and location of frost events is likely to change, affecting the conservation strategies required at heritage sites. We use a multi-model ensemble approach to investigate three types of frost events in East Asia: freeze–thaw cycles; deep frost days and wet frosts. The study uses nine CMIP6 models for the period 1850 to 2100, with future projections run under the SPS585 scenario. Additional analysis is undertaken for five specific 2° ✕ 2° areas located across East Asia. The three frost event parameters are spatially and temporally distinct. A decrease in all three frost parameters is found in Japan, South Korea and East China, with some areas projected to have no frost events by the end of the twenty-first century. However, Northwest China is distinctive as wet frosts are projected to increase over the twenty-first century, while on the Tibetan plateau of Southwest China, freeze–thaw cycles are projected to increase. This suggests that except in some localised regions, heritage managers can focus on risks other than frost weathering in developing plans to address climate change.Graphical

Potential Risk of Frost in the Growing Season in Poland

Fruits, garden plants, and agricultural crops grown in Poland exhibit wide variations in their sensitivity to frost, particularly in early spring. In the case of frost, generally, the yield and quality are reduced, and sometimes, entire plants can be destroyed. This article characterizes the occurrence of ground frosts (at 5 cm agl) and air frosts (at 200 cm agl) in Poland gathered from 52 meteorological stations affiliated with IMGW-PIB between 1971 and 2020. To assess the real risk of frost to plants, the variability of this phenomenon was analyzed per thermal growing season (defined as air temperature &gt;5 °C), rather than in traditional calendar terms as presented in most studies. In the climatic conditions of Poland, the growing season is characterized by a reported 28 days with ground frost and 13.3 days with air frost, approximately. In spring, the last ground frost disappears, on average, on a country scale, on May 14, and air frost on April 27. In turn, in autumn, the first ground frost is recorded, on average, on 1 October and air frost on 14 October. On the basis of the selected characteristics of frost and the growing season, four areas of potential risk of ground and air frost in the growing season, as well as in spring, were determined with the use of cluster analysis.

Growing‐season climate as an explanation of spatial variations in temperature sensitivity of green‐up on Tibetan Plateau

AbstractTemperature sensitivity (TS) of the green‐up date (GUD) of plants is crucial for the prediction of grassland phenology that is important for animal husbandry and pasture management. Spatial variations in the TS are known to reflect interannual temperature variability and/or accumulated precipitation preceding the GUD (pre‐GUD). However, whether spatial TS variations are related to the interaction between pre‐GUD temperature variability and precipitation, which is a potential indicator of frost risk, remains unclear. Furthermore, because the interaction between interannual temperature variability and accumulated precipitation following the GUD (post‐GUD) can exert selection pressure on the plant life cycle, it may also be involved in shaping the spatial TS pattern. Using long‐term ground observations of GUD on the Tibetan Plateau, we show that TS is more negative (greater GUD advance per unit temperature increase) in areas with more pre‐GUD precipitation and low pre‐GUD interannual temperature variability, but less negative in areas with more pre‐GUD precipitation and high pre‐GUD interannual temperature variability. This result is likely because more pre‐GUD precipitation facilitates sprout and leaf development under stable temperature conditions, whereas it increases frost risk when the temperature variability is high. In contrast, TS magnitude decreases with increases in post‐GUD precipitation in areas where post‐GUD interannual temperature variability is low, but increases with post‐GUD precipitation in areas where post‐GUD interannual temperature variability is high. We speculate that because hydrothermal demands for leaf growth from the onset of green‐up to maturity are more easily fulfilled when interannual temperature variability is lower and precipitation is higher, green‐up need not be sensitive to pre‐GUD temperature. In contrast, high post‐GUD precipitation likely aggravates low‐temperature constraints on leaf growth when temperature variability is high, resulting in greater TS to maximize growing season length. These results suggest that spatial TS variations on the Tibetan Plateau are likely associated with adaptations of leaf‐out phenology to background pre‐GUD climatic conditions together with selection pressure from post‐GUD conditions.

MODELING OF APPLE CHEMICAL FRUIT THINNING

Crop load management in intensive apple orchards must be done precisely to produce a high yield with marketable fruit size. It also ensures the formation of flower buds on the tree for the next season and prevents alternative bearing. In addition to pruning, flower and fruit thinning is another management method that has a major impact on crop yield. Compared to other methods, chemical thinning is the cheapest, can be done quickly and allows fruit thinning at the right time, which guarantees better fruit quality. The decision on the type of chemical agent, concentration and timing of application is very complex and depends on the apple variety, flowering intensity and fruit growth phase, weather conditions during treatment and a few days after. Flower thinning is applied to very high-yielding varieties where fruit thinning is very difficult and tends to bear alternately. Ammonium thiosulphate or ethephon can be used for this purpose only in years with abundant flowering and in conditions where there is no risk of spring frosts. Regardless of whether flower thinning has been carried out or not, the fruits are chemically thinned in the period shortly after flowering. The usual chemical treatment(s) is (are) applied at the early stage of fruit development, when the diameter of the central fruits in a cluster on 2-year-old wood is 5 to 16 mm (in exceptional cases up to 20 mm). At this time, naphthalene acetamide (NAD), naphthalene acetic acid (NAA), 6-benzyladenine (6- BA), and metamitron are used to induce abscission of young fruit. These chemicals are used alone or in various combinations to improve the effect. If the thinning efficacy of the single application is weak, sequential applications of chemical thinners with different modes of action must be made 1-3 weeks after the previous application to reduce fruit set to a commercially acceptable level. To avoid under- or over-thinning of fruit of a particular variety, models that predict the effectiveness of chemicals based on short-term light and temperature forecasts are used to determine the optimal time to apply thinners. Immediately after the first application of thinning agents, the “fruit growth rate model” can be used for early assessment of apple tree response to thinning and the need for a new application.

Thermal performance of wedge pile slab foundation without frost protection insulation and highly insulated slab on ground floor – first year measurements

In the Nordic countries frost insulation is necessary if the foundation is above the frost-free depth. The thermal performance of the pile foundations is between a shallow ground foundation and a frost wall foundation. The pile ends extend below the frost line to help insulate the ground beneath a building’s foundation. The ends of the piles extend below the frost line to prevent the foundation of the building from frost heaving. However, there may be a risk that the ground below the slab on ground may freeze and frost heaving may occur there. The risk of frost below the slab on ground floor and/or basement increases because increasing thickness of floor insulation remarkable influences frost insulation dimensioning. In this study a 6.5 × 17-meter size uninsulated wedge pile slab foundation with highly insulated (U=0.07 W/(m2·K)) slab on ground floor was constructed for a heated building and equipped with temperature, soil moisture, relative humidity, and heat flux sensors. Seven temperature measurement piles below the building and one for reference 8 meters far from the building reached a depth of up to 3.2 meters, which is deeper than the usual 1.4 m depth to avoid freezing in foundation design. In three places, the temperature below the insulation of slab on the ground is measured at 0.5 meters step up to 3 meters from the outer wall of the building. The first-year measurement results showed that temperature did not drop below the zero degree below the foundation and floor. Even though during winter the daily average absolute minimum temperature was -24 °C the sum of degree hours below the zero degree was -7300 °Ch. The historic 50-year absolute sum of minimum degree hours below the zero degree was -28600 °Ch. In addition to real measurement results this three-dimensional temperature sensor field helps to calibrate and validate dynamic model for temperature simulation of thermal performance of wedge pile slab foundation without frost protection insulation and highly insulated slab on ground floor.

Can agronomic options alleviate the risk of compound drought-heat events during the wheat flowering period in southeastern Australia?

The impacts of compound drought-heat (DH) events on crops are more devastating than a single extreme event of drought or heat. Previous studies mainly assessed the change of individual extreme climate events. However, studies quantifying the characteristics of DH events during crop growth periods are still lacking. To the best of our knowledge, there is no study that has quantified the potential of adjusting sowing time and changing cultivars to reduce the risk of DH events for wheat in Australia. We aimed to (1) develop a combined index to capture the DH events occurring during the wheat flowering period at six study sites in southeastern Australia’s wheat belt; (2) quantify the changes in the frequency (DHF), duration (DHD), and intensity (DHI) of DH events under future climate; and (3) identify feasible agronomic options to reduce the risk of DH events. We used the APSIM model driven by climate projections from 27 GCMs for the period of 1981–2100 to simulate the wheat flowering time and daily plant available water (PAW) at 0–100 cm soil layer. The wheat sensitive period (WSP) was defined as the period from 2 weeks before flowering to 2 weeks after flowering time. A DH event occurs when the daily maximum temperature is higher than 28 ℃ and daily PAW is less than 40% of plant available water capacity for three consecutive days or more. Then, we assessed the DHF, DHD, and DHI under projected climate change. Finally, we investigated the potential of changing sowing time and cultivars to alleviate DHF, DHD, and DHI under different climate scenarios. According to the average values across six sites, the DHF, DHD, and DHI during the WSP increased by 15%, 12%, and 0.9% in 2040 s, and 49%, 44%, and 5% in 2080 s, respectively, compared to 2000 s. Such increases in DH events were mainly due to enhanced heat events. Early sowing and planting better-performing wheat cultivars with early flowering had great potential to lower the risk of future DH events. They could reduce the DHF, DHD, and DHI by 15%− 100%, 18%− 100%, and 16%− 100%, respectively, compared to without adaptation options. However, the strategy may introduce an increased frost risk across six sites, especially in regions with climates that are less dry and hot, such as Mudgee and Wagga Wagga. We expect our modelling work can provide useful information for developing effective agronomic management practices to help Australian wheat growers better prepare for DH events under climate change. The newly proposed DH framework can be applied to other dryland wheat growing regions globally.

Past and present risk of spring frosts for fruit trees in the Czech Republic

Recent climate warming is reflected in the advanced onset of spring phenological phases of fruit trees and in so-called false springs. This then manifests as an increased risk of trees being damaged by late frosts in the sensitive growing stage. Based on the homogenised temperature series of 155 climatological stations divided into two altitudinal groups (below 300 m a.s.l. and 301–600 m a.s.l.), a climatological analysis of selected variables in relation to atmospheric circulation over the territory of the Czech Republic during the period 1961–2021 was performed. The number of frost days and the dates of their latest onset exhibited negative linear trends; however, only 16% and 20% were statistically significant. The onset of false spring (at least ten consecutive days with daily maximum ≥ 10 °C) was also characterised by decreasing trends, which significantly deepened after 1980. Spring frost days were particularly attributed to higher frequencies of anticyclonic circulation types such as the central anticyclone and circulation types with northeastern, eastern and southeastern airflow. False spring onset was particularly connected with the central anticyclone and circulation types with western and southwestern airflow. The increasing trends of frost risk days (days between the beginning of the false spring and the date of the latest frost with daily minimum < −1.5 °C) were statistically nonsignificant. Local series of fruit trees from southeastern Moravia proved to have significantly earlier onset of the first blossom and full blossoming phenophases. Although the damage by late frosts has been identified as an important factor contributing to low yields of fruit trees during the period 1996–2021 in the Czech Republic, other factors (e.g. other weather phenomena, diseases, pests, site, taking preventive measures against frost) must also be taken into account.

Better Inversion of Wheat Canopy SPAD Values before Heading Stage Using Spectral and Texture Indices Based on UAV Multispectral Imagery

In China’s second-largest wheat-producing region, the mid-lower Yangtze River area, cold stress impacts winter wheat production during the pre-heading growth stage. Previous research focused on specific growth stages, lacking a comprehensive approach. This study utilizes Unmanned Aerial Vehicle (UAV) multispectral imagery to monitor Soil-Plant Analysis Development (SPAD) values throughout the pre-heading stage, assessing crop stress resilience. Vegetation Indices (VIs) and Texture Indices (TIs) are extracted from UAV imagery. Recursive Feature Elimination (RFE) is applied to VIs, TIs, and fused variables (VIs + TIs), and six machine learning algorithms are employed for SPAD value estimation. The fused VIs and TIs model, based on Long Short-Term Memory (LSTM), achieves the highest accuracy (R2 = 0.8576, RMSE = 2.9352, RRMSE = 0.0644, RPD = 2.6677), demonstrating robust generalization across wheat varieties and nitrogen management practices. This research aids in mitigating winter wheat frost risks and increasing yields.

Investigation of energy recovery performance and frost risk of membrane enthalpy exchanger applied in cold climates

The membrane enthalpy exchanger (MEE) is a viable energy recovery device to alleviate building energy consumption. In this paper, a quasi-counter-flow MEE's energy-saving effect and frost risk under severe cold conditions is investigated experimentally and numerically. The experimental results demonstrate that frost occurs when the outdoor air temperature falls below −14 °C. At an outdoor temperature of −26 °C, the enthalpy effectiveness decreases from 63.8% to 43.3% after one hour of frosting, accompanied by a significant increase in the exhaust air's pressure drop by 2.7 times. Furthermore, the simulation results reveal that the lower latent effectiveness compared to sensible effectiveness contributes to the highest risk of saturation near the exhaust air outlet. Moreover, this study analyzes the influence of MEE's geometrical and physical characteristics on its recovery effectiveness and frost risk. The findings indicate that increasing the membrane spacing can prolong MEE's operation duration at the expense of recovery effectiveness. Specifically, the MEE's total energy recovery during the whole heating season in Shenyang, China, increases by 18% when the membrane spacing is extended from 2 mm to 5 mm with a membrane thickness of 70 μm. This study provides insights into the MEE design.

Climate warming may accelerate apple phenology but lead to divergent dynamics in late-spring frost and poor pollination risks in main apple production regions of China

Frost exposure and poor pollination are great challenges for the cultivation of perennial orchard systems such as apples, whose adaptive capacity to climate impacts is limited. Unfortunately, such climatic risks remained largely unexplored due to the complexity in future climate predictions, uncertainties in apple phenological simulations, and difficulties in quantifications of risks of late-spring frost and poor pollination. Here, focusing on the main apple production Sub-regions I–IV (i.e., the Loess Plateau, the Bohai Bay, the Southwest Cool Highland, and Xinjiang) in China, we used an ensemble of seven phenological models to estimate changes in apple first flowering and fruit-setting. Based on phenological sensitivity window proposed, we evaluated the late-spring frost risk and climatic risk of poor pollination based on two individual indices developed for these two kinds of meteorological risks. The phenology model ensemble was driven by climatic data derived from an ensemble of 27 global climate models (GCMs) from CMIP6 to simulate apple phenology in two periods of 2021 − 2060 (Near Future) and 2061 − 2100 (Far Future) under two climate scenarios of SSP245 and SSP585. Model ensemble could largely improve phenology prediction accuracy. Our results also confirmed the general earlier occurrence of apple phenological stages and the shortening of phenological sensitive windows. The first flowering advanced about 0.19 − 0.32 d∙y-1 and fruit-setting advanced about 0.24 − 0.47 d∙y-1. Although the shortening of phenological sensitivity window might decrease frost frequency in some regions and reduce the general risk of late-spring frost (e.g. in Sub-region II), the increase of frost intensity could offset this kind of alleviation and even exacerbate frost risks in Sub-regions I and IV. Finally, except for Sub-region III and a few sites in Sub-regions I and IV, shifts in climatic risks of poor pollination in spatial contrasts were lower than late-spring frost risk. This highlighted late-spring frosts would be more possibly the reason for apple yield or quality losses than the unfavorable climatic pollination conditions under climate change. Model ensemble provides a realistic assessment for quantifying future risks of late spring frost and poor pollination in apple production systems, and helps to identify urgent meteorological risks and provide options for apple production systems in response to climate change.