Effects Of Frost Research Articles

Estimating late spring frost-induced growth anomalies in European beech forests in Italy.

Weather extremes and extreme climate events, like late spring frosts, are expected to increase in frequency and duration during the next decades. Although spring phenology of European beech is well adapted to escape freeze damages on longer time scales, the effects of occasional late spring frosts (LSF) are among the main climatic damages to these forests to such an extent that they limit beech distribution and elevation range, especially at its southern margin. The aim of this work was to evaluate the short-term effects of two consecutive LSF events occurred in 2016 and 2017 in Italy on the beech forest vegetation activity. Remotely sensed land surface temperature (LST) data were used to detect the pixels where LSF occurred, while enhanced vegetation index (EVI) data were used to quantify LSF effects by computing a spring vegetation activity anomaly index (sAI). In 2016 and 2017, the LSF covered, respectively, about 29% and 32% of the total Italian beech-dominated area. The two LSF widely differed in their spatial patterns and their effects. In 2016, the pixels belonging to the sAI classes with the highest spring anomalies were also those where prolonged LSF occur, while, in 2017, the pixels belonging to the highest sAI classes were those that underwent the shorter (but probably more intense) LSF events. Under scenarios of increased frequency risk of repeated LSF, the proposed methodology may represent an automatic and low-cost tool both for monitoring and predicting European beech growth patterns.

Canopy damage by spring frost in European beech along the Apennines: effect of latitude, altitude and aspect

Late spring frost plays a major role in the structure and function of forest ecosystems with potential consequences on species distribution at both local and regional scales. Paradoxically, in a warmer world the incidence and impact of frost is increasing because of earlier leaf unfolding and flowering as a response to warmer temperatures. In this regard, European Beech (Fagus sylvatica L.), a native tree species widely distributed in European forests, is considered particularly sensitive to changes in spring temperature regimes associated with climate change and thus especially subject to the risk of frost damage. Although several studies concerning F. sylvatica frost damage have been conducted in northern and central Europe, no extensive studies are available for the southern part of its range, i.e. central and southern Italy as well as Greece.In this paper the effect of a late spring frost occurring at the end of April 2016 is extensively documented with high spatial detail all along the Apennine Chain through satellite image data. Three different remote-sensing greenness indexes, namely the normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), and the greenness index (GI) derived from Landsat-8 satellite images acquired from May to July in the years 2014, 2015, and 2016 at a spatial resolution of 30 m, were used to gauge the spatial response of common beech forests to this late frost event with relation to latitude, altitude and slope exposure. Frost damage was evaluated as a difference (Δ) of NDVI, GI and EVI between the mean of years 2014 and 2015 (i.e. MRY, mean of reference years), and 2016 (i.e. FEY, frost reference year). The three satellite remote-sensing indexes were efficient at detecting leaf damage with detailed spatial resolution and proved consistent with one another.The greatest damage occurred in the middle altitudinal range between 1500 and 1700 m a.s.l. with a decreasing trend toward both lower and higher elevations due to warmer temperatures below, and delayed phenology above. Exposure also influenced frost injury, with south-facing slopes of the mountain more damaged than the north. This difference was due to earlier spring leaf phenology of southern beech trees in response to a greater heat sum in the warm weeks preceding. Less damage in the northern Apennines is consistent with the spatial extent of minimum freezing temperatures. To sum up, frost damage is strongly related to site-specific conditions, i.e. on the one hand to minimum temperatures, and on the other to the phenological stage of the trees involving both altitude and exposure. Hence focusing on detailed sub-regional studies can be helpful for predicting future consequences of climate change on forests.

PROCEDURES FOR DIMENSION OF FLEXIBLE ROAD CONSTRUCTIONS

Experience and procedures for dimension of flexible road construction structures is a complex process. Therefore, several dimension methods are used: ASHTO formed in 1959 in the state of Illinois, USA, Federal Association for Public Roads and Transport AASHTO 2004, methods of the Institutes for asphalt formed in 1955 in England ASSHO and WASHO, method of the SHELL group and method of (FAA) Federal Aviation Administration USA. Methods for collecting data and accumulating them in an appropriate project include design levels, predictions of damage, unevenness, assessment of characteristics, design reliability, expected costs, dimension, and predicting the behavior of pavement structures. The AASNTO method is based on the results of an experiment made in the state of Illinois in 1959 and 1960, and the first guideline was published in 1961 since then, updates have been published regularly to track down the latest findings in the area of pavement structures. There are also computer programs designed for using this method, one of which is "FLEXPAVE". The ASSOA and WASHO method appeared in 1955 in England, it is implemented by the asphalt institute. In the upcoming years this method was upgraded in collaboration with the US engineering corps, the US government agencies and the most famous numerical procedures for the time, as well as computer programs "DAMA" "BISAR "And" CHEVRON ". This software enables the monitoring of monthly changes in condition and destruction by entering the corresponding input data. Through the SHELL group method, the pavement structure is viewed as a linear elastic multi-layer system whose layers have their own characteristics that are expressed through the modulus of elasticity Poisson's coefficient. The traffic is expressed through an ESA - an equivalent standard axis, which acts vertically and it is equally distributed over one or more circular surfaces. Through the (FAA) method, the Federal Aviation Administration in the United States has issued a manual for the dimension of pavement structures depending on the mass of the plane, based on its own classification of the ground, the characteristics of the materials that are part of the pavement structure, the loading of the main aircraft, repetition of the load and the frost effect. Based on these parameters, the thickness of the pavement structure is determined. Today, there is software based on the finite element principles of FEAFAA, FEDFAA, BAKFAA return program, and a program for determining the ACN number COMFAA

Defining optimal sowing and flowering periods for canola in Australia

Increasingly variable rainfall and temperatures and larger farm size in Australia have prompted earlier sowing of canola (Brassica napus L.). Improved agronomy and the release of cultivars suited to a wider range of environments have facilitated the expansion of canola production into new environments. To maximise grain yield at earlier sowing dates and in new environments, growers need to know the most suitable development pattern for their environment and sowing date to reduce production losses associated with frost, heat and drought at flowering. A simulation analysis was conducted at 77 locations across the Australian cropping zone to determine the optimal period for flowering to start in order to maximise long-term yield. The simulation accounted for effects of frost, heat and water stress on yield as well as duration of biomass accumulation. The optimal start of flowering period (OSF) was a function of the environment rather than the cultivar, and the relative importance of frost, heat and water stress varied with location. We found that the OSF was earlier (mid to late July), in most Mediterranean environments of Western Australia, South Australia and Victoria and later (August to September) in the southern temperate environments of Tasmania, Victoria and New South Wales (NSW). In medium and low rainfall areas of NSW, temperature extremes and rainfall interacted so that the OSF occurred in mid-July to mid-August. In low rainfall environments the duration of the optimal period was shorter (19–35 days) in most cases than in high rainfall environments (30–52 days). Knowledge of the OSF for a location, will allow breeders to develop cultivars with appropriate phenological characteristics for target environments. For growers, an understanding of the OSF, combined with an appropriate phenology classification of commercial cultivars, will allow selection of cultivar and sowing date combinations which decrease the risk of stress and maximise productivity.

Bond Behavior of Reinforcing Steel Bars in Thermal Insulation Concrete Exposed to Freeze-Thaw Cycles

An experimental study on the bond behavior of reinforcing steel bars in thermal insulation concrete (TIC) mixed with glazed hollow beads (GHBs) and exposed to freeze-thaw (F-T) cycles was carried out. In order to investigate the effects of GHBs on freezing and thawing, the experimental results were compared with those of normal concrete (NC). The comparison shows that, after 300 F-T cycles, both bond behavior and mechanical properties of the TIC specimens are better than those of the NC specimens. Furthermore, in order to investigate the mechanism of frost effect on TIC, the CT scanning method was used to investigate the evolution of the inner structure of a TIC specimen exposed to F-T cycles. The CT images show that the deterioration of bond performance and mechanical properties of the TIC specimen appears to be caused by the increase of micropores in the TIC.

Soil frost effects on streamflow recessions in a subarctic catchment

AbstractThe Arctic is warming rapidly. Changing seasonal freezing and thawing cycles of the soil are expected to affect river run‐off substantially, but how soil frost influences river run‐off at catchment scales is still largely unknown. We hypothesize that soil frost alters flow paths and therefore affects storage–discharge relations in subarctic catchments. To test this hypothesis, we used an approach that combines meteorological records and recession analysis. We studied streamflow data (1986–2015) of Abiskojokka, a river that drains a mountainous catchment (560 km2) in the north of Sweden (68° latitude). Recessions were separated into frost periods (spring) and no‐frost periods (summer) and then compared. We observed a significant difference between recessions of the two periods: During spring, discharge was linearly related to storage, whereas storage–discharge relationships in summer were less linear. An analysis of explanatory factors showed that after winters with cold soil temperatures and low snowpack, storage–discharge relations approached linearity. On the other hand, relatively warm winter soil conditions resulted in storage–discharge relationships that were less linear. Even in summer, relatively cold antecedent winter soils and low snowpack levels had a propagating effect on streamflow. This could be an indication that soil frost controls recharge of deep groundwater flow paths, which affects storage–discharge relationships in summer. We interpret these findings as evidence for soil frost to have an important control over river run‐off dynamics. To our knowledge, this is the first study showing significant catchment‐integrated effects of soil frost on this spatiotemporal scale.

The frost wave hypothesis: How the environment drives autumn departure of migratory waterfowl

Migration phenology plays a critical role in shaping bird life histories. While the spring migration phenology of birds has been widely studied, our understanding about the mechanisms underlying autumn migration is limited. Frost is an indicator of cold weather, food scarcity, and water unavailability, but how frost drives the autumn departure of migratory birds has not yet been quantified. In this study we propose the ‘frost wave hypothesis’, which posits that the autumn departure of waterfowl is driven by a successive wave of the onset of frost. Using bird satellite tracking data and generalized linear mixed models, we analyze how the departure probability of two waterfowl species during autumn migration is affected by frost, accumulated temperature, food, snow, ice, short-term weather conditions (i.e., wind, temperature and precipitation), remaining migration distances, relative stopover duration, and flight distances between stopover sites. We find that bird autumn departure probability sharply increases after the first frost spell when the accumulated temperature reaches 0 °C, facilitated by surface meridional wind and longer remaining migration distances. We underline the dominant effect of frost on autumn departure, as birds tend to leave even under head wind if the time lag since the onset of frost is large. Time constraints that trigger southward departure are likely to be stronger when migrating birds are still far from their wintering site. By riding the frost wave, birds manage to maximize stopover site utilization while escaping harsh environmental conditions. Our findings improve the understanding of annual avian migration and help quantify the impact of global climate change on migratory waterfowl.

Contrasting wheat phenological responses to climate change in global scale

Comprehensive analysis of how wheat phenology responds to environmental factors in global scale is helpful for tackling the possible adverse effects of ongoing climate change on wheat production. In this study, six phenological parameters of global wheat, i.e., the growing season start (SGS), peak (PGS), end (EGS), length (LGS), as well as the vegetative period length (LVP) and reproductive period length (LRP), were retrieved from remote sensing data (1981–2014) by threshold-, logistic-, and shape-based methods. And then, we analyzed the effects of temperature, precipitation, short-wave (SW) radiation, and frost on spatiotemporal patterns of wheat phenology. In addition, haze impacts on wheat phenology were investigated in China and India where haze weather appears frequently in winter-spring seasons. Results showed that the occurrence time of SGS/PGS/EGS is gradually advanced from the pole to the equator and annual mean air temperature can explain >70% of their spatial variations. A dominant advanced SGS/PGS/EGS and a shortened LGS/LVP/LRP were detected in the study region due to the significant increase in temperature and SW radiation, as well as the decrease in frost days. Interannual fluctuations of SGS/PGS/EGS are primarily controlled by air temperature, while precipitation and frost only exerted some obvious impacts in some locations. Higher preseason temperature would induce an earlier wheat phenology and a shorter growing season, while adequate precipitation and frequent frost in preseason could delay the occurrence timing of wheat phenology and lead to a longer growing season. Besides, the decreased temperature resulted from severe haze weather may have partly counteracted the global-warming-induced advancing trend of wheat phenology in China, but further advanced the occurrence timing of wheat phenology through prompting vernalization in India. Overall, though wheat growth is largely constrained by human management, we still highlight the strong impacts of global climate change on wheat phenology.

Effects of experimental frost–thaw cycles on sandstones with different weathering degrees: a case from the Bingling Temple Grottoes, China

Numerous ancient sandstone grottoes remain in northwest and central China, and weathering issues have significantly influenced their preservation conditions. The dramatic naturally cyclic changes in water content and temperature in the environment have been considered to be the main drivers of the physical weathering that commonly occurs at these archaeological sites. Therefore, comparing and understanding the behaviors of sandstone with different weathering degrees under variable environmental conditions would be helpful for further study on predicting the type, location and extent of deterioration of sandstone relics in a small region (such as the surrounding rock of grottoes). This study examines Cretaceous sandstones with two weathering degrees from Bingling Temple Grottoes, China. Standard thin section photomicrographs provide petrographic and mineralogical data and show that the sandstones have identical lithologies. Three types of specifically designed frost weathering tests are then conducted on the samples. After every six weathering cycles, the weathering processes are suspended, and the corresponding parameters, such as dry weight loss, dry density, effective porosity, porosity, P wave velocity, surface hardness and drilling resistance, are measured. At the end of the weathering cycles, the sample variations in grain size distributions are compared, and statistical tests are performed to show the statistical significance of the results. The results indicate that similar deterioration patterns occur on the samples with two weathering degrees under the same weathering tests. The increase in effective porosity surpasses that of the porosity only when the weathering effect is large enough. Furthermore, sandstone with a high degree of weathering might be more susceptible to changes in the internal pores due to its greater initial interconnectivity. In an open system, physical weathering (frost–thaw and dry–wet cycles) would cause the superficial grain size distributions of different rocks to become relatively uniform. Finally, when exposed to the same weathering process, the decreases in the overall mechanical strength in the two sandstones do not differ significantly, but the loss of superficial strength may be different.

Effect of frost on flavonol glycosides accumulation and antioxidant activities of mulberry (Morus alba L.) leaves

Background: Both Pharmacopoeia of the People's Republic of China and the ancient Chinese herbal formulas recorded that mulberry leaves collected after frost had good quality. However, the reason has not yet been fully elucidated. Objective: We investigated the effect of frost on the accumulation of flavonoids and antioxidant activities of mulberry leaves. Materials and Methods: Liquid chromatography-mass spectrometry and high-performance liquid chromatography were used to analyze chemical components and determine the content of five flavonol glycosides from mulberry leaves collected before and after frost, respectively. Antioxidant activities of the same mulberry leaves were evaluated by total antioxidant capacity (TAC), Fe2+ equivalent (FeE), reducing power (RP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay, and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS) free radical scavenging assay. Results: Ten compounds were identified as flavonol glycosides exception of chlorogenic acid. Quantitative analysis showed that content of isoquercitrin, astragalin, and kaempferol-3-O-(6''-acetyl)-β-D-glucopyranoside reached a maximum of 3.05 mg/g, 0.70 mg/g, and 0.69 mg/g after Frost's Descent, respectively. Moreover, the lowest value of flavonol glycosides appeared in August. The antioxidant activities were also found to have the same tendency. The maximum value of TAC, FeE, RP, DPPH and ABTS were 64.3 rutin equivalent (RE) mg/g, 46.2 RE mg/g, 31.3 RE mg/g, 22.5 RE mg/g and 26.7 RE mg/g, respectively, in November. They were 1.4 times, 1.4 times, 1.6 times, 1.6 times, and 1.9 times of the minimum values, respectively, in August. There was a significantly and positively correlation between antioxidant activities and content of flavonol glycosides (P

Effect of Simulating Hail and Late Spring Frost on Certain Parental Forms of Registered Maize Hybrids in the North-West of Transylvania

A study was performed in the North-West of Transylvania to test the reaction of certain parental forms of maize hybrids (single hybrids and inbred lines) to the following risks: simulated late spring frost in two stages and simulated hail in four stages. Being able to quantify the effects of these phenomena on maize makes it possible to estimate the losses that are involved, losses related to yield, crop tolerance and crop production costs. In 2014, due to the effect of frost, yield losses were from 8% up to 51% in hybrids and from 12% up to 70% in inbred lines. Simulated hail caused losses from 1% up to 71% in hybrids and from 0.5% up to 70% in inbred lines. In 2015, simulated frost caused a yield decrease from 43% up to 71% for hybrids and 76% for inbred lines. Frost and hail in early stages produced smaller losses, but if these risks appeared later or with higher intensity the yield decreases were significantly higher. Breaking resistance was assessed before harvest. In a favourable year, after simulating these mentioned risks, the percent of erect plants was lower compared to a drought year when the yield was smaller. The influence of frost and hail combined with drought during pollination could seriously affect the yield of maize parental genotypes. Within this study, the parental genotypes of maize used showed a remarkable re-growth capacity in early stages, being able to adapt to stressful weather condition.

Assessing the effects of subgrade frost heave on vehicle dynamic behaviors on high-speed railway

The subgrade frost heave of high-speed railways has an inevitable effect on track irregularity in severely cold regions. To research the influence of the subgrade frost heave on the dynamic behavior of high-speed railway vehicles, a multi-body dynamics rigid vehicle model and the finite element method flexible track model are coupled using the rigid-flexible coupling dynamics method. The typical frost heave deformation is used as the excitation source, and the effects on dynamic behaviors of the wheel/rail system are analyzed considering various conditions of frost heave, slab track stochastic irregularity, and train speed. The calculation results show that subgrade frost heave has a significant influence on the safety index (the vertical wheel/rail force and the wheel load reduction rate) and the stability index (the vertical acceleration of the carbody and the vertical sperling index) of the vehicle. Both the safety index and the stability index increases linearly as the frost heave amplitude grows and decreases nonlinearly as the frost heave wavelength grows. The safety index is more sensitive to the wavelength, while the stability index is more sensitive to the amplitude. The frost heave region that has an amplitude greater than 15 mm and a wavelength of less than 15 m should be focused on more. Compared to the frost heave deformation, the growth of slab track stochastic irregularity has greater influence on the vertical wheel/rail force. The influence on the other vertical indexes are relatively insignificant. Higher train speeds lead to a worse safety and stability index, and slowing down the speed is an effective way to ensure the safe and stable operation of the high-speed vehicle.

Geotechnical problems on freezing ground soil and experimental investigation in Kazakhstan

Frost susceptibility should be considered in the design and construction of foundations and retaining-wall structures in regions with the seasonally freezing-soil ground condition. When planning construction that goes deep into this soil, one has to understand the impact of horizontal forces to an underground wall and realize the potential effect of frost heaving upon, deep foundations. This article presents a few soil tests for frost heaving and the results of those tests show dangerous data for retaining structures under the soil conditions in Kazakhstan. The main parameters of the soil include frost penetration and heaving rate and amount. So, in designing underground structures, one must understand and consider that frost heaving occurs in various directions; this factor is very important for predicting on the restriction of deformations of structures in the seasonally freezing-soil ground condition.

Frost damage on grain number in wheat at different spike developmental stages and its modelling

Abstract Frosts may damage wheat (Triticum aestivum L.) spikes and severely reduce their yield. The objective of this study was (i) to quantify the level of susceptibility to frost at different spike developmental stages, and (ii) to develop a theoretical-empirical model to estimate successive frosts damage on grain number ( G N ) at different spike and crop developmental stages based on the meteorological characteristics of the event. Three experiments were performed under field conditions at Balcarce (Argentina), using Klein Roble and Floripan 100 spring cultivars, sown on seven dates. The proportion of aborted grains in spikes was evaluated at different spike developmental stages, from stem elongation to the beginning of grain filling, with all spikes receiving the same natural frosts. The higher the frost severity (defined as the number of hours with temperatures G N (28 to 88%, depending on the experiment). The duration of the period in which maximum damage on G N was registered was variable, but it always included anthesis. Based on collected data, a theoretical-empirical model to estimate successive frosts damage on G N at different spike or crop developmental stages was proposed and validated. This study provides a detailed quantification of the damage caused by natural frosts under field conditions and it allows to achieve a better estimation of frost effect on crop.

Characteristics and thickness effect of phase change material and frost on heat transfer and thermal performance of conventional refrigerator: Theoretical and experimental investigation

In order to design more energy-efficient refrigeration systems through means that have no impact on the environment, the use of phase change materials (PCMs) coupled to the refrigeration systems could be one of the most economically attractive solutions. Among the many possible arrangements of the PCM within a refrigerator, PCM is often on the surface of the evaporator, the location where frost forms. However, beyond a certain thickness, frost would cause an excessive increase in the refrigerator air temperature and a reduction in the energy performance of the refrigerator. The aim of the present study is to clarify the nature and characteristics of frost compared to water as phase change material (PCM), along with the mechanisms with which they affect energy performance and heat transfer within the refrigerator. This is based on a theoretical and experimental investigations conducted on a conventional refrigerator equipped with a flat plate evaporator.

Ultrasound processing of fresh and frozen semi-skimmed sheep milk and its effects on microbiological and physical-chemical quality

The objective of this study was to evaluate the effect of ultrasound treatment on the microbiological quality, protein and free amino acid profile of fresh and frozen stored semi-skimmed sheep milk. Milk was treated as fresh or frozen and stored up to one, three and six months. Output power time and pulse time were the parameters combined to design four different ultrasound (US) treatments: power 78 W and duration 6 min (US1); power 78 W and duration 8 min (US2); power 104 W and duration 4 min (US3) power 104 W and duration 6 min (US4). Pulse duration was of 4 s for each treatment. Sample US1 was discarded due to non effectiveness of US treatment, while other samples showed interesting results. Also, it was verified a frost effect on microorganisms in all samples which were frozen before treatment. No relevant change was reported on amino acid profile. The study showed promising results: the ultrasound treatment inactivated or eliminated the studied contaminant bacteria in semi-skimmed sheep milk, while maintained acceptable amount of lactic bacteria, which could be advantageous for dairy products processing.

Breeding of a fine apricot cultivar, ‘Xiajin’, for protected cultivation

‘Xiajin’ is an early maturing apricot cultivar suitable for protected cultivation. It was selected from seedlings of ‘Jintaiyang’ with desirable traits. Under greenhouse conditions, ‘Xiajin’ flowered 3-5 days later than ‘Jintaiyang’. However, ‘Xiajin’ has a short fruit development period (58 days). The fruits matured approximately 7 days earlier than those of ‘Jintaiyang’. The average fruit weight of ‘Xiajin’ was 90.42 g, which is 22 g greater than that of ‘Jintaiyang’, and the weight of its biggest fruit was 114.7 g. The dormant period of ‘Xiajin’ is very short, with a very limited chilling requirement. A low temperature treatment at ≤7°C for 400 h terminated dormancy and initiated blooming and normal fruit bearing. The percentage of full flowers, with pistils either longer than or equal in length to that of the stamens, was over 90%, whereas those with pistils shorter than stamens or degraded stamens was lower than 10%. After planting, the fruit yield of individual trees in the fifth year was 5.6 kg, equivalent to 940.8 kg mu‑1. In the sixth year, the density of trees was adjusted to 168 trees mu‑1. From the sixth to the eighth year, the fruit yield of individual trees stabilized at 8.99 kg, corresponding to 1510 kg mu‑1 and 30,200 RMB yuan output value. Grown in greenhouses in Yuncheng district of Shanxi Province, the cultivar can completely avoid the effects of late frost and other natural disasters and realize stable and efficient production and, therefore, it is a promising greenhouse-grown apricot cultivar.

Effects of a large-scale late spring frost on a beech (Fagus sylvatica L.) dominated Mediterranean mountain forest derived from the spatio-temporal variations of NDVI

A remote sensing-based approach was implemented to detect the effect of a late spring frost on beech forests in the Mediterranean mountain region. The analysis of spatio-temporal variability of frost effects on normalised difference vegetation index (NDVI) highlighted the distribution of the canopy damage across the forest according to geomorphic factors such as slope, aspect, and altitude. Increased intensity and frequency of extreme temperatures such as late spring frosts and heat waves represent the main drivers affecting forest ecosystem structure and composition in the Mediterranean region. The main objective of this study was to evaluate the effects of a late spring frost disturbance, which occurred during spring 2016 in southern Italy, through the assessment of the spatial pattern of the damage to the beech forest canopy associated with the peak decrease in normalised difference vegetation index (NDVI), and the analysis of the NDVI temporal recovery after this frost disturbance. The forest areas affected by frost were detected through the NDVI differencing technique based on Landsat 8 (OLI/TIRS) imagery time series. The influence of local geomorphic factors (i.e., aspect, elevation, and slope) on forest NDVI patterns was assessed by means of a generalized additive model (GAM). A rather counterintuitive NDVI patterns emerged according to the forest exposition, with NDVI significantly higher on the north facing areas than the southerly ones. The main canopy damage occurred at about 1250 m and reached up to 1500 m asl, representing the altitudinal range affected by the frost disturbance. Finally, the full canopy recovery occurred within 3 months of the frost event. The analysis of seasonal Landsat 8 image time series related to local geomorphic factors, such as aspect, slope, and altitude, and plant phenology on a frost event date, contributed to highlight the NDVI spatio-temporal variation and canopy recovery of a Mediterranean mountain beech forest.

Late Spring Frost in Mediterranean Beech Forests: Extended Crown Dieback and Short-Term Effects on Moth Communities

The magnitude and frequency of Extreme Weather Events (EWEs) are increasing, causing changes in species distribution. We assessed the short-term effects of a late spring frost on beech forests, using satellite images to identify damaged forests and changes in v-egetation phenology, as well as to support the analyses on associated moth communities. The EWE caused crown dieback above 1400 m of altitude, recovered only after several weeks. Nine stands for moth sampling, settled in impacted and non-impacted forests, allowed us to study changes in moth communities and in the wingspan of the most impacted species. The EWE modified community structures, reducing the abundance of beech-feeder species, but leaving species richness unaltered. Operophtera fagata and Epirrita christyi, dominant before the EWE, lost 93% and 89% of their population, respectively. We found a general increase in the average wingspan for these species, caused by the loss of small specimens in most impacted forests, suggesting a re-colonization from non-impacted forests. According to our results, populations of some species could be more resilient than others after an EWE due to their different dispersal ability. Forest ecosystems appear to be dynamic entities able to cope with extreme weather events but, likely, only if they continue to occur in the future at the current rate.

EFFECT OF FROST ON GERMPLASM USED IN RESTORATION OF DEGRADED AREA IN THE SERRA DO ITAJAÍ NATIONAL PARK

Frosts that occur in the Southern Brazil limit the development and survival of seedlings used for restoration projects and may cause significant losses. The objectives of this study were: evaluating the effect of frosts on seedlings produced by seeds collected around a degraded area inside the Serra do Itajaí National Park (PNSI) and used to restore this area; and validating the use of polyester printed labels for marking seedlings. Planting was carried out in adapted Anderson Groups, with 25 seedlings per module. Survival rates for frost were evaluated in 750 seedlings, identified at the species level, classified according to their ecological group, and used in three areas designated as A, B and C. 80% of the seedlings were planted in sloping area and 20%, in lowland area. For the identification of the seedlings, labels printed by a laser printer were used on matte polyester film and affixed with plastic polyamide clamps. This method proved to be practical, inexpensive and resistant to the climate action (heat, humidity and precipitation). Besides, it does not suffer attacks from the local fauna. The overall survival rate was 55.87%, whereas survival rates by ecological groups were 76.67% for shadow tolerant climax, 53.75% for light demanding climax, and 55.63% for the pioneer. The highest survival rates were the ones from seedlings located on the slopes. It was possible to verify that the local germplasm is well adapted to the frosts that occur in the region.