Effects of deicing salt on the vitality and health of two spruce species, Picea abies Karst., and Picea glehnii Masters planted along roadsides in northern Japan

Pest categorisation of Dendrolimus superans

The EFSA Panel on Plant Health performed a pest categorisation of Dendrolimus superans Butler (Lepidoptera: Lasiocampidae), the larch caterpillar, for the EU territory. D. superans is a major pest of conifer forests in Japan, northeast China and non‐European Russia. However, reports of damage are to conifer species not grown in EU forestry. Larix gmelinii and Pinus pumila are regarded as major hosts. Eggs are laid on host needles and developing larvae feed on host foliage. Larvae overwinter in the soil. In its native range, D. superans usually takes one or two years to develop. In principle, host plants for planting and plant products, such as cut branches and wood with bark, could provide pathways into the EU. However, prohibitions on the import of Abies, Cedrus, Larix, Picea, Pinus and Tsuga from areas where D. superans occurs closes such pathways. Nevertheless, a derogation for specific dwarfed Pinus plants from Japan exists. Climates similar to those in some of its existing range occur in the EU. Norway spruce (Picea abies) is a known host in Japan although reports of any impact are lacking. Experiments on the related species D. sibiricus indicated that larvae were able to develop on forestry conifer species occurring in the EU, but which are found outside the native range of D. sibiricus. Were D. superans to be introduced into the EU, impacts on P. abies are possible and it is conceivable that D. superans could expand its host range, as seems possible with D. sibiricus. However, this remains uncertain. Other hosts are grown in the EU as ornamentals or amenity trees. D. superans satisfies all the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest. Some uncertainty exists over the magnitude of potential environmental and economic impacts.

Winter Climate Variability, De-Icing Salt and Streetside Tree Vitality

De-icing salts are applied to roads and walking surfaces to mitigate winter hazards resulting from ice, snow and freezing rain. The vitality of streetside trees, especially those growing in densely built urban areas, is compromised by repeated exposure to de-icing salts. Such trees already experience unfavorable establishment and growing conditions resulting from poor soil quality, inadequate moisture, physical abuse and air pollution−exposure to de-icing salt aggravates these challenges and can be an essential catalyst in tree mortality. Climate change is creating less predictable weather and, in some cases amplifying the intensity of winter storms. Cities that undertake snow and ice management may adopt modified approaches, and those less familiar with this practice may require its episodic adoption. We identify three pathways by which future climate warming may, counterintuitively, result in cities increasing their use of de-icing salt: (a) Warming winter temperatures in cities that were historically too cold to make effective use of sodium chloride (NaCl) for de-icing; (b) cities where daily high temperatures in winter may increase the frequency of freeze-thaw cycles; and, (c) cities in North America and Eurasia that may experience more severe winter weather resulting from greater variability in the circumpolar vortex (CPV). To offset potential damage to existing urban streetside trees and to ensure adequate soil and growing conditions for future trees, there is an immediate need for city foresters to collaborate with traffic safety and public works departments. We present a toolbox of approaches that can facilitate synchronized management efforts, including identifying the location of existing vulnerable trees and re-envisioning future infrastructure that would mitigate tree exposure to de-icing salts. At the same time, we call for the prioritization of research that investigates new potential pathways along which climate change may contribute to the novel adoption of de-icing salts.

Monitoring of the impact of road salting on spruce forest ecosystem in the vicinity of the highway D1 in the Bohemian-Moravian Highlands, Czech Republic

Monitoring of pollution in the vicinity of roads connected to winter road maintenance is one of the important tools for optimising winter maintenance technology and reducing its environmental impact. The aim of this study was to determine the relationship between winter road maintenance and the increased concentration of sodium ion to characterise the harm caused by the de-icing agents on selected types of individual components grown in the Norway spruce ecosystem. The model area is located in the immediate vicinity of the D1 motorway connecting Prague and Brno (Czech Republic), at 103 km. The area is thus exposed to long-term contamination from automobile transport, and the monitoring was carried out for 3 consecutive years. A clear effect of the de-icing agents on conifers near the road has been demonstrated by the symptoms of salt damage visually observed in close proximity to the road (at a sampling distance of 5 m). The needles of these spruce trees also showed increased sodium concentrations, regardless of the age of the needles. The study also confirms that sodium accumulates in all selected components of the analysed ecosystem (moos, humus, soil). The sodium concentration has been found to decrease with increasing distance from the road for all of the components.

Effect of NaCl road salt on the ionic composition of soils and Aesculus hippocastanum L. foliage and leaf damage intensity

We investigated the accumulation of sodium chloride in roadside soils and common horse chestnut Aesculus hippocastanum L. under urban conditions to evaluate changes in soil and leaf ionic content and their relationship with foliar damage, considering the visual assessment of trees of the same health status. A total of 15 field sites were assessed in late June 2016. The analysis included soil granulometric composition, pH, electrical conductivity, and the content of Cl⁻, Na⁺, K⁺, Ca²⁺, and Mg²⁺ ions in soil and foliage samples. The results showed increased salinity and alkalization of roadside soils together with the decreased magnesium content. Foliage samples manifested significantly higher concentrations of Na⁺ and Cl⁻. A wide range of Cl⁻ content was noted in leaves (2.0–11.8% d.w.) regardless of their damage index. On the contrary, leaf damage was strongly correlated with increasing Na⁺ concentrations and decreasing K⁺ and Mg²⁺. A severe imbalance of nutrients, and therefore poor urban tree vitality, can be attributed to the excessive accumulation of de-icing salt. However, further research would be needed to clarify the discrepancy between the extent of leaf damage and chloride content.

Effect of salt stress in urban conditions on two Acer species with different sensitivity

Background

The benefits of trees in urban areas include the following: an increase in ecosystem health, an increase in human health, the mitigation of the effects of heat and drought at microclimate level, the storage and sequestration of carbon, and a reduction in air pollution and noise. These ecosystem services can be provided only by trees that are in good health. The main cause of salt stress in urban environments is the use of de-icing salts on the streets in winter. Salt stress is a complex process that includes changes in plants on the physiological, histological, cellular and molecular levels, leading to limitations in nutrient uptake, disrupting the ionic balance of trees and resulting in the death of roadside trees. In response to salinity, trees have developed a variety of defence mechanisms that allow them to minimize the effects of stress and maintain homeostasis.

Methodology

The reactions of two species Acer species: A. platanoides and A. campestre, which have different sensitivities to the unfavourable conditions of the urban environments (mainly salt stress), were investigated. The research included two experiments: a field experiment with city trees and a controlled pot experiment with young trees treated with increasing doses of salt. In both experiments, the following were performed: an assessment of the health condition of the trees and the content of macroelements as well as the Cl and Na in leaves and a qualitative and quantitative analysis of polyprenols.

Results

A. campestre had a more specific strategy than A. platanoides for dealing with Na and Cl, which resulted in undamaged leaves. Under the same conditions, A. platanoides leaves contained more Cl and Na and were severely damaged. The disruption of the ion balance due to salt stress was lower in A. campestre than in A. platanoides. Compared with A. platanoides, A. campestre synthesized more polyprenols in the field experiment. This ability was acquired during the process of acclimation, because it occurred only in the mature trees in the field experiment and not in the young trees in the pot experiment.

Conclusions

The use of two experimental methods (i.e., the field and pot experiments) allowed for a more complete assessment of tree strategies to mitigate salt stress. A. campestre displayed a more specific strategy than A. platanoides. This strategy was based on several elements. A. campestre limited Cl and Na transport to the leaves, which resulted in a lack of damage to those organs. Under the same conditions, A. platanoides individuals contained more Cl and Na in their leaves and were seriously damaged. A. campestre synthesized larger amounts of polyprenols, which probably have the ability to mitigate salt stress. This ability was acquired during the process of acclimation, because it occurred only in the mature trees in the field experiment and was not observed in the young trees in the pot experiment.

Evaluation and Selection of De-Icing Salt Based on Multi-Factor

De-icing salts can greatly ease traffic congestion but introduce corrosion of concrete and damage to plant growth. The decision of which de-icing salt to use becomes a crucial issue. In this study, several representative de-icing salts were investigated, and the effects of de-icing ability, salt freezing corrosion on concrete, and plant growth were comprehensively tested. Finally, the decision of de-icing salt was made based on analytic hierarchy process (AHP). Results show that de-icing salts achieving the best de-icing effect are not the same at different concentrations. De-icing salts of 3% concentration have the greatest corrosion to concrete. Notably, magnesium chloride and calcium magnesium acetate have the least impact on plants among all studied de-icing salts. Using AHP, ethylene glycol and calcium magnesium acetate are selected as optimal items under different priorities.

Ecophysiological Responses of Carpinus turczaninowii L. to Various Salinity Treatments

Carpinus turczaninowii L., commonly known as hornbeam, has significant economic and ornamental importance and is largely distributed in the northern hemisphere, including parts of China and Korea, with high adaptation to harsh conditions in very unfertile soils. In this study, the ecophysiological responses of C. turczaninowii seedlings to various salinity stress treatments (NaCl: 0, 17, 34, 51, 68, and 85 mM) were studied for 42 days by determining stress-induced changes in growth parameters and biochemical markers. Salinity stress affected the values of all the examined parameters, both morphological and physiological, and caused the inhibition of plant growth, the degradation of photosynthetic capacity and stomatal behavior, a decrease in the photosynthetic pigments contents and relative water content, an increase in the Malondialdehyde (MDA) content and relative electrolytic conductivity, and the accumulation of Na+ and Cl− content. The presence of relatively high concentrations of organic osmolytes, the activation of antioxidant enzymes, and the ionic transport capacity from the root to shoots may represent a constitutive mechanism of defence against stress in C. turczaninowii seedlings. Our results suggest that C. turczaninowii can tolerate salinity at low and moderate concentrations (17–51 mM) under nursery conditions and can be widely used in roadsides, gardens, parks, and other urban areas.

De-icing salt contamination reduces urban tree performance in structural soil cells

Salts used for de-icing roads and sidewalks in northern climates can have a significant impact on water quality and vegetation. Sub-surface engineering systems, such as structural soil cells, can regulate water runoff and pollutants, and provide the necessary soil volume and irrigation to grow trees. However, the ability of such systems to manage de-icing salt contamination, and the impact of this contamination on the trees growing in them, have not been evaluated. We report on an field investigation of de-icing salt contamination in structural cells in two street-revitalization projects in Toronto, Canada, and the impact of this contamination on tree performance. We analyzed soil chemistry and collected tree attributes; these data were examined together to understand the effect of salinity on tree mortality rates and foliar condition. Data collected from continuous soil salinity loggers from April to June for one of the two sites were used to determine whether there was a long-term accumulation of salts in the soils. Results for both sites indicate that both sites displayed high salinity and alkalinity, with levels elevated beyond those suggested before those reported to cause negative tree effects. For one site, trees that were alive and trees that had a better foliar condition had significantly lower levels of soil salinity and alkalinity than other trees. High salinity and alkalinity in the soil were also associated with lower nutrient levels for both sites. Although tests for salinity accumulation in the soils of one site were negative, a longer monitoring of the soil conditions within the soil cells is warranted. Despite structural cells being increasingly utilized for their dual role in storm-water management and tree establishment, there may be a considerable trade-off between storm-water management and urban-forest function in northern climates where de-icing salt application continues to be commonplace.

Experimental Investigation of Concrete Runway Snow Melting Utilizing Heat Pipe Technology

A full scale snow melting system with heat pipe technology is built in this work, which avoids the negative effects on concrete structure and environment caused by traditional deicing chemicals. The snow melting, ice-freezing performance and temperature distribution characteristics of heat pipe concrete runway were discussed by the outdoor experiments. The results show that the temperature of the concrete pavement is greatly improved with the heat pipe system. The environment temperature and embedded depth of heat pipe play a dominant role among the decision variables of the snow melting system. Heat pipe snow melting pavement melts the snow completely and avoids freezing at any time when the environment temperature is below freezing point, which is secure enough for planes take-off and landing. Besides, the exportation and recovery of geothermal energy indicate that this system can run for a long time. This paper will be useful for the design and application of the heat pipe used in the runway snow melting.

Quantitative and qualitative characteristics of cell wall components and prenyl lipids in the leaves of Tilia x euchlora trees growing under salt stress

The study was focused on assessing the presence of arabinogalactan proteins (AGPs) and pectins within the cell walls as well as prenyl lipids, sodium and chlorine content in leaves of Tilia x euchlora trees. The leaves that were analyzed were collected from trees with and without signs of damage that were all growing in the same salt stress conditions. The reason for undertaking these investigations was the observations over many years that indicated that there are trees that present a healthy appearance and trees that have visible symptoms of decay in the same habitat. Leaf samples were collected from trees growing in the median strip between roadways that have been intensively salted during the winter season for many years. The sodium content was determined using atomic spectrophotometry, chloride using potentiometric titration and poly-isoprenoids using HPLC/UV. AGPs and pectins were determined using immunohistochemistry methods. The immunohistochemical analysis showed that rhamnogalacturonans I (RG-I) and homogalacturonans were differentially distributed in leaves from healthy trees in contrast to leaves from injured trees. In the case of AGPs, the most visible difference was the presence of the JIM16 epitope. Chemical analyses of sodium and chloride showed that in the leaves from injured trees, the level of these ions was higher than in the leaves from healthy trees. Based on chromatographic analysis, four poly-isoprenoid alcohols were identified in the leaves of T. x euchlora. The levels of these lipids were higher in the leaves from healthy trees. The results suggest that the differences that were detected in the apoplast and symplasm may be part of the defensive strategy of T. x euchlora trees to salt stress, which rely on changes in the chemical composition of the cell wall with respect to the pectic and AGP epitopes and an increased synthesis of prenyl lipids.

The influence of chloride deicers on mineral nutrition and the health status of roadside trees in the city of Kielce, Poland

Application of chemical road deicers has a negative impact on roadside vegetation. Every year, the trees in cities suffer from direct and indirect effects of salt application for winter road maintenance. To elucidate this problem in the city of Kielce, the chemistry of snow, soil, tree bark, and leaf samples has been investigated together with an assessment of the health status of the trees. Twelve investigation sites were selected along the roads with different traffic intensity. Snow samples were collected twice during the winter and analyzed for pH, EC, Na(+), Ca(2+), Mg(2+), and Cl(-). In soil (collected from two depth intervals), tree bark, and leaf samples, the concentrations of B, Ca, Fe, K, Mg, Mn, N, Na, P, S, and Zn were determined. The contents of total organic carbon (TOC) in soils, as well as the pH of soil and tree bark samples were also measured. Negative symptoms revealed by roadside trees included the loss of assimilative apparatus and decreased vitality. The results of chemical analyses indicated that the snowmelt might be a substantial source of chloride ions and alkalizing substances that influenced higher pH of soils. The soil samples displayed elevated concentrations of S and Zn and lower than typical for soil contents of B, Mg, and TOC. The pH of alkaline soils favored greater bioavailability of B and reduced bioavailability of Na and Zn by the trees examined.

Effect of long-term changes in soil chemistry induced by road salt applications on N-transformations in roadside soils

Of several impacts of road salting on roadside soils, the potential disruption of the nitrogen cycle has been largely ignored. Therefore the fates of low-level ammonium-N and nitrate-N inputs to roadside soils impacted by salting over an extended period (decades) in the field have been studied. The use of road salts disrupts the proportional contributions of nitrate-N and ammonium-N to the mineral inorganic fraction of roadside soils. It is highly probable that the degree of salt exposure of the soil, in the longer term, controls the rates of key microbial N transformation processes, primarily by increasing soil pH. Additional influxes of ammonium-N to salt-impacted soils are rapidly nitrified therefore and, thereafter, increased leaching of nitrate-N to the local waterways occurs, which has particular relevance to the Water Framework Directive. The results reported are important when assessing the fate of inputs of ammonia to soils from atmospheric pollution.

Growth and photosynthetic responses of two pine species (Pinus koraiensis and Pinus rigida) in a polluted industrial region in Korea

We investigated the effects of pollutants on two pine species (Pinus koraiensis and Pinus rigida) in an industrial region in Korea, using a physiological approach. The concentrations of fluorine (F) and chlorine (Cl) in the atmosphere, in precipitation and soil water at the damaged site were all significantly higher than at a control site. Moreover, the concentrations of F, Cl and Mn in pine needles were significantly higher, and essential elements and chlorophyll in needles were significantly lower at the damaged site than at the control site. The photosynthetic capacities, shoot length and survival statistics of needles of the two pines were all significantly reduced at the damaged site compared to the control site, especially P. rigida. Based on our comparison of photosynthetic responses and the concentrations of F, Cl and Mn in needles of the two pine species, P. koraiensis is more resistant to excess Mn in its needles than P. rigida.