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The wide variability in functional traits that enable the cosmopolitan distribution of lichens often includes the water storage capacity, S, of their thallus. Lichen S in forest canopies can be large enough to intercept and evaporate significant amounts of rainwater, contributing to the runoff-reduction ecosystem services provided by urban forests; however, S is likely influenced by the presence of air pollutants (polycyclic aromatic hydrocarbons, PAHs) in urban areas. PAHs, being both chemically hydrophobic and damaging to lichen thalli, are expected to reduce lichens’ S and, thereby, limit their contribution to hydrologic ecoservices of urban forests. Hence, the relationship between PAH accumulation and rainwater uptake was examined for two lichen species, common in urban forests around the world – Platismatia glauca and Pseudevernia furfuracea. Samples were collected from an area of low air pollution and another area in a highly urbanized city centre with high air pollution exposure (Kraków, Poland). Lichen S was determined using laboratory-simulated rainfall. PAH bioaccumulation differed between species and among the samples from clean and polluted environments. After exposure to polluted air, the concentration of PAHs was higher in P. glauca than P. furfuracea. Samples from the non-urban setting, however, showed no differences between the two species. In the case of P. glauca, S decreased from 35.8% in samples from clean environment to 8.3% after six months of exposure in the urban setting. The respective S values for P. furfuracea were 25.4% and 12.4%. Results strongly suggest that PAH exposure reduces S in both lichen species.

Many activities are conducted with the view of reducing CO2 emission from fossil fuels, but mining extraction will continue to be important for energy sources, mineral and metal ores, and the general economy. This activity has negative environmental consequences such as habitat loss, water scarcity, and soil degradation in novel ecosystems. Additionally, climate change, drought, and desertification accelerate important problems with water retention. From one point of view, identifying and conserving critical regions for ecological sustainability are issues of fundamental importance, but on the other hand, post-mine sites could provide additional carbon sinks and improve regional water retention (WR). This review paper analyses different studies focusing on the impact of the reclamation of mining sites on the water retention properties of soil. Water retention in reclaimed mining soil (RMS) increased considerably after various restoration efforts were implemented. The amount of water holding capacity in RMS was mostly affected by reclamation methods, soil properties, soil biota, restoration duration, and vegetation type. The major conclusions from the analysis were that (i) the bulk density of reclaimed mining soil ranges from 1.35 to 1.50 g/cm3 and decreases with restoration duration; (ii) Soil fauna increases soil water storage capacity and plant litter and earthworms convert litter to fecal pellets, which increases water field capacity; and (iii) water holding capacity increases with duration of reclaimed sites and type of plants, i.e., afforestation and tree communities have higher WR than younger grasslands. Therefore, identification of the suitable reclamation method, restoration duration, vegetation type, and soil fauna are important factors for increasing water retention capacity at a regional scale. [ABSTRACT FROM AUTHOR]

Leaf surface wettability and factors which determine it are key in determining the water storage capacity of tree crowns and thus the interception of entire stands. Leaf wettability, expressed as the droplet inclination angle, and the surface free energy largely depend not only on the chemical composition of the leaves but also on their texture. The study concerns 12 species of trees common in Central Europe. The content of epicuticular waxes was determined in the leaves, and values ranging from 9.145 [µg/cm2] for horse chestnut (Aesculus hippocastanum L.) to 71.759 [µg/cm2] for birch (Betula pendula Roth.) were obtained. Each additional µg/cm2 increases the canopy water storage capacity by 0.067 g g−1. For all species, the inclination angles of water, diiodomethane and glycerin droplets to the leaf surface were measured and the surface free energy was calculated. It is shown that it is the wax content and the species that constitute independent predictors of water storage capacity. These factors explain the 95.56% effect on the value of canopy water storage capacity. The remaining 4.44% indicate non-species-related individual features or the ability to mitigate pollutants as well as possible environmental factors. Wax analyzed separately from other factors causes a slight increase (by 0.067 g/g) of S. Nevertheless, the influence of the surface condition as a result of species-related variability is decisive for the value of the canopy water storage capacity. [ABSTRACT FROM AUTHOR]

Two species of coniferous trees (Taxus bacata L.; Abies alba L.) were tested for their capacity to retain rainwater on their surface under the influence of various degrees of pollution with commonly occurring aromatic hydrocarbons.Samples of branches were obtained from various places in the crown, in various locations in Krakow (southern Poland; 50 ° 05'01.2 "N 19 ° 56'57.5" E), after the winter period, when air pollution is the highest, and the pollution was washed away in the laboratory as a method of intensive rainfall simulation under controlled conditions. The content of 18 aromatic hydrocarbons, wettability, surface free energy (SFE) and canopy water storage capacity were tested before and after washing.The aim of the study was to show how the hydrological properties of branches change at different degrees of pollution with hydrophobic aromatic hydrocarbons.The analysis of influence of needle surface quality on the value of surface free energy focussed on the comparison of total free energy and its polar and dispersive component. A comparison of SFE values obtained from the van Oss-Good model using three measuring liquids (water, diiodomethane and glycerol) revealed significant differences in the values between the top and bottom sides of the needles. In the polluted needles the difference was 39.68% in favour of the bottom side, and after the washing process 33.74% in favour of the top side. After washing the needles, the share of the polar component clearly decreased. The effect of the change in polarity was a decrease in water storage capacity from 28 to 24% of the total rainfall simulated in the laboratory for both species jointly and an increase of the water drop slope angle on the upper surface of the needles from an average of 60° to 77°, which is equivalent to a decrease in hydrophobicity.Changes in hydrological properties are associated with a decrease in the average content of PAHs on needles from 1670 to 1437 [μg kg-1], which results from washing the pollution off the needles. In terms of species, Taxus bacata L. responded more intensively to needle surface washing by changing its water storage capacity but it was also a species more severely polluted by PAHs. [ABSTRACT FROM AUTHOR]