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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. The obtained results are important both in ecohydrology and microclimatology and are part of the research on the condition of urban forests. [ABSTRACT FROM AUTHOR]

As poikilohydric organisms, lichens are capable of storing significant amounts of atmospheric water. Epiphytes that intercept rainfall change the amount and chemical composition of throughfall water, affecting water balance and microclimate of forest ecosystems. The aim of the study was to investigate the differences in the process of changes/increase in the amount of water in three lichen species: Evernia prunastrii, Hypogymnia tubulosa and Platismatia glauca. In the experiment, conducted under laboratory conditions, samples of thalli were wetted with constant doses of water and weighed in order to determine the amount of water storage capacity from simulated rainfall. The studied lichen species differed in terms of process dynamics and values of water storage capacity, probably due to the morphological structure of thalli. Average water retention was the highest in Platismatia glauca (33.58 %), lower in Evernia prunastrii (19.77 %) and the lowest in Hypogymnia tubulosa (15.38 %). Analyzed taxa with larger water storage capacity are also known to be more sensitive to air pollution. [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]

The aim of the study was to determine the water storage capacity and absorbability of deadwood of different tree species with varying degrees of decomposition. Coniferous (Silver fir—Abies alba Mill.) and deciduous (Common hornbeam—Carpinus betulus L., Common ash—Fraxinus excelsior L., Common alder—Alnus glutinosa Gaertn., and Common aspen—Populus tremula L.) species were selected for the research. The study focuses on the wood of dead trees at an advanced stage of decomposition. Deadwood samples were collected at the Czarna Rózga Nature Reserve in central Poland. Changes over time of the water absorbability and water storage capacity of deadwood were determined under laboratory conditions. The research confirmed the significance of the wood species and the degree of wood decomposition in shaping the water storage capacity and absorbability of deadwood in forest ecosystems. Fir wood was characterized by having the highest water storage capacity and water absorbability. Among deciduous species under analysis, aspen wood was characterized by having the highest water storage capacity and absorbability. Our research has confirmed that deadwood may be a significant reservoir of water in forests. [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]

The canopy water storage capacity and wettability of the plant material are significantly dependent on the condition of the leaf surface. The aim of the present research was an analysis of the influence of infection with oak powdery mildew, seasonal changes occurring on leaves and factors related to location on the surface of leaves and their hydrological properties. This study performed a series of experiments connecting the direct spraying of tree branches with simulated rainfall under laboratory conditions; an analysis of the content of aromatic hydrocarbons in leaves with the use of the chromatograph; and measurements of the angles of adherence of raindrops to the leaf surface. Degree of wettability was determined and, additionally, photographs were taken with a scanning electron microscope. The experiments were performed on common oak (Quercus robur L.) both in the city and in the forest, on two dates: in May and September. All series of measurements were done on healthy leaves and on leaves covered with oak powdery mildew (Microsphaera alphitoides Griff. et Maubl.) to various degrees. Oak powdery mildew has the largest influence on the canopy water storage capacity and on hydrophobicity. In September, the leaves retained an average of 7.2 g/g more water than in May; and, in the leaves from the city, the canopy water storage capacity was 3.1 g/g higher. A decreasing angle of inclination of raindrops to leaves testified to growing wettability and increased the amount of water retained in tree crowns. An additional analysis of SEM photographs points to a dependency of the canopy water storage capacity on the condition of the surface of leaves. [ABSTRACT FROM AUTHOR]