Trace elements and nitrogen in naturally growing moss Hypnum cupressiforme in urban and peri-urban forests

We monitored trace metals and nitrogen using naturally growing moss Hypnum cupressiforme Hedw. in urban and peri-urban forests of the City Municipality of Ljubljana. The aim of this study was to explore the differences in atmospheric deposition of trace metals and nitrogen between urban and peri-urban forests. Samples were collected at a total of 44 sites in urban forests (forests within the motorway ring road) and peri-urban forests (forests outside the motorway ring road). Mosses collected in urban forests showed increased trace metal concentrations compared to samples collected from peri-urban forests. Higher values were significant for As, Cr, Cu, Hg, Mo, Ni, Pb, Sb, Tl and V. Within the motorway ring road, the notable differences in element concentrations between the two urban forests were significant for Cr, Ni and Mo. Factor analysis showed three groups of elements, highlighting the contribution of traffic emissions, individual heating appliances and the resuspension of contaminated soils and dust as the main sources of trace elements in urban forests

Measuring techniques for concentration and stable isotopologues of CO2 in a terrestrial ecosystem : a review

Measurements of carbon dioxide and their stable isotopes are propulsive research tool in ecology and environmental science as they can give us insight into carbon cycle. They are widely used to investigate both natural and anthropogenic carbon sources in the atmosphere, hydrosphere and geosphere, as well as the exchange between these reservoirs. In this paper, we provide a basic overview of two different analytical measurement techniques, isotope ratio mass spectrometry (IRMS) and laser-absorption spectroscopy (LAS) which have been developed and utilized for monitoring of CO2 isotopologues in ecosystem. We present the basics for each technique, however with the emphasis on LAS measurement technique we are targeting readers who are not familiar with this topic. A major objective of this paper is to illustrate the current value and future potential of various analytical instruments in a wide range of applications deployed in the terrestrial ecosystem. Finally, we draw a conclusion from recent research campaigns by presenting a decision tree to better understand and choose a correct application combination for a selected scale of ecosystem

Isotopic and water relation responses to ozone and water stress in seedlings of three oak species with different adaptation strategies

The impact of global changes on forest ecosystem processes is based on the species-specific responses of trees to the combined effect of multiple stressors and the capacity of each species to acclimate and cope with the environment modification. Combined environmental constraints can severely affect plant and ecological processes involved in plant functionality. This study provides novel insights into the impact of a simultaneous pairing of abiotic stresses (i.e., water and ozone (O3) stress) on the responses of oak species. Water stress (using 40 and 100% of soil water content at field capacity - WS and WW treatments, respectively) and O3 exposure (1.0, 1.2, and 1.4 times the ambient concentration - AA, 1.2AA, and 1.4AA, respectively) were carried out on Quercus robur L., Quercus ilex L., and Quercus pubescens Willd. seedlings, to study physiological traits (1. isotope signature [delta 13C, delta 18O and delta 15N], 2. water relation [leaf water potential, leaf water content], 3. leaf gas exchange [light-saturated net photosynthesis, Asat, and stomatal conductance, gs]) for adaptation strategies in a Free-Air Controlled Exposure (FACE) experiment. Ozone decreased Asat in Q. robur and Q. pubescens while water stress decreased it in all three oak species. Ozone did not affect delta 13C, whereas delta 18O was influenced by O3 especially in Q. robur. This may reflect a reduction of gs with the concomitant reduction in photosynthetic capacity. However, the effect of elevated O3 on leaf gas exchange as indicated by the combined analysis of stable isotopes was much lower than that of water stress. Water stress was detectable by delta 13C and by delta 18O in all three oak species, while delta 15N did not define plant response to stress conditions in any species. The delta 13C signal was correlated to leaf water content (LWC) in Q. robur and Q. ilex, showing isohydric and anisohydric strategy, respectively, at increasing stress intensity (low value of LWC). No interactive effect of water stress and O3 exposure on the isotopic responses was found, suggesting no cross-protection on seasonal carbon assimilation independently on the species adaptation strategy

Effects of ethanol storage and lipids on stable isotope values in a large mammalian omnivore

Ethanol storage and lipid extraction can alter the isotopic composition of animal tissues, which can bias dietary estimates calculated by stable isotope mixing models (SIMMs). We examined the effects of ethanol storage and lipid extraction on [delta]13C, [delta]15N, and [delta]34S values measured in brown bear (Ursus arctos) muscles and livers. We also used isotopic data from our experiment to understand the effect of ethanol storage and lipid extraction on dietary contributions calculated by SIMMs. We found that ethanol storage and lipid extraction caused small increases in [delta]13C values for both muscles (ethanol storage: +0.4 - 0.5 prom., lipid extraction: +0.4 - 0.4 prom.) and liver (ethanol storage: +0.6 - 0.3prom., lipid extraction: +0.8 - 0.5 prom.). In contrast, [delta]15N and [delta]34S values did not change when stored in ethanol or when lipids were extracted from tissues. Ethanol storage and lipid extraction had negligible effects on estimated dietary contributions. We show that a relatively high lipid content in the muscles and livers of some large-bodied terrestrial omnivores do not necessarily have an effect on dietary estimates that rely on carbon stable isotopes. Our results suggest that ethanol storage could be a valuable alternative method for preserving animal tissue prior to stable isotope analysis when freezing or drying is impractical. Nevertheless, further research is needed on the mechanisms that control changes in stable isotope composition in tissues stored in ethanol. We recommend investigating the effects of ethanol on stable isotope values in species and tissues of interest before storing samples in ethanol