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1.
Generalized cut method for computing Szeged-like polynomials with applications to polyphenyls and carbon nanocones
Simon Brezovnik, Niko Tratnik, 2023, original scientific article

Abstract: Szeged, Padmakar-Ivan (PI), and Mostar indices are some of the most investigated distance-based Szeged-like topological indices. On the other hand, the polynomials related to these topological indices were also introduced, for example the Szeged polynomial, the edge- Szeged polynomial, the PI polynomial, the Mostar polynomial, etc. In this paper, we introduce a concept of the general Szeged-like polynomial for a connected strength-weighted graph. It turns out that this concept includes all the above mentioned polynomials and also infinitely many other graph polynomials. As the main result of the paper, we prove a cut method which enables us to efficiently calculate a Szeged-like polynomial by using the corresponding polynomials of strength-weighted quotient graphs obtained by a partition of the edge set that is coarser than ▫$\Theta^*$▫-partition. To the best of our knowledge, this represents the first implementation of the famous cut method to graph polynomials. Finally, we show how the deduced cut method can be applied to calculate some Szeged-like polynomials and corresponding topological indices of para-polyphenyl chains and carbon nanocones.
Keywords: graph theory, carbon nanocone, topological indices
Published in DiRROS: 20.03.2024; Views: 62; Downloads: 20
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Payments for forest ecosystem services with focus on CO2 removal
Davide Matteo Pettenella, 2023, published scientific conference contribution abstract (invited lecture)

Keywords: European Green Deal, policy measures, European Union, Carbon Removals Regulation
Published in DiRROS: 06.10.2023; Views: 316; Downloads: 94
.pdf Full text (73,47 KB)

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Soil organic carbon stock capacity in karst dolines under different land uses
Mateja Breg Valjavec, Andraž Čarni, Daniel Žlindra, Matija Zorn, Aleksander Marinšek, 2022, original scientific article

Abstract: The soil organic carbon (SOC) was determined in soils of enclosed karst depressions (dolines) (NW Dinaric Mts.) to define their potential for organic carbon sequestration. SOC was measured in the forest, succession (scrubland), and grassland plots at the bottom of dolines at four depths (0–40 cm) and for 40 cm soil layer SOC stock was calculated. We demonstrated that the prevailing fine soil fractions, the C/N ratio and soil thickness play a positive role in the storage capacity of SOC in dolines regardless land use type. Grasslands have the lowest SOC storage capacity (106 t/ha/40 cm), while the highest SOC storage capacity is in succession plots (130 t/ha/40 cm). The last are covered by shrub communities dominated by Prunus spinosa, forming dense communities, and are typical of abandoned croplands or meadows that have been impacted by high levels of nutrients during cultivation phase. At this stage, there is no additional nutrient input in studied plots, which lowers the nutrient content and increases the C/N ratio. C/N ratio is the highest in the forest, where SOC stock capacity is 116 t/ha/40 cm. Given the trend towards the abandonment of agricultural land at Kras Plateau (SW Slovenia), we can expect more overgrowth of dolines, and thus an increase in carbon stocks and stabilization of organic carbon in forest soils. In contrary, we noticed the alarming decrease in grasslands and increase in urban land. The SOC storage in 2020 was for 12,538 t/ha/40 cm lower than in 2002. Although grasslands showed the lowest SOC storage, their contribution to total SOC storage in dolines is very important. Since there is a lack of studies on carbon stocks in doline soils, our research is of great importance and a novelty and gives an important background for further research on SOC stock in karst landscapes worldwide.
Keywords: organic carbon sequestration, karst, grassland, forests, scrubland, dolines
Published in DiRROS: 20.04.2023; Views: 353; Downloads: 225
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Stable isotope composition in tree rings of Fagus sylvatica L. saplings reflects environmental variation induced by silviculture and microsite factors
Janez Kermavnar, Tom Levanič, Lado Kutnar, 2023, original scientific article

Abstract: Natural regeneration of tree species is sensitive to silvicultural interventions. This study aimed to investigate the effects of different cutting intensities and local topographic and soil conditions on the composition of stable carbon (δ13C) and oxygen (δ18O) isotopes in wood of young beech (Fagus sylvatica L.) trees. Beech saplings in the regeneration layer were sampled in summer 2018 at three study sites in Dinaric fir-beech forests in the karst area of Slovenia. Three different cutting intensities were performed in 2012: i) no cutting (control), ii) 50% cutting of the stand’s growing stock creating thinned stands, and iii) 100% cutting of the stand’s growing stock creating 0.4 ha canopy gaps. We show that δ13C increased along the gradient of cutting intensity. On average, δ13C values in the tree rings were ∼ 2‰ increased in trees from canopy gaps than from closed control stands. Furthermore, δ13C was higher on south-facing slopes characterized by higher air temperatures and lower relative humidity compared to north-facing slopes of karst sinkholes. Additionally, the results suggest a dependence of δ18O on interannual and cross-site climatic variations, particularly in the case of summer precipitation amount. δ18O also responded to soil depth, with beech individuals exhibiting lower values on deeper soils, presumably characterized by higher soil water availability compared to shallow soils. The results are discussed in the context of future climate change, as many beech-dominated forests on karst terrain in the Dinaric Mountains are particularly affected by climate warming and drying due to prolonged and reoccurring summer droughts, intensified large-scale disturbances, and often shallow soils with low water storage capacity.
Keywords: stable carbon isotopes, stable oxygen isotopes, tree cutting, microclimate, drought stress, dinaric fir-beech forests
Published in DiRROS: 05.04.2023; Views: 807; Downloads: 232
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7.
Turkey oak (Quercus cerris L.) is more drought tolerant and better reflects climate variations compared to pedunculate oak (Quercus robur L.) in lowland mixed forests in northwestern Serbia : ǂa ǂstable carbon isotope ratio (δ13C) and radial growth approach
Saša Kostić, Tom Levanič, Saša Orlović, Bratislav Matović, Dejan Stojanović, 2022, original scientific article

Abstract: Tree-ring width (TRW), stable carbon isotope ratio (δ13C) and intrinsic water use efficiency (iWUE) data set chronologies were built for the period 1961–2000 for two oak species (pedunculate oak – Quercus robur L. and Turkey oak – Quercus cerris L.) in northwestern Serbia (Vojvodina province). We focused on the response of the two oak species to measured meteorological data (temperature, precipitation and cloud cover), drought events expressed by six meteorological drought indices, and river water level to better understand their drought tolerance and stress and to assess the reliability of the species response to climate and drought indices when using TRW or δ13C. Turkey oak exhibited better drought tolerance (and less drought stress) compared to pedunculate oak, as manifested, respectively, by less negative δ13C and lower iWUE values. Based on a generalised additive mixed model (GAMM) among the six drought indices studied, the standardised precipitation evapotranspiration index and the standardised precipitation index showed the best fit with both TRW and δ13C, while the Palmer drought severity index exerted a strong influence only on TRW. It was thus concluded that δ13C responds more strongly and rapidly to climate variations than TRW.
Keywords: dendrochronology, stable carbon isotope, tree ring, Quercus robur, Quercus cerris, drought, climate change
Published in DiRROS: 04.08.2022; Views: 599; Downloads: 448
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Chemical and isotopic composition of CO2-rich magnesium- sodium-bicarbonate-sulphate-type mineral waters from volcanoclastic aquifer in Rogaška Slatina, Slovenia
Nina Rman, László Palcsu, Andrej Lapanje, Teodóra Szőcs, 2022, original scientific article

Abstract: Bottled natural mineral waters from an andesitic aquifer in Slovenia are enriched in magnesium (1.1 g/l), sulphate (2.2 g/l) and dissolved inorganic carbon (204 g/l). We analysed major ions, trace elements, tritium activity, 14 C, d18 OH2O , d2 HH2O, d13 CDIC, gas composition and noble gases in six wells. In addition, 87 Sr/ /86 Sr, d34 SSO4 and d11 B were analysed here for the first time. Stable isotopes with d18 O = -11.97 to -10.30% and d2 H = -77.3 to -63.8 confirm meteoric origin. CO2 degassing is evident at three wells, causing the oxygen shift of about -1.3%. Tritium activity was detectable only in the shallowest well, where the freshwater component was dated to the 1960s. d13 CDIC in five waters is -1.78 to ? 1.33%, typical of carbonate dissolution. Radiocarbon is low, 1.03–5.16 pMC. Chemical correction with bicarbonate concentration and d13 C correction methods gave best mean residence times, slightly longer than previously published. Sulphate has d34 S 26.6–28.9% and d18 O 8.9–11.1% due to dissolution of evaporites in carbonate rocks. Boron at concentrations of 1.2–6.1 mg/l has two origins: d11 B = 11.3–16.4% from hydrothermal alteration and d11 B = 26.6–31.7% from carbonate dissolution. Strontium at concentrations of 0.5–22.0 mg/l has 87 Sr/ /86 Sr, indicating three sources: 0.7106 for Miocene clastic rocks, 0.7082 for Triassic carbonates and 0.7070 for Lower Oligocene andesitic rocks. CO 2 represents the majority of the dissolved ([ 98.84 vol%) and separated gas ([ 95.23 vol%). Methane is only found in two wells with a max. of 0.30 vol%. All waters show excess helium and 16–97% of mantlederived helium. Since all show subsurface degassing, the paleo-infiltration temperature could not be calculated.
Keywords: natural tracers, carbon, sulphur, strontium and boron isotopes, noble gases
Published in DiRROS: 24.03.2022; Views: 690; Downloads: 254
.pdf Full text (3,11 MB)

10.
Empirical vs. light-use efficiency modelling for estimating carbon fluxes in a mid-succession ecosystem developed on abandoned karst grassland
Koffi Dodji Noumonvi, Mitja Ferlan, 2020, original scientific article

Abstract: Karst systems represent an important carbon sink worldwide. However, several phenomena such as the CO2 degassing and the exchange of cave air return a considerable amount of CO2 to the atmosphere. It is therefore of paramount importance to understand the contribution of the ecosystem to the carbon budget of karst areas. In this study conducted in a mid-succession ecosystem developed on abandoned karst grassland, two types of model were assessed, estimating the gross primary production (GPP) or the net ecosystem exchange (NEE) based on seven years of eddy covariance data (2013%2019): (1) a quadratic vegetation index-based empirical model with five alternative vegetation indices as proxies of GPP and NEE, and (2) the vegetation photosynthesis model (VPM) which is a light use efficiency model to estimate only GPP. The Enhanced Vegetation Index (EVI) was the best proxy for NEE whereas SAVI performed very similarly to EVI in the case of GPP in the empirical model setting. The empirical model performed better than the VPM model which tended to underestimate GPP. Therefore, for this ecosystem, we suggest the use of the empirical model provided that the quadratic relationship observed persists. However, the VPM model would be a good alternative under a changing climate, as it is rooted in the understanding of the photosynthesis process, if the scalars it involves could be improved to better estimate GPP.
Keywords: eddy covariance, carbon flux, GPP, NEE, vegetation indices, remote sensing, satellite data, GPP map
Published in DiRROS: 03.01.2022; Views: 656; Downloads: 443
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