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1.
The effects of large-scale forest disturbances on hydrology : an overview with special emphasis on karst aquifer systems
Urša Vilhar, Janez Kermavnar, Erika Kozamernik, Metka Petrič, Nataša Ravbar, 2022, original scientific article

Abstract: Large-scale forest disturbances (LSFD) are an essential component of forest ecosystem dynamics. The effects of rapid loss of forest cover and other changes in forest ecosystems are inextricably linked to hydrologic processes such as evapotranspiration, soil and recharge processes. Among all hydrogeological systems, karst aquifers are important because of their exceptionally rich and unique biodiversity, biomass, and groundwater resources. At the same time, they are characterized by specific hydrological processes that make them highly vulnerable to environmental changes. Therefore, this study paid special attention to the effects of LSFD on karst hydrology. Using the PRISMA checklist, a thorough literature review of studies published between 2001 and 2020 was compiled into a comprehensive matrix dataset. In addition, an initial assessment of the global and regional distribution of forests on carbonate rocks was made based on publicly available geodatabases of forests and karst aquifers. The compiled information provides the first global overview of hydrological processes affected by LSFD, and identifies important knowledge gaps and future research challenges. The matrix dataset contained 117 full-text articles with a total of 160 case studies. Most publications were from 2011 to 2017, with more than half of the studies at the plot level and more than one-third at the catchment level. Studies on the effects of fires and pest and diseases infestations predominated. However, no articles were found on the effects of ice storms on hydrology in general or on the effects of pest and disease infestations on hydrology in karst areas. Of the 45.6 M km2 of forested land worldwide, 6.3 M km2 or 13.9% of all forests are underlain by carbonate rocks. Carbonate rocks cover about 15% of the land surface, which means that 31.3% of the world's karst aquifers are covered by forest. 29% of all case studies were conducted in karst areas, which is a high proportion compared to the proportion of forests in karst areas. However, these studies are unevenly distributed geographically. Most studies were conducted at the plot level, and only 21% of studies focused on natural LSFD, so forest management and land use change studies predominated. Although studies on the effects of LSFD on evapotranspiration processes between vegetation, air and soil are fairly well represented, infiltration and recharge processes in karst areas remain poorly understood and knowledge is lacking, particularly on groundwater flow and related hydrological processes. Regional studies and impacts on groundwater resources are also insufficient. The results indicate an urgent need for an integrated holistic interdisciplinary approach and a comprehensive understanding of the individual influencing factors, which would allow more accurate modelling of hydrological processes in forested karst aquifers.
Keywords: natural disasters, climatic changes, evapotranspiration, hydrology, karst aquifers
Published in DiRROS: 19.05.2023; Views: 317; Downloads: 186
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2.
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: 351; Downloads: 225
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3.
Ob požaru na Krasu smo gozdarji stopili skupaj
Boris Rantaša, Aleš Poljanec, 2022, preface, editorial, afterword

Keywords: forest fire, Slovenian Karst
Published in DiRROS: 13.12.2022; Views: 566; Downloads: 80
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The effect of bedrock and species mixture on wood density and radial wood increment in pubescent oak and black pine
Luka Krajnc, Polona Hafner, Jožica Gričar, 2020, original scientific article

Abstract: Wood density and radial wood increment were examined in trees of pubescent oak (Quercus pubescens Willd.) and black pine (Pinus nigra Arnold., subsp. nigra) in relation to stand mixture and underlying bedrock. Trees of both species from pure and mixed stands were sampled across two types of bedrock, limestone and flysch. Trees from each species were similar in age. Wood density was estimated in standing trees using resistance drilling and increment cores were taken from a smaller subsample of trees of both species. Tree-ring, earlywood and latewood widths were measured and compared to radial profiles of wood density. The influence of stand mixture, diameter at breast height and bedrock on wood density was examined using a Bayesian general linear model. Wood density was significantly higher in pubescent oak than in black pine. Stand mixture was found to affect wood density positively, although the magnitude of the effect was relatively small when compared to other influencing factors also included in the current study. The effect of diameter on wood density was positive on both bedrocks in pubescent oak and negative or neutral in black pine. The size of the effect varied by bedrock and species. On flysch bedrock, the influence of diameter on wood density was stronger than it was on limestone. These indirect bedrock effects on wood density are probably a result of different soil fertility rather than the bedrock itself. There was a notable difference in radial wood increment in both species across the two bedrocks, whereas the differences in densities were smaller. Higher wood densities found on flysch in the subsample of pubescent oaks are likely an effect of higher proportions of latewood, while the opposite trend was observed in black pine. Higher wood density was found on limestone in black pine despite higher latewood percentages on flysch. In the context of forest management, the species composition of the naturally occurring mixtures in the sub-Mediterranean region should be adjusted slightly to favor pubescent oak, since it is a climax species and will bind more carbon for longer than black pine due to higher wood densities. Future forest management should also promote the overall development of pubescent oak trees in sub-Mediterranean stands. The results are especially important in the European context, because the share of sub-Mediterranean stands is expected to rise with global warming.
Keywords: Karst, wood structure, resistograph, resistance drilling, Quercus pubescens, Pinus nigra, limestone, flysch
Published in DiRROS: 14.01.2021; Views: 1084; Downloads: 362
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6.
Effects of various cutting treatments and topographic factors on microclimatic conditions in Dinaric fir-beech forests
Janez Kermavnar, Mitja Ferlan, Aleksander Marinšek, Klemen Eler, Andrej Kobler, Lado Kutnar, 2020, original scientific article

Abstract: Forest microclimate is strongly affected by local topography and management activities, as these directly alter overstory structure. In the present work we analysed the dependence of observed patterns of spatio-temporal microclimatic variations on topographic, canopy- and management-related factors. A forestry experiment was conducted in managed fir-beech forests in the Dinaric Mountains (Slovenia), which are characterized by rugged karstic terrain with numerous sinkholes. In 2012, cutting treatments representing a range in the intensity of overstory removal were performed: uncut controls (CON), 50% cut of stand growing stock (intermediate management intensity % IMI) and 100% cut (high management intensity % HMI) creating 0.4 ha canopy gaps. Fine-scale variation in aspect and slope and its effects on microclimate was assessed by comparing central, south-facing and north-facing within-sinkhole positions. We measured microclimatic variables (air temperature % T, relative humidity % RH) 0.5 m above the ground over three consecutive post-treatment growing seasons. Microclimatic variables showed an increase (T and vapour pressure deficit % VPD) or decrease (RH) with management intensity. Daily Tmax and VPDmax in HMI treatment were up to 5.9°C (on average 3.5°C) and up to 1.4 kPa (on average 0.6 kPa) higher than those in CON treatment, respectively, whereas daily RHmin was up to 22.7 (on average 13.0) percentage points lower. Regarding intra-seasonal patterns, microclimatic differences between treatments were largest during the summer. South-facing plots in the HMI treatment overall exhibited the most extreme conditions, i.e. the highest Tmax and lowest RHmin. Differences in microclimate between treatments were strongly modulated by canopy cover. The results also suggest that overstory removal increases topography-mediated variation in microclimate, as evidenced by significant differences in T, RH and VPD along the fine-scale topographic gradient within the created canopy gaps.
Keywords: tree cutting, air temperature, relative humidity, vapour pressure deficit, karst topography, canopy cover
Published in DiRROS: 08.10.2020; Views: 1274; Downloads: 524
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7.
Evaluating short-term impacts of forest management and microsite conditions on understory vegetation in temperate fir-beech forests : floristic, ecological, and trait-based perspective
Janez Kermavnar, Aleksander Marinšek, Klemen Eler, Lado Kutnar, 2019, original scientific article

Abstract: Forest understory vegetation is largely influenced by disturbances and given local abiotic conditions. Our research focuses on the early response of understory vegetation to various forest management intensities in Dinaric fir-beech forests in Slovenia: (i) control, (ii) 50% cut of stand growing stock, and (iii) 100% cut of stand growing stock. Apart from identifying overstory removal effects, we were interested in fine-scale variation of understory vegetation and environmental determinants of its species composition. Vegetation was sampled within 27 karst sinkholes, which represent a dominant landform in studied forests. Within each sinkhole, five sampling plots, varying in slope aspect (centre, north, east, south, west), were established (135 in total), where pre-treatment (in 2012) and post-treatment (in 2014) floristic surveys were conducted. The sampled understory species were characterized in terms of Ellenberg's indicator values (EIVs) and plant functional traits (plant height, seed mass, specific leaf area, leaf dry matter content). Diversity metrics (species richness, total cover, Shannon index) increased in plots where the silvicultural measures were applied. Tree species richness also increased in 100% cutting. A redundancy analysis revealed that species composition was related to environmental variables, which are directly influenced by management interventions (overstory canopy cover, microclimate maximum daily temperature, soil properties thickness of organic soil layer) as well as by topographic factors (slope inclination and surface rockiness). EIVs for light were significantly affected by treatment intensity, whereas soil-related EIVs (moisture, reaction, nutrients) depended more on the within-sinkhole position. Canopy gaps, compared with uncut control plots, hosted a higher number of colonizing species with a higher plant height and smaller seeds, while leaf traits did not show a clear response. We found a negative correlation between pre-treatment species (functional) richness and post-treatment shifts in floristic (functional) composition. Plots with higher richness exhibited smaller changes compared with species-poor communities. Incorporating different perspectives, the results of this study offer valuable insights into patterns of understory vegetation response to forest management in fir-beech forests.
Keywords: canopy gap, microsite environment, Ellenberg indicator values, plant functional traits, compositional resistance, karst topography, fir-beech forest
Published in DiRROS: 06.12.2019; Views: 2443; Downloads: 1522
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8.
Ectomycorrhizae of Norway spruce from its southernmost natural distribution range in Serbia
Marina Katanić, Saša Orlović, Tine Grebenc, Marko Bajc, Saša Pekeč, Milan Drekić, Hojka Kraigher, original scientific article

Abstract: Norway spruce (Picea abies Karst.) reaches its southernmost limit in the mountainous regions of south Serbia and Bulgaria. The species is a regionally important timber species for the wood industry and a significant host for various ectomycorrhizal fungi, including edible species. We analysed ectomycorrhizal community and fine root parameters of high continental / subalpine Norway spruce stands at three sites (Stara planina, Kopaonik, Tara) located in protected areas in Serbia. In addition, we assessed the potential effects of altitude and growing season on the ectomycorrhizal diversity and fine root parameters. Using standardised sampling in combination with morpho-anatomical and molecular identification of ectomycorrhizae, we recorded 29 different anatomorphotypes. None of the identified fungi belonged to commercial edible fungal species. Compared to other Norway spruce ectomycorrhiza studies in central Europe, sites in Serbia exhibited lower species diversity and different dominant species composition, with Cenococcum spp. and Russula spp. as the dominant ectomycorrhizal fungi. A number of ectomycorrhizal types and the value of the species richness index differed between Stara planina and Tara in the autumn, but the influence of site and season on the studied diversity indices was not significant. The total number of fine roots increased in the spring, while percentage of vital ectomycorrhizal root tips increased in the autumn. This study was the first examination of Norway spruce ectomycorrhizal communities at the edge of the natural geographical range of the species.
Keywords: ectomycorrhiza, Picea abies Karst, community structure, fine roots
Published in DiRROS: 22.01.2019; Views: 2624; Downloads: 1554
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9.
Resin yield of Pinus nigra and Pinus sylvestris in the Slovenian Karst
Domen Gajšek, Miha Brecelj, Kristjan Jarni, Robert Brus, 2018, original scientific article

Abstract: The aim of our research was to study the impact of various environmental factors on the resin production of pines in the Slovenian Karst. Five plots were established % three in Pinus nigra (Arnold) stands and two in Pinus sylvestris (L.) stands. On each plot, the 19-20 most vigorous dominant or codominant trees with a minimum diameter at breast height (DBH) of 20 cm were selected and their resin yield analysed in 2012. Resin yield in P. nigra was considerably higher than that in P. sylvestris. The average resin yield per tree during the study period of 102 days was 1.144 kg for P. nigra and 0.612 for P. sylvestris. There were substantial differences in resin yield among individual trees in the study period: 0.336-2.487 kg for P. nigra and 0.249-1.270 kg for P. sylvestris. The resin yield in P. nigra was considerably higher for the trees with larger DBH, while this was not the case in P. sylvestris. Tree species was the most important factor in resin yield. Increased precipitation resulted in higher resin yields on most plots, whereas better site productivity positively affected resin yield on all P. nigra plots but not on P. sylvestris plots.
Keywords: Black pine, Scots pine, resin production, resin yield, Slovenian Karst
Published in DiRROS: 05.07.2018; Views: 4964; Downloads: 3260
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10.
Genetic diversity of core vs. peripheral Norway spruce native populations at a local scale in Slovenia
Marjana Westergren, Gregor Božič, Hojka Kraigher, original scientific article

Abstract: We investigated the levels of genetic diversity and population differentiation among core and peripheral populations of Norway spruce along an altitudinal gradient (from inversions to upper tree line) using isoenzymes (ISO) and nuclear simple-sequence repeats (SSR) markers on overlapping set of populations. Twenty-seven to seventy trees from 11 and 7 populations were genotyped with isoenzymes and SSRs, respectively. The results partially conform to the expectations of the central-peripheral hypothesis (CPH) and are consistent for both marker sets. Genetic differentiation among peripheral populations was low but significantly different from zero (FST-ISO = 0.013, FST-SSR = 0.009) and higher than that among core populations (FST-ISO = 0.007, FST-SSR = 0.005), conforming to central peripheral hypothesis. Contrastingly, levels of genetic diversity assessed by both richness and equitability measures did not significantly differ between peripheral and core populations (AR-ISO = 2.20 vs. 2.14, AR-SSR = 17.16 vs. 17.68, HE-ISO = 0.183 vs. 0.185, and HE-SSR = 0.935 vs. 0.935 for peripheral and core populations, respectively).
Keywords: central peripheral hypothesis, Picea abies (L.) Karst., genetic diversity, genetic differentiation, upper tree line, inversion
Published in DiRROS: 07.05.2018; Views: 7994; Downloads: 1738
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