SW Slovenia Research Articles

The role of seasonal and hydrological conditions in regulating dissolved inorganic nitrogen budgets in a forested catchment in SW Slovenia

During two consecutive years the monitoring of rainfall nitrate (NO3−) and ammonium (NH4+) concentrations, combined with high-frequency measurements of streamwater NO3− concentrations, provided insight into the mechanisms controlling the dissolved inorganic nitrogen (DIN) budgets of the forested Padež stream catchment in SW Slovenia. During both years, the catchment's annual wet atmospheric DIN deposition (12.6 and 13.8kg-N/ha) exceeded the annual DIN export (10.7kg-N/ha and 8.8kg-N/ha). The analysis of the monthly DIN budgets discloses seasonal patterns. In winter and early spring, the catchment behaves as a net source of DIN, whereas during late spring, summer, and early fall the catchment generally behaves as a net sink of the atmospheric DIN. Due to large evapotranspiration in the growth period, most of the DIN remains in the catchment and is flushed during the dormant season. Despite high evapotranspiration and consequently low runoff coefficients characteristic for the Mediterranean climate, large rainfall events in the growth period can cause intensive washout of DIN from the catchment. At a monthly basis, the DIN flushing might exceed the catchment's DIN retention capacity and the catchment might behave as a net source of DIN. Therefore, the hydrological conditions have the ability to shift the catchment's role in regulating the DIN budgets. The high responsiveness of the streamwater NO3− concentration in the growth period indicates a large pool of DIN in the forest soils which can become mobile by runoff formation. Wet atmospheric DIN deposition at the Padež catchment is considerable; highest DIN inputs can be expected when air masses approach the catchment from the southwest to southeast where there are extensive urban areas along the Italian, Slovenian and Croatian coast. However, the Padež catchment does not appear to be approaching N saturation, presumably due to strong internal N cycle in the forest soils.

Soil CO2 sources above a subterranean cave—Pisani rov (Postojna Cave, Slovenia)

The objective of this research is to detect abiotic sources of soil CO2 above a subterranean cave in the Slovenian karst region. The research was performed in the forest above Pisani rov (Postojna Cave) near the town of Postojna (SW Slovenia) and also in the cave. Soil gas, atmospheric air and cave air carbon stable isotope composition (δ13CCO2) and CO2 concentration were measured. Sampling and measurements were performed bi-monthly at the test and control sites above the cave. The abiotic source of soil CO2 was estimated using a stable isotope mass balance calculation. Similar seasonal patterns of soil CO2 and δ13CCO2 values were observed at both the test and control sites until spring, with higher levels of CO2 observed in summer and lower in winter. The δ13CCO2 showed the opposite trend, i.e. lower values (−26 to −20 ‰) in summer and higher values (up to −17 ‰) in winter and early spring. In spring, the soil CO2 concentration decreases and the δ13CCO2 value increases only at the control site. A time series of a modelled “isotopically light” endmember revealed large shifts in the data values, due to the presence of an abiotic CO2 source. Results suggest that the subterranean CO2 pool and its ventilation is the main source of soil CO2, accounting for up to 80 % of the soil gas during cold periods. Ventilation from subterranean cavities is an important source of soil CO2 in karstic areas and should be taken into account during carbon cycling studies.

Geology of the Classical Karst Region (SW Slovenia–NE Italy)

ABSTRACTThe paper aims to present the geology of the western part of the Classical Karst (NW Dinarides), located at the border between Slovenia and Italy. The work is based on archive, published and new data collected by Slovenian and Italian researchers within several scientific national and Cross Border Cooperation projects. The map, produced at a scale of 1:50,000, summarizes the lithological and structural setting and is supplemented by three geological cross-sections of the study area.

Palaeomagnetic Research of Cave Sediments in SW Slovenia

Trije profili jamskih sedimentov (v fosilni jami blizu Divace, v Divaski jami in v Trhlovci) so bili preuceni na Krasu blizu Divace. Mineraloska analiza izpricuje relativno enotno sestavo lahke frakcije in kaže na glavni izvor v preperelih ostankih eocenskega flisa. Nekaj mineralov je produkt preparevanja (npr. gibbsit). Podrobna magnetostratigrafska raziskava treh profilov kaže na normalno in reverzno polarnost magnetocon in kaže na korelacijo med profiloma v Divaski jami in Trhlovci. Ozke normalne magnetocone verjetno sovpadajo z Jaramillo polarnostjo (0.90 do 0.97 Ma) v Matuyama epohi. Podatki kažejo na precejsnjo starost jame, v kateri je nastopilo zadnje obdobje zapolnjevanja pred 0,97 Ma in se koncalo pred mejo med Brunhes/Matuyama, pred približno 0.73 Ma. Magnetostratigrafski podatki profila pri Divaci so zabeležili dve ozki normalni magnetoconi v dolgi reverzni polarni coni, kar verjetno sovpada z Olduvai oz. Reunion (okrog 1.67 do 1.87 Ma) reverzne Matuyama epohe ali z normalnimi magnetoconami (okrog 3.8 d0 5.0 Ma) v reverzni Gilbert epohi. Podatki nakazujejo možnost, da je jama nastala v mesinski stopnji, za katero je znacilen padec morske gladine in razvoj globokega krasa v Mediteranu. Three profiles of caves sediments (Divaca fossil cave, Divaska Jama and Trhlovca Cave) were studied in the Kras near Divaca village. Mineralogical study proved relatively uniform mineral composition of the light fraction indicating the main source from weathered sediments of Eocene flysch. Some minerals are derived from weathering profiles and crusts (e.g. gibbsite). Detailed magnetostratigraphic investigations of three profiles defined normal and reverse polarity magnetozones and shows the correlation between the profiles in the Divaska Jama and Trhlovca Cave. The narrow normal magnetozones probably correlate with the Jaramillo polarity event (0.90 to 0.97 Ma) of the Matuyama epoch. Those data indicate the substantial age of cave in which the last phase of filling started before 0.97 Ma and finished before the Brunhes/Matuyama boundary, i.e. around 0.73 Ma. Magnetostratigraphic data of the Divaca profile detected two narrow normal magnetozones in the long reverse polarity zone which probably correlate with Olduvai and Reunion polarity events (about 1.67 to 1.87 Ma) of reverse Matuyama epoch or with some of normal magnetozones (about 3.8 to 5.0 Ma) within reverse Gilbert epoch. Data indicate the possibility that the cave was originated during the Messinian period characteristic by sea-level fall and evolution of deep karst in the Mediterranean Basin.

Morphological and Geological Characteristics of Two Denuded Caves in SW Slovenia

Denudirane ali brezstrope jame lahko velikokrat dolocimo iz originalne kraske topografije. Za ta clanek sem preucila morfologijo in geologijo dveh denudiranih jam. V letu 1994 je bila pri vasi Povir odkrita prva denudirana jama, in sicer ko je gradnja avtoceste Divaca-Dane že potekala. Originalno jamsko morfologijo smo lahko dolocili iz topografskih kart 1:1.000. V letu 1996 pa smo s predhodnimi krasoslovnimi raziskavami se pred zacetkom gradnje avtoceste Divaca-Kozina dolocili 4 denudirane jame. Posebno denudirana jama pri kraju Kacice-Pared je bila morfolosko zelo dobro izražena. Denuded or unroofed caves can be identified from original karst topography many times. For this article the morphology and geology of 2 denuded caves were studied. In 1994 first denuded cave was discovered near village Povir when the highway construction Divaca-Dane was already taking place. Original cave morphology was realized from topographic maps 1:1.000. In 1996 with preliminary karst studies before beginning of highway construction Divaca-Kozina 4 denuded caves were discovered. The one near Kacice-Pared was very well morphologically expressed.

Palaeomagnetic Research of a Fossil Cave in the Highway Construction at Kozina, SW Slovenia

Jama brez stropa je bila zapolnjena s pescenimi naplavinami dinamicne strukture ter teksture svetlo rjave in oker barve. Na vrhu 5 m debelega prereza naplavin so bile rjava prst in skale. Pobranih je bilo 38 vzorcev naplavin. Posamezne magnetne cone nakazujejo, da je naplavina starejsa od zgornjega Olduvaja (1,77 M); kot kozinski prerez se konca z reverzno polarizirano magnetno cono in ima dve normalni polarizirani coni. Prerez naplavin je podoben divaskemu. Predvidevamo, da je jama iz mesinskega obdobja in da so naplavine v njej posledica hitrega zvisanja gladine podzemeljske vode po ponovni zapolnitvi mediteranskega bazena z vodo, torej da so bile odložene pred 5,2 milijoni let. A fossil channel was filled by sandy sediments of light brown to ochreous color with dynamic structures and textures (lower sequence) unconformably overlain by remains of collapsed roof with brown and ochreous matrix (upper sequence). The sedimentary profile was about 5 m high. In all 38 samples taken from the profile, only one was cemented. Samples were demagnetised by alternating field (AF) at 10 to 1,000 Oe. The cemented one was demagnetised by gradual thermal process from 80 to 560 °C in the MAVACS apparatus. Detected remanent magnetisation in a natural state varied between 95 and 36,470 pT, values of volume magnetic susceptibility are from 55 to 998 x 10-6 SI. Rocks showed low or medium magnetisation. Normal and inverse polarization was detected after demagnetisation. The primary component of magnetisation and resulting polarity could not be stated in samples with expressive viscose component (up to 90 %). According to arrangement of individual magnetozone, it can be stated that sediments are older than the top of Olduvai chron (1.77 Ma), as the magnetostratigraphic profile at Kozina terminated by reverse polarised magnetozone and contains two normal polarised zones. The profile can be correlated with the Divaca profile, not only from the palaeomagnetic point of view, but also from a lithological point of view. We suppose, as in Divaca, that the cave is a result of the Messinian speleogenetic epoch and its fossilization was connected with rapid base level uplift after refilling of the Mediterranean basin by water. If this hypothesis is close to reality, the fossilization process can be dated from about 5.2 Ma up.

Drinking Water Supply from Karst Water Resources (The Example of the Kras Plateau, SW Slovenia)

Na Krasu je bil od nekdaj najvecji problem oskrba s kakovostno pitno vodo, ki je omejevala poselitev in gospodarski razvoj obmocja. Sodobna oskrba ne zagotavlja zadostne kolicine pitne vode za gospodinjstva in gospodarstvo le na Krasu, temvec jo v poletnem casu oddaja celo na Obalo. Oskrba s pitno vodo temelji na crpanju kraske podtalnice iz vrtin pri Klaricih in na dveh izvirih pod Nanosom. Pri snovanju vodne oskrbe kaže v prihodnosti vkljuciti stevilne lokalne vodne vire v povezavi s tradicionalno obliko vodne oskrbe. Pri tem ni izkljucena morebitna uporaba kapnice za potrebe namakanja vrtov, pranje avtomobilov, za komunalne dejavnosti (pranje ulic) in v kmetijstvu ter ponovna uporaba odpadnih voda za tehnolosko vodo v industriji. In the past the biggest economic problem on the Kras plateau used to be drinking water supply, which has also been one of the reasons for sparsely populated Kras plateau.Today the Water Supply Company provides drinking water to households and industry on the Kras plateau and the quantity is suffi cient to supply the coastal region in the summer months as well. Water supply is founded on effective karst groundwater pumping near Klarici. Some water is captured from karst springs under Nanos Mountain as well. In water supply planning in future, numerous other local water resources linked to traditional ways of water supply need to be considered. Eventual rainwater usage for garden irrigation or car washing, for communal activity (street washing) or for the needs of farming and purifi ed wastewater usage for industry (as technological water) is not excluded.

Hydrogeological research as a basis for the preparation of the plan of monitoring groundwater contamination: A Case Study of the Stara Vas Landfill near Postojna (SW Slovenia)

V Sloveniji je na krasu trenutno aktivnih devet odlagališč komunalnih odpadkov, med drugimi tudi Stara vas pri Postojni. Ker je za kraška območja značilna močna razpokanost kamninske osnove in zelo dobra prepustnosti, izcedne vode z odlagališč še posebej ogrožajo podzemno vodo. Sposobnost naravne filtracije je v krasu majhna,obseg možnega negativnega vpliva pa zelo velik. Sedaj veljavna zakonodaja predpisuje obratovalni monitoring, del katerega je tudi merjenje parametrov onesnaženosti podzemnih vod z nevarnimi snovmi, če so v vplivnem območju odlagališča. Temelj za izdelavo načrta monitoringa so ustrezne hidrogeološke raziskave. Za primer Stare vasi smo poleg osnovnih geoloških in hidrogeoloških podatkov uporabili še rezultate sledilnih poskusov, ožje območje odlagališča pa smo podrobno tektonsko-litološko kartirali v merilu 1:5000. Na osnovi ugotovljenih značilnosti pretakanja vode v podzemlju in v skladu s predpisi smo določili 3 točke monitoringa znotraj (izvira Malenščica in Vipava, jama Fužina) in eno izven vplivnega območja odlagališča (Matijeva jama) ter določili način spremljanja kakovosti vode in izdatnosti For the present 9 land fills on karst are still active in Slovenia, among them also the Stara vas land fill near Postojna. As strong fissuration of the rock base and very good permeability istypical for karst areas, the waste waters from the landfills particularly endanger the groundwater.The capacity of natural filtration in karst is very low and the dimension of possible negative impact is very high. The actual legislation regulates the performance of operational monitoring, a part of which is also the measurement of parameters of contamination of groundwater by hazardous substances, if they are in the area of influence of the landfill. Preparation of the monitoring plan is based on adequate hydrogeological researches. Besides basic geological and hydrogeological data also the results of tracer tests were used in the case study of the Stara vas landfill.Additionally, the detailed tectonic-lithological mapping in the scale 1:5000 was performed in the narrow area of the landfill.Based on defined characteristics of underground water flow and in accordance with the regulations 3 monitoring points inside (Malenščica and Vipava springs, Fužina cave) and one point outside the area of influence of the landfill (Matijeva jama cave) were selected. The monitoring plan for the observation of water quality and capacity was suggested.

A catchment as a simple dynamical system: Characterization by the streamflow component approach

Summary The simple dynamical system approach was implemented to analyze, explain and simulate streamflow fluxes in diverse seasonal hydrological conditions within the forested Padež stream catchment in SW Slovenia. The catchment is characterized by the flushing, torrential hydrological response conditioned by the flysch geological settings of a low hydraulic conductivity. Consequently, the streamflow formation is not controlled solely by the deeper subsurface catchment storage but is also strongly influenced by the rainfall–runoff that bypasses the deeper subsurface part of the total catchment storage. Therefore, fast component of the streamflow is identified using two-component hydrograph separation; the component recession behavior is described by a separate sensitivity function and used in a simple model to simulate the streamflow. According to the simulation results, the Padež stream catchment behaves primarily like a deeper subsurface storage-dependent system during most of the hydrological conditions. When rainfall intensities increase (rainfall intensities close to 10 mm/h or higher), triggering of the secondary streamflow formation mechanism described by separate, bypassing flow sensitivity function becomes evident and causes fast hydrograph formation with steeply rising and falling limbs. To be able to implement the modeling concept for streamflow predictions, the rainfall losses, most likely associated with interception losses not covered under the potential evapotranspiration calculation, would have to be more thoroughly analyzed through rainfall interception measurements. Our study shows the possible way that two hydrological concepts, the streamflow recession analysis and the two-component hydrograph separation based on relatively easily measurable tracers, such as electrical conductivity, could be combined for analyzing streamflow fluxes.

Structural–geological and karst feature investigations of the limestone–flysch thrust-fault contact using low-frequency ground penetrating radar (Adria–Dinarides thrust zone, SW Slovenia)

The Karstic thrust edge, a pronounced geomorphologic step, which is a result of the tectonostratigraphic evolution of the active Adria–Dinarides thrust zone, represents a major obstacle for the planned new railway route Divaca–Koper. Thus, the geotechnical and structural properties as well as the geometry of the thrust-fault planes in this area are of great importance. Since geological mapping cannot give insight into the subsurface to reveal a complex 3D structure, and the numerous boreholes needed to investigate the area would be too expensive and time consuming, the application of a geophysical method such as ground penetrating radar (GPR) is needed. To test the method for determining near surface features and detecting low-angle inclined thrusts, a low frequency GPR system with 50 MHz rough terrain antenna was used to record 13 GPR profiles along all three floors of the Crnotice quarry, where the spatial position of the Socerb thrust fault that separates limestones above and flysch layers below is relatively well documented. The profiles were positioned across selected existing boreholes. The GPR results were correlated with borehole data as well as geological mapping results. The GPR provided not only precise information on the geometry of the Socerb thrust fault, but was also very useful for establishing the position of some known as well as several potential cavities, both air- and sediment-filled. In areas further from the thrust-fault zone, where the limestone is less tectonically damaged, it was also possible to determine apparent dip angles of the strata, which after reconstruction matched the true dips gathered from geological mapping.

Yellow goatsbeard Tragopogon dubius Scop. (Asteraceae): confirmation of its dubious occurrence in Central Slovenia

Tragopogon dubius is a species native to SW Slovenia and with several dubious records in central and eastern parts of the country. Its locus classicus is in SW Slovenia at Senožeče, but there is a slight doubt about the type description as no herbarium material has been preserved. All records (and herbarium vouchers in University of Ljubljana’s (LJU) collection) of the species from continental Slovenia have been critically assessed, but none of them has proved to be reliable. Three new recently discovered records linked to the railways in central and E Slovenia are presented and discussed.

A lidar, GIS and basic spatial statistic application for the study of ravine and palaeo-ravine evolution in the upper Vipava valley, SW Slovenia

The analysis of high resolution airborne lidar topography represents an essential tool for the geomorphological investigation of surface features. Here we present a detailed lidar-based geomorphological analysis of the ravines cut into the slopes of the upper Vipava valley, NW Slovenia. The NE slopes are defined by an Oligocene thrust-front of Mesozoic carbonates overthrusted on Tertiary flysch and covered by numerous fan-shaped Quaternary gravity flows, deposited in palaeo-ravines cut into the flysch base rock. In contrast, the opposite SW slopes are composed solely of flysch. The large dextral-slip Vipava fault extending in the NW–SE direction is present in the central part of the valley. Our research revealed that although the ravines on both slopes of the Vipava valley are lithologically and tectonically controlled, significant statistical differences in their directions exist. Thus, ravines on opposite slopes are not solely related to the Vipava fault system deformation, but instead reflect a more complex tectonic setting. We believe that the ravines are controlled by second-order faults and fault zones that connect the Vipava fault with adjacent faults. On the SW slopes, these include connecting faults between the Vipava and the southwestern Raša fault, with the ravines on the NE slopes formed in fault zones connecting the Vipava and northeastern Predjama faults.

Conservation Genetics ofDichoropetalum schottii(Apiaceae): Is the Legal Protection of Edge Populations Consistent with the Genetic Data?

Dichoropetalum schottii is a species that lives at low to medium altitudes in the southern European mountain ranges, from the Balkans (N Greece) to the Pyrenees. Its legal protection status is not homogeneous along its distribution range, as only some of its edge populations, in the Pyrenees, are protected. Here, by means of allozyme electrophoresis, we examine the genetic variability of populations representing four different regions within its distribution area (Pyrenees, Maritime Alps, Karst Plateau in the SW Slovenia—NE Italy border region, and Pindus Mountains in Greece). The species as a whole exhibits relatively high levels of genetic diversity, partly due to the occurrence of several duplications among the loci surveyed. Genetic differentiation among populations and regions was low, which could be interpreted as the result of recent allopatric fragmentation. We conclude that the species as a whole is not threatened, and that the currently protected populations are, paradoxically, the least valuable from the genetic point of view.

Geomorphic activity in flysch badlands of the Istria peninsula (SW Slovenia)

Geomorphic activity in flysch badlands of the Istria peninsula (SW Slovenia)

Hydrogeological study of the Malenščica karst spring (SW Slovenia) by means of a time series analysis

Time series analyses are often used for the investigation of karst aquifers, but are only rarely employed in a way of using a large number of spatially distributed time series. Furthermore, only a small number of applications employ other types of hydrologi­cal data apart from rainfall, water level and discharge. The pre­sented study of the Malenscica karst spring aquifer underlines the usefulness of the simultaneous auto- and cross-correlation analysis of daily and hourly hydrological data sets, including discharge, water level, temperature, electrical conductivity and rainfall on a regional scale. The results of the autocorre­lation analysis show that the storage capacity of the spring is moderate, but this does not indicate that the system, whichis characterized by prevailing conduit porosity, is less intensively karstified. This suggests that well-karstified systems of a more complex structure can have higher memory effects than less complex systems. The results of the cross-correlation analysis show that karst springs and watercourses in the investigated area react instantly and simultaneously to rather homogeneous precipitation, yet withdifferent intensity. In suchcases a cross-correlation analysis between rainfall or ponors as inputs and springs as outputs does not provide sufficient information on the hydrogeological functioning of the system, whereas the results of a cross-correlation analysis of electrical conductivity data sets provide valuable information on its functioning and can be easily compared to those obtained by tracer tests. On the other hand, the applicability of a temperature time series in suchcomplex karst systems is limited. A comparative analysis of the results of the time series analyses performed in succes­sive hydrological years has proven that the selection of the hy­drological year can have strong effects on the results of a time series analysis.

Križna jama (SW Slovenia): Numerical-and correlated-ages from cave bear-bearing sediments

Križna jama is a large river cave located between Loško and Cerkniško poljes under Križna gora Mount in southern Slo­venia. It has been known since the mid-19thcentury due to numerous cave bear finds. The cave is filled by complicated sequences of cave fluvial and lacustrine sediments, whichare recently partly eroded. We studied two paleontological exca­vations and profiles in the Medvedji rov to contribute to the solution of dating of bone-bearing lithological horizons. The Križna jama I profile consists of alternation of speleothem lay­ers (flowstone sheets withsmall stalagmites, sometimes within situ cemented Ursus gr. spelaeus bones) and fine-grained silici­clastics often withbones of cave bear. It can be correlated withthe upper part of the Križna jama II profile, but witha slightly less preserved stratigraphic record. Radiocarbon and U-series dates clearly indicate two different ages of cave bear thanato­cenoses in the Križna jama I profile: those above flowstone crusts were dated to ca. 47–45 ka by radiocarbon dating; those included in speleothem layers and clay interbeds are older than 94 ka (U-series date). The details of internal lithology, low thicknesses of layers and the state of bone preservation exclude expected sandwiching of younger layers into eroded/washed spaces among flowstones. Numerical dating excludes re-depo­sition of bear bones from older assemblage to sediments above flowstones. According to the paleomagnetic parameters (pre­vailing normal polarization), the deposition took place within the Brunhes Chron (< 780 ka). There were discovered in total four short-lived reverse excursions of the magnetic field. Ac­cording to U-series data, the upper one (profile I) might be correlated withthe Blake excursion. The lower ones are older than ca 190 ka and can be correlated withsome of the Jamaica-Pringle Falls, Namaku, Calabrian Ridge, Portuguese margin or Calabrian Ridge 1 excursions. Sediments in studied profiles were deposited during the Last Glacial (Weichselian), Eemian interglacial, Saalian glacial and Holsteinian interglacial.

The study of hydrodynamic behaviour of a complex karst system under low-flow conditions using natural and artificial tracers (the catchment of the Unica River, SW Slovenia)

In this study a multi-tracer test with fluorescent tracers was combined with time series analyses of natural tracers to characterize the dynamics of the solute transport through different recharge pathways and to study hydraulic behaviour of a binary karst system under low-flow conditions. Fluorescent tracer testing included the introduction of uranine, amidorhodamine G, or naphthionate at three injection points. Sampling and monitoring took place at two karst springs (Malenscica, Unica) and at two underground rivers (Pivka, Rak) recharging the Unica River at the Polje of Planina, SW Slovenia. Other monitored parameters included precipitation, spring or underground river discharge, water temperature, and electrical conductivity. Water samples were collected and analyzed for total organic carbon, Mg2+, SO42−, and NO3− in the laboratory. In the study area, results of the tracer test suggest that contaminant transport in karst may be retarded for several weeks during low-flow conditions followed by increases in contaminant concentrations after subsequent rainfall events. Based on interpretation of tracer concentration breakthrough curves, low apparent dominant flow velocities (i.e., between 5.8 and 22.8 m/h through the well developed karst conduits, and 3.6 m/h through the prevailing vadose zone with a dominant influence of a diffuse recharge) were obtained. Together with analyses of hydro-chemographs the artificial tracing identified different origins of water recharging the studied aquifer. During prolonged low-water conditions the Malenscica spring is mainly recharged from the karst aquifer and the Unica spring by the sinking Pivka River. After more intensive rainfall events allogenic recharge from Cerknica prevails in the Malenscica spring, while the Unica spring drains mainly the allogenic water from the Pivka Valley. These findings of alternating hydraulic connections and drainage areas due to respective hydrological conditions are important and should be considered when monitoring water quality, implementing groundwater protection measures, and optimizing future water exploitation.

The evolution of mid Paleocene-early Eocene coral communities: How to survive during rapid global warming

Today, diverse communities of zooxanthellate corals thrive, but do not build reef, under a wide range of environmental conditions. In these settings they inhabit natural bottom communities, sometimes forming patch-reefs, coral carpets and knobs. Episodes in the fossil record, characterized by limited coral-reef development but widespread occurrence of coral-bearing carbonates, may represent the fossil analogs of these non-reef building, zooxanthellate coral communities. If so, the study of these corals could have valuable implications for paleoenvironmental reconstructions. Here we focus on the evolution of early Paleogene corals as a fossil example of coral communities mainly composed by zooxanthellate corals (or likely zooxanthellate), commonly occurring within carbonate biofacies and with relatively high diversity but with a limited bioconstructional potential as testified by the reduced record of coral reefs. We correlate changes of bioconstructional potential and community compositions of these fossil corals with the main ecological/environmental conditions at that time. The early Paleogene greenhouse climate was characterized by relatively short pulses of warming with the most prominent occurring at the Paleocene-Eocene boundary (PETM event), associated with high weathering rates, nutrient fluxes, and pCO2 levels. A synthesis of coral occurrences integrated with our data from the Adriatic Carbonate Platform (SW Slovenia) and the Minervois region (SW France), provides evidence for temporal changes in the reef-building capacity of corals associated with a shift in community composition toward forms adapted to tolerate deteriorating sea-water conditions. During the middle Paleocene coral–algal patch reefs and barrier reefs occurred from shallow-water settings, locally with reef-crest structures. A first shift can be traced from middle Paleocene to late Paleocene, with small coral–algal patch reefs and coral-bearing mounds development in shallow to intermediate water depths. In these mounds corals were highly subordinated as bioconstructors to other groups tolerant to higher levels of trophic resources (calcareous red algae, encrusting foraminifera, microbes, and sponges). A second shift occurred at the onset of the early Eocene with a further reduction of coral framework-building capacity. These coral communities mainly formed knobs in shallow-water, turbid settings associated with abundant foraminiferal deposits. We suggest that environmental conditions other than high temperature determined a combination of interrelated stressors that limited the coral-reef construction. A continuous enhancement of sediment load/nutrients combined with geochemical changes of ocean waters likely displaced corals as the main bioconstructors during the late Paleocene-early Eocene times. Nonetheless, these conditions did not affect the capacity of some corals to colonize the substrate, maintain biodiversity, and act as locally important carbonate-sediment producers, suggesting broad environmental tolerance limits of various species of corals. The implications of this study include clues as to how both ancient and modern zooxanthellate corals could respond to changing climate.

Erratum to paper Križna Jama (SW Slovenia): Numerical-and Correlated-Ages from Cave Bear-Bearing Sediments, by p. Bosak et al., ac 39/3

Erratum to paper Križna Jama (SW Slovenia): Numerical-and Correlated-Ages from Cave Bear-Bearing Sediments, by p. Bosak et al., ac 39/3

The Canadian fire weather index system and wildfire activity in the Karst forest management area, Slovenia

The Canadian fire weather index system (CFFWIS) has been adopted for fire danger rating throughout Europe as part of the European Forest Fire Information System. However, its performance has not been thoroughly assessed, especially in environments less prone to fire. In this study, we characterised fire activity between 1995 and 2009 in the sub-Mediterranean Karst forest management area of SW Slovenia. Five fire danger classes (very low, low, moderate, high and very high) were derived from percentile analysis of the CFFWIS Fire Weather Index. These classes were found to be related with fire activity descriptors. Logistic regression prediction of fire-days based on CFFWIS indices had low accuracy, and better discrimination was achieved by classification tree modelling. Fire activity was found to be driven by current weather conditions rather than by drought. Our findings highlight the potential of fire danger rating to guide fire management but also the limitations imposed by relatively low incidence of fire and the spatial scale of analysis.