The CO
2
concentration of the air in Postojna Cave (400–7900 ppm) is found to be induced by CO
2
sources (human respiration contributing ~ 20,000–58,000 ppm per breath, outgassing of dripwater and ...water seeping from the vadose zone/epikarst with a
p
CO
2
values of 5000–29,000 ppm, and underground Pivka River having
p
CO
2
at 2344–4266 ppm) and CO
2
dilution (inflow of outside air with a CO
2
concentration of ~ 400 ppm). Measurements show that sinking Pivka River has the lowest CO
2
concentration among plausible CO
2
sources but still continuously exceeds the surrounding cave air CO
2
concentration. During the winter months, intensive ventilation reduces the cave air CO
2
concentration to outside levels (~ 400 ppm), even in the centre of the cave system. CO
2
dilution is less pronounced in summer (CO
2(min)
≈ 800 ppm), since the ventilation rate is not as strong as in winter and the outside air that enters the cave through breathing holes and fractures is enriched with soil CO
2
. During spring and autumn, the daily alternation of the ventilation regime with a smaller rate of air exchange results in yearly cave air CO
2
peaks of up to ~ 2400 ppm. Some dead-end passages can be much less affected by ventilation, resulting in a cave air CO
2
concentration of up to 7900 ppm. The strongest diurnal CO
2
peaks due to human respiration were recorded during the spring holidays (increase of up to 1300 ppm day
−1
), compared to considerably smaller summer peaks despite peak visits (increase of ~ 600 ppm day
−1
).
Historical air temperatures at three karst caves in Slovenia have been compared to current data time series. In Postojnska Jama (PJ), the most visited show cave in Slovenia, the significant ...temperature difference between historical and modern measurements at the Pulpito site relates to the months April to November. Mean monthly temperatures measured at the Sepolcro site (PJ) in the modern period (2016–2019) are year round significantly higher than in the historical period (1935–1937). The temperature increase over the last 85 years in PJ is attributed to outside temperature rise and additional heat input from visitors, especially for Sepolcro site. A comparison of current (2017–2019) and historical (1956–1957) temperature data in touristically poorly visited Predjama Cave shows lower increase as in PJ and is completely related to outside cave conditions. In the case of Škocjanske Jame (Tiha Jama), air temperature has not significantly increased since the historical 1928 measurements because the monitoring site looks to be morphologically isolated from significant impacts of outside climate and visitors.
The Biospeleological Station (BS) in Postojna Cave, with a volume of 36,000 m3, has served as an underground biological laboratory since 1931, receiving 100,000 visitors annually. Historical cave ...micro-climate monitoring was performed in 1933 and 1963, and continuous monitoring of cave air temperature and carbon dioxide concentration at hourly intervals started in 2015. Micro-climatic data collected between 2015 and 2024 has helped us to understand the relationship between natural underground environment and anthropogenic impact, thereby aiding expert recommendations to cave managers for the mitigation of anthropogenic micro-climatic effects. Results strongly support the policy that, during summer, when outdoor temperatures are higher than in the cave, solid metal doors connecting the BS with the rest of the cave (Stara Jama) should be kept open. Such a simple mitigation act helps to decrease anthropogenically increased air temperature and carbon dioxide concentrations, thereby maintaining suitable micro-climatic conditions for the exhibition of cave animals. Closure during the COVID-19 pandemic (2020–2021) resulted in the lowest temperatures recorded. BS visitation increases air temperature by 1 °C, highlighting the need for management strategies to maintain suitable conditions for cave fauna exhibition.
Črna Jama is the coldest section of cave within the Postojna Cave System. Mean annual air temperatures at the Črna Jama 2 site are 5.6 °C (2015) and 5.7 °C (2016), and at the Črna Jama 3 site 7.1 °C ...(2015) and 7.2 (2016), whereas the mean external air temperature was 10.3 °C (2015) and 10.0 °C (2016). In Lepe Jame, the passage most heavily visited by tourists, the mean cave-air temperature is 10.7 °C (2014–2017). Črna Jama exhibits winter and summer temperature regimes. During warm periods (T
cave
< T
out
), it acts as a cold air trap, exchanging no air with the outside atmosphere. Under such conditions the cave-air temperature shows no short-term diurnal temperature oscillations. Cave-air temperature is significantly stable and affected only by elevation of the groundwater table, which is associated with precipitation. During cold periods (T
cave
> T
out
), ventilation takes place and dense, cold, outside air sinks into Črna Jama because of the favourable cave entrance morphology. Recent Črna Jama air temperature data (2014–2017) indicate a < 0.5 °C higher temperature than that recorded in historical data since 1933. Črna Jama is the most appropriate place within the Postojna Cave System to study long-term climatic changes. There are hardly any tourist visits to the cave, and human impacts on the cave climate are essentially reduced.
Air and groundwater temperatures were measured in a rimstone pool in Postojna Cave, to advise evaluation of the impact of natural and anthropogenic influences related to heat being initially ...transmitted into cave air by visitors. Such heat can accumulate both in the rock mass and in water. Results show that attention must be paid to temperature changes of rimstone pool water rather than those of cave air, especially during the winter. Thanks to good ventilation deep inside the cave, short-term air temperature increases related to higher visitor numbers have not influenced flowstone precipitation or the cave fauna. However, this situation might change if winter visitor numbers increased greatly. This study does not support a suggested increase in winter visits (currently the tourism low-season) and reduction of summer visits (currently the tourism high-season).
•Postojna Cave is one of the World's most-visited show caves, attracting around 500,000 visitors per year.•The potential impact of mass tourism on the cave air and water temperature was studied.•The susceptibility of cave water temperature to anthropogenic influences is higher than the susceptibility of cave air.•Higher visitor numbers during winter represent a greater disturbance to the cave microclimate than in summer.
•Karst areas need to be managed in an appropriate and careful manner.•A critical overview of current protection legislation in Slovenia has been prepared.•A new comprehensive management approach for ...karst areas and resources has been proposed.•It provides general, non-prescriptive guidelines for addressing challenges of karst protection.•It is principally based on the enforcement of karst-specific detailed management plans.
Karst terrain offers a great range of economic assets, provides unique habitats and valuable ecosystem services. Owing to its particular nature, this environment is highly susceptible to destruction. Any interference is likely to have irreversible impacts and disturb the natural balance of the elements (water, soil, flora and fauna) and processes (e.g. corrosion, CO2 sequestration, speleothem growth) that constitute it. Karst areas must therefore be holistically managed in an appropriate and careful manner. A critical overview of current protection legislation in Slovenia has been prepared, with particular reference to karst areas. The major problem is a lack of harmonised multi-sector policies regulating land use and planning throughout the karst region, the absence of detailed guidelines and insufficient pursuance of karst in all its complexity and vulnerability. A comprehensive management approach for karst areas has been proposed and could subsequently be adopted by other karst-rich countries. Management is based on the enforcement of karst-specific legislation, including provision of detailed management plans and their strict implementation. Common database maintenance, reconciliation between various stakeholders and raising public awareness are additional important parts of the approach.
In situ micro-displacement monitoring in caves at the seismically active junction of the Southern Alps, Dinarides and Southwestern Pannonian Basin revealed active tectonic micro-deformations. The ...largest total vertical movement of 0.35 mm (2008–2018) occurred at Kostanjeviška Jama (Southwestern Pannonian Basin–Dinarides). Two abrupt displacements observed at that cave location correspond to pre- and post-seismic episodes in 2014 and 2015. At Pološka Jama (Southern Alps), more gradual and continuous displacement on a monitored bedding plane of 0.13 mm down-slip (2008–2018) was observed. This movement is attributed to slope relaxation as well as tectonic activity on the Julian Alps thrust fault and the seismogenic Ravne Fault, which generated earthquakes at
M
w
= 5.6 in 1998 and
M
w
= 5.2 in 2004. At Jama pri Svetih Treh Kraljih in Dinarides, activity on the Ravne Fault was shown as sinistral-horizontal (0.1 mm) and vertical (0.15 mm) movement along an E–W-oriented tectonic structure. This shallowly buried site also experienced cyclic seasonal displacements. At Županova Jama, multiple short-term horizontal dextral and sinistral strike-slip pulses (2016–2018) demonstrated active tectonic micro-deformations within the wider zone of the Dobrepolje and Želimlje faults. At Postojnska Jama, two episodes of vertical movement on a NW–SE-oriented fault are associated with earthquake swarms: the first episode was in 2010 (
M
LV
= 3.7) and the second in 2014 (
M
LV
= 4.3). In-cave flood events do not coincide with periods of micro-displacement activity in the studied caves, and therefore are not the drivers of the micro-displacement.
Microclimatic monitoring (air T, air pressure, CO2, ventilation, humidity, methane, and radon) in selected show caves in Slovenia has been a continuous process for more than 10 years, a process that ...aims to supervise the use of the caves for tourism in the sense of sustainable environmental management. After the cataclysmic eruption of the Hunga Tonga–Hunga Ha’apai (HTHH) volcano on 15 January 2022, global propagation of ionospheric disturbances was reported worldwide as barometric pressure changes and seismic noise events. Weather stations in Slovenia reported 2–4 hPa changes in atmospheric pressure 16 h after the eruption at 20:30 CET (19:30 UTC). Changes in atmospheric pressure were also detected at 15 air monitoring sites in 3 different caves (20–120 m below the surface), at 8 water monitoring sites in 4 different caves (1–10 m below the water surface), and on the surface (4 air and 2 water monitoring sites), where we identified a small but significant increase in atmospheric pressure of <1 hPa, with the highest signal at 21:00 CET (20:00 UTC). At some cave monitoring locations, air T fell during this global event induced by a far-field volcanic eruption. Cave CO2, methane, and radon measurements did not show significant changes related to the eruption. This is the first evidence of atmospheric pressure changes due to the HTHH volcano eruption in karst caves and waters.
Within the UNESCO Škocjan Caves, detailed geological structural mapping of the cave passages and of the surface above the cave revealed interesting structural-lithological characteristics of two ...major collapse dolines, Velika Dolina and Mala Dolina. As a result of the karst processes effects and the formation of collapse dolines, older—stratigraphically lower—carbonates of the Sežana Formation (K
2
2−4
) crop out at the surface, underlying rocks of the younger Lipica Formation (K
2
4−5
). Here we do not recognize karst windows only in a geomorphological sense but, acknowledging the characteristic lithostratigraphical relationships involved, we suggest use of the new expression “karst stratigraphical window”. Recognizing that karstic areas contain numerous collapse dolines and other doline types, we presume that many more examples of karst stratigraphical windows exist, and that these are distinct from tectonic windows. Our study showed the importance that during the making of detailed geological surface maps of karst areas, it is essential to examine features such as collapse dolines, which may be identified as karst stratigraphical windows. Therefore, providing additional geological data, information about the stratigraphic boundaries and geological structure, in areas without abundance of outcropping rocks is resulting in a more inclusive and comprehensive geological maps.
Article highlights
Detailed (in-situ) geological mapping of the karst surface and subsurface is emphasized as important base for all future karst studies.
Karst stratigraphical windows that differ from tectonic windows, were reported for the first time.
The geology of Škocjan Caves with collapse dolines, is a reference point for other sites, that might have karst stratigraphical windows.
Denudirane ali brezstrope jame lahko velikokrat določimo iz originalne kraške topografije. Za ta članek sem preučila morfologijo in geologijo dveh denudiranih jam. V letu 1994 je bila pri vasi Povir ...odkrita prva denudirana jama, in sicer ko je gradnja avtoceste Divača-Dane že potekala. Originalno jamsko morfologijo smo lahko določili iz topografskih kart 1:1.000. V letu 1996 pa smo s predhodnimi krasoslovnimi raziskavami še pred začetkom gradnje avtoceste Divača-Kozina določili 4 denudirane jame. Posebno denudirana jama pri kraju Kačiče-Pared je bila morfološko 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 Divača-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 Divača-Kozina 4 denuded caves were discovered. The one near Kačiče-Pared was very well morphologically expressed.
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