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Iskalni niz: "ključne besede" (temperature) .

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A single-tree approach to determine climate-growth patterns of European beech and their seasonality in the species southern distribution area
Roberto Serrano-Notivoli, Jernej Jevšenak, Katarina Čufar, Nina Škrk Dolar, Angela Balzano, Jožica Gričar, Maks Merela, Klemen Novak, Peter Prislan, Martin De Luis, 2025, izvirni znanstveni članek

Povzetek: Dry and warm climate conditions in southern Europe represent clear limits for European beech (Fagus sylvatica) growth near the species southern distribution limit, but it is unclear how aridification and changes in seasonal precipitation regimes will affect these forests at the individual level. We explored climate-growth relationships and the seasonality of peak climate signals in European beech using daily climate data and a large collection of tree-ring width series from southern and southeastern Europe through Generalised Linear Mixed Models (GLMMs). In most cases we found a positive and significant influence of precipitation on tree growth, and a significant negative effect of maximum temperature. Predictions from the GLMMs revealed a positive impact of precipitation during an 88 day window from spring to early summer (mid-April to mid-July), for an average tree across our network. This critical growing time window ranged from 75 days in warmer and drier conditions, and extended up to 100 days in areas with mild temperatures and moderate summer precipitation. Maximum temperatures negatively affected trees for an average of 27 day window in summer (June-July). This period was reduced to <10 days in locations with wetter and colder summers, rising up to 45 days in sites with drier and warmer summers. The positive effect of precipitation on growth was stronger and commenced earlier in larger trees. Similarly, the negative effects of maximum temperatures were more pronounced for larger trees. The use of daily climate data and a tree-centred approach allowed for capturing critical temporal dynamics in climate-growth relationships that are often overlooked by conventional methods. These insights significantly enhance our understanding of climatic factors influencing individual beech growth at the edge of its distribution range and their seasonal variations.
Ključne besede: European beech, daily climatic variables, precipitation, maximum temperature, tree-ring width, range limit
Objavljeno v DiRROS: 06.06.2025; Ogledov: 136; Prenosov: 70
.pdf Celotno besedilo (9,90 MB)
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Investigating transient seepage flow and heat transfer using optical fiber distributed temperature sensors and hydrothermal modeling
Yaser Ghafoori, Stanislav Lenart, Uroš Bohinc, Andrej Kryžanowski, 2025, izvirni znanstveni članek

Povzetek: Seepage during the first filling of a reservoir is a critical aspect for earth dams and embankments safety, which requires precise monitoring. The thermometric method has demonstrated significant potential for detecting seepage anomalies through continuous temperature measurements using optical fiber distributed temperature sensing (DTS). However, most previous research has primarily focused on thermal monitoring when seepage flow reached a steady-state condition, which highlights the need for more research on seepage and heat transfer in transient state, particularly in unsaturated soils during the reservoir’s first filling. This paper addresses the transient seepage flow and heat transfer during the first filling of a laboratory sand model. Temperature variations within the sand were recorded using an optical fiber DTS, while seepage progression was tracked through digital imaging at regular intervals, followed by image processing. A coupled hydrothermal numerical model was also developed to simulate transient seepage flow and heat transfer within the unsaturated and variably saturated sand. In numerical modeling, heat dispersion and the thermal conductivity of sand were investigated through parameter calibration. Results indicate that thermal monitoring using optical fiber DTS is an effective method for estimating the development of the phreatic line during the first filling of the reservoir. Numerical simulations further revealed that seepage velocity plays a key role in the heat transfer process during transient seepage. Additionally, the results highlight that heat dispersion significantly influences heat transfer, particularly during transient seepage flow, whereas the effect of thermal conductivity is relatively minor as seepage progresses.
Ključne besede: seepage, phreatic line, temperature, heat dispersion, optical fiber DTS
Objavljeno v DiRROS: 09.05.2025; Ogledov: 177; Prenosov: 80
.pdf Celotno besedilo (16,17 MB)
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Comparison of some epigean and troglobiotic animals regarding their metabolism intensity. Examination of a classical assertion
Tatjana Simčič, Boris Sket, 2019, izvirni znanstveni članek

Povzetek: This study determines oxygen consumption (R), electron transport system (ETS) activity and R/ETS ratio in two pairs of epigean and hypogean crustacean species or subspecies. To date, metabolic characteristics among the phylogenetic distant epigean and hypogean species (i.e., species of different genera) or the epigean and hypogean populations of the same species have been studied due to little opportunity to compare closely related epigean and hypogean species. To fill this gap, we studied the epigean Niphargus zagrebensis and its troglobiotic relative Niphargus stygius, and the epigean subspecies Asellus aquaticus carniolicus in comparison to the troglobiotic subspecies Asellus aquaticus cavernicolus. We tested the previous findings of different metabolic rates obtained on less-appropriate pairs of species and provide additional information on thermal characteristics of metabolic enzymes in both species or subspecies types. Measurements were done at four temperatures. The values of studied traits, i.e., oxygen consumption, ETS activity, and ratio R/ETS, did not differ significantly between species or subspecies of the same genus from epigean and hypogean habitats, but they responded differently to temperature changes. Higher Q10-values for oxygen consumption of N. stygius than N. zagrebensis in the temperature range 10-20°C and higher Ea indicated higher thermal sensitivity in the subterranean species. On the other hand, lower Q10 and Ea-values for ETS activity of N. stygius than N. zagrebensis indicated more thermally stable enzymatic machinery in N. stygius than N. zagrebensis. In Asellus, we observed a similar trend of lower Ea for oxygen consumption and higher Ea for ETS activity in epigean than the troglomorphic subspecies, but the values did not differ significantly between the two. Our most important conclusion is that the low metabolic rate is not a universal property of troglobiotic animals, and the degree of metabolic adaptation is not necessarily in agreement with the degree of morphological adaptation (troglomorphy).
Ključne besede: food scarcity, temperature, oxygen consumption, ETS activity, amphipod, isopod
Objavljeno v DiRROS: 12.03.2025; Ogledov: 182; Prenosov: 180
.pdf Celotno besedilo (580,17 KB)
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Simulation of temperature field in steel billets during reheating in pusher-type furnace by meshless method
Qingguo Liu, Umut Hanoglu, Zlatko Rek, Božidar Šarler, 2024, izvirni znanstveni članek

Povzetek: Using a meshless method, a simulation of steel billets in a pusher-type reheating furnace is carried out for the first time. The simulation represents an affordable way to replace the measurements. The heat transfer from the billets with convection and radiation is considered. Inside each of the billets, the heat diffusion equation is solved on a two-dimensional central slice of the billet. The diffusion equation is solved in a strong form by the Local Radial Basis Function Collocation Method (LRBFCM) with explicit time-stepping. The ray tracing procedure solves the radiation, where the view factors are computed with the Monte Carlo method. The changing number of billets in the furnace at the start and the end of the loading and unloading of the furnace is considered. A sensitivity study on billets' temperature evolution is performed as a function of a different number of rays used in the Monte Carlo method, different stopping times of the billets in the furnace, and different spacing between the billets. The temperature field simulation is also essential for automatically optimizing the furnace’s productivity, energy consumption, and the billet’s quality. For the first time, the LRBFCM is successfully demonstrated for solving such a complex industrial problem.
Ključne besede: pusher-type reheating furnace, steel, temperature field, radiation, convection, diffusion, strong form meshless method, radial basis functions
Objavljeno v DiRROS: 20.12.2024; Ogledov: 362; Prenosov: 189
.pdf Celotno besedilo (4,35 MB)
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Phloem : a missing link in understanding tree growth response in a changing environment
Jožica Gričar, 2024, izvirni znanstveni članek

Povzetek: Although the activities of various tree organs and tissues are under different environmental and internal constraints, they need to be coordinated to ensure whole-tree functioning. Dusart et al. (2024) conducted a heating experiment on branches of Juglans regia saplings during the entire growing season to examine the effect of temperature on primary (bud) and secondary (xylem) growth. They found that primary and secondary meristems responded asynchronously to elevated temperature, which suggests that lack of coordination mechanisms between primary and secondary growth at crown scale could have a potential impact on canopy and tree architecture.
Ključne besede: phloem, wood anatomy, tree growth, angiosperms, bark, meristem, non-structural carbohydrates, primary growth, radial growth, secondary growth, temperature, xylem
Objavljeno v DiRROS: 05.12.2024; Ogledov: 277; Prenosov: 202
.pdf Celotno besedilo (952,41 KB)
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