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Iskalni niz: "avtor" (Jernej Jevšenak) .

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Local site conditions reduce interspecific differences in climate sensitivity between native and non-native pines
Marcin Miroslav Klisz, Radosław Puchałka, Marcin Jakubowski, M. Koprowski, Maksym Netsvetov, Yulia Prokopuk, Jernej Jevšenak, 2023, izvirni znanstveni članek

Povzetek: Two European pine species, Pinus sylvestris and Pinus nigra, are experiencing dieback as a result of the increasing frequency and intensity of extreme climatic events. Recent species distribution models predicted shrinkage of ecological niches in the near future and shifted their habitat range towards the northeast. Consequently, P. sylvestris may contract its range and P. nigra may expand in Central Europe. To test whether native pine species have an advantage over introduced pine species in acclimation to a novel climate in Central Europe, we investigated the climate sensitivity and vitality of P. sylvestris, P. nigra and P. rigida. We sampled mature stands of each pine species at three sites in Central Europe, for which we determined climate–growth relationships: temporal stability of temperature and precipitation correlations with tree-ring width and resilience indices. Based on remote sensing data, we assessed differences in surface reflectance and photosynthetic activity obtained from the normalised difference vegetation index (NDVI). Our analyses revealed that the climate sensitivity and surface reflectance of pines are not due to their nativeness in Central Europe but better explained by local site conditions. The specificity and variability of drought events may determine both the homogeneous and diverse susceptibility of species to a negative water balance. Therefore, the character of future climatic extremes seems to be the key to understanding the acclimation of native and non-native pine species in Central Europe. Because our study do not provide evidence of the superiority of non-native pine species over P. sylvestris, and the potential impacts of introduced species on local habitats seem poorly understood in the face of climate change, we urge particular caution in introducing species with unrecognized invasive potential.
Ključne besede: Pinus sylvestris, Pinus nigra, Pinus rigida, acclimation, climate sensitivity, drought resilience
Objavljeno v DiRROS: 18.09.2023; Ogledov: 44; Prenosov: 8
.pdf Celotno besedilo (2,25 MB)
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Analiza izbranih drevesnih modelov razvoja gozdov, primernih za modeliranje na velikoprostorski ravni, in možnosti njihove uporabe v Sloveniji
Jernej Jevšenak, Boštjan Mali, Mitja Skudnik, 2023, izvirni znanstveni članek

Povzetek: Prispevek obravnava drevesne modele razvoja gozdov, ki so pomembno orodje pri odločanju, upravljanju in strateških odločitvah na področju gospodarjenja z gozdovi. V Sloveniji smo šele v zadnjih letih pričeli s sistematičnim razvojem področja modeliranja gozdov, ki vključuje razvoj matričnega populacijskega modela, testiranje izbranih modelov iz tujine ter razvoj posameznih komponent modelov. Namen prispevka je predstaviti področje empiričnih drevesnih modelov za modeliranje razvoja gozdov na velikoprostorski ravni. Podrobneje predstavljamo uveljavljene metode za modeliranje posameznih komponent drevesnih modelov, kot so debelinska in višinska rast, razvoj krošnje, mortaliteta ter vrast in pomlajevanje. Opravili smo presojo primernosti izbranih drevesnih modelov z vidika možnost njihove uporabe v Sloveniji. Ugotavljamo, da imajo modeli SILVA, WEHAM, MASSIMO in CALDIS največje možnosti za uporabo v Sloveniji, saj so vsi primerni za različne gozdne tipe in mešane gozdove z raznomerno zgradbo, ki prevladujejo v Sloveniji. Poleg testiranja obstoječih modelov predlagamo razvoj novih modelov, prilagojenih raznomernim in mešanim sestojem v Sloveniji. Predlagamo tudi razširitev nabora kazalnikov pri gozdnih inventurah ter dodatne meritve značilnosti dreves, npr. lastnosti krošenj, ki bi razširile možnosti modeliranja razvoja gozdov v Sloveniji. V zaključkih razpravljamo tudi o možnosti uporabe strojnega učenja na področju modeliranja razvoja gozdov, saj bi tovrstni modeli lahko predstavljali naslednjo generacijo modelov.
Ključne besede: modeliranje, razvoj gozda, velikoprostorska gozdna inventura, stalne vzorčne ploskve, simulator razvoja gozdov, napovedovanje, gozdarska politika
Objavljeno v DiRROS: 27.06.2023; Ogledov: 606; Prenosov: 298
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Causes and consequences of large-scale windthrow on the development of fir-beech forests in the Dinaric mountains
Matjaž Čater, Ajša Alagić, Mitja Ferlan, Jernej Jevšenak, Aleksander Marinšek, 2023, izvirni znanstveni članek

Povzetek: We investigated several aspects of windthrow that are relevant to our understanding and management of forest ecosystems. As an example, we used an extreme event in December 2017, when the strongest storm in recent history occurred in the Slovenian Dinaric High Karst. We examined influential factors such as soil properties, wind speed, precipitation and ecological consequences for the affected forests. Soil properties were measured around standing and fallen silver fir trees at all three research sites. Tree species composition in the regeneration was observed on plots with chemical and acoustic ungulate deterrents and on control plots without deterrents. Economic estimates of yield loss due to damage were calculated at the national level. A model of the potential threat from windthrow was also developed based on data collected from windthrow events and meteorological data over the past 20 years. Our results indicate that soil depth and mineral fraction depth were similar at sites with and without damaged trees and were not the determining factors for tree toppling. Plots with acoustic deterrents showed the most effective regeneration development, the least decline in silver fir and the greatest increase in noble hardwood seedlings, while plots with chemical deterrents showed the least browsing damage. The estimated economic loss of €16.1 million is 6.6% less than the harvest under normal conditions. The economic loss was relatively low due to the nature of the storm, with the predominant type of damage being uprooted trees with no damaged trunks. The windthrow hazard model revealed that a large number of consecutive events with strong winds in each section weakened the stand, which was subsequently knocked down during the next extreme wind and rainfall event.
Ključne besede: natural forest regeneration, windthrow, economic loss, browsing, ungulate deterrents, forest soil properties, potential threat model
Objavljeno v DiRROS: 27.06.2023; Ogledov: 539; Prenosov: 259
.pdf Celotno besedilo (2,26 MB)
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Climate–growth relationships in Laurus azorica - a dominant tree in the Azorean Laurel forest
Diogo C. Pavão, Jernej Jevšenak, Lurdes Borges Silva, Rui Bento Elias, Luis Silva, 2023, izvirni znanstveni članek

Povzetek: Forests on oceanic islands, such as the Azores archipelago, enable interesting dendroclimatic research, given their pronounced climatic gradients over short geographical distances, despite the less pronounced seasonality. The Lauraceae play an essential ecological role in Macaronesian natural forests. An example is Laurus azorica (Seub.) Franco, a relevant species given its high frequency and physiognomic dominance in Azorean laurel forests. This study aims to quantify climate–growth relationships in L. azorica using a dendroecological approach. We sampled four stands at São Miguel and two stands at Terceira islands, for a total of 206 trees. Following standard dendrochronological methods and rigorous sample selection procedures, we obtained relatively low rbar values and high temporal autocorrelation. Using a stepwise Random Forest analysis followed by Generalized Linear Models calculation, we found prominent effects of present and previous year temperature, but a low precipitation signal on growth rings, with some model variation between stands. Our results agreed with previous observations for broad-leaved species with diffuse porous wood, contributing to increase the baseline dendroecological knowledge about Azorean forests. Due to the high levels of within- and between-stand variation, and to refine the climatic signal analysis, complementary approaches should be explored in the future.
Ključne besede: Azores, dendroclimatology, generalized linear models, laurel forest, Macaronesia, random forest
Objavljeno v DiRROS: 18.01.2023; Ogledov: 165; Prenosov: 102
.pdf Celotno besedilo (11,11 MB)
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Tree rings, wood density and climate–growth relationships of four Douglas-fir provenances in sub-Mediterranean Slovenia
Luka Krajnc, Jožica Gričar, Jernej Jevšenak, Polona Hafner, Robert Brus, 2022, izvirni znanstveni članek

Povzetek: Tree rings, wood density and the climate–growth relationship of four Douglas-fir provenances were analysed separately for the juvenile and adult phases. Four provenances were selected from an existing IUFRO provenance trial planted in 1971 based on their diameter at breast height and vitality. Increment cores were extracted from individual trees, on which we measured tree-ring widths (RW), earlywood widths (EWW) and latewood widths (LWW). Wood density was assessed in standing trees using resistance drilling. The climate–growth correlations were calculated between provenance chronologies of RW, EWW, LWW and latewood share, and the day-wise aggregated Standardised Precipitation-Evapotranspiration Index (SPEI). The analysis was done separately for the juvenile and mature phases of growth. Provenances 1064 (Jefferson) and 1080 (Yelm) exhibited larger annual radial increments than provenances 1028 (Merrit) and 1089 (Cathlamet). The two provenances with the highest annual radial increment in the juvenile phase did not exhibit the same trend in the adult phase. In all provenances, RW, and consequently EWW and LWW, were wider in the juvenile than in adult phase. The share of latewood was in all cases higher in juvenile wood than in mature wood. All four provenances had similar wood densities in both analyzed growth phases. Our analysis showed that when selecting the most promising provenance for planting, possible changes in relative growth rate from the juvenile to adult phase need to be considered.
Ključne besede: Pseudotsuga menziesii, SPEI, juvenile phase, adult phase, latewood share, resistance drilling
Objavljeno v DiRROS: 21.11.2022; Ogledov: 255; Prenosov: 48
.pdf Celotno besedilo (3,07 MB)
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Different wood anatomical and growth responses in European beech (Fagus sylvatica L.) at three forest sites in Slovenia
Domen Arnič, Jožica Gričar, Jernej Jevšenak, Gregor Božič, Georg von Arx, Peter Prislan, 2021, izvirni znanstveni članek

Povzetek: European beech (Fagus sylvatica L.) adapts to local growing conditions to enhance its performance. In response to variations in climatic conditions, beech trees adjust leaf phenology, cambial phenology, and wood formation patterns, which result in different treering widths (TRWs) and wood anatomy. Chronologies of tree ring width and vessel features [i.e., mean vessel area (MVA), vessel density (VD), and relative conductive area (RCTA)] were produced for the 1960%2016 period for three sites that differ in climatic regimes and spring leaf phenology (two early- and one late-flushing populations). These data were used to investigate long-term relationships between climatic conditions and anatomical features of four quarters of tree-rings at annual and intra-annual scales. In addition, we investigated how TRW and vessel features adjust in response to extreme weather events (i.e., summer drought). We found significant differences in TRW, VD, and RCTA among the selected sites. Precipitation and maximum temperature before and during the growing season were the most important climatic factors affecting TRW and vessel characteristics. We confirmed differences in climate-growth relationships between the selected sites, late flushing beech population at Idrija showing the least pronounced response to climate. MVA was the only vessel trait that showed no relationship with TRW or other vessel features. The relationship between MVA and climatic factors evaluated at intra-annual scale indicated that vessel area in the first quarter of tree-ring were mainly influenced by climatic conditions in the previous growing season, while vessel area in the second to fourth quarters of tree ring width was mainly influenced by maximum temperature and precipitation in the current growing season. When comparing wet and dry years, beech from all sites showed a similar response, with reduced TRW and changes in intra-annual variation in vessel area. Our findings suggest that changes in temperature and precipitation regimes as predicted by most climate change scenarios will affect tree-ring increments and wood structure in beech, yet the response between sites or populations may differ.
Ključne besede: Fagus sylvatica, wood anatomy, tracheograms, dendrochronology, intra specific plasticity
Objavljeno v DiRROS: 22.07.2022; Ogledov: 311; Prenosov: 207
.pdf Celotno besedilo (15,28 MB)
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Modelling seasonal dynamics of secondary growth in R
Jernej Jevšenak, Jožica Gričar, Sergio Rossi, Peter Prislan, 2022, izvirni znanstveni članek

Povzetek: The monitoring of seasonal radial growth of woody plants addresses the ultimate question of when, how and why trees grow. Assessing the growth dynamics is important to quantify the effect of environmental drivers and understand how woody species will deal with the ongoing climatic changes. One of the crucial steps in the analyses of seasonal radial growth is to model the dynamics of xylem and phloem formation based on increment measurements on samples taken at relatively short intervals during the growing season. The most common approach is the use of the Gompertz equation, while other approaches, such as general additive models (GAMs) and generalised linear models (GLMs), have also been tested in recent years. For the first time, we explored artificial neural networks with Bayesian regularisation algorithm (BRNNs) and show that this method is easy to use, resistant to overfitting, tends to yield s-shaped curves and is therefore suitable for deriving temporal dynamics of secondary tree growth. We propose two data processing algorithms that allow more flexible fits. The main result of our work is the XPSgrowth() function implemented in the radial Tree Growth (rTG) R package, that can be used to evaluate and compare three modelling approaches: BRNN, GAM and the Gompertz function. The newly developed function, tested on intra-seasonal xylem and phloem formation data, has potential applications in many ecological and environmental disciplines where growth is expressed as a function of time. Different approaches were evaluated in terms of prediction error, while fitted curves were visually compared to derive their main characteristics. Our results suggest that there is no single best fitting method, therefore we recommend testing different fitting methods and selection of the optimal one.
Ključne besede: artificial neural networks, cambium, generalized additive model, Gompertz function, growing season, intra-annual time series
Objavljeno v DiRROS: 21.07.2022; Ogledov: 303; Prenosov: 205
.pdf Celotno besedilo (1,26 MB)
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Artificial neural networks as an alternative method to nonlinear mixed-effects models for tree height predictions
Mitja Skudnik, Jernej Jevšenak, 2022, izvirni znanstveni članek

Povzetek: Tree heights are one of the most important aspects of forest mensuration, but data are often unavailable due to costly and time-consuming field measurements. Therefore, various types of models have been developed for the imputation of tree heights for unmeasured trees, with mixed-effects models being one of the most commonly applied approaches. The disadvantage here is the need of sufficient sample size per tree species for each plot, which is often not met, especially in mixed forests. To avoid this limitation, we used principal component analysis (PCA) for the grouping of similar plots based on the most relevant site descriptors. Next, we compared mixed-effects models with height-diameter models based on artificial neural networks (ANN). In terms of root mean square error (RMSE), mixed-effects models provided the most accurate tree height predictions at the plot level, especially for tree species with a smaller number of tree height measurements. When plots were grouped using the PCA and the number of observations per category increased, ANN predictions improved and became more accurate than those provided by mixed-effects models. The performance of ANN also increased when the competition index was included as an additional explanatory variable. Our results show that in the pursuit of the most accurate modelling approach for tree height predictions, ANN should be seriously considered, especially when the number of tree measurements and their distribution is sufficient.
Ključne besede: height-diameter models, national forest inventory, permanent sample plot, mixed forests, model comparison, principal component analysis
Objavljeno v DiRROS: 08.06.2022; Ogledov: 329; Prenosov: 138
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