11. Early-warning signals of individual tree mortality based on annual radial growthMaxime Cailleret, Vasilis Dakos, Steven Jansen, Elisabeth M.R. Robert, Tuomas Aakala, Mariano M. Amoroso, Joe A. Antos, Christof Bigler, Harald Bugmann, Marco Caccianaga, Katarina Čufar, Tom Levanič, 2019, original scientific article Abstract: Tree mortality is a key driver of forest dynamics and its occurrence is projected to increase in the future due to climate change. Despite recent advances in our understanding of the physiological mechanisms leading to death, we still lack robust indicators of mortality risk that could be applied at the individual tree scale. Here, we build on a previous contribution exploring the differences in growth level between trees that died and survived a given mortality event to assess whether changes in temporal autocorrelation, variance, and synchrony in time-series of annual radial growth data can be used as early warning signals of mortality risk. Taking advantage of a unique global ring-width database of 3065 dead trees and 4389 living trees growing together at 198 sites (belonging to 36 gymnosperm and angiosperm species), we analyzed temporal changes in autocorrelation, variance, and synchrony before tree death (diachronic analysis), and also compared these metrics between trees that died and trees that survived a given mortality event (synchronic analysis). Changes in autocorrelation were a poor indicator of mortality risk. However, we found a gradual increase in interannual growth variability and a decrease in growth synchrony in the last %20 years before mortality of gymnosperms, irrespective of the cause of mortality. These changes could be associated with drought-induced alterations in carbon economy and allocation patterns. In angiosperms, we did not find any consistent changes in any metric. Such lack of any signal might be explained by the relatively high capacity of angiosperms to recover after a stress-induced growth decline. Our analysis provides a robust method for estimating early-warning signals of tree mortality based on annual growth data. In addition to the frequently reported decrease in growth rates, an increase in inter-annual growth variability and a decrease in growth synchrony may be powerful predictors of gymnosperm mortality risk, but not necessarily so for angiosperms.
Keywords: tree mortality, ring-width, forest, growth, resilience indicators, drought, biotic agents, variance
Published in DiRROS: 20.07.2022; Views: 610; Downloads: 395
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12. Effects of climate on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) growth Southeast of the European AlpsTom Levanič, Hana Štraus, 2022, original scientific article Abstract: Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) is a non-native tree species in Slovenia with the potential to partially replace Norway spruce in our native forests. Compared to spruce, it has several advantages in terms of volume growth, wood quality and tolerance to drought. This is important given the changing climate in which spruce is confronted with serious problems caused by increasing temperatures and drought stress. At three sites (one on non-carbonate bedrock and deep soils, and two on limestone with soil layers of varying depths), 20 Douglas-fir and 20 spruce per site were sampled in order to compare their radial growth response to climate and drought events. The radial growth of Douglas-fir exceeds that of spruce by about 20% on comparable sites. It is more responsive to climate than spruce. Above-average temperatures in February and March have a significant positive effect on the radial growth of Douglas-fir. In recent decades, above-average summer precipitation has also had a positive influence on the radial growth of Douglas-fir. Compared to spruce, Douglas-fir is less sensitive to extreme drought events. Our results indicate that Douglas-fir may be a good substitute for spruce in semi-natural managed forest stands in Slovenia. The planting of Douglas-fir should be allowed in Slovenian forests, but the proportion of it in forest stands should be kept lower than is the case with spruce today.
Keywords: climate change, climate response, drought, radial increment, dendrochronology
Published in DiRROS: 15.06.2022; Views: 545; Downloads: 456
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13. Jet stream position explains regional anomalies in European beech forest productivity and tree growthIsabel Dorado Liñán, Blanca Ayarzagüena, Flurin Babst, Guobao Xu, Luis Gil, Giovanna Battipaglia, Allan Buras, Vojtěch Čada, Jesús J. Camarero, Liam Cavin, Tom Levanič, Peter Prislan, 2022, original scientific article Abstract: The mechanistic pathways connecting ocean-atmosphere variability and terrestrial productivity are well-established theoretically, but remain challenging to quantify empirically. Such quantification will greatly improve the assessment and prediction of changes in terrestrial carbon sequestration in response to dynamically induced climatic extremes. The jet stream latitude (JSL) over the North Atlantic-European domain provides a synthetic and robust physical framework that integrates climate variability not accounted for by atmospheric circulation patterns alone. Surface climate impacts of north-south summer JSL displacements are not uniform across Europe, but rather create a northwestern-southeastern dipole in forest productivity and radial-growth anomalies. Summer JSL variability over the eastern North Atlantic-European domain (5-40E) exerts the strongest impact on European beech, inducing anomalies of up to 30% in modelled gross primary productivity and 50% in radial tree growth. The net effects of JSL movements on terrestrial carbon fluxes depend on forest density, carbon stocks, and productivity imbalances across biogeographic regions.
Keywords: atmospheric dynamics, climate-change ecology, climate-change impacts, environmental impact
Published in DiRROS: 20.04.2022; Views: 726; Downloads: 606
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14. Priraščanje navadne smreke (Picea abies (L.) Karst.) in evropskega macesna (Larix decidua Mill.) na nekdanjih novinah v Koprivni v KaravankahJanez Golob, Tom Levanič, David Hladnik, 2021, original scientific article Abstract: Na podlagi meritev v obdobju 1962–2017 smo na raziskovalnih ploskvah na nekdanjih novinah v katastrski občini Koprivna izračunali debelinske, višinske in volumenske prirastke za najpomembnejši drevesni vrsti - smreko in macesen. Na raziskovalnih ploskvah, ki so bile prepuščene naravnemu razvoju, so srednjetemeljnični premeri manjši, število dreves pa večje od tistih v primerljivih gospodarskih gozdovih. V zadnjih tridesetih letih se je zaradi visokih sestojnih gostot zmanjšalo debelinsko priraščanje dreves smreke in macesna. Z dendrokronološko analizo smo ocenili vpliv klimatskih dejavnikov na priraščanje smreke in macesna. Na podlagi dendrokronološke analize smo ugotovili, da se leta z negativnim odzivom dreves v debelinskem prirastku od leta 1984 pojavljajo pogosteje.
Keywords: raziskovalne ploskve, smreka, macesen, debelinski prirastek, volumenski prirastek, indeks gostote SDI, dendrokronološka analiza
Published in DiRROS: 02.12.2021; Views: 3153; Downloads: 1901
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16. Stabilni izotopi v gozdnem ekosistemu - analizne metode in uporabaSaša Zavadlav, Grega E. Voglar, Polona Hafner, Mitja Ferlan, Tom Levanič, 2016, published scientific conference contribution abstract Keywords: stabilni izotopi, masna spektrometrija, laserska absorpcijska spektroskopija, EA-IRMS, OA-ICOS
Published in DiRROS: 03.11.2021; Views: 749; Downloads: 265
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17. SciVie - Sciences de le Vie from the past and for the future : [presented at European Forest Research and Innovation, 1st ex post evaluation programme, Ljubljana, 19. 1. 2016]Maja Peteh, Irena Rebov, Tina Drolc, Žiga Lipar, Tom Levanič, Hojka Kraigher, 2016, unpublished conference contribution Published in DiRROS: 03.11.2021; Views: 1155; Downloads: 389
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