1. Autumn phenology of mountain birch at the sub-arctic treeline in comparison with silver birch in the cold and mild temperate zonePaolo Zuccarini, Friederike Gehrmann, Manuela Balzarolo, Omar Flores, Jožica Gričar, Bertold Mariën, Matteo Campioli, 2025, original scientific article Abstract: Lack of knowledge on autumn phenology of deciduous trees still exists for high-latitude regions. We studied the leaf and wood growth autumn phenology of mountain birch in a sub-arctic climate (northern Sweden) and compared them with the same dynamics for silver birch in a temperate climate (southern Norway and Belgium). The first autumn phenophase for mountain birch was the decline of the remotely sensed Terrestrial Chlorophyll Index (TCI) at the end of July. This was followed by wood growth cessation, onset of chlorophyll degradation and of loss of canopy greenness, and the latter accompanied by onset of anthocyanin production and flavonoids degradation. The earlier timing of TCI decline than chlorophyll degradation was probably due to the different scales of measurements (ecosystem level vs. tree leaves, respectively). In 2020, the decline in canopy greenness started in the same period at the three studied sites, showing an unexpected early timing for Belgium, likely due to the very warm late summer conditions and drought stress or intraseasonal legacy effects. Accordingly, wood growth cessation also occurred unexpectedly earlier in Belgium than in Norway. The end of senescence was inversely related to latitude. Our study presents, for the first time, the autumn timeline of a deciduous species at the northern treeline, and indicates that the timing of autumn phenology of birch populations does not consistently follow the latitudinal gradient but varies according to the phenophase, the scale of measurements and the current year meteorological conditions.
Keywords: Betula pendula, Betula pubescens, deciduous trees, leaf senescence, terrestrial chlorophyll index, wood phenology
Published in DiRROS: 19.12.2024; Views: 108; Downloads: 51
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4. Phloem : a missing link in understanding tree growth response in a changing environmentJožica Gričar, 2024, original scientific article Abstract: 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.
Keywords: phloem, wood anatomy, tree growth, angiosperms, bark, meristem, non-structural carbohydrates, primary growth, radial growth, secondary growth, temperature, xylem
Published in DiRROS: 05.12.2024; Views: 124; Downloads: 66
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5. Differences in xylem and phloem structure in living stumps of Norway spruce (Picea abies (L.) Karst.) and silver fir (Abies alba Mill.)Jožica Gričar, Miha Drolc, Peter Prislan, Helena Šircelj, 2024, original scientific article Abstract: Living stumps reported in many tree species were the first, circumstantial evidence of root grafting. Although stump overgrowth has been extensively studied in various tree species, anatomical observations have mainly focused on the xylem part. Here, we investigated the xylem and phloem structure in living stumps of two conifer species: Norway spruce (Picea abies (L.) Karst.) and silver fir (Abies alba Mill.). The mechanism of wound closure was similar in the two species, however, there were differences in the structure of wound tissues in wood and bark. Immediately after the injury, a callus consisting of parenchymal cells was formed, followed by wound-wood with wide increments. In addition, the wood structure and morphology of tracheids were changed. Tracheids lost their typical elongated and tapering structure; instead, numerous crooked and forked tracheids were present. Traumatic resin canals were present in both species but were more abundant in P. abies, which also had normal resin canals. While the structure of the xylem growth rings eventually normalized in both species, the width of the annual xylem increments was diminished. In both species, the typical structure of annual phloem increment was lost in the non-collapsed phloem and sclereids were very abundant in the collapsed phloem. In A. alba, the collapsed phloem was rich in swollen parenchyma cells containing blue-stained contents, while in P. abies, numerous large traumatic resin canals were conspicuous. The study showed that similar patterns of vascular tissue restoration exist in A. alba and P. abies in response to tree felling. However, there are certain species-specific peculiarities in the wood and phloem anatomical response, which might affect long-term stump functioning and survival.
Keywords: wood physiology, phloem, xylem, Norway spruce, Picea abies, silver fir, Abies alba
Published in DiRROS: 03.12.2024; Views: 176; Downloads: 1402
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6. Different patterns of inter-annual variability in mean vessel area and tree-ring widths of beech from provenance trials in Slovenia and HungaryJožica Gričar, Domen Arnič, Luka Krajnc, Peter Prislan, Gregor Božič, Marjana Westergren, Mátyás Csaba, Hojka Kraigher, 2024, original scientific article Abstract: International provenance trials of ecologically and economically important tree species are crucial to deciphering the influence of environmental factors and intraspecific variability on tree growth and performance under climate change to guide assisted gene flow and assisted migration of tree provenances and species. In this context, we compared inter-annual trends in tree-ring widths (carbon sequestration potential) and vessel characteristics (conductivity optimisation) of four beech provenances in two international provenance trials, one in Slovenia (Kamenski hrib, a core beech growing site) and one in Hungary (Bucsuta, a marginal beech site) in 2009–2019. We found different patterns of inter-annual variability in mean vessel area and tree-ring widths among provenances and sites, pointing to diverse genetic background and environmental influence on these two wood-anatomical traits. The average values of the vessel area varied less between provenances at Kamenski hrib than at Bucsuta. Weather conditions differently affected tree-ring width and mean vessel area. Furthermore, the length of the period of response of vessel area to the analysed weather conditions differed in summer and winter periods. The differences in the mean vessel area within the tree ring were more pronounced in the weather-wise extreme years, regardless of the provenance. Consistent with previous studies, we confirmed that site conditions affect the climate sensitivity of trees, which is more pronounced at marginal sites or in extreme years. The findings on how different environmental conditions affect the radial growth of young beech trees of different origin are very important for future forest management.
Keywords: Fagus sylvatica, quantitative wood anatomy, common gardens, intraspecific variation, juvenile period, weather conditions
Published in DiRROS: 03.12.2024; Views: 134; Downloads: 605
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10. Načrt središča za Jugovzhodno EvropoYannis Fallas, Nikolaos Ntavos, Panagiotis Karagiannis, Dimitris Tsimplinas, Georgios Ntalos, Polona Hafner, Andreja Vedenik, Jožica Gričar, Iva Božić, Danijela Šarić Bartolović, Ivan Ambroš, 2024, treatise, preliminary study, study Keywords: transport lesa, dobre prakse, inovacije, trajnost
Published in DiRROS: 26.07.2024; Views: 472; Downloads: 2 |
