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Povzetek: European beech (Fagus sylvatica L.) is an important component of forests in the alpine and continental biogeographical regions of Croatia. This study aimed to (1) analyze the long-term response of beech to climate, (2) identify potentially critical climatic conditions that could negatively affect the radial increment (RI) and vitality of beech, and (3) evaluate differences in the response of beech between the two biogeographical regions in Croatia. We used the 16 × 16 km Croatian ICP Forests Level 1 network. On a total of 25 plots, we cored between 5 and 24 trees for dendrochronological analysis. Tree-ring widths (TRW) were measured and standardized using cubic spline. TRW chronologies for the two regions were calculated and correlated to the temperature and precipitation data and Standardized Precipitation and Evapotranspiration Index (SPEI) using bootstrapped correlations. Continental region precipitation from April to August and alpine region precipitation from June to August were significantly important for RI. Temperature was less important for RI than precipitation in both regions, but the importance of the negative impact of above-average temperatures in the continental region and the positive impact of above-average precipitation in the alpine region has increased over the last two decades. A comparison with the 3-month SPEI confirmed the significant influence of high temperatures and the lack of precipitation in August on the RI of beech trees in both regions.
Ključne besede: climate change, tree growth, forest productivity, drought, European beech
Objavljeno v DiRROS: 28.06.2023; Ogledov: 251; Prenosov: 123
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Povzetek: Natural regeneration of tree species is sensitive to silvicultural interventions. This study aimed to investigate the effects of different cutting intensities and local topographic and soil conditions on the composition of stable carbon (δ13C) and oxygen (δ18O) isotopes in wood of young beech (Fagus sylvatica L.) trees. Beech saplings in the regeneration layer were sampled in summer 2018 at three study sites in Dinaric fir-beech forests in the karst area of Slovenia. Three different cutting intensities were performed in 2012: i) no cutting (control), ii) 50% cutting of the stand’s growing stock creating thinned stands, and iii) 100% cutting of the stand’s growing stock creating 0.4 ha canopy gaps. We show that δ13C increased along the gradient of cutting intensity. On average, δ13C values in the tree rings were ∼ 2‰ increased in trees from canopy gaps than from closed control stands. Furthermore, δ13C was higher on south-facing slopes characterized by higher air temperatures and lower relative humidity compared to north-facing slopes of karst sinkholes. Additionally, the results suggest a dependence of δ18O on interannual and cross-site climatic variations, particularly in the case of summer precipitation amount. δ18O also responded to soil depth, with beech individuals exhibiting lower values on deeper soils, presumably characterized by higher soil water availability compared to shallow soils. The results are discussed in the context of future climate change, as many beech-dominated forests on karst terrain in the Dinaric Mountains are particularly affected by climate warming and drying due to prolonged and reoccurring summer droughts, intensified large-scale disturbances, and often shallow soils with low water storage capacity.
Ključne besede: stable carbon isotopes, stable oxygen isotopes, tree cutting, microclimate, drought stress, dinaric fir-beech forests
Objavljeno v DiRROS: 05.04.2023; Ogledov: 665; Prenosov: 145
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Povzetek: The research aimed to determine the start, end and duration of leafing phases, the degree of plant damage caused by late spring frost, and the retention of leaves in autumn. The research was conducted in the international common beech provenance test in Bosnia and Herzegovina. The test contains eight provenances from Bosnia and Herzegovina, four from Germany, three from Serbia, two each from Croatia, Romania and Switzerland, and one from Hungary. Leafing phenology, canopy damage caused by late spring frost, and leaf retention were assessed in 2019. Most provenances started opening buds on 17 April 2019. Complete canopy damage affected the highest percentage of plants in provenance BW Bad Wildbad, Germany (68 %), and the lowest in provenance Konjuh Kladanj, Bosnia and Herzegovina (3.2 %). Provenance Herzogenbuchsee from Switzerland had the highest percentage of winter leaf retention (37.5 % of plants). The results can be used in choosing provenances that are resistant to low temperatures in zones of late spring and early autumn frost.
Ključne besede: common beech, international provenance test, leafing phenophases, frost damage, winter leaf retention
Objavljeno v DiRROS: 01.12.2021; Ogledov: 3090; Prenosov: 1778
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Povzetek: Cessation of xylem formation or wood growth (CWG) and onset of foliar senescence (OFS) are key autumn phenological events in temperate deciduous trees. Their timing is fundamental for development and survival of trees, ecosystem nutrient cycling, the seasonal exchange of matter and energy between the biosphere and atmosphere and affect the impact and feedback of forests to global change. A large-scale experimental effort and improved observational methods have allowed us to compare the timing of CWG and OFS for different deciduous tree species in Western Europe, in particularly silver birch, a pioneer species, and European beech, a late-succession species, at stands of different latitudes, of different levels of site fertility, and for two years with contrasting meteorological and drought conditions i.e., the low-moderately dry 2017 and the extremely dry 2018. Specifically, we tested whether foliar senescence started before, after or concurrently with CWG. OFS and CWG occurred generally between late September and early November, with larger differences across species and sites for OFS. Foliar senescence started concurrently with CWG in most cases, except for the drier 2018 and, for beech, at the coldest site, where OFS occurred significantly later than CWG. Behavior of beech in Spain, the southern edge of its European distribution, was unclear, with no CWG, but very low wood growth at the time of OFS. Our study suggests that OFS is generally triggered by the same drivers of CWG or when wood growth decreases in late summer, indicating an overarching mechanism of sink limitation as a possible regulator of the timing of foliar senescence.
Ključne besede: autumn phenology, xylem formation, foliar senescence, cambium, chlorophyll, radial growth, wood, decidiuous trees, common aspen, common beech, pedunculate oak, silver birch
Objavljeno v DiRROS: 10.06.2020; Ogledov: 1718; Prenosov: 1043
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Povzetek: Forest understory vegetation is largely influenced by disturbances and given local abiotic conditions. Our research focuses on the early response of understory vegetation to various forest management intensities in Dinaric fir-beech forests in Slovenia: (i) control, (ii) 50% cut of stand growing stock, and (iii) 100% cut of stand growing stock. Apart from identifying overstory removal effects, we were interested in fine-scale variation of understory vegetation and environmental determinants of its species composition. Vegetation was sampled within 27 karst sinkholes, which represent a dominant landform in studied forests. Within each sinkhole, five sampling plots, varying in slope aspect (centre, north, east, south, west), were established (135 in total), where pre-treatment (in 2012) and post-treatment (in 2014) floristic surveys were conducted. The sampled understory species were characterized in terms of Ellenberg's indicator values (EIVs) and plant functional traits (plant height, seed mass, specific leaf area, leaf dry matter content). Diversity metrics (species richness, total cover, Shannon index) increased in plots where the silvicultural measures were applied. Tree species richness also increased in 100% cutting. A redundancy analysis revealed that species composition was related to environmental variables, which are directly influenced by management interventions (overstory canopy cover, microclimate maximum daily temperature, soil properties thickness of organic soil layer) as well as by topographic factors (slope inclination and surface rockiness). EIVs for light were significantly affected by treatment intensity, whereas soil-related EIVs (moisture, reaction, nutrients) depended more on the within-sinkhole position. Canopy gaps, compared with uncut control plots, hosted a higher number of colonizing species with a higher plant height and smaller seeds, while leaf traits did not show a clear response. We found a negative correlation between pre-treatment species (functional) richness and post-treatment shifts in floristic (functional) composition. Plots with higher richness exhibited smaller changes compared with species-poor communities. Incorporating different perspectives, the results of this study offer valuable insights into patterns of understory vegetation response to forest management in fir-beech forests.
Ključne besede: canopy gap, microsite environment, Ellenberg indicator values, plant functional traits, compositional resistance, karst topography, fir-beech forest
Objavljeno v DiRROS: 06.12.2019; Ogledov: 2335; Prenosov: 1380
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