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Two comparable sites with uneven-aged mixed forest stands with more than 20% Douglas-fir in the growing stock at an altitude of 650 m a.s.l. were selected. The physiological response of young trees to different light intensities was measured during the main growing season in three consecutive years, and four different light categories, which were determined from hemispherical photographs. The four light intensity categories were defined according to Indirect Site Factor (ISF%): in the open (A-ISF &gt, 35%), at the outer forest edge (B-25% &lt, ISF &lt, 35%), at the inner forest edge (C-15% &lt, 25%), and under complete canopy under mature forest stand (D-ISF &lt, 15%). Climate data were obtained from the Royal Netherlands Meteorological Institute ‘Climate Explorer’ website. For the intensive micrometeorological observations, four monitoring sites were established along the elevation gradient at each site during summer and late fall to record relative humidity (RH%) and temperature (°C) with a 30 min recording interval sequence. Measured assimilation responses (A) and light use efficiency (Φ) at one site followed the expected pattern, while humidity combined with microsite conditions proved significant in explaining the specific response of young Douglas-fir to the different light intensity at the other site. For higher survival and optimal future development of Douglas-fir in the changing environment, microsites with higher capacity for storage moisture and favorable microclimate should generally be preferred to exposed and dry sites.

The present study addresses the short-term effects of different harvest intensities under close-to-nature selective management on the upper soil layers in Slovenian and Bosnian Dinaric karst fir-beech forests. The different harvest intensities coincided with the single-tree and irregular shelterwood management, common in the region. The effect of harvesting intensity on the upper soil layers (Ol, Of, Ol and 0–10 cm mineral soil) was investigated by a repeated measurements experiment in Slovenia on 27 research plots in close-to nature managed forests. The properties of the upper layers (concentration of SOC and TN, C/N ratio, weights, BD and SOC stocks) were analyzed twice, before (2011) and after (2014) treatment of 50% and 100% harvest intensity in relation to the total standing growing stock of trees. As a control, we used no-treatment &lt, 20% harvesting intensity plots. To extend this experiment, we added three comparable plots from the Bosnian site: one in an old-growth forest with 0% harvest intensity and two in the managed forest with &lt, 20% harvest intensity. The results of the assessment of mean differences indicated a significant influence of harvesting intensity on the decrease in SOC, TN concentrations, weights and SOC stocks in the organic layers and the increase in BD and SOC stocks in the 0–10 cm mineral soil. The highest relative decreases in Ol, Of and Oh SOC stocks occurred in 50% (−10 and −38%) and 100% (−16 and −49%) harvest intensities. Negligible relative differences in both organic and 0–10 cm mineral layers were found for the &lt, 20% harvest intensity in the region. The change in forest light conditions resulting from differences in canopy openness as a function of applied harvest intensity explained the significant difference in the properties of the upper soil layers. The impact of the short-term losses in SOC stocks, in terms of overall soil productivity, may depend on the regeneration dynamics and melioration methods.

In the December 2017, 211 000 ha of Slovenian forests or 2 201 000 m3 were severely damaged by the windstorm. The damage was greatest in the adult beech-silver fir forest stands. In each management district (FMD) with different share of damaged forested area - Kočevje (69%), Postojna (22%) and Ljubljana (19%), research location were established to evaluate soil properties, root characteristics and ecophysiological regeneration response of predominating tree species in damaged stands as well as the economic effect of the windstorm on sensitive high karst sites. The restoration and regeneration efficiency of latest disaster (2017) was also compared with restoration efficiency of areas damaged in 2008, identifying possible specifics / differences and providing guidelines for their optimal recovery.Timber database from Slovenian Forest Service with data about felling and felling reasons between Dec. 2017 and the end of 2019 was used to evaluate economic losses. The total amount from the database was multiplied by the shares of individual quality category, obtaining the quantitative assortment structure according to the actual felling. We used tables of assortment losses caused by wind to estimate the actual assortment loss and multiplied those with 2018 roundwood market prices. Estimated cumulative biomass loss amounted 205 855 m3 - 5.6% less, compared to regular felling, or 16.1 million €.Physical soil properties between plots damaged by wind and control areas without damage did not confirm any significant difference in relation to weather and microsite conditions (rootstock, exposition, altitude, species structure of stands, microrelief). Characteristics of root systems of the most affected tree species - fir, spruce and beech did not differ between damaged and neighboring undamaged sites. An overview of fir and spruce windbreaks during the 1995 - 2018 period outlined the cumulative effect of multiple site conditions with strong wind, severely reducing the mechanical stability of fir and spruce; consequently, the following weather events with even mild wind intensities resulted in calamity.Natural regeneration ability on all plots of recent windthrow shows successful regeneration of beech, maple, and fir in all light categories of damaged stands, but questionable regeneration of fir, which is in tight relation with ungulate browsing. For comparison with regeneration after windthrow in 2017, we analyzed successional development in three windthrow areas from 2008. Seedling densities ranged from 5000 to 9000 ha-1, with the highest densities in the 150-300 cm height class. Within plots with natural regeneration, height and species diversity were better compared to planted plots. Shade-tolerant species increased in plots at lower elevations, while pioneer species still increased at higher elevations. Overall browsing was moderate, but silver fir and sycamore had difficulty establishing. The results indicate that regeneration spreads from areas that were covered with seedlings shortly after windthrow and that certain parts will not be covered with regeneration for a longer period.

Soil respiration is the second largest flux of carbon between terrestrial ecosystems and the atmosphere and it is substantially sensitive to climate change. Monitoring CO2 efflux and its upscaling from field measurements to the ecosystem level is a complex task, due to the high spatial and temporal variability of the fluxes. Human intervention, e.g. through forest harvest, may change both CO2 efflux and its spatial heterogeneity. The objective of our study was to quantify spatial heterogeneity of soil CO2 efflux within and among plots distributed within a topographically variable sessile oak forest stand before and after harvesting. Forest floor CO2 efflux, soil temperature and soil water content were measured monthly in a sessile oak forest during two growing seasons: one before and one after harvesting. Stand structure characteristics (gap fraction, leaf area index, tree number and size) and the amount of understory also were determined. Relationships between individual variables and spatial heterogeneity were analyzed. The small-scale spatial heterogeneity (expresses as the coefficient of variation) of forest floor CO2 efflux and soil water content (SWC) in the undisturbed forest was low, at maximum 0.22 and 0.13, respectively. Studied variables had no effect on spatial heterogeneity of forest floor CO2 efflux except for the amount of understorey vegetation which positively correlated with forest floor CO2 efflux. Although the studied forest was situated in topographically variable terrain, we observed that inter-plot heterogeneity of forest floor CO2 efflux was lower than that within plots. Stand harvest increased the intra-plot heterogeneity of forest floor CO2 efflux but did not affect the inter-plot heterogeneity. This leads to the conclusion that the number of positions within an individual plot should increase after harvest but the number of plots may remain unchanged to determine adequately ecosystem forest floor CO2 efflux.

Physiological response to rapid light exposure due to canopy disintegration in young beech, fir, Norway spruce and sycamore trees was measured in three consecutive years after the severe ice storm in 2014 and after windthrow in 2017. Nitrogen amount (Ntot), maximum assimilation response to light (Amax) and quantum yield (Φ) were measured in three categories of different light intensities under closed canopy with indirect site factor (ISF) 25%). Tree responses with number of seedlings per hectare were compared between damaged and undamaged sites, with young trees gradually adapting to light conditions in the two years following the two disturbance events. Nitrogen levels were in the optimal range for all species studied. Rapid exposure to elevated light reduced efficiency in fir and increased efficiency in beech and especially sycamore. No differences in response were observed in spruce. Assimilation efficiency, where both tree species were equal, shifted towards shade. Recovery was similar for all species studied after both disturbances: better after the windstorm, compared to the ice storm, indicating the severity of the event. Reductions in seedling numbers followed the pattern observed for physiological traits.

A comparative study of young European beech, silver fir and Norway spruce in the Slovenian mixed forest stands was made at four locations, exposed to the rapid canopy disintegration after the severe ice storm in 2014. Nitrogen amount (N tot ), Leaf mass per area (LMA), maximal Assimilation response to light (A max ) and Quantum yield (Φ) were measured in three categories of different light intensities under closed canopy with Indirect Site Factor (ISF) 25%). Tree responses were compared between damaged plots – rapidly exposed to light and undamaged sites, where young trees gradually adapted to the light environment during two years (2015 and 2016) after the disturbance event. Nitrogen content of all three species was within optimal range values, highest in the open and lowest under canopy conditions on every plot. Rapid exposure to increased light levels affected most directly fir in the category of forest edge and under open canopies. Contrary to fir, beech responded in a favourable way, while no differences in response were evident in spruce. Assimilation efficiency, where both fir and beech were equal shifted towards the shade in both years.

At the 1000km geographical distance in Dinaric montane forests of silver fir (Abies alba Mill.) and European beech (Fagus sylvatica L.), the tree response from the north-western sites towards southern, warmer and dryer sites was performed during three consecutive growing seasons (2011, 2012 and 2013). On eleven permanent plots, positioned in uneven-aged beech and fir forests above 800m along the geographical gradient, the physiological and morphological response to light intensity were measured in predefined light categories based on the analysis of hemispherical photos. Radial growth was analysed on all plots and compared to precipitation, temperature and two drought indexes. Analysis showed a decrease in the cumulative precipitation and no change in temperature between plots. Beech was most efficient in the open area light conditions, while fir proved most efficient under shelter. Physiological response for beech increased towards SE and reached its maximal values in the middle of transect, while fir%s response decreased from the NW towards SE. Tendency to plagiotropic growth decreased from NW to SE in both species. Growth response to climatic parameters is weak, stronger in fir than in beech and decreasing towards SE. Nasl. iz nasl. zaslona. Opis vira z dne 12. 11. 2019. Dokument v formatu PDF obsega 14 str. Bibliografija: str. 11-13.

UDK 630*114:630*242(497.4) In three high karst forest complexes, same spatial design was applied to observe the effect of silvicultural treatment - the degree of mature stand removal on soil efflux. In every forest complex nine subplots were established during the time of experiment according to predominating tree species in growing stock of the mature canopy stand - silver fir, Norway spruce and European beech. In 2012 silvicultural measures with different intensity - 50% and 100% removal of growing stock around the centre of the plot with minimal diameter of two tree heights were applied. The seasonal pattern of CO2 efflux rates was mostly accountable by changes in soil temperature. Spatial heterogeneity in CO2 efflux rates was clearly reflected in management practice; release rates and recovery period were extreme in beech predominating sites, followed by the silver fir and norway spruce. It is our belief, that more oscillations may be expected in carbon release dynamics in the future, as the number of extreme weather events increases and the withdrawal of silver fir with its poor recruitment may have long-term consequences on these high karst high productive sites.

Soil CO2 efflux accounts for about 45-80% of total ecosystem respiration and is therefore an important part of the ecosystem carbon cycle. Soil CO2 efflux has been poorly studied in forests managed in the ancient coppicing manner. In our study, soil CO2 efflux, temperature, and moisture were measured in sessile oak stands with different harvesting intensity (control: 0% intensity; V1: 75%; V2: 80 %; V3: 85%; and V4: 100%) during the fifth and sixth years after harvesting. Soil CO2 efflux was in the range 2-8 µmol CO2 m-2 s-1 and indicated an increasing pattern with increasing harvesting intensity. The slope of that pattern became less steep from the fifth to the sixth year after harvesting, thus indicating gradual recovery of soil carbon dynamics in the coppiced stand toward the equilibrium state existing before harvesting. Temperature sensitivity of soil CO2 efflux ranged between 2.1 and 2.8, with the lowest values measured in the control stand. Soil CO2 efflux in the control stand was more sensitive to changes in soil moisture than was that on harvested plots. By our calculations, 6.2 tC ha-1 was released from the control stand and 6.2-6.8 tC ha-1 from the harvested stands during the sixth year after harvesting. If mean temperature were to rise by 1 °C, the amount of soil carbon released would increase by 7.7% in the control stand and, depending on harvesting intensity, by 9.0-10.8% in the harvested stands.

Forest management, especially thinning and harvesting measures, has a significant impact on the forest carbon balance especially in the forests with long-term continuous cover history. We measured soil CO2 efflux (Rs) in three forest complexes of mixed, uneven-aged Dinaric forests with predominating silver fir (Abies alba Mill.), beech (Fagus sylvatica L.), and Norway spruce (Picea abies Karst.). Rs was measured after removal of mature forest stands with 50% and 100% intensity of living stock and compared with Rs on the control plots without any applied silvicultural measures. Rs was measured monthly in three consecutive 2012, 2013 and 2014 growing periods. Soil CO2 efflux increased after harvest of both intensities in all studied forest stands. The biggest increase was measured in beech stands and amounted up to 47 and 69% for 50% and 100% harvest intensities, respectively. The effect of harvest on Rs in spruce and fir stands was similar – up to 26% for 50% harvest intensity and 48% for 100% harvest intensity. Despite the biggest increase after harvest, Rs in beech stands returned the fastest to the level of the uncut forest and this levelling period (LP) took 14–17 months with a little delay of the stands with 100% harvest intensity. The LP for all fir stands, for spruce stands with 50% harvest intensity and for one spruce stand with 100% harvest intensity, was 26–29 months. At two spruce stands with 100% harvest intensity we did not record Rs levelling during our three-year study. This study involved forest stands of three predominating tree species growing under the same conditions, which allowed us to determine the species-specific sensitivity of soil CO2 efflux to the different harvesting intensities.

In managed Dinaric montane fir (Abies alba Mill.) and European beech (Fagus sylvatica L.) forests, the light response of young beech and fir in gap microsites was studied during three consecutive growing periods (2009, 2010, and 2011) under controlled environmental conditions in stands of single-tree and irregular shelterwood silvicultural system. According to maximal quantum yield, the different response between species in microsite light categories was evidenced for silver fir on microsites with predominating diffuse light and for beech on microsites with predominating direct light, respectively. Abundance and change of share in microsite light categories was compared over different elevation belts on comparable sites between two silvicultural systems. The share of forest edge area was bigger in the irregular shelterwood system. Change in width of forest edge (20, 30 and 40 m) did not affect the proportion and share of the microsite in both regions of different silvicultural system. Separation of microsite areas between both silvicultural systems, evident in lower elevation belts was not evident in the most conflict and highest elevation zone, while the absolute values of all categories above 700 m in both systems were almost identical, indicating the same, small-scale irregular shelterwood system, known also as the freestyle silvicultural approach.

Montane forests of silver fir ( Abies alba Mill.) and European beech ( Fagus sylvatica L.) in the Dinaric region are the largest continuous forest area in Central Europe, where silver fir’s regression is one of the region’s major concerns. Designing appropriate sized canopy gap spatio-temporal dynamics is the main silvicultural tool for indirect promotion of silver fir. Within gap microsites, categories based on shares of direct and diffuse radiation proved to be an interesting conceptual model for explaining microsite variation and seedling success induced by light and general climate variability. In order to evaluate the response of beech and fir in different gap microsites, different light regimes were evaluated based on the proportion between direct and diffuse radiation in three different sizes of forest gap in managed forests. The photosynthesis response to different light conditions (max. photosynthetic rate – A max and quantum yield – Φ ) in beech and silver fir was compared on all microsites during three consecutive g periods (2009, 2010, and 2011) under controlled environmental conditions. A different response between species in microsite light categories was shown between different gap sizes. In all microsite categories of both species, quantum yield appeared at lower light intensities with increasing gap size, with the exception of beech with a predominant direct light component, in which yield significantly increased. In order to favour fir, gaps with low direct light levels should be created, while existing gaps should be extended towards the southern gap edge. Our conclusions emphasize the importance of gaps, relatively smaller in size (0.03–0.11 ha) but significant in contributing to increasing the competitive advantage of fir in mountainous, mixed-species Dinaric forests.

Among all silver fir forest types in Slovenia, most changes in forest composition are evident in Dinaric silver fir and beech forests, in which ageing and reduction of silver fir populations compared to European beech is evident. The situation has worsened due to a high browsing rate and environmental changes, causing a decline in abundance and a shift in silver fir′s spatio-temporal distribution. The photosynthesis response to different light and CO2 (max. photosynthetic rate – Amax, compensation points – Ic, quantum yield – Φ), the morphological response in young beech and fir to shade, and the growth response of adult trees were compared on sites with a single selection method, group selection method and old growth, during three consecutive vegetation periods (2009, 2010 and 2011). Three plots were established on each site, each with comparable light conditions according to the indirect site factor – ISF (%) under mature shelter, forest edge and open light conditions. In the old growth forest, beech and fir were more shade-tolerant and had a greater reaction to different light levels or elevated CO2 concentrations, compared to managed forest sites. Fir and beech express more physiological and morphological shade-tolerant characteristics on sites with single selection treatment, and differences are also evident in the growth responses of the two species. To establish conditions under which fir would be able to compete with beech, longer regeneration periods should be applied, with a gradual opening of the mature canopy, similar to conditions in old growth. In our study, group selection treatment proved more effective under the present environmental conditions.

Increased frequency and intensity of drought events consequently affect oak high forests with the process of further decline, compromised growth and questionable natural regeneration. To overcome such difficulties, new adaptive strategies are required. Coppicing, as the oldest way of forest management, might provide some solutions. In our study two contrasting management systems, sessile oak coppice and high forest, were compared at the initial stages of regeneration and forest development. The transpiration of young oak sprouts and seedlings was monitored using sap flow systems during the 2015 growing season. The study of transpiration also included leaf water potential measurements during three measurement campaigns with contrasting weather conditions. Coppice sprouts transpired significantly more than seedlings on the individual tree and stand level during the entire growing season 2015; particularly large differences were observed during drought conditions. Coppice sprouts experienced lower water limitations due to the voluminous and deeper root system as indicated by leaf water potential results. Presented results attribute young coppices as one of the promising adaptable forest management types with a better adaptive strategy at the extreme sites under water limiting conditions. info:eu-repo/semantics/openAccess

This volume should be interpreted as a manual of best practices for sustainable forest management deriving from the experience of the project LIFE09ENV/IT/000078 ManFor C.BD coordinated by the National Research Council through the Institute of Agro-environmental and Forest Biology (CNR-IBAF). The other Project partners are: the Council for Agricultural Research and Economics (CREA), the University of Molise (UNIMOL), the Slovenian Forestry Institute (SFI) and the regions of Veneto and Molise. In addition, the National Centre for Forest Biodiversity of Verona and the Regional Office to biodiversity of Castel di Sangro of the Italian National Forest Service (CFS), as well as the Slovenian Forest Service (SFS) collaborated to the project. This manual consists of several individual articles dealing with specific issues related to the project. These articles are conceptually organized into five categories that from the description of the project and of its activities arrive at providing operative indications for forestry operators.

In even-aged, 120-year-old Norway spruce stands with underplanted beech (in 1995) four permanent research plots were established, each 100 × 100 m in size. Twelve subplots were selected on each plot along a light gradient from complete canopy closure to open light conditions. On each plot, photon flux density (PFD) was measured continuously, and during same time interval (August 2008, 2009), color digital hemispherical photographs were taken. Cumulative PFD values for measuring points were compared with potential PFD radiation obtained from hemispherical photograph analysis for different angle of hemisphere and different parameters from hemispherical image analysis (gap fraction, total openness and direct, indirect and total amount of radiation). Cumulative and average daily values for the plots were compared; 120° hemispherical photograph angle, gap fraction and total openness were the variables that explained the largest proportion of variance in light transmittance. Determination coefficients between direct and total light component were highest for the total potential radiation and lowest for the diffuse light component. Comparison between potential and instantaneous light measurements for radial, height increment and SLA of young beech showed that instantaneous radiation measurements explained height increment best; 120° of hemisphere proved to be the best explaining angle.

The objective of this study is to estimate the contribution of various sources that influence soil CO2 concentrations in calcareous grassland. The research was performed at the Podgorski Kras plain (45 °33′ N, 13 °55′ E, 400–430 m.a.s.l.) in the sub-Mediterranean region of Slovenia (SW Slovenia), where many meadows and pastures have been abandoned. In parallel to the measurement of soil respiration R s, soil gas was sampled for stable isotope analysis. Samples were taken biweekly at two sites, Grassland and Invaded, from July 2008 until November 2010. In addition, daily variations in concentration and stable isotope composition of soil CO2 were determined in May 2009. The partitioning of soil CO2 concentrations was performed using stable isotope mass balance calculation. The concentration and isotope composition of soil CO2 exhibited similar seasonal variations at both sites. Lower δ13CCO2 values, ranging from −28.2 to −15.2 ‰, which occurred during warm periods and higher values, up to −12.1 ‰, were typical of cold winter periods, from December to March. Organic sources were estimated to constitute between 78 and 99 % of total soil CO2 during warmer periods from May until October. This contribution was lower during the winter, ranging from 46 to 77 %. In winter, the atmospheric component to soil CO2 dominated, constituting up to 60 %. On average, the inorganic contribution was estimated to comprise 12 % of the soil CO2 at all sampling locations. The contribution of this source to soil CO2 concentration, at up to 41 %, was highest in Grassland during the growing season. The inorganic source of soil CO2 was also an important component during daily variations. The highest contribution was observed during the day, in parallel to the highest respiration rates. The inorganic pool is shown to be an important part of soil CO2 in calcareous areas and should be considered as equal to organic CO2 as a source in soil CO2 partitioning.

Soil respiration rates were studied as a function of soil type, texture and light intensity at five selected natural beech forest stands with contrasting geology: stands on silicate bedrock at Kladje and Bricka in Pohorje, a stand on quartz sandstone at Vrhovo and two stands on a carbonate bedrock in the Karstic-Dinaric area in Kocevski Rog, Snežna jama and Rajhenav, Slovenia, during the growing season in 2005–2006. Soil respiration exhibited pronounced seasonal and spatial variations in the studied forest ecosystem plots. The CO2 flux rates ranged from minimum averages of 2.3 μmol CO2 m−2 s−1 (winter) to maximum averages of about 7 μmol CO2 m−2 s−1 (summer) at all the investigated locations. An empirical model describing the relationship between soil respiration and soil temperature predicted seasonal variations in soil respiration reasonably well during 2006. Nevertheless, there were also some indications that soil moisture in relation to soil texture could influence the soil CO2 efflux rates in both sa...

Data on the impact of forest management practices on ectomycorrhizal community structure remains fragmentary and mainly originates from studies in northern coniferous forests. This study focuses on a comparison of ectomycorrhizal communities between canopy gaps and closed canopy areas within natural and managed beech-dominated forests at four locations in Europe. We used high resolution rDNA techniques to identify ectomycorrhiza-forming fungi and attempted to extract potential stand-, gap-, soil-, and selected environmentally derived variables by applying multivariate analysis and ordination for pooling of ecological groups of ectomycorrhiza. A significant reduction of diversity indices, ectomycorrhizal and fine root dynamics, in gaps in comparison with closed canopy stands indicates an effect of forest management practice and the high importance of maintaining and protecting natural forest areas for conservation of soil biodiversity and forest genetic resources. The ordination analysis revealed three groups of ectomycorrhiza correlated with changing environmental conditions. The litter and soil pH, number of beech seedlings, and presence of a gap had a pronounced effect on the ectomycorrhizal community. Combined analysis of ectomycorrhiza and environmental factors using correspondence analysis provided an insight into the ecological preferences of the analysed species and confirmed that environmental factors drive ectomycorrhizal community changes.

Pedunculate oak (Quercus robur L.) forests in Slovenia are experiencing widespread mortality. Changes in lowlands are reflected in decline of complete forest complexes, high mortality, uneven stand structure and associated forest regeneration problems. Prediction of the present-tree response in disturbed forest ecosystems may significantly contribute to better guideline policies for the silvicultural and forest management practice in the changing environment in both stressed and stabile forest ecosystems. Data from annual crown condition surveys for the 1995–2014 period from four permanent plots have been compared with parameters from hemispherical photo analysis and hydrometeorological data. Good agreement has been confirmed between crown defoliation and total openness, all parameters from the hemispherical photo analysis, which were corrected for winter period values, also indicated a better agreement. Mortality rate and crown defoliation correlated well with extreme drought events in 2003 and 2013. Pattern of agreement among compared parameters was different for the plots Krakovski gozd, Dobrava and some other plots. Mortality is influenced by the average air temperatures much more than by precipitation and groundwater table oscillations.

A noticeable decline and physiological weakening of pedunculate oak (Quercus robur L.) has been recorded in the past decade in lowland parts of Slovenia. The triggers were dry climate, unfavourable precipitation patterns and human influence that brought about changes in watercourses and water tables. Regeneration and future management of this tree species is therefore questionable. To define a critical groundwater table which would permit successful regeneration, planted and naturally grown seedlings were compared in two forests differing in the degree of decline and physiological weakness of adult pedunculate oak trees. Comparison of stomatal conductance and pre-dawn water potential (PWP) showed differences of seedlings between and within forest complexes. Stomatal conductance dropped below 100 mmol m−2 s−1 at PWP values below −1.0 MPa, while closure of stomata was caused by a PWP between −1.6 and −1.9 MPa. Increased water stress equalized photosynthetic yield in both natural and planted oaks below −1.4 MPa.

Observations of forest mortality are increasing globally, but relatively little is known regarding the underlying mechanisms driving these events. Tree rings carry physiological signatures that may be used as a tool for retrospective analyses. We capitalized on a local soil water drainage event in 1982 that resulted in increased mortality within a stand of oak trees (Quercus robur), to examine the underlying physiological patterns associated with survival and death in response to soil water limitations. Pre-dawn water potentials showed more negative values for trees in the process of dying compared with those that survived. We used tree rings formed over the 123 years prior to mortality to estimate productivity from basal area increment (BAI, mm 2 ), multiple xylem hydraulic parameters via anatomical measurements and crown-level gas exchange via carbon isotope discrimination (Δ, ‰). Oaks that died had significantly higher BAI values than trees that survived until the drainage event, after which the BAI of trees that died declined dramatically. Hydraulic diameter and conductivity of vessels in trees that died were higher than in surviving trees until the last 5 years prior to mortality, at which time both groups had similar values. Trees that died had consistently lower Δ values than trees that survived. Therefore, tree mortality in this stand was associated with physiological differences prior to the onset of soil water reduction. We propose that trees that died may have been hydraulically underbuilt for dry conditions, which predisposes them to severe hydraulic constraints and subsequent mortality. Measurements of above-ground/below-ground dry mass partitioning will be critical to future tests of this hypothesis. Based on these results, it is probable that pedunculate oak trees will experience greater future mortality if climate changes cause more severe droughts than the trees have experienced previously.

In view of evident changes in the reaction of European beech (Fagus sylvaticaL.) to environmental changes, five plots with young trees of the same age were established and studied on natural beech sites. Beech trees were equally distributed along the light gradient and were divided according to light conditions. The parameter used for evaluation of light conditions was the indirect site factor (ISF) obtained by the WinScanopy analysis. Three groups of canopy – light conditions were defined: stand conditions (ISF25). In all categories light saturation curves and curves describing dependence between intercellular CO2concentration in leaves and assimilation rate (A-Ci) were measured under the same fixed parameters (temperature, flow and CO2concentration, humidity, and light intensity) with Li-6400, to compare responses between different light categories and different plots within comparable light conditions. Differences between canopy, edge and open area responses were confirmed with high significance on all plots as well as between studied forest complexes. On plots from Kočevje region, young beech indicated more shade tolerance, the response to increased light intensity and different CO2concentration was greater than the response of young beech on Pohorje plots within the same light intensities. Responses of trees on plots in managed and virgin forest were also different: young beech response in virgin forest plot was more shade-tolerant, compared to response of young beech from plots in managed forest., Glede uočenih promjena u reakciji bukve (Fagus sylvaticaL.) u odnosu na ekološke promjene, odabrano je pet ploha mlade bukve jednake starosti na prirodnim staništima, koje su bile jednakomjerno raspoređene na svjetlosnom gradijentu od zastora odrasle sastojine, šumskog ruba do svjetlosnih uvjeta na otvorenome. Kriterij za grupiranje bio je neizravni stanišni čimbenik (ISF), dobiven analizom hemisfernih snimaka pomoću sustava Win-Scanopy: zastor krošanja (ISF25), koji su bili jednaki na svim plohama. Za izmjere fotosintetskog kapaciteta, krivulje svjetlosnog zasićenja (0, 50, 250, 600 i 1200 µmol/m2s) i A-Ci krivulje (0, 100, 400, 700 i 1000 µmol CO2/l) dobivene su pomoću Li-Cor LI-6400 u kontroliranom okruženju (temperatura, protok i koncentracija CO2, zračna vlaga). Analize sadržaja dušika u lišću napravljene su Leco CNS-2000 analizatorom. Potvrđene su signifikantne razlike u reakciji mladih bukava između odabranih kategorija, kao i između različitih šumskih kompleksa. Mlade bukve na plohama iz Kočevskog pokazale su veću toleranciju na sjenu, a odziv na porast koncentracije CO2je pri istim intenzitetima osvijetljenosti bio veći nego kod mladih bukava iz Pohorskog kompleksa. Odziv mladih bukava bio je signifikant no različit između prašume (Rajhenav) i gospodarske šume unutar istog šumskog kompleksa: odziv u prašumi pokazuje veću toleranciju na sjenu.

Sušenje obične jele (Abies alba Mill.) većih razmjera, prisutno u Hrvatskoj u zadnjih dvadesetak godina, dovelo je do netipičnih stanišnih uvjeta za rast podmlatka obične bukve (Fagus sylvatica L.) na područjima bu kovo-jelovih šuma. Ovakav razvoj događaja u kontradikciji je s prihvaćenom šumarskom praksom i poznatim ekološkim zahtjevima bukve (skiofilnost, osje tljivost na sušu). Da bismo odredili osnovne parametre ekofiziološkog odziva klijanaca bukve na uvjete punog osvjetljenja, postavljen je rasadnički pokus s tri razine gnojidbe (2, 4 i 6 g Osmocote Exact kompleksnog mineralnog gnojiva po litri uzgojnog supstrata), s ciljem oponašanja različitih uvjeta plodnosti tla (niska, optimalna i visoka dostupnost hraniva). Za svako tretiranje utvrđena je ukupna biomasa klijanaca (lišće, stabljika, korijen) a biljni materijal analiziran je na sadržaj biogenih elemenata (du šika, fosfora, kalija, kalcija i magnezija). Izmjerena je visina i promjer korije novog vrata biljaka, a morfologija korijena analizirana je pomoću WinRhizo softverskog paketa. Za mjerenja fotosintetskog kapaciteta, krivulje svjetlo snog zasićenja (0, 50, 250, 600 i 1200 µmol/m2s) i A-Ci krivulje (0, 100, 400, 700 i 1000 µmol CO2/l) dobivene su pomoću Li-Cor LI-6400 u kontroliranom okruženju. Visina, promjer i biomasa sadnica povećavala se s dozom gnojiva. Kon centracije N, P i K rasle su s dozom gnojiva, dok su koncentracije Ca i Mg po kazivale negativni učinak prekomjerne gnojidbe pri najvišoj dozi gnojiva. Duljina korijena, površina korijena i broj vrhova bili su najveći u srednjem tretiranju, a korijen se najslabije razvijao pri najvećoj dozi gnojidbe. U svim tretiranjima asimilacijska sposobnost bila je povezana s masom lišća (r2=0,59), koncentracijom N u lišću (r2=0,44) i korijenu (r2=0,58) kao i koncentracijom P u lišću (r2=0,45)., The large-scale dieback of Silver fir (Abies alba Mill.), pre sent in Croatia in the past two decades, has led to atypical growth conditions for young Common beech (Fagus sylvatica L.) trees on beech-fir sites. This is in contradiction with recent forestry practice and ecological requirements of beech (skiophytic, drought sensitive). The aim of this study was to improve the fundamental understanding of the influence of light and nutrient availability in early stages of the development of beech seedlings. To determine the ecophysiological response of beech see dlings to full sunlight conditions, a nursery experiment was established with three fertilization treatments (2, 4 and 6g of Osmocote Exact per 1 liter of sub strate) to simulate various soil fertility conditions (low, optimal and high avai lability of nutrients). For every treatment, total biomass of seedlings (foliage, stem, roots) and the elemental concentrations of nitrogen, phosphorous, potassium, calcium and magnesium in the plant material determined by chemical analysis. Height and root-collar diameter have been measured and roots morphologi cally analyzed (WinRhizo software package). Light saturation curves (0, 50, 250, 600 in 1200 µmol/m2s) and A-Ci curves (0, 100, 400, 700 in 1000 µmol CO2/l) have been measured (Li-Cor LI-6400) in a controlled environment. Height, diameter and biomass of seedlings increased with fertilizer dose. Concentrations of N, P and K were growing with fertilizer dose, while Ca and Mg concentrations showed negative effects of overfertilization at the highest fertilizer dose. Root length, surface area and number of root tips were highest in the intermediate treatment while roots were least developed at the highest fertilizer dose. In all cases assimilation rates of seedlings corresponded well with leaf mass (r2 = 0,59), leaf (r2 = 0,44) and root total nitrogen (r2 = 0,58) and total leaf phosphorus (r2 = 0,45). Regardless of the conditions of full sunlight and an irregular water supply to seedlings while growing in the nursery, they showed a standard ecophysio logical response to fertilization treatments, indicating that despite the chan ged site conditions in beech and fir stands, the seedlings may keep the capacity to adapt to the environment. The most successful development of see dlings can be expected on nutrient-rich sites.