No description available.

No description available.

The research of the dissertation thesis was focused on the ability of forests to activate and immobilize metals in the environment with their huge grants from deep mining of mineral resources. The research was be located in the area of Rožná with ongoing uranium mining, and area of Olší with ended uranium mining in the Czech Republic. During the years 2014 and 2015 was at the alluvial streams of Nedvědička (Rožná) and Hadůvka (Olší) recipients of pollution by radionuclides and metals from mining, taken in spring and autumn aspect of the overall 380 samples of leaves from trees, herb layer and river sediments. The samples were analyzed by the XFR and ICP-OES methods. In the organic matter were found such as elements Al, Cl, Cu, Cr, Fe, Mn, Mo, Ni, Rb, S, Sr, U, Zn and Zr, in many cases at high concentrations corresponding to polluted areas in the mining or industrial areas. A statistically significant difference in the concentrations of chemical elements in the fytomasss and river sediment between the upper, middle and lower stream areas of interest was not found. In the area of Nedvědička were found higher concentrations of a greater range of metals than in the area of Hadůvka. In the area of Hadůvka were by ICP-OES found significantly higher levels of uranium in the leaves than in the area of Nedvědička, reaching up to 34.86 mg.kg-1 in the dried material.The seasonal dynamics of the content of chemical elements in fytomass was confirmed. The species composition of the forest growth in the areas of interest with a predominance of Picea abies and the type of management has been evaluated as unfavorable for immobilization of metals in the environment. In the area of Nedvědička were suggested corrective actions - planting vegetation with a predominance of Fagus silvatica which should have a beneficial effect on soil and water pH by a suitable character of waste and contribute to the spread of inhibition of metals in the environment. In the area of Hadůvka are the suggested measures focused on the redevelopment of existing vegetation with a predominance of Picea abies on vegetation with a predominance of deciduous trees, especially Fagus silvatica, in order to adjust gradually the pH of the soil and thereby reduce the mobility of metals in the environment.

<p>Prognoze Međuvladinog panela o klimatskim promenama govore da će&nbsp;prostor Jugoistočne Evrope biti&nbsp; pod snažnim uticajem izmenjenih klimatskih&nbsp;uslova u 21. veku. Očekuje se da će leta biti toplija i suvlja sa vi&scaron;e&nbsp;ekstremnih događaja i temperaturama koje mogu u proseku porasti i za čak&nbsp;3,8&deg;C, &scaron;to predstavlja veliki izazov za &scaron;umarstvo. Da bi se odgovorilo na taj&nbsp;izazov neophodno je načiniti i sprovesti adekvatne mere adaptacije, &scaron;to bi&nbsp;značilo prilagođavanje mera gazdovanja &scaron;umama novonastlim ekolo&scaron;kim&nbsp;uslovima. Jedan od značajnih alata u tom prilagođavanju predstavljaju&nbsp;različiti &nbsp;modelarski pristupi. U&nbsp; ovoj disertaciji su upotrebljene&nbsp;najsavremenije metode modeliranja uticaja klimatskih promena na &scaron;ume.&nbsp;Radi se o pionirskom istraživanje koje je prvo takve vrste u regionu. Dva&nbsp;različita metodska pristupa, vezanih za distribuciju, rast, adaptivno i&nbsp;multifunkcionalno gazdovanja bukovim &scaron;umama u Srbiji u klimatskim&nbsp;uslovima 21. veka su uputila na nekoliko najbitnijih rezultata i zaključaka. &nbsp;Izmenjeni klimatski uslovi će imati uticaj na rast i distribuciju bukovih &scaron;uma&nbsp;u 21. veku na osnovu simulacija sa 4C modelom i predikcija pomoću&nbsp;Elenbergovog koeficijenta. Na &nbsp;kraju simuliranog perioda 2001-2030 pomoću&nbsp;4C modela zabeležene su &nbsp;veće zapremine za devet sastojina&nbsp;monodominantnih bukovih &scaron;uma u odnosu na referentni period 1961-1990,&nbsp;dok su zapremine na kraju perioda 2071-2100 po pravilu bile veće ili &nbsp;slične&nbsp;referentnom period. Simulacije u period 2001-2030 su proseku imale najveće&nbsp;godi&scaron;nje priraste i najvi&scaron;e mrtvog drveta, a one u period 1961-1990 &nbsp;najmanje.&nbsp;Najbolje rezultate za vezivanje ugljenika i očuvanje biodiverziteta je pokazao&nbsp;scenario gazdovanja u kojem nije bilo intervencija. Suprotno tome, &nbsp;najvi&scaron;e prinosa drveta je zabeleženo u scenarijima sa najintenzivnijim&nbsp;intervencijama. U adaptivnom multifunkcionalnom gazdovanju bukovim&nbsp;&scaron;umama za scenarija preferencija koje su kreirale tri grupe zainteresovanih&nbsp;strana (Uprava za &scaron;ume, sektor za&scaron;tite prirode i JP &bdquo;Srbija&scaron;ume&ldquo;) pokazalo se&nbsp;da gazdovanje koje podrazumeva če&scaron;će zahvate (pet godina između seča)&nbsp;daje bolje rezultate u odnosu scenarija koji podrazumevaju desetogodi&scaron;nje&nbsp;intervale. Scenariji gazdovanja u kojima su posečena visoka stabla su&nbsp;pokazale bolje rezultate u multifunkcionalnom gazdovanju u odnosu na&nbsp;scenarija gde su sečena niža stabla u istom zapreminskom odnosu za sva&nbsp;<span style="font-size: 12px;">scenarija preferencija zainteresovanih strana. Elenbergov koeficijent je&nbsp;</span><span style="font-size: 12px;">pokazao dobru prediktivnu sposobnost za određivanje donje granice&nbsp;</span><span style="font-size: 12px;">distribucije bukovih &scaron;uma u &nbsp;Srbiji. Do kraja 21. veka okvirno 90% dana&scaron;njih&nbsp;</span><span style="font-size: 12px;">bukovih &scaron;uma će se naći izvan bioklimatske ekolo&scaron;ke ni&scaron;e u kojoj su bili u&nbsp;</span><span style="font-size: 12px;">20. veku, dok će se 50% naći u zoni u kojoj je &nbsp;zabeležen njen masovni&nbsp;</span><span style="font-size: 12px;">mortalitet u Mađarskoj. Izračunate granice EQ su bile ne&scaron;to niže od dobijenih&nbsp;</span><span style="font-size: 12px;">u sličnim studijama u region &scaron;to implicira striktan regionalni i lokalni pristup&nbsp;</span><span style="font-size: 12px;">problem. Poređenje rezultata simulacija sa 4C modelom i EQ za posmatranih&nbsp;</span><span style="font-size: 12px;">devet sastojina je pokazalo različite trendove vezano za rast (distribuciju)&nbsp;</span><span style="font-size: 12px;">bukovih &scaron;uma u Srbiji do kraja 21. veka. 4C model je predvideo pobolj&scaron;anje&nbsp;</span><span style="font-size: 12px;">uslova, dok je EQ predvideo pogor&scaron;anje uslova. Iz tog razloga potrebna su&nbsp;</span><span style="font-size: 12px;">dalja kontinuirana dugoročna istraživanja bukovih &scaron;uma kako bi smo dobili&nbsp;</span><span style="font-size: 12px;">pouzdaniju osnovu za procenu budućeg rasprostranjenja, rasta i planiranja&nbsp;</span><span style="font-size: 12px;">gazdovanja ovim &scaron;umama u budućnosti.</span></p> / <p>Predictions of the Intergovernmental Panel on Climate Change suggest that&nbsp;the region of Southeast Europe will be strongly influenced by the altered&nbsp;climate conditions in 21 century. It is expected that the summers will be&nbsp;hotter and drier with more extreme events and temperatures that can rise on&nbsp;average as much as 3.8 &deg;C. That is a big challenge for forestry. To respond&nbsp;to this challenge it is necessary to make and implement appropriate&nbsp;adaptation measures which would mean adapting forest management&nbsp;practice to changed environmental conditions. Different models are one of&nbsp;the important tools which can be used in this purpose. In this dissertation&nbsp;state-of-the art methods for calculating the impact of climate change on&nbsp;forests have been applied. This is a pioneering work and the first of its kind&nbsp;in the region. Two different methodological approaches, related to the&nbsp;distribution, growth, adaptive and multifunctional management of&nbsp;European beech forests in Serbia has been performed and provided&nbsp;following results and conclusions. Changed climatic conditions will have&nbsp;<br />an impact on the growth and distribution of beech forests in 21st century&nbsp;based on simulations with the 4C model and predictions of Ellenberg&rsquo;s&nbsp;climate quotient (EQ). At the end of the simulated period 2001-2030 higher&nbsp;volumes were recorded for the nine beech stands in comparison to the&nbsp;reference period 1961 to 1990, while the volume at the end of the period&nbsp;2071-2100 were higher or similar to the reference period. Simulations in&nbsp;the period 2001-2030&nbsp; have had the greatest average annual increment and&nbsp;the biggest amount of dead wood. The best results for carbon sequestration&nbsp;and biodiversity were provided by management scenario in which there&nbsp;were no management measures. In contrast, the highest yield&nbsp; of timber is&nbsp;recorded in the scenarios with the most intensive management measures.&nbsp;The adaptive multifunctional &nbsp;management of beech forests including three&nbsp;<span style="font-size: 12px;">scenarios of preferences&rsquo; (Forest Directorate , Nature Protection Sector and&nbsp;</span><span style="font-size: 12px;">Public Enterprise &quot;Srbija&scaron;ume&quot; ) suggested that management measures that&nbsp;</span><span style="font-size: 12px;">involved more frequent interventions (five years between felling) gives</span><span style="font-size: 12px;">better results than scenario which include a ten-year periods. Scenarios in&nbsp;</span><span style="font-size: 12px;">which higher trees are cut provide better results than scenario where the&nbsp;</span><span style="font-size: 12px;">lower trees are cut. EQ showed good predictive capability for determining&nbsp;</span><span style="font-size: 12px;">the lower (xeric) limit of the distribution of beech forests in Serbia. By the&nbsp;</span><span style="font-size: 12px;">end of 21st century, approximately 90 % of today&#39;s beech forests will be&nbsp;</span><span style="font-size: 12px;">found outside the bioclimatic niches in which they were in the 20th century,&nbsp;</span><span style="font-size: 12px;">while the 50 % of them will be in the zone in which their mass mortality is&nbsp;</span><span style="font-size: 12px;">observed in Hungary. Calculated EQ beech threshold distribution for Serbia&nbsp;</span><span style="font-size: 12px;">were slightly lower than in similar studies in the region (Hungary) , which&nbsp;</span><span style="font-size: 12px;">implies strict regional and local approach to the problem. Comparison of&nbsp;</span><span style="font-size: 12px;">simulated results with the 4C model and EQ for nine stands showed </span><span style="font-size: 12px;">different trends related to growth (distribution) of beech forests in Serbia by&nbsp;</span><span style="font-size: 12px;">the end of 21st century. 4C model predicted improvement of environmental </span><span style="font-size: 12px;">conditions, while the EQ predicted their worsening. For this reason,&nbsp;</span><span style="font-size: 12px;">continuing long-term studies of beech forests are needed in order to get a&nbsp;</span><span style="font-size: 12px;">more reliable basis for estimating future distribution, growth and planning&nbsp;</span><span style="font-size: 12px;">of forest management in the future.</span></p>

Vor dem Hintergrund sich verändernder Umweltbedingungen durch den allgegenwärtigen Klimawandel wächst das Interesse an Vorhersagen zur zukünftigen Waldentwicklung. Der prognostizierten Häufung von Witterungsextremen wird ein wesentlicher Einfluss auf das Wachstum und die Vitalität der Waldbaumarten zugeschrieben. Wichtige Erkenntnisse bringen hier Untersuchungen zu den physiologischen Wachstumsgrenzen der Gehölze, die sich besonders deutlich an deren heutigen Verbreitungsgrenzen nachweisen lassen. An diesen offenbart sich das Potential einer Baumart, die Migration unter zukünftigen Bedingungen fortsetzen zu können. Großes Interesse herrscht an ökonomisch wichtigen Baumarten wie der Gemeinen Fichte (Picea abies [L.] Karst.) und der Rot-Buche (Fagus sylvatica L.). Deren Wuchsverhalten unter natürlichen Bedingungen, in natürlich erwachsenen Mischwäldern wurde in der vorliegenden Arbeit an den derzeitigen Arealsgrenzen beider Arten in Südschweden (Rågetaåsen, Siggaboda, Tolseboda) untersucht. Als Vergleichsstandort diente ein Naturwald im Harz (Rehberg), welcher geografisch zentral im Verbreitungsgebiet der Buche liegt und durch seine montane Höhenlage ideale Wuchsbedingungen für die Fichte liefert. Mittels dendroklimatologischer Analysemethoden wurden die wesentlichen, den radialen Zuwachs beeinflussenden Witterungsvariablen bestimmt und deren Anpassung bzw. Veränderung über verschiedene Zeitintervalle untersucht. Dendroökologische Untersuchungen ermöglichten einen Blick in die vergangene Entwicklung der Mischbestände und das Konkurrenzverhalten beider Baumarten untereinander. Diese Untersuchungen wurden auf zwei Ebenen durchgeführt: auf der Bestandesebene und auf der Ebene kleinerer Untersuchungsgruppen, durch welche direkte Konkurrenzsituationen der intra- und interspezifischen Beeinflussung analysiert werden konnten. Beide Methoden sind retrospektiver Natur und ermöglichen daher in der Hauptsache eine Analyse und Interpretation des vergangenen Zuwachsverhaltens. Doch erlauben beobachtete Trends in der Vergangenheit eine vorsichtige Prognose der Entwicklung von Waldbeständen auf vergleichbaren Standorten. Die dendroklimatologischen Analysen zeigten, dass beide Baumarten eine interessante Variabilität in den jeweiligen zuwachsbeeinflussenden Witterungsvariablen aufweisen. Die Haupteinflussgröße für den Buchenzuwachs ist ein trocken-heißer Vorjahres-Sommer mit Schwerpunkt auf den Monaten Juli und August. Dieser Einfluss zeigt sich seit Beginn des Beobachtungszeitraums, aber seit etwa 1950 verstärkt er sich bedeutend und erfährt seit Mitte der 1990er Jahre eine weitere Steigerung. Die wesentliche Witterungsvariable für den Fichtenzuwachs war bis etwa in die 1950er Jahre ein positiver Einfluss der Niederschläge im Sommer der Ringbildung mit Schwerpunkt auf dem Juni. Seither verschwindet dieser Einfluss jedoch auf fast allen Standorten und weicht einer, der Buchen ähnlichen Dürreempfindlichkeit gegenüber den vorjährigen Spätsommern. Die retrospektive Analyse der Bestandesgeschichte mittels langjähriger Zuwachszeitreihen ermöglicht eine Interpretation der vergangenen Entwicklung der Waldbestände und liefert eine Erklärung für das aktuelle Erscheinungsbild. Auf den schwedischen Standorten zeigt sich im radialen wie im Höhenzuwachs ein deutlicher Vorteil der Fichten. Auf den Standorten Siggaboda und Tolseboda bildet die Buche unter der Fichte sogar die zweite Baumschicht. Im Gegensatz zum Standort Rågetaåsen liegen diese beiden Standorte bereits außerhalb des natürlichen Verbreitungsgebiets von Buchenwäldern, aber im Gebiet der Buchen-Fichten-Wälder. Hier erkennt man deutlich einen Konkurrenzvorteil der Fichte. Am Vergleichsstandort Rehberg erkennt man dagegen das grundsätzlich große Potential der Buche, ähnliche Zuwächse zu leisten wie die Fichte. Das Konkurrenzverhältnis wirkt hier relativ ausgeglichen. Direkte Konkurrenzsituationen zwischen den Baumarten ergeben sich an Randzonen der natürlich gewachsenen reinartigen Gruppen. Es zeigte sich, dass die Buche in unmittelbarer Konkurrenz zur Fichte benachteiligt wird. Im umgekehrten Falle kann die Fichte in Abhängigkeit von ihrer sozialen Stellung sogar von einer Mischung mit Buche profitieren. Diese Ergebnisse gelten für die schwedischen Standorte wie auch für den Harz, wobei die Buchen am Rehberg ein größeres Potential erkennen lassen, dem Druck der Fichten entgegenzustehen. Der Einfluss singulärer Witterungsextreme auf das Wachstum beider Baumarten konnte an starken Zuwachseinbrüchen nachgewiesen werden. Doch in den meisten Fällen zeigte sich bereits im Folgejahr wieder ein ausgeglichenes Wachstum. Eine Herausforderung wird die zukünftige Häufung von Extremen mit fehlenden Erholungsphasen sein. Im letzten Jahrzehnt konnten bereits Sekundärfolgen großer Trockenheiten und deren Einfluss auf den Zuwachs beobachtet werden. Ergeben sich aus derartigen Situationen Schwierigkeiten für eine Baumart, ist dies ein sicheres Zeichen dafür, dass sie an ihre physiologischen Grenzen gerät. Am Standort Siggaboda konnte dies bereits für die Fichten beobachtet werden. Auch am Rehberg stellten sich in den letzten Jahren Bedingungen ein, die der Buche Schwierigkeiten bereiten. Aus den gewonnenen Erkenntnissen lässt sich entnehmen, dass das Konkurrenzverhältnis zwischen Buche und Fichte seit den letzten zwei Jahrzehnten begonnen hat, sich zu verändern. Am südexponierten Hangstandort im Harz scheint die bisher sehr konkurrenzstarke Buche an ihre physiologische Grenze zu geraten. Auf den schwedischen Standorten wird die Buche möglicherweise von wärmeren Sommern und verlängerten Vegetationsperioden profitieren, während die Fichte an die südliche, klimatische Verbreitungsgrenze der borealen Wälder gelangt zu sein scheint. / Against the background of a changing environment due to climate change the interest in prognoses of the development of forest ecosystems increases. The growth and the vitality of forest tree species will mainly be influenced by increased frequency of extreme weather conditions. The analysis of the physiological limits of tree growth has to be conducted at the borders of the natural distribution range of species. Main focus lies on economical important tree species as Common beech (Fagus sylvatica L.) and Norway spruce (Picea abies [L.] Karst.).Growth and competition performance of these two species was investigated under natural conditions in naturally grown mixed forests at both species distribution limits in Southern Sweden (Rågetaåsen, Siggaboda, Tolseboda). As a reference a natural forest in the Harz Mountains (Rehberg) was chosen. By means of dendroclimatological methods the main influencing climate variables and their modifications over time were analysed. Dendroecological methods allow the retrospective analysis of forest history and the development of the competition behaviour of both species in the past. These analyses were conducted on two levels: stand level and plot level. The latter permits the analysis of direct competition situations, intra- and interspecific. By means of these retrospective methods potential trends might be detected and thus allow forecasts for the development of forest stands on comparable sites. Dendroclimatological analyses showed, that both tree species exhibit interesting variability in its main influencing climate variables. The radial growth of beech is mainly determined by warm-dry summers of the previous year with focus on July and August. This influence increases since the 1950s and even stronger since the mid 1990s. Main factor for spruce growth was summer precipitation with focus an June. This influence nearly vanished on all sites since the 1950s. Since then the main climate signal of spruce growth is a sensitivity to drought of previous summers, equally to beech. The retrospective analysis of forest history by means of long-term tree-ring series allows an interpretation of past development of the forest stands and provides explanations for the current appearance. On the Swedish sites the advance of spruce in radial as in height growth is obvious. In Siggaboda and Tolseboda beech even forms the secondary species. These sites lie beyond northern limits of Fagus forests but within Fagus-Picea forests. The advantage of spruce is considerable. Though, on the reference site Rehberg the high potential of beech, to achieve comparable tree-ring widths, is distinct. Here, the competition performance is nearly balanced. At borders of naturally grown pure groups direct competition situations between the species can be found. It could be shown, that beech is disadvantaged under immediate competition with spruce. But in inverse situations, spruce, depending on its social state, even benefits of growing in mixture with beech. These results can be found on the Swedish sites as well as in the Harz Mountains, though, beech at the Rehberg shows a much higher potential to stand against the competition of spruce. Singular impacts of extreme weather conditions on tree growth can be clearly, but in most cases growth is regulated one year later. However, future challenge for tree species will be the increased frequency of extreme conditions without phases of recovery. In the past decade secondary complications of drought and its influence on growth could already be detected. This affects both species similarly. Does a species get disadvantaged due to such situations, would mean that it reaches its physiological limits. In Siggaboda this could be already shown for spruce and at the Rehberg for beech. As a result this study shows, that the competition situation between beech and spruce has begun to change since the last two decades. On exposed sites as the Rehberg, beech trees might reach its physiological limits. On the Swedish sites, however, beech trees could benefit from warm summers and prolonged vegetation periods. In contrast, spruce probably has reached its southern, climatically determined distribution limit of boreal forests.

No description available.

Les dépérissements forestiers rapportés dans la littérature ont fortement augmenté durant la dernière décennie. Si cette augmentation semble attribuable au moins en partie aux changements globaux, les mécanismes écophysiologiques sous jacents restent encore mal connus. La littérature sur ce sujet a initialement permis de dégager deux principales hypothèses sur les mécanismes fonctionnels à l’œuvre lors d’un dépérissement : un manque de réserves carbonées et un dysfonctionnement du système hydraulique. Ces deux hypothèses ne sont pas mutuellement exclusives, ni exhaustives : les fonctionnements carboné et hydraulique interagissent à de multiples niveaux, et une implication du cycle interne de l’azote n’est pas à exclure. L’objectif principal de cette thèse est de documenter les mécanismes écophysiologiques à l’œuvre dans un dépérissement de hêtres (Fagus sylvatica L.) matures en forêt de Fontainebleau, lié principalement à des sécheresses répétées. Le dépérissement a ici été étudié en dehors de fortes contraintes climatiques. Ce sont donc majoritairement des arrières-effets de stress passés qui ont été renseignés. Au cours de ce travail, une approche intégrant des aspects hydraulique, carboné et azoté du fonctionnement du système arbre-sol a été adoptée afin de développer une vision intégrée de l’impact du dépérissement sur les grandes fonctions de l’arbre. Le transfert de composés de l’arbre vers le sol via la rhizodéposition a également été pris en compte. En dehors de périodes de stress, le fonctionnement des arbres sains et dépérissants à l’échelle de l’organe est similaire, à l’exception d’une diminution de la croissance radiale du tronc chez les arbres dépérissants. Au niveau du tronc, la croissance radiale apparait donc comme la variable d’ajustement des arbres dépérissants à une assimilation de carbone diminuée du fait de la détérioration de l’état de santé du houppier. Suite à une contrainte hydrique modérée, les arbres dépérissants présentent un déficit en réserves carbonées par rapport aux arbres sains dans certains organes. Ce déficit se trouve compensé après une année favorable. Une forte résilience des concentrations en réserves carbonées pourrait expliquer la capacité des arbres dépérissants à survivre de nombreuses années avec un houppier très endommagé. Des différences de proportion et de structure des rayons ligneux détectées entre les arbres sains et dépérissants laissent entrevoir l’intérêt qu’aurait dans le futur l’étude de caractéristiques anatomiques fonctionnelles dans le xylème. De plus, une approche rétrospective grâce aux cernes permettrait d’affiner notre compréhension de la mise en place du dépérissement à long terme. Par ailleurs, une étude actuellement en cours sur la structure des communautés microbiennes de la rhizosphère devrait permettre de compléter notre connaissance de l’impact du dépérissement sur les relations arbre-sol. / The cases of forest decline reported in the literature have strongly increased during the last decade. This increase seems at least in part attributable to global change. However, the ecophysiological mechanisms underlying tree declines remain poorly understood. Two main hypotheses initially emerged from the recent literature: a deficit of carbon reserve compounds, or a failure of the hydraulic system of the tree. These hypotheses are not mutually exclusive, nor exhaustive: multiple couplings exist between the carbon and hydraulic functionings, and the internal nitrogen cycle of the trees could also be involved in tree decline. The main objective of this work was to document the ecophysiological mechanisms underlying a case of mature beech (Fagus sylvatica L.) drought-related decline in the Fontainebleau state forest. The decline was studied under non extreme climatic conditions. Therefore, we documented maily after-effects of past stresses. In this thesis, we developed an approach integrating the hydraulic, carbon and nitrogen aspects of functioning of the tree-soil system. The transfer of carbon compounds from tree roots to soil via the rhizodeposition process was also taken into account. Under non-stressful conditions, the functioning of healthy and declining trees is similar at the organ level, apart from a decreased stem radial growth in declining trees. In the trunk, radial growth thus appears to be the “adjustment variable” of declining trees in response to a lower whole-tree carbon assimilation due to their severely thinned crowns. Our results show that after a moderate hydric constraint, declining trees show a carbon reserve deficit in some organs compared to healthy trees. This deficit is compensated after a favourable year. A high resilience of carbon reserve concentrations could explain the ability of declining trees to survive for several years with a strongly reduced whole-tree leaf area. Healthy and declining trees presented different parenchyma ray proportions and structures in the stem xylem. Therefore, it could be interesting to study functional anatomical features in the future. Besides, tree rings characteristics could offer an insightful retrospective view of the history of this decline. Furthermore, an ongoing study on the structure of the microbial communities in the rhizosphere of healthy and declining trees will improve our knowledge about the impact of tree decline on the tree-soil interactions.

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Grindžiant sąsajas tarp ežero ir paežerės ekosistemų ir remiantis tuo, kad medžių lapų paklotės irimo produktai yra alochtoninės ištirpusios organinės anglies (IOA) šaltinis, buvo tiriamas paprastojo buko (Fagus sylvatica L.) ir paprastojo ąžuolo (Querqus robur L.) lapų vandeninių ekstraktų poveikis žvaigždėtojo maurašakio (Nitellopsis obtusa (Desv.) J. Groves) ląstelei fermentiniu, plazmalemos ir ląstelės gyvybingumo lygmeniu. Koncentracinėmis ir laiko priklausomybėmis parodyta, kad ekstraktai, tarp jų ir gauti per 30 dienų savaiminio lapų irimo, sukelia oksidacinio streso fermentų aktyvumo ir ląstelės membranos potencialo pakitimus bei ląstelių žūtį – taip preziumuojamas priežastinis ryšys tarp ankstyvųjų reakcijų ir letalumo. Santykinai jautresnės reakcijos vyko fermentiniame lygmenyje, negrįžtamiems ląstelės membranos ramybės potencialo pokyčiams ir mirtingumui aptikti reikia didesnių nei aptinkamų gamtiniuose vandens telkiniuose IOA koncentracijų arba ilgesnės poveikio trukmės. Tai leidžia manyti, kad paklotės lapai yra svarbus aplinkos veiksnys, turintis įtakos vandens augalijos rūšinei įvairovei gėlavandenėse ekosistemose. / Aqueous extracts of common beech (Fagus sylvatica L.) and European oak (Quercus robur L.) leaves from leaf litter were used as allochthonous source of dissolved organic carbon (DOC) to investigate cell response of starry stonewort (Nitellopsis obtusa (Desv.) J. Groves) at enzymatic, cell membrane and whole cell levels. Dose and time dependent exposure experiments with leaf litter extracts including 30 day leaf litter degradation ones, were carried out to show activity modulations of oxidative stress enzymes, cell resting potential (RP) and survivorship. Charophytes manifested a certain level of antioxidative resilience depending on the DOC source. Relatively more sensitive reactions were detected at enzymatic level, however, to identify irreversible cell RP changes and lethality, higher than those of natural aquatic bodies DOC concentrations or prolonged exposure were needed. Changes in activities of oxidative stress enzymes and cell membrane potential invoked by extracts predicted cell mortality, which allowed us to presume causality between more sensitive initial reactions and lethality. By linking lake and lake shore ecosystems it was concluded that beech and oak leaf litter has the potential to adversely affect algae and, thus, might eventually be important environmental factor impacting aquatic vegetation species diversity in freshwater ecosystems.

Aqueous extracts of common beech (Fagus sylvatica L.) and European oak (Quercus robur L.) leaves from leaf litter were used as allochthonous source of dissolved organic carbon (DOC) to investigate cell response of starry stonewort (Nitellopsis obtusa (Desv.) J. Groves) at enzymatic, cell membrane and whole cell levels. Dose and time dependent exposure experiments with leaf litter extracts including 30 day leaf litter degradation ones, were carried out to show activity modulations of oxidative stress enzymes, cell resting potential (RP) and survivorship. Charophytes manifested a certain level of antioxidative resilience depending on the DOC source. Relatively more sensitive reactions were detected at enzymatic level, however, to identify irreversible cell RP changes and lethality, higher than those of natural aquatic bodies DOC concentrations or prolonged exposure were needed. Changes in activities of oxidative stress enzymes and cell membrane potential invoked by extracts predicted cell mortality, which allowed us to presume causality between more sensitive initial reactions and lethality. By linking lake and lake shore ecosystems it was concluded that beech and oak leaf litter has the potential to adversely affect algae and, thus, might eventually be important environmental factor impacting aquatic vegetation species diversity in freshwater ecosystems. / Grindžiant sąsajas tarp ežero ir paežerės ekosistemų ir remiantis tuo, kad medžių lapų paklotės irimo produktai yra alochtoninės ištirpusios organinės anglies (IOA) šaltinis, buvo tiriamas paprastojo buko (Fagus sylvatica L.) ir paprastojo ąžuolo (Querqus robur L.) lapų vandeninių ekstraktų poveikis žvaigždėtojo maurašakio (Nitellopsis obtusa (Desv.) J. Groves) ląstelei fermentiniu, plazmalemos ir ląstelės gyvybingumo lygmeniu. Koncentracinėmis ir laiko priklausomybėmis parodyta, kad ekstraktai, tarp jų ir gauti per 30 dienų savaiminio lapų irimo, sukelia oksidacinio streso fermentų aktyvumo ir ląstelės membranos potencialo pakitimus bei ląstelių žūtį – taip preziumuojamas priežastinis ryšys tarp ankstyvųjų reakcijų ir letalumo. Santykinai jautresnės reakcijos vyko fermentiniame lygmenyje, negrįžtamiems ląstelės membranos ramybės potencialo pokyčiams ir mirtingumui aptikti reikia didesnių nei aptinkamų gamtiniuose vandens telkiniuose IOA koncentracijų arba ilgesnės poveikio trukmės. Tai leidžia manyti, kad paklotės lapai yra svarbus aplinkos veiksnys, turintis įtakos vandens augalijos rūšinei įvairovei gėlavandenėse ekosistemose.