Osmotska komponenta vodnega potenciala in prilagoditev odraslih dobovih sestojev (Quercus robur L.) na sušni stres z različno sestojno gostoto

Pressure volume curves were applied to define differences in stress adaptation between two managed forest complexes and virgin forest remnantin Murska šuma, Krakovo forest and Krakovo old growth forest. Species response between adult stands after stronger thinning and comparable stand without any silvicultural measures within same forest complex was compared in two consecutive years, 2003 and 2004. Significant differences in osmotic potential (full turgor) component for plots in Murska šuma in 2003 as well as in Krakovo forest between managed forest and old growth-forest were confirmed. In all cases, values became more negative, indicating slight capability of oaks to adapt with increasing drought stress. Reaction/stress adaptation of forests after thinning indicated well adapted mechanism to address drought stress in spite of the age. We may connect such improved drought response with increased individual space for growth and lower stand density.Za primerjavo in opredelitev razlik stresnega prilagajanja na sušo odraslih dobovih sestojev smo uporabili P/V-krivuljeprimerjali smo odzive gospodarskega gozda v Murski šumi, v Krakovskem gozdu in pragozdnega rezervata Krakovo kot tudi gospodarska sestoja z različno drevesno gostoto (redčen sestoj, neredčen) v poletnih mesecih 2003 in 2004. Potrdili smo značilne razlike v osmotski komponenti vodnega potenciala pri polnem turgorju med ploskvama Murske šume in Krakovskega gozda. Na vseh ploskvah je bilo opaziti povečevanje osmotske komponente z naraščanjem sušnega stresa. Sestoj po redčenju / uvajanju v obnovo je pokazal dobro oblikovan mehanizem in prilagajanje kljub starosti, najverjetneje zaradi sproščene konkurence in povečanega rastnega prostora

Mortaliteta in osutost krošenj doba (Quercus robur L.) na trajnih ploskvah - 20-letni pregled

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 in 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 opennessall 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. Pattern of agreement among compared parameters was different for the Krakovski gozd and Dobrava plots on one hand and Cigonca and Hraščica plots on the other hand. Mortality is influenced by the average air temperatures much more than by precipitation and groundwater table oscillationsV dobovih sestojih Slovenije ugotavljamo povečano mortaliteto. Spremembe v nižinskih delih se kažejo kot upad vitalnosti celotnih gozdnih kompleksov, povečanje smrtnosti, porušeno razmerje razvojnih faz in težave, povezane z naravno obnovo. Napovedi sedanjega odziva dreves lahko v prihodnje prispevajo pomembne informacije za nadaljnje gospodarjenje in gojenje tako v poškodovanih kot ohranjenih dobravah. Podatke vsakoletnega popisa stanja krošenj na štirih stalnih vzorčnih ploskvah smo vzporejali s podatki analize hemisfere krošenj in hidrometeorološkimi podatki. Potrdili smo dobro ujemanje med osutostjo in odprtostjo krošenj (hemisferna analiza). Parametri, od katerih smo odšteli zimske vrednosti in jih vzporejali z osutostjo, so pokazali boljše ujemanje od osnovnih. Potrdili smo korelacijo med smrtnostjo in osutostjo krošenj ter ekstremnimi sušnimi razmerami. Vzorci ujemanja so se med sabo razlikovali za Krakovski gozd in Dobravo na eni strani ter Cigonco in Hraščico. Povezava med smrtnostjo in povprečno temperature zraka je bila večja od povezave s podtalnico in padavinami

Mortality and crown conditions on Quercus robur L. permanent plots - a 20-year overview

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 in 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. Pattern of agreement among compared parameters was different for the Krakovski gozd and Dobrava plots on one hand and Cigonca and Hraščica plots on the other hand. Mortality is influenced by the average air temperatures much more than by precipitation and groundwater table oscillations

Fotosintetski odziv mladih stabala bukve (Fagus sylvatica L.) na odabranim plohama u različitim svjetlosnim uvjetima

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

Transpiration and water potential of young Quercus petraea (M.) Liebl. coppice sprouts and seedlings during favourable and drought 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.O