Modelling the potential distribution of three climate zonal tree species for present and future climate in Hungary = Három klímazonális fafaj hazai potenciális elterjedésének modellezése jelenlegi és jövőbeni klímában

The potential distribution and composition rate of beech, sessile oak and Turkey oak were investigated for present and future climates (2036–2065 and 2071–2100) in Hungary. Membership functions were defined using the current composition rate (percentage of cover in forest compartments) of the tree species and the long-term climate expressed by the Ellenberg quotient to model the present and future tree species distribution and composition rate. The simulation results using the regional climate model REMO showed significant decline of beech and sessile oak in Hungary during the 21st century. By the middle of the century only about 35% of the present beech and 75% of the sessile oak stands will remain above their current potential distribution limit. By the end of the century beech forests may almost disappear from Hungary and sessile oak will also be found only along the Southwest border and in higher mountain regions. On the contrary the present occurrences of Turkey oak will be almost entirely preserved during the century however its distribution area will shift to the current sessile oak habitats. | The potential distribution and composition rate of beech, sessile oak and Turkey oak were investigated for present and future climates (2036–2065 and 2071–2100) in Hungary. Membership functions were defined using the current composition rate (percentage of cover in forest compartments) of the tree species and the long-term climate expressed by the Ellenberg quotient to model the present and future tree species distribution and composition rate. The simulation results using the regional climate model REMO showed significant decline of beech and sessile oak in Hungary during the 21st century. By the middle of the century only about 35% of the present beech and 75% of the sessile oak stands will remain above their current potential distribution limit. By the end of the century beech forests may almost disappear from Hungary and sessile oak will also be found only along the Southwest border and in higher mountain regions. On the contrary the present occurrences of Turkey oak will be almost entirely preserved during the century however its distribution area will shift to the current sessile oak habitats

The Effect of Soil Moisture on the Reflectance Spectra Correlations in Beech and Sessile Oak Foliage

Reflectance inten sities of foliage are mostly due to bio materials synthesised by plant s . A daptation to the continuously changing environment requires the regulated alteration of m etabolic processes, which also influences the UV - VIS (Ultraviolet - Visible) and IR (Infra Red) spectra of leaves . For the calculation of various Vegetation Indices (VIs), e.g. NDVI (Normalized Difference Vegetation Index) , t he common practice is to use the reflectance spectrum of the whole foliage and when individual leaves of th e same plant are sampled , an average VI is derived . On the contrary , our method exploits the small differences between individual leaves of the same plant , making use of the similar distribution s of measured reflectance values . Using particular wavelength pairs, l inear regressions of reflectance intensities have been investigated . T he parameters of th ese regression s (slope and intercept) have been compared to the temporal variations of the environmental factors, such as temperature, vapour pressure deficit a n d soil moisture . By assessing the sensitivity of the regression coefficient (slope) to the changing environment , wavelength pairs can be selected whose sensitivity change reflect s the effect of soil moisture deficit on the plant . B ased on the state - dependent correlations of the reflectance spectra of plant foliage , a new concept is presented that is capable of indicating the level of environmental stress, e.g. drought stress

Accelerated Height Growth Versus Mortality of Quercus petraea (Matt.) Liebl. in Hungary

Background and Purpose: Due to climate change, it is important to know to what extent forests will be impacted by atmospheric changes. This study focuses on the height growth response of sessile oak (Quercus petraea (Matt.) Liebl.) to counteracting effects of fostering and interfering changes under contrasting climatic conditions with special attention to the xeric limit zone of this species. Materials and Methods: Twenty-eight sites were selected along a climatic gradient from the humid region in southwest Hungary to the continental-semiarid region in northeast Hungary where neighbouring old and young sessile oak stands were available for pair-wise comparison of height growth. While these young stands developed entirely in the significantly changed atmospheric conditions, the older trees lived only a part of their life time in such changed environment. The Ellenberg quotient (EQ) was used for describing climate aridity. Stand top height in each pair of old and young stands was measured to calculate the relative stand top height using yield tables of sessile oak for Hungary. Additionally, stand densities of old stands were measured. To demonstrate the height growth differences of old and young stands their relative stand top heights were compared as functions of EQ and stand density. Results: The relative top heights of the young stands were significantly higher than of the older stands, which means that the overall growing conditions were better in the last 30-35 years due to atmospheric changes than the mean conditions during the lifetime of old stands. Although extreme drought events associated with climate change caused reduced stand density due to periodic tree mortality at the xeric limit of sessile oak, the synergetic effect of all atmospheric changes was still sufficient enough to accelerate height growth. Conclusions: There has been an acceleration of height growth during the last decades despite the increased frequency of droughts. It cannot be concluded that height growth acceleration will continue in the future since climate models show an increasing tendency of dry extremes in Hungary that may overrule the positive fostering effect of atmospheric changes

The timing of leaf flush in European beech (Fagus sylvatica L.) saplings

Spring phenology is considered one of the most important determinants of growth and survival in young stands. It is relatively easy to monitor and is expected to respond to climate changes that will affect the favourable period for growth in temperate regions. The response of trees to the environmental cues that govern spring phenology is largely under genetic control and inter-populational differences exist within species. This suggests that the trait undergoes site-specific selection. Data obtained through monitoring of bud burst at multiple beech provenance-trials were compared with specific site and weather data to reveal geographical clines in beech phenology. We fitted the Weibull function to harmonise phenology data collected using various flushing scales and at different intensities of monitoring. By comparing data from 20 annual census of phenology performed across 13 sites throughout Europe, we showed that accumulated temperature sum > 5°C modelled the timing and duration of flushing more consistently than other temperature sum models > 0°C or > 8°C, or simply Julian Day. Inconsistency in the number of degree hours required for flushing among sites, reinforced the need for testing of more complex mechanistic models that include photoperiod, chilling period, and summer drought in addition to temperature sum. South-North, East-West, and low-high elevational clines were confirmed from the analysis. These findings; reinforce the need for caution in planting provenances from the south-east of Europe, suited to warmer-drier summers, in more north-westerly sites; and highlight the location of some potentially valuable late-flushing populations that also tolerate warm dry temperatures.Peer reviewe

Erdőtársulások és fafajaik átrendeződési lehetőségei a változó klímában

Kutatásunk sokrétű megközelítést tükröz. Honos fafajaink becsült reakciói alapján elemeztük őshonos fafajú erdőtársulásaink várható átrendeződését. Az elméleti becsléseket összedolgoztuk az újulatra és mortalitásra vonatkozó terepi vizsgálatok eredményeivel. Potenciális, invázióbiológiai szempontból alacsony kockázatú cserefafajokat kerestünk a várhatóan visszaszoruló fafajaink esetleges helyettesítésére. A honos és inváziós fafafajok esetében országos adatokon nyugvó, cserefafajok esetében európai léptékű modellezéssel is becsültük a fajok potenciális és prognosztikus elterjedését. Potenciális természetes erdőtársulás (PTE) adatbázist építettünk fel az ország erdőterületeire az Országos Erdőállomány Adattár alapján, a jelenre és jövőre vonatkozóan egyaránt. Eredményeink alapján az erdő- és erdőssztyep-társulások esetében egyaránt a magas összetételi (elegyesség) és szerkezeti diverzitás (gyepekkel, cserjésekkel mozaikoló állományok) jelenthet nagyobb alkalmazkodóképességet. A kiválasztott tájidegen fafajok alkalmazására csak az új körülmények között is vitális, őshonos taxonok és az általuk alkotott (akár újszerű) társulások által nyújtott lehetőségek kimerülését követően kerülhet sor