Search

Važno je znati kako će klimatske promjene utjecati na pojedine šumske vrste, a pritom je jednako važno istraživati i mjeriti značajke biljaka koje je relativno lako kvantificirati, a koje su snažno povezane s cjelokupnim funkcioniranjem biljke. Iz toga je razloga provedeno istraživanje funkcionalnih značajki lišća na petogodišnjim sadnicama obične bukve (Fagus sylvatica L.) i hrasta kitnjaka (Quercus petraea /Matt./ Liebl.) porijeklom iz dviju provenijencija čija se staništa odlikuju sličnim orografskim i edafskim, a različitim klimatskim značajkama, što je posebno izraženo u količini oborine. Prema tomu, jedna je provenijencija s područja Slavonskoga Broda koja raste na staništu s manjom količinom oborine (suha provenijencija), a druga s područja Karlovca koja uspijeva na staništu s većom količinom oborine (vlažna provenijencija). Na lišću biljaka iz tih provenijencija mjerena je površina lišća (LA), gustoća puči (SD), lisna masa izražena po površini (LMA) i sadržaj suhe tvari u lišću (LDMC). Provedeno istraživanje funkcionalnih značajki lišća potvrdilo je da je hrast kitnjak u odnosu na običnu bukvu bolje prilagođen na sušne stanišne uvjete pa se može pretpostaviti da će pod utjecajem globalnih klimatskih promjena biti kompetitivniji u odnosu na običnu bukvu. Međutim, obična je bukva pokazala veću fenotipsku plastičnost koja joj može omogućiti bolju prilagodbu na buduće suše stanišne uvjete. Nadalje, utvrđeni obrazac diferencijacije sušnije i vlažnije provenijencije, uzimajući u obzir obje vrste, pokazuje njihovu ekotipsku diferencijaciju. Pri razmatranju utjecaja klimatskih promjena na prirodne populacije tih dviju vrsta treba uzeti u obzir njihovu fenotipsku plastičnost, ali i uočenu funkcionalnu ekotipsku diferencijaciju.

The objective was to examine the effects of optimal leaf nitrogen levels > 2.0% and suboptimal levels ˂ 2.0%, nitrogen nutrition on net photosynthetic rate, stem diameter increment, height growth increment and acorn mass of pedunculate oak during 2010 in the absence of drought stress and during 2011 under the impact of moderate drought stress. According to the results, moderate drought stress significantly reduced net photosynthetic rate, stem diameter increment and height growth increment, while acorn mass was not affected. Suboptimal nitrogen nutrition significantly reduced the net photosynthetic rate and stem diameter increment only in the wet year, acorn mass in both wet and dry years, while height growth increment was not significantly reduced by suboptimal nitrogen nutrition in either year. The results indicate that optimal nitrogen levels can stimulate photosynthetic rate and stem diameter increment of pedunculate oak only in the absence of moderate drought stress. Moreover, the results show that moderate drought stress is a more dominant stressor for photosynthesis and growth of pedunculate oak than suboptimal nitrogen nutrition, while for acorn development, it is the more dominant stressor.

U ovome radu prikazani su rezultati rasta bukovih sadnica pod utjecajem suboptimalne ishrane s dušikom (N), fosforom (P), magnezijem (Mg) i željezom (Fe). Cilj rada bio je približiti ovu problematiku šumarskoj praksi kroz raspravu dobivenih rezultata u kontekstu dosadašnjih spoznaja o rastu biljaka pod utjecajem suboptimalne ishrane s mineralnim hranivima. U rano proljeće 2019. godine 30 bukovih jedinki u razvojnom stadiju ponika, porijeklom iz jedne prirodne mješovite sastojine hrasta kitnjaka i obične bukve, presađeno je u sterilni supstrat (agroperlit). Nakon presadnje tijekom sljedeće tri godine po šest presađenih biljaka redovito je zalijevano (tretirano) s kompletnom hranjivom otopinom (KO tretman), odnosno hranivim otopinama u kojima su izostavljeni dušik (-N tretman), fosfor (-P tretman), magnezij (-Mg tretman) ili željezo (-Fe tretman). Prema tomu, na šest biljaka unutar svakog od pet prethodno opisanih tretmana bilježeni su početak i trajanje razvoja lišća (2020. i 2021. godine), broj listova te prosječna i ukupna površina lišća (2019., 2020. i 2021. godina). Promjer stabljike na vratu korijena i visina stabljike mjereni su u proljeće 2019. i jesen 2021. godine, na temelju čega je izračunat debjinski i visinski prirast bukovih sadnica, te njihova vitkost na početku i na kraju pokusa. Uz to, tretiranim sadnicama utvrđena je masa suhe tvari lišća, stabljike i korijenja te ukupna dužina krupnog i sitnog korijenja, kao i broj račvanja i vrhova sitnog korijenja, što je obavljeno u jesen 2021. godine nakon njihova vađenja iz agroperlita. Na temelju usporedbe dobivenih rezultata između biljaka u kontrolnom i ostalim tretmanima bilo je moguće zaključiti da je pod utjecajem suboptimalne ishrane bukovih sadnica s P došlo je do odgode proljetnog otvaranja pupova i početka razvoja lišća. Najsporiji razvoj lišća zabilježen je pod utjecajem suboptimalne ishranjenosti s N i Mg. Prosječna površina lišća nije bila značajnije utjecana suboptimalnom ishranjenošću niti s jednim hranivom. Smanjenje broja listova i njihove ukupne površine pod utjecajem suboptimalne ishranjenosti sa svim hranivima zabilježeno je tek u posljednjoj godini provedbe pokusa. Debljinski i visinski prirast stabljike također su bili negativno utjecani suboptimalnom ishranjenošću sa svim hranivima, a smanjena vitkosti sadnica zabilježena je samo pod utjecajem suboptimalne ishranjenosti s Fe. Ukupna, duljina krupnog i sitnog korijenja također je bila negativno utjecana suboptimalnom ishranjenošću sa svim hranivima, izuzev N. Pod utjecajem suboptimalne ishranjenosti s N došlo je do povećanja ukupne dužine sitnoga korijenja, kao i do povećanja broja račvanja i vrhova sitnog korijenja. Unatoč tomu, na masu suhe tvari krupnog i sitnog korijenja suboptimalna ishranjenost sa svim hranivima imala je negativan utjecaj, uključujući i N.

The few studies dealing with leaf phenological responses to elevated nutrients in forest trees have given ambiguous results, i.e., while some reported delayed leaf-out and autumn leaf senescence, others reported advanced leaf phenology caused by increased nutrition. This study aimed to determine the effects of experimentally increased phosphorus (+P treatment) on the leaf phenologies of two juvenile provenances of common beech and sessile oak. Other objectives were to determine whether there were interspecific differences as well as intraspecific variations. Saplings were excavated in two mixed beech–oak stands and transplanted into four wooden boxes filled with a commercial soil substrate. Phosphorus fertilizer was added to two of the boxes, while the remaining boxes served as controls. Both species responded to +P treatment with advanced autumn leaf senescence in the first year of the experiment. Leaf senescence in common beech began significantly earlier, while in both species, the process was accelerated compared to that in the control. In the second year, the leaf senescence response to +P treatment was even more pronounced in both species. The +P effect on leafing phenology was absent in both common beech provenances and in an oak provenance. However, the other oak provenance showed advanced leafing, indicating the existence of intraspecific differences.

Hrast crnika (Quercus ilex L.) je sredozemna vazdazelena vrsta drveća, koja na svom području pridolaska pokazuje veliku morfološku i funkcionalnu varijabilnost. Cilj ovoga rada bio je utvrditi postoji li diferencijacija hrasta crnike na klimatskom gradijentu istočne obale Jadranskoga mora (opisanom s prosječnom godišnjom količinom oborina, prosječnom količinom oborina tijekom ljetnog perioda i klimatskim deficitom vlage) s obzirom na funkcionalne značajke lišća (opisane sa specifičnom lisnom površinom, indeksom relativnog sadržaja ukupnih klorofila u lišću i stopom neto fotosinteze mjerene u lišću). Specifična lisna površina mjerena je na lišću uzorkovanom u tri provenijencije na prirodnom staništu te lišću uzorkovanom u pokusnom nasadu na mladim biljkama porijeklom iz tih istih provenijencija. U pokusnom nasadu mjeren je i indeks relativnog sadržaja ukupnih klorofila i stopa neto fotosinteze. Provenijencija Pula u odnosu na provenijencije Zadar i Bar ima veću specifičnu lisnu površinu te manji indeks relativnog sadržaja ukupnih klorofila i stopu neto fotosinteze. To potvrđuje prilagodbu provenijencije Pula na vlažnije stanište, a provenijencija Zadar i Bar na suše stanište te ujedno ukazuje na funkcionalnu diferencijaciju provenijencija hrasta crnike na istočnoj obali Jadranskoga mora s obzirom na klimatske prilike. Isti obrazac diferencijacije prema specifičnoj lisnoj površini u prirodnim sastojinama i pokusnom nasadu ukazuje na ekotipsku diferencijaciju istraživanih provenijencija. Prema tomu, hrast crnika mogao bi imati značajnu mogućnost funkcionalne prilagodbe na promijenjene klimatske uvjete., Holm oak (Quercus ilex L.) is an evergreen tree species with natural distribution within the Mediterranean, from Portugal and Morocco on the west to the western coast of Turkey on the east part of its range. On the eastern coast of the Adriatic Sea, it occupies warmer localities on the coast of Istria and northern Adriatic islands while on the southern Adriatic islands as well as on the narrower coastal area south of Zadar it has a more continuous distribution. Given the size of the area of distribution, holm oak shows a big morphological and functional variability so certain populations differ according to the climate conditions in their area. This fact has been very well researched in the western and central part of its range, while the data for the eastern part, and thus for the eastern coast of the Adriatic Sea, are scarce. The great morphological and functional variability of holm oak reflects its great phenotypic plasticity. Although phenotypic plasticity is conditioned by the environment, it can also have a genetic basis through local adaptation to the established environmental conditions in different parts of the species’ area of distribution. The aim of this study was to determine whether there is a differentiation of holm oak down the climatic gradient of the eastern Adriatic coast with respect to the functional characteristics of its leaves.The research was conducted on three provenances of holm oak from the area of ​​Pula and Zadar in the Republic of Croatia and Bar in Montenegro. During the winter of 2019, 12 leaves were sampled per 12 trees in each provenance in order to determine the specific leaf area (SLA). Additionally, acorns were collected beneath those trees with which an greenhouse experiment was established. In the experiment, a total of 64 plants were grown, of which 22 plants from the provenances of Pula and Zadar, and 20 plants from the provenance of Bar. In the second part of the vegetation period in 2020, one leaf was sampled from each plant with the aim of determining the specific leaf area (SLA). In addition, the rate of net photosynthesis (A) and the relative total chlorophyll content index (CCI) were measured in the greenhouse experiment. Measurements were performed in July and September of 2020. A was measured using a portable gas exchange measuring device LCpro + (ADC BioScentific, 2007), while the CCI was measured using the CCM-200 (Opti-Sciences, Tyngsboro, MA).Analysis of the variance revealed a statistically significant difference among the studied provenances for most of the measured characteristics both on the leaves sampled in the natural habitat and on the young plants in the experimental plantation. Previous research on holm oak indicates that there is a functional differentiation of provenances on different climatic gradients in the central and western Mediterranean, with our results confirming this on the eastern coast of the Adriatic Sea. Young plants in the experimental plantation retain the same pattern of differentiation with respect to SLA as their mother trees in natural stands (Figure 1c). Such a result indicates that the differentiation of holm oak provenances is at least partly the result of genetic adaptation to local habitat conditions, i.e. that the holm oak on the eastern Adriatic coast as well as in other parts of its range could distinguish ecotypes. The sclerophilicity of the leaves described by SLA (Figure 1c) does not coincide with the average annual rainfall (Figure 1a), but with the amount of precipitation in the summer (Figure 1b) and the climate deficit of moisture (Figure 2a). The established pattern of provenance differentiation with respect to SLA and climatic conditions is followed by A measured on young plants in the experimental plantation. Therefore, Pula, which has the highest SLA and comes in the least arid climatic conditions, has the lowest A, while Zadar, which has the lowest SLA and comes in the most arid conditions, shows the highest values of A (Figures 1 and 2). This is in line with the literature that shows that the intensity of photosynthesis per unit leaf area in holm oak decreases with increasing SLA (Niinemets 2015, Peguero-Pina et al. 2017). Namely, the anatomical structure of holm oak leaves is adapted in such a way that those leaves that have a lower SLA also have better conductivity of CO2 through the mesophilic leaves and contain more nitrogen per unit area. Accordingly, the provenances of Zadar and Bar compared to the provenance of Pula had a lower SLA (Figure 1c) and a higher CCI (Figure 2b) which has a positive correlation with the nitrogen content in the leaves.Holm oak could have a significant ability to functionally adapt to different climatic conditions. Accordingly, when considering the impact of climate change on natural populations of holm oak, its phenotypic plasticity should be considered, as well as the observed functional ecotypic differentiation.

The Žumberak and Samobor highlands are situated in the north-western part of Croatia where the characteristics of the Dinarides, the Alps and the Pannonian Plain meet. The greater part of the area is occupied by beech forests. The aim of the study was to determine the syntaxonomic affiliation of these forest communities, and to explore their floristic and main ecological features. Numerical analyses of floristic compositions were conducted on a data-set consisting of 144 new relevés and 99 relevés from the existing literature. Relevés were made following the standard Braun-Blanquet method. For descriptions of ecological conditions Ellenberg’s indicator values were used. Six plant associations and two subassociations of beech forests were established in Luzulo-Fagion and Aremonio-Fagion alliances. The higher altitudes of the studied area are occupied by ass. Cardamini savensi-Fagetum, whereas the lower altitudes are occupied by ass. Lamio orvalae-Fagetum and Hacquetio-Fagetum. Ass. Hacquetio-Fagetum spreads on southern slopes and ridges, whereas ass. Lamio orvalae-Fagetum occurs in ditches and on northern slopes. In the warmer habitats with shallow soils on a dolomite base ass. Ostryo-Fagetum occurred. A small part of the area is characterized by silicate substrate which is occupied by ass. Luzulo-Fagetum and Gentiano asclepiadeae-Fagetum.

Coarse woody debris (CWD), aside its contribution to forest ecosystem productivity and biodiversity, has a significant role in nutrient cycling and carbon storage. Still, CWD chemical features, as well as its density, are less studied in comparison to other plant traits. This is evident from the statistics of the most recent version 5 of TRY Plant Trait Database where CWD traits are underrepresented. Nevertheless, also due to the carbon (C) accounting requirements under UNFCCC and EU regulations, where dead wood (DW) is recognized as one of five mandatory C pools in forest ecosystems, interest in CWD has been increasing. The aim of this research was to provide national DW biomass conversion factors, i.e. dead wood densities (DWD) and C concentrations, which can be used for reporting on C stocks in DW pool. We hypothesize that there are differences in DW biomass conversion factors with respect to tree species group (ring-porous, diffuse-porous, non-porous) and biogeographical region. Additionally, we explored the content of N, K, Ca, P, Mg mineral macronutrients in CWD of different decay classes and tree species. The research was conducted on ten forest tree species that represent main forest ecosystems in Croatia located in three biogeographical regions, i.e. Continental, Alpine and Mediterranean. In the field, stem discs were sampled from lying CWD, with diameter between 5 and 30 cm, that was categorized into five decay classes, from 0 (raw wood) to 4 (very decayed dead wood). In total, we collected 446 CWD samples evenly distributed between tree species and decay classes. All samples were analysed for density, C and N content, with selected 165 samples analysed further on K, Ca, P, Mg content. Overall, DWD, as expected, showed decreasing trend with respect to decay class, while for C, N and mineral macronutrients no trend regarding decay classes was observed. For each tree species group, DWDs by decay classes were compared between different biogeographical regions. In ring-porous species a significant difference was observed in DWD between samples collected in Continental and Mediterranean biogeographical region for decay classes 0-2, while in non-porous species DWD between samples collected in Alpine and Mediterranean biogeographical region were significantly different for decay classes 2-4. Results on C, N and mineral macronutrients were were compared with those published in TRY database and other available sources.

Cilj ovoga rada bio je usporediti dvije mješovite sastojine (provenijencije) obične bukve i hrasta kitnjaka, iz istočne (provenijencija Slavonski Brod - SB) i sjeverozapadne (provenijencija Karlovac - KA) Hrvatske, s obzirom na klimatske i edafske prilike te raspraviti njihov utjecaj na rast i produkciju suhe tvari prirodnog pomlatka hrasta kitnjaka i obične bukve u kontekstu njegove funkcionalne prilagodbe na prethodno spomenute stanišne prilike. Glavna razlika između provenijencija s obzirom na klimatske prilike ogleda se u prosječno većoj količini oborina na području provenijencije KA. Unatoč tomu, zbog nepovoljnog rasporeda oborina za vrijeme rasta i razvoja istraživanog pomlatka u razdoblju 2016. – 2020. godine područje provenijencije KA odlikovalo se učestalijom pojavom sušnih perioda nego područje provenijencije SB. S obzirom na edafske prilike (fizikalne i kemijske značajke tla) provenijencije se nisu značajnije razlikovale. Međutim, tlo provenijencije KA odlikovalo se nešto lakšom strukturom (manje gline i više skeleta) u odnosu na tlo provenijencije SB. Razlike između provenijencija i vrsta s obzirom na cijeli niz mjerenih parametara koji opisuju rast i produkciju suhe tvari istraživanog pomlatka uključujući i njihove alometrijske odnose ispitan je pomoću dvofaktorske ANOVA-e. Dobiveni rezultati ukazuju da je pomladak iz provenijencije KA ulagao više suhe tvari u rast i razvoj korijenja s posebnim naglaskom na sitno korijenje i pri tom se dublje zakorjenjivao te razvijao deblju i nižu stabljiku nego pomladak iz provenijencije SB. To ukazuje da je pomladak iz provenjencije KA funkcionalno prilagođeniji sušem staništu. Takav rezultat mogao bi biti posljedica različito ispoljene fenotipske modifikacije (reakcije na sušu) i/ili stvarnih genetskih razlika između provenijencija, što ovom prilikom nije bilo moguće točnije razlučiti. Dobivene razlike u rastu i produkciji suhe tvari između kitnjakova i bukova pomlatka odgovaraju već otprije poznatom načinu njihove funkcionalne prilagodbe na vlažnost, odnosno suhoću staništa. To znači da se kitnjakov pomladak dublje zakorjenjivao i pri tom je više suhe tvari ulagao u rast krupnog korijenja u odnosu na bukov pomladak koji se pliće zakorjenjivao i pri tom više suhe tvari ulagao u rast sitnog korijenja., The aim of this study was to examine the influence of climatic and edaphic conditions in two mixed stands (provenances) of common beech and sessile oak from eastern (Slavonski Brod - SB provenence) and northwestern (Karlovac - KA provenence) Croatia on the functional adaptation of growth and dry matter production of their natural saplings. The main differences between the provenances with regard to climatic conditions is reflected in the amount of precipitation. The amount of precipitation in the area of ​​KA provenance is much higher than in the area of ​​SB provenance (Table 1 and 2). In spite of, due to the unfavorable distribution of precipitation during the growth of the investigated saplings in the period 2016 – 2020, dry periods were more frequent in the KA provenance than in the SB provenance (Figure 1). Edaphic conditions (physical and chemical soil traits), did not significantly differ between the provenances. However, the soil of KA provenance was characterized by a slightly lighter structure (less clay and more skeletons) compared to the soil of SB provenance (Table 3 – 5 and Figure 2). Differences in growth and dry matter production, as well as in allometric growth relations between provenances and species were examined using two-way ANOVA. The obtained results indicate that the saplings from the KA provenance compared to the saplings from the SB provenance invested more dry matter in root growth (especially fine roots) and took root deeper. In addition, the saplings from the KA provenance developed a thicker and lower stem compared to the saplings from the SB provenance (Table 6 – 8). This indicates that the saplings from the KA provenance are functionally more adapted to the drought habitat. It could be the result of differently manifested phenotypic modification (drought response) and/or real genetic differences between provenances, which our research could not distinguish more accurately. The obtained differences in the growth and dry matter production between the sessile oak and the common beech saplings correspond to the already known patterns of their functional adaptation to the habitat humidity. It means that sessile oak saplings took deeper roots and invested more dry matter in the coarse roots compared to common beech saplings that took root more shallowly and invested more dry matter in the fine roots (Table 9).

U ovom radu prikazani su rezultati izmjere parametara koji opisuju fotosintetsku aktivnost bukovih klijanaca pod utjecajem suboptimalne ishranjenosti s mineralnim hranivima. Cilj rada bio je približiti ovu problematiku šumarskoj praksi kroz raspravu dobivenih rezultata u kontekstu dosadašnjih spoznaja o utjecaju mineralne ishrane na fotosintetski proces šumskoga drveća. U rano proljeće 2019. godine bukovi klijanci porijeklom iz jedne prirodne mješovite sastojine hrasta kitnjaka i obične bukve presađeni su u sterilni supstrat (agroperlit). Nakon presadnje redovito su zalijevani (tretirani) kompletnom hranivom otopinom (KO tretman), odnosno hranivim otopinama u kojima su izostavljeni dušik (–N tretman), fosfor (–P tretman), magnezij (–Mg tretman) ili željezo (–Fe tretman). Na šest klijanaca unutar svakog od pet prethodno opisanih tretmana tijekom vegetacijskog razdoblja 2019. godine redovito su mjereni sljedeći parametri: stopa fotosinteze (A), provodljivost puči (gs), intercelularna koncentracija CO2 (ci), indeks relativnog sadržaja klorofila u lišću (CCI) te indeks fotosintetske učinkovitosti (PIABS). Svi parametri bili su lošiji kod klijanaca iz –N, –P i –Mg tretmana u odnosu na klijance iz KO tretmana. Takav rezultat vjerojatno proizlazi iz fizioloških funkcija N, P i Mg koji sudjeluju u građi proteina i enzima, prometu i skladištenju energije te građi klorofila, što je sve skupa neophodno za uredno funkcioniranje cjelokupnog fotosintetskog procesa. Unatoč važnoj ulozi Fe u gotovo svim životnim procesima biljaka pa tako i fotosintezi svi mjereni parametri kod klijanaca iz –Fe i KO tretmana bili su podjednaki. Međutim, za razliku od N, P i Mg koji pripadaju skupini makrohraniva, Fe pripada skupini mikrohraniva, čije su koncentracije u biljnom tkivu relativno niske. Prema tome, moguće je pretpostaviti da su istraživani klijanci iz tla prirodne sastojine i/ili iz rezervi u sjemenu tijekom početne faze svoga razvoja uspjeli usvojiti i/ili mobilizirati dovoljnu količinu Fe koja im je bila dostatna za normalno funkcioniranje tijekom cijelog vegetacijskog razdoblja, bez obzira na kasniju primjenu tretmana. S obzirom na ovakav rezultat, inicijalno praćenje parametara fotosintetske aktivnosti bit će nastavljeno tijekom sljedećih nekoliko vegetacijskih razdoblja. U tom periodu planira se započeti s praćenjem dinamike vegetativnoga rasta, fenologije listanja i razvoja vizualnih simptoma pri suboptimalnoj ishranjenosti obične bukve s mineralnim hranivima s ciljem dodatnog približavanja ove problematike šumarskoj praksi.

Kroz dugo vremensko razdoblje, aromatično, ljekovito, kao i začinsko bilje pronalazi svoju primjenu u različite svrhe. U novije vrijeme, kada raste svijest i potreba o sve većoj integraciji prirodnog okruženja u urbanoj sredini (biofilni dizajn), sve je aktualnije uređenje unutarnjih i vanjskih zelenih prostora s terapijskom i rehabilitacijskom namjenom. Aromatična i druga svojstva takvih biljaka potencijalnom prostoru dodaju novi aspekt (uz onaj dekorativni) u vidu jačanja motoričkih, senzoričkih, kognitivnih te socijalnih potencijala osjetljivih skupina posjetitelja, čime doprinose njihovom skladnijem životu i zdravlju. Specifičnim mirisima, raznolikošću oblika, struktura, boja i listova, ove biljke omogućuju višeosjetilni doživljaj uređenog prostora. S obzirom na svoje biološke značajke i ekološke zahtjeve, iziskuju različite stupnjeve njege i održavanja te ih u tom pogledu treba promišljeno odabrati i uklopiti u prostor koji se uređuje kako bi kontinuirano održavale svoju namjenu, kako u estetskom, tako i u terapijskom smislu, pružajući potpuni učinak za osjetila posjetitelja.

U radu je predstavljena nedestruktivna procjena koncentracije fotosintetskih pigmenata (ukupnih klorofila i karotenoida) u lišću hrasta lužnjaka pomoću prijenosnog optičkog klorofilmetra CCM-200. Istraživanje je provedeno 2015. godine na biljnom materijalu izloženom različitim tretmanima vlažnosti tla. U kontrolnom tertmanu sadržaj vlage u tlu održavan je iznad poljskog vodnog kapaciteta, dok je u sušnom tretmanu biljkama voda bila uskraćena 112 dana (1. 4. – 21. 7.). U drugom dijelu vegetacijskog razdoblja (22. 7. – 22. 10.) u oba tretmana vlaga tla održavana je iznad poljskog vodnog kapaciteta. Na temelju lišća uzorkovanoga istovremeno u oba tretmana i to sredinom jeseni (27. 10.) izrađene su kalibracijske jednadžbe koje opisuju odnos indeksa relativnog sadržaja klorofila izmjerenoga pomoću klorofilmetra i stvarne koncentracije fotosintetskih pigmenata (utvrđene laboratorijski) pred sam kraj vegetacijskog razdoblja. Jednadžbe su konstruirane posebno za kontrolni, a posebno za sušni tretman. S obzirom na takav dizajn pokusa i vrijeme uzorkovanja, primarni cilj rada bio je ispitati utjecaj dugotrajnog sušnog razdoblja na homogenost parametara kalibracijskih jednadžbi (Y-odsječaka i nagiba pravaca). Na temelju dobivenih rezultata zaključeno je da parametri kalibracijskih jednadžbi nisu bili utjecani sušnim tretmanom. Prema tome, rezultati istraživanja ukazuju na to da klorofilmetar CCM-200, uz primjenu odgovarjućih kalibracijskih jednadžbi, predstavlja pouzdan alat za nedestruktivnu procjenu koncentracije ukupnih klorofila i karotenoida u lišću hrasta lužnjaka, bez obzira na različite režime vlažnosti tla kojima je biljni materijal bio izložen tijekom vegetacijskog razdoblja. Uz to, u radu je utvrđeno da bi preciznost procjene stvarne koncentracije fotosintetskih pigmenata bilo moguće i dodatno poboljšati korekcijom klorofilnog indeksa sa specifičnom lisnom masom., The concentration of photosynthetic pigments (chlorophylls and carotenoids) in leaves of forest trees is a good indicator of the photosynthetic efficiency, level of nutrition with nitrogen and autumn leaf senescence. Thus the photosynthetic pigment concentrations is one of the most significant parameters related to the physiological status of plant. Change in pigment concentrations of leaves indicate presence of environmental stress. Well-timed detection of environmental stress play a crucial role in preventing damage on seedlings and saplings in forest nurseries and wood mass production in forest cultures and plantations. Traditional methods for determining the concentrations of photosynthetic pigments represent an obstacle to continuous monitoring concentrations of photosynthetic pigment in leaves of forest trees, primarily because they are relatively expensive, long lasting and require destruction of plant material. However, portable optical chlorophyll meters such as CCM-200 (Opti-Sciences, Tyngsboro, Massachusetts, USA) and SPAD-502 (Minolta Camera Co., Osaka, Japan) is a reliable alternative to traditional laboratory methods. To use chlorophyll meters as a tool for estimating photosynthetic pigment concentrations in leaves, it is necessary to construct regression equations (calibration equations) that reliably describe the relationships between the relative index of the total chlorophyll content in leaves (CCI) and the total pigment concentrations in leaves, determined by standard laboratory methods. In the present study, we set up experiment to establish the ability of the hand-held CCM-200 chlorophyll meter to accurately estimate the content of the photosynthetic pigments in leaves of Quercus robur L. with contrast level of soil moisture. The objectives of the present work were: (i) determine whether the long-lasting drought period significantly influences the relationship between the CCI obtined by CCM-200 and the concentration of photosynthetic pigments (total chlorophyll and carotenoid); (ii) construct calibration equations for non-destructive estimation of photosynthetic pigments in Q. robur leaves; (iii) to analyse the improvement estimation of photosynthetic pigments concentration when CCI was corrected with specific leaf mass. The research was carried out during the year 2015 on 60 two-years old plants grown in the greenhouse located in the Croatian Forestry Institute Jastrebarsko. Plant material was grown in 50 liter containers previously filled with soil originating from a natural oak stand. In the spring of the 2015, at the beginning of the study the mean height of investigated plants was 23.9 ± 4.8 cm. During the study, plant material was exposure to different level of soil moisture. In control treatment soil water content was kept above field capacity, while in drought treatment plants were exposed to water reduction during 112 days (1st of April – 21st of July). In second part of growing season (22nd of July – 22nd of October) in both treatments soil water content was kept above field capacity (Figure 1). Calibration equations, that describe relationship between relative chlorophyll content index measured with chlorophyll meter and actual photosynthetic pigment concentrations in sampled leaves (laboratory determined) at the end of growing season (27th of October), were constructed for both treatments (Table 2 and 3; Figure 4 and 5). Obtined results show that parameters of calibration equations were not affected by drought treatment (Table 4). Therefore, when using appropriate calibration equations, clorophyll meter CCM-200 can be considered as reliable tool for non-destructive estimation of total chlorophylls and carotenoids in Q. robur leaves, regardless of different soil water regimes during the growing season. Additionaly, this research confirmed that it is possible to improve the estimation of actual photosynthetic pigment concentration by using chlorophyll content index corrected with specific leaf mass (Table 2 and 3; Figure 4 and 5).

Research on drought impact on tree functioning is focussed primarily on water and carbon (C) dynamics. Changes in nutrient uptake might also affect tree performance under drought and there is a need to explore underlying mechanisms. We investigated effects of drought on (a) in situ nitrogen (N) uptake, accounting for both, N availability to fine roots in soil and actual N uptake, (b) physiological N uptake capacity of roots and (c) the availability of new assimilates to fine roots influencing the N uptake capacity using 15N and 13C labelling. We assessed saplings of six different tree species (Acer pseudoplatanus L., Fagus sylvatica L., Quercus petraea (Mattuschka) Liebl., Abies alba Mill., Picea abies (L.) H.Karst. and Pinus sylvestris L.). Drought resulted in significant reduction of in situ soil N uptake in deciduous trees accompanied by reduced C allocation to roots and by a reduction in root biomass available for N uptake. Although physiological root N uptake capacity was not affected by drought in deciduous saplings, reduced maximum ammonium but not nitrate uptake was observed for A. alba and P. abies. Our results indicate that drought has species-specific effects on N uptake. Even water limitations of only 5 weeks as assessed here can decrease whole-plant inorganic N uptake, independent of whether the physiological N uptake capacity is affected or not.

24th International Conference on Computing in High Energy and Nuclear Physics, CHEP 2019, Adelaide, Australia, 4 Nov 2019 - 8 Nov 2019; The European physical journal / Web of Conferences 245, 07003 (2020). doi:10.1051/epjconf/202024507003, Within WLCG, the DESY site in Hamburg is one of the largest Tier-2 sites with about 18500 CPU cores for Grid workloads. Additionally, about 8000 CPU cores are available for interactive user analyses in the National Analysis Factory [NAF]. After migrating these two batch systems onto a common HTCondor based set-up during the previous four years, we recapitulate the lessons learned during the transition especially since both use cases differ in their workloads. For Grid jobs start-up latencies are negligible and the primary focus is on an optimal utilization of the resources. Complementary, users of the NAF expect a high responsiveness of the batch system as well as the storage for interactive analyses. In this document, we will also give an outlook to future developments and concepts for the DESY high-throughput computing. In the ongoing evolution of the HTC batch system, we are exploring how to integrate anonymous jobs with the batch system as back-end for Function-as-a-Service workflows as well as an option for dynamic expansions to remote computing resources., Published by EDP Sciences, Les Ulis

U radu je istražen potencijal prijenosnog optičkog klorofilmetra CCM-200 (Opti-Sciences, Tyngsboro, MA, USA) u svrhu utvrđivanja stanja ishrane hrasta lužnjaka s dušikom na temelju uzorkovanja različitih tipovia lišća (lišće proljetnih i sekundarnih izbojaka). Istraživanje je provedeno na 30 biljaka uzgajanih u pokusnom nasadu tijekom dva vegetacijska razdoblja (2009. i 2010. godine). Meteorološke prilike i gnojidbeni tretman koji je bio proveden u rano proljeće 2009. godine uvjetovali su razlike između istraživanih godina s obzirom na razvoj izbojaka tijekom tercijarnoga porasta (što predstavlja potencijalni pokretač translokacije dušika u krošnjama istraživanih biljaka). Na temelju lišća proljetnih i sekundarnih izbojaka, uzorkovanoga u srpnju i rujnu 2009. i 2010. godine konstruirano je ukupno osam kalibracijskih jednadžbi. Te jednadžbe pouzdano opisuju (p < 0,001) odnos između klorofilnoga indeksa izmjerenoga pomoću klorofilmetra i koncentracije ukupnoga dušika u lišću proljetnih i skundarnih izbojaka s obzirom na vrijeme uzorkovanja. Pomoću ANCOVA-e ispitan je utjecaj tipa uzorkovanoga lišća na homogenost parametara kalibracijskih jednadžbi (Y-odsječaka i nagiba pravaca) s obzirom na vrijeme uzorkovanja. Tip lišća nije značajno utjecao na nagibe pravaca, ali značajno je utjecao na njihove Y-odsječke u tri od ukupno četiri promatrana vremena uzorkovanja. Homogenost parametara kalibracijskih jednadžbi konstruiranih na temelju različitih tipova lišća utvrđena je samo u rujnu 2009. godine, kada je pod utjecajem produkcije tercijarnih izbojaka došlo do izjednačenja koncentracije ukupnoga dušika u oba tipa uzorkovanoga lišća. Prema tomu, jednom konstruiranu kalibracijsku jednadžbu nije moguće istovremeno koristiti za preciznu procjenu ukupne koncentracije dušika u različitim tipovima lišća. Takav rezultat dovodi u pitanje praktičnost i pouzdanost procjene stanja ishrane hrasta lužnjaka s dušikom pomoću klorofilmetra CCM-200., In this paper we investigated potential of portable chlorophyll meter CCM-200 (Opti-Sciences, Tyngsboro, MA, USA) to estimate total nitrogen concentration in different types of Pedunculate oak leaves. Research was conducted on 30 plants grown in field trial, during two vegetation periods (in years 2009 and 2010). Fertilization treatment (carried out in early spring in 2009) and meteorological conditions caused differences between investigated years regarding third-flush shoots (that can be considered as potential trigger for translocation of nitrogen in leaves and branches of investigated plants). Eight calibration curves was constructed based on spring and second-flush leaves, sampled in July and September in 2009 and 2010. These equations shown to be are reliable (p < 0,001) in describing relationship between chlorophyll content index, measured with chlorophyll meter, and total nitrogen concentration in spring and second-flush leaves, regarding moments of sampling (July and September 2009 and 2010). Influence of leaf flush type on homogeneity of equation parameters (i.e. slope and intercept), regarding moment of sampling, was tested using ANCOVA. Leaf flush type (spring or second-flush) did not have significant influence on slope, but did influenced intercepts in three moments of sampling (July 2009, and July and September 2010). Homogeneity of equation parameters was observed only for one moment of sampling, e.g. September in 2009, when third-flush shoots occurred which resulted in levelling of total nitrogen concentration in sampled leaves.

Research highlights: The susceptibility of oaks to late spring and early autumn frosts is directly related to their leaf phenology. Drought may alter the leaf phenology and therefore frost tolerance of oaks. However, the effects of drought on oak leaf phenology and frost resistance have not been thoroughly studied. Background and objectives: One of the consequences of climate change is an increase in the frequency of dry episodes during the vegetation period. Pedunculate oak (Quercus robur L.) is an economically and ecologically important forest tree species that prefers humid habitats. Therefore, knowledge of the impact of drought on this species is of great importance for the adaptation of forestry strategies and practices to altered environmental conditions. The aim of this study was to determine the impact of drought on leaf phenology and spring frost susceptibility in nine provenances. Materials and methods: One-year-old saplings originating from nine European provenances were used in the trial. The saplings were exposed to experimental drought and then re-watered in two subsequent years. Spring and autumn leaf phenology were scored. The trial was impacted by a late spring frost in the third year, and the resulting leaf frost injury was scored. The effects of drought treatment on the phenology and frost susceptibility of plants from the provenances were analysed. Results: Leaf phenology of plants from most of the studied provenances was significantly influenced by the drought treatment (p &lt, 0.001). Drought induced a carry-over effect on flushing phenology, which was observed as delayed bud burst (from 0.6 to 2.4 days) in the second year and as advanced bud burst (from 0.1 to 6.3 days) in the third year. Therefore, opposite shifts in flushing phenology may be induced as a result of differences in the time span when plants sense water deficits. In contrast to flushing, autumn leaf phenology was unambiguously delayed following the drought treatments for all studied provenances (from 2.1 to 25.8 days). Differences in late frost susceptibility were predominantly caused by among-provenance differences in flushing phenology. However, the drought treatment significantly increased frost susceptibility in the plants (the rate of frost-injured plants per provenance increased from 3% to 78%). This higher susceptibility to spring frost was most likely caused by the advanced flushing phenology that resulted from the drought treatment in the previous year.

A major environmental pollution problem is the release into the atmosphere of particulate matter, including nanoparticles (NPs), which causes serious hazards to human and ecosystem health, particularly in urban areas. However, knowledge about the uptake, translocation and accumulation of NPs in plant tissues is almost completely lacking. The uptake of silver nanoparticles (Ag-NPs) and their transport and accumulation in the leaves, stems and roots of three different tree species, downy oak (Quercus pubescens Willd.), Scots pine (Pinus sylvestris L.) and black poplar (Populus nigra L.), were assessed. In the experiment, Ag-NPs were supplied separately to the leaves (via spraying, the foliar treatment) and roots (via watering, the root treatment) of the three species. Uptake, transport and accumulation of Ag were investigated through spectroscopy. The concentration of Ag in the stem was higher in the foliar than in the root treatment, and in poplar more than in oak and pine. Foliar treatment with Ag-NPs reduced aboveground biomass and stem length in poplars, but not in oaks or pines. Species-specific signals of oxidative stress were observed; foliar treatment of oak caused the accumulation of H2O2 in leaves, and both foliar and root treatments of poplar led to increased O2− in leaves. Ag-NPs affected leaf and root bacteria and fungi; in the case of leaves, foliar treatment reduced bacterial populations in oak and poplar and fungi populations in pine, and in the case of roots, root treatment reduced bacteria and increased fungi in poplar. Species-specific mechanisms of interaction, transport, allocation and storage of NPs in trees were found. We demonstrated definitively that NPs enter into the tree stem through leaves faster than through roots in all of the investigated tree species.

Decomposition is an important carbon flux that must be accounted for in estimates of forest ecosystem carbon balance. Aim of this research is to provide estimate of fine woody debris decomposition rates for different tree species and sample sizes also taking into account the influence of specific microsite meteorological conditions on decomposition rates. In this paper we present results of the first two years of the experiment designed to last six years. Study was conducted in managed lowland oak forest in central Croatia. Decomposition rates (k) of fine woody debris (diameter 0.5–7 cm) for four species (Querus robur L., Carpinus betulus L., Alnus glutinosa Gaernt., Fraxinus angustifolia L.) in four size classes were estimated using litter bag method and mass loss equation of Olson (1963). Overall average k in our study was 0.182 ± 0.011 year–1. Results indicate that decomposition rate is affected by the size of the debris, with the smallest diameter branches (

The forests in the Spačva Basin are a complex of lowland forests in the region of Slavonia (eastern Croatia). The present state of the forests is strongly influenced by intensive exploitation and hydro-ameliorative activities carried out in the past. The aim of this study was to consider the extent of changes in species composition, and the extent of environmental changes in forest communities of the Spačva Basin in relation to research conducted between 1969 and 1971. The species composition of four communities (Carpino betuli- Quercetum roboris, Genisto elatae- Quercetum roboris aceretosum tatarici, and caricetosum remotae, and Leucojo-Fraxinetum angustifoliae) is studied by comparing 41 old and 57 new relevés. Changes were estimated using ordinations (RDA, CCA, DCA) and changes in species frequency and cover. A general trend of moisture reduction was noticeable among all communities. All vegetation types are becoming floristically more similar. An increase in frequency and cover of flood intolerant woody species (such as Carpinus betulus, Cornus sanguinea, Tilia tomentosa, and Acer tataricum) as well as a decrease of vernal species related to wet habitats are particularly evident. The succession of all studied communities is resulting in loss of the mosaic community pattern characteristic of lowland alluvial forests.

Climate projections predict higher precipitation variability with more frequent dry extremes(1). CO2 assimilation of forests decreases during drought, either by stomatal closure(2) or by direct environmental control of sink tissue activities(3). Ultimately, drought effects on forests depend on the ability of forests to recover, but the mechanisms controlling ecosystem resilience are uncertain(4). Here, we have investigated the effects of drought and drought release on the carbon balances in beech trees by combining CO2 flux measurements, metabolomics and (13)CO2 pulse labelling. During drought, net photosynthesis (AN), soil respiration (RS) and the allocation of recent assimilates below ground were reduced. Carbohydrates accumulated in metabolically resting roots but not in leaves, indicating sink control of the tree carbon balance. After drought release, RS recovered faster than AN and CO2 fluxes exceeded those in continuously watered trees for months. This stimulation was related to greater assimilate allocation to and metabolization in the rhizosphere. These findings show that trees prioritize the investment of assimilates below ground, probably to regain root functions after drought. We propose that root restoration plays a key role in ecosystem resilience to drought, in that the increased sink activity controls the recovery of carbon balances.

The paper deals with the impact of meteorological conditions on in vitro pollen germination and pollen tube growth during the initial phases of male flowers development of pedunculate oak. Phenological observations of male flowers and pollen sampling were performed on the field trial established with grafted pedunculate oak clones. During the investigation, weather conditions (absolute minimum and maximum daily air temperature, minimum absolute relative humidity of air and amount of precipitation) were recorded by an automatic meteorological station installed at the field trial. Influence of meteorological conditions on pollen germination and pollen tube growth was studied in the following stages of male flower: (i) during the last ten days of flower buds dormancy, (ii) during their swelling, (iii) during the bud burst and beginning of male catkins elongation, (iv) during the final stage of male catkins elongation. Pollen germination after incubation times of 2, 4, 6 and 24 hours ranged from 0, 0 to 8, 9 % ; from 0, 0 to 55, 6 % ; from 0, 0 to 59, 3 % and from 5, 9 to 90, 7 %, respectively. Pollen tube lengths after the same incubation times ranged from 15, 3 to 45, 0 μm, from 17, 0 to 88, 3 μm, from 20, 9 to 101, 9 μm and from 39, 9 to 241, 1 μm, respectively. High temperatures and low relative air humidity during the bud burst and beginning of male catkins elongation reduced pollen germination and pollen tube growth. Weather conditions did not significantly affected pollen germination and pollen tube growth during the swelling of flower buds, as well as in the final stage of male catkins elongation.

Trees experience frequent periods of severe drought during their long lives and must therefore be able to recover and compensate for the limitations of previous stresses. In this study, the response of photosynthesis to a severe, long-lasting summer drought and drought release was followed in saplings of a mesic and xeric provenance of European beech transplanted to mesocosms with experimentally controlled water supply. Photosynthesis was assessed in stressed and non-stressed saplings over the course of an entire vegetation season. The drought response was divided into three phases: (1) limitation, (2) recovery and (3) post-drought stimulation. Limitation of photosynthesis developed gradually and caused, in both provenances, a major loss of cumulated photosynthetic activity. It was accompanied by impaired PSII photochemistry indicating severe stress. Recovery started rapidly after re-watering and was fully accomplished within 20 and 10 days in the mesic and xeric provenances, respectively. After recovery, photosynthesis remained at high levels while decreasing in control trees. This post-drought stimulation was sustained until the end of the vegetation period, partly counterbalancing the previous loss of photosynthetic activity. It was attributable to an altered leaf ontogeny as indicated by a delay of autumnal leaf senescence. These observed responses might be important factors when modelling seasonal carbon uptake and phenology of forest ecosystem under future climate change.

Kontinentalni suhi travnjaci na području Papuka su biološki i krajobrazno vrlo vrijedna staništa i ubrajaju se među najugroženije tipove vegetacije kako u našoj zemlji tako i u drugim dijelovima Europe. Osim što se odlikuju velikom bioraznolikošću, na njima rastu i brojne rijetke i ugrožene vrste, poput kaćuna (Orchis spp., Ophrys spp.), karanfila (Dianthus spp.) i dr. Njihove su se površine, zbog izostanka tradicionalnog načina gospodarenja (ispaše i košnje) u posljednjih pedesetak godina značajno smanjile, a nalaze se u stalnoj dinamici i pod prijetnjom od nestanka uslijed progresivne sukcesije vegetacije. Stoga ovo istraživanje ima svrhu prikupiti nove i upotpuniti postojeće spoznaje o takvim staništima, kako bi se spriječio njihov daljnji nestanak i gubitak rijetkih i zaštićenih svojti koje rastu na njima. Istraživanje je provedeno tijekom 2011. godine na južnim broncima Papuka, uz samu granicu Parka prirode Papuk pri čemu je utvrđeno ukupno 240 svojti vaskularne flore iz 143 roda i 52 porodice. Zabilježeno je 29 novih svojti za ovo područje. Najzastupljenija je porodica mahunarki (Fabaceae), a od životnih oblika dominiraju hemikriptofiti. Visok udio fanerofita ukazuje na uznapredovale procese prirodne sukcesije. Prema analizi flornih elemenata, na suhim travnjacima dominiraju biljke euroazijskog flornog elementa, što u biogeografskom pogledu potvrđuje pripadnost istraživanog područja eurosibirsko-sjevernoameričkoj regiji. Zabilježene su i dvije ugrožene (EN), šest osjetljivih (VU) i 15 strogo zaštićenih vrsta (ZZ), što ukazuje na osobitu vrijednost i potrebu za zaštitom i očuvanjem ovakvih staništa., Continental dry grasslands in the area of Papuk are from the biological and landscape point of view very valuable habitats and are among the most threatened types of vegetation in our country, as well as in other parts of Europe. They are characterized not only by a high biodiversity, but also many rare and endangered species grow on them, such as orchids (Orchis spp., Ophrys spp.), carnations (Dianthus spp.) and others. Due to the absence of traditional farming (grazing and mowing) the areas of dry grasslands significantly reduced in the last fifty years. Due to progressive succession they are in constant dynamics and under threat of extinction. Therefore, the purpose of this study is to collect new and complement existing knowledge of such habitats, in order to prevent their further loss and loss of rare and protected taxa that grow on them. The study was conducted during the vegetation period of 2011 in the southern part of Papuk Mt. near the border of Nature Park Papuk, where a total of 240 vascular plant taxa have been recorded and classified into 143 genera and 52 families. New 29 taxa were recorded for the first time for this area. The most numerous is the family of legumes (Fabaceae), and in the life form spectrum hemicryptophytes dominated. A high proportion of phanerophytes indicates advanced processes of natural succession. According to the analysis of floral elements, dry grasslands are dominated by plants of Eurasian floral element, which biogeographically confirms the affiliation of the study area to the Euro-Siberian-North American region. On the researched area two endangered (EN), six vulnerable (VU) and 15 strictly protected species (ZZ) were recorded, which indicates a particular value and the need for protection and conservation of these habitats.

Likelihood ratio tests in parametric mixture models suffer from several sources of instability, therefore tests against a nonparametric alternative are proposed. Their performance depends on the strategies for likelihood maximization. This article develops a fast and statistically powerful combination of methods under the null hypothesis and under the alternative hypothesis; the method also includes elimination of spurious components.Modifying a strategy proposed by McLachlan, a sequence of such tests is applied for assessing the number of components and its performance is analyzed in a number of simulation studies in exponential mixture models. Although critical values have to be bootstrapped, the probability of overestimating is still bounded by the nominal level of the individual tests. Taking into account the number of components that can be reliably detected on the basis of a certain sample size, the proposed procedure yields the minimum number of components that is required for an adequate represent...

U radu je raspravljeno o problematici definiranja i upotrebe termina „puni“ ili „obilan urod“ na temelju usporedbe strane i domeće literature. Predstavljene su dosadašnje spoznaje o plodonošenju šumskoga drveća u Hrvatskoj. Prikazan je utjecaj nekih ekofizioloških čimbenika na razvoj rasplodnih organa (cvjetova i plodova) šumskoga drveća i predstavljene su dosadašnje spoznaje o mogućem utjecaju klimatskih promjena (npr. sve učestalija sušna razdoblja i povećanje količine CO2 u atmosferi) na rasplodni ciklus šumskoga drveća. Naposljetku, obilan urod predstavljen je kao određena evolucijska prednost koja je pojedinim vrstama osigurala opstanak sve do današnjih dana., Masting, or an abundant fruiting of forest trees in intermittent intervals in a broader geographical area, represents an evolutionary advantage which has ensured survival of certain forest tree species up till today. Due to the selection pressure, surviving individuals are the ones which underwent initiation and differentiation of flowers under the influence of strong interactive control of climatic factors and nutrients which a particular individual tree had at its disposal. In other words, initiation and differentiation of a large number of flowers occurs only under the influence of both, sufficient amount of nutrients and favourable climatic conditions, which is also a basic requirement for the occurrence of masting. The advantage of masting occurrence is reflected in an increased success of pollination, decreased populations of pests affecting reproductive organs of forest trees, and dissemination of particular amounts of seed to greater distances from parent trees. Particular phases of forest tree fruit development take place under the influence of a specific interaction of physiological processes within the plant organism (hormonal control, mineral nutrition and carbohydrate metabolism) which are stimulated, and to a certain degree controlled, by the climatic factors (air temperature,amount of precipitation, relative humidity of air, etc.). Under favourable climatic conditions, a portion of nutrients which forest trees have at their disposal gets used in fruit development, which is reflected in great amount of initiated anddifferentiated flowers. The amount of nutrients which would be invested in fruit development depends greatly on the site quality. Trees grown in high quality environment, as opposed to those grown in lower site quality, replenish their nutrient reserves more rapidly despite having identical climatic growth conditions, thanks to a more intensive photosynthetic activity, which in turn results in an increased seed production.

The inadequate nutrition of forest trees with mineral nutriments is usually manifested through lowered efficiency of photosynthetic pigments on the leaf’s cellular level and in the production of insufficient amount of carbohydrates necessary for a vegetative growth. The objectiv of this study was to determine the effect of soil’s various chemical traits on the intensity of photosynthesis and vegetative growth of pedunculate oak. The research was conducted on 4-year-old plants. Eight plants were planted per plot, two plots in all (plots A and B, for a total of sixteen plants). The plot A, compared to the plot B, was characterized by a higher soil pH, greater content of humus and nitrogen, and physiologically active phosphorus and potassium in the soil. Infra red gas analizer (LCpro+) has been used to measure the intensity of photosynthesis. The research determined height and diameter increment, number of primary and secondary branches, and the total number of leaves for the plants under study. There was a statistically significant difference in the intensity of photosynthesis between the plot A (28, 4 μmol CO2 m-2 s-1) and plot B (19, 3 μmol CO2 m-2 s-1), as well as the difference in diameter increment, which amounted to 6, 4 mm for the plot A, and 1, 9 mm for the plot B. It was also determined that the plot A had statistically significant advantage in the number of leaves and secondary branches compared to the plot B. There was not a statistically significant difference in the number of primary branches and the height increment between the studied plots. The higher values for the intensity of photosynthesis, as well as more intensive vegetative growth was recorded for the plants grown on the soil with a greater concentration of humus, nitrogen, phosphorus and potassium. This indicates that the chemical composition of soil has a significant effect on the intensity of photosynthesis and the vegetative growth of pedunculate oak.

U radu je analiziran utjecaj mikrostaništa na fiziološke značajke i vegetativni rast hrasta lužnjaka. Istraživanje je provedeno na dvije pokusne plohe koje se odlikuju različitim kemijskim značajkama, sadržajem vlage i temperaturom tla. Cilj rada bio je utvrditi utjecaj različitih kemijskih značajki tla na vegetativni rast i intenzitet fotosinteze hrasta lužnjaka, kao i odnos koncentracije klorofila i intenziteta fotosinteze. Biljke uzrasle na tlu s većom koncentracijom humusa, dušika, fosfora i kalija imaju veći intenzitet fotosinteze, veću koncentaraciju klorofila te bolji vegetativni rast. Zbog povoljnog odnosa volumetrijskog sadržaja vlage u tlu i vodnog potencijala istraživanih biljaka, njihov značajniji utjecaj na fiziološke i vegetativne značajke hrasta lužnjaka nije utvrđen. Rezultati ukazuju na visoku pozitivnu korelaciju između indeksa ukupnih klorofila u proljetnim listovima i većine fizioloških te vegetativnih značajki istraživanih biljaka., The effect of various types of environmental stress factors on forest trees is most often manifested through the reduced absorption of mineral nutriments. This results in lowered efficiency of photosynthetic pigments on the leaf’s cellular level and production of insufficient amounts of carbohydrates necessary for normal vegetative growth. Due to sudden increase in concentration of carotenoids in relation to chlorophyll, which is susceptible to a sudden destruction under the effect of stress factors, a change takes place in the relative amounts of chlorophyll and carotenoids. Because of this, the leaves in the crown of a tree temporarily lose their green color and turn yellow, which is indicative of plant’s lack of nitrogen nutrition, i.e. the nitrogen deficiency in the soil. The role of nitrogen as a plant nutriment is connected with numerous physiological processes responsible for successful growth and development of plants. For example, nitrogen is an essential element responsible for an uninterrupted continuation of photosynthetic process and vegetative plant growth, primarily because of its role in the synthesis of chlorophyll and certain proteins, such as ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco), which is responsible for CO2assimilation. In the previous studies of forest trees, significant differences were determined in the intensity of photosynthesis and vegetative development regarding the diverse conditions in the habitats. These variations are usually due to the lengths of summer droughts and high temperatures, the intensity of illumination, and the differences between dry and wet years. The aim of this study was to, (1) determine the effect of various chemical characteristics of the soil on the intensity of photosynthesis and the vegetative growth of pedunculate oak, (2) establish a connection between content index of the total amount of chlorophyll in the leaf, and the intensity of photosynthesis and the vegetative growth of pedunculate oak. The study was conducted during the vegetative period in 2010, on 4-yearold plants, planted with 2 – 2,5 meters of space between plants. Based on visual differences in the leaf color, two plots have been set aside – the chlorotic and the control plots (without chlorosis). Each field contained 8 plants, i.e. 16 in total. The average height of the plants under study before the start amounted to 1.96 ± 0.44 meters, and the diameter of the trunk 2.5 centimeters, measured 30 centimeters above ground. In order to determine the differences in the soil’s chemical characteristics between the two studied plots, the samples were taken on the depth of 0–30 centimeters. The soil reaction was determined with a potentiometer in the suspension of soil and water, i.e. soil and nKCl. Humus was determined by the Thorin method, and the total nitrogen level by the Kendahl method. The content of physiologically active phosphorus and potassium was determined by the Al-method. The study determined height and diameter increment for the plants studied, and also height and diameter increment for primary branches of each plant. The number of spring and summer shoots with its attending leaves was also determined. Based on the number and surface area of leaves, as well as the projection of crown surface on the ground, index of leaf surface was calculated for each tree. The measurements of photosynthesis intensity and the index of total chlorophyll content were performed early in September. The photosynthesis intensity was measured with the help of the infrared gas analizer portable device LCpro + (ADC BioScientific). While taking photosynthesis intensity measurements, each leaf was subjected to illumination intensity of 1500 µmol m-2 s-1, CO2concentration of 380 ± 10 µmol mol-1and the air temperature of 25 ± 2 °C. The chlorophyll content index was determined by using chlorophyll content meter CCM-200. By using a portable chamber for measuring water potential, the measurement of water potential was taken in the leaves (.) of plants under study. The chemical characteristics of the soil in the test plots were shown in Table 1. There was an extremely acidic reaction in the chlorotic plot, and acidic in the control plot. The chlorotic plot was marked by an extremely low nitrogen supply, while the control plot had a medium to good nitrogen supply. The content of physiologically active phosphorus in the chlorotic plot was extremely low, while the control plot was averagely supplied with physiologically active phosphorus. Both plots under study featured accessible potassium levels on the lower margins of an average supply. The humus content in the studied plots was very low, especially in the chlorotic plot. Statistically significant difference in the measured values of water potential of the plants grown in the plots was determined only during noon measuring throughout July. In August and September, statistically significant differences in the measured values of water potential were not determined (Table 3). All the parameters of the vegetative growth of the plants under study which were grown on the control plot had statistically significant higher values compared to the plants grown on the chlorotic plot, except for the number of primary branches, which showed no statistically significant differences between the two studied plot trials (Table 4). Leaf surface index, value of which was taken in the middle and near the end of the vegetative cycle, was statistically significantly higher in the control plot than in the chlorotic plot (Figure 2). There was statistically significant difference in the intensity of photosynthesis measured on spring leaves of studied plants between the control and the chlorotic plot. The intensity of photosynthesis on the control plot was 28.4 µmol CO2m-2 s-1, while its value on the chlorotic plot was 19.3 µmol CO2m-2 s-1. Content index values of total chlorophyll in the leaves of the studied plants were statistically significantly different regarding the plots under study, no matter whether the measuring of chlorophyll content was conducted on spring or summer leaves (Figure 4). Regression analysis determined a high positive correlation between the content index of total chlorophyll measured on spring leaves of studied plants with the intensity of photosynthesis, leaf surface index, tree’s girth increment, and also length and girth increment in the primary branches (Table 5). The correlation between content index of total chlorophyll and tree’s height increment was very weak. The results of the study indicate that the soil’s chemical characteristics have an effect on the photosynthetic activity and the concentration of chlorophyll in the leaves of pedunculate oak. The higher values of the total chlorophyll’s content index and the intensity of photosynthesis were recorded for plants grown on the soil with a higher concentration of humus, nitrogen, phosphorus and potassium. Positive correlations between the content indexes of total chlorophyll in leaves and the intensity of photosynthesis, as well as most of the parameters of vegetative growth, indicate the possibility of successful application of chlorophyll measuring methods when determining vitality of particular trees and forest stands of pedunculate oak.

U park-šumi Maksimir, u mješovitoj sastojini hrasta lužnjaka i običnoga graba (Carpino betuli-Quercetum roboris/Anić 1959/ Rauš 1969), analiziran je utjecaj svjetla na brojnost i kvalitetu mladog hrastovog naraštaja. Pokusna ploha obuhvatila je dvije pomladne jezgre u razvojnom stadiju mladika i površinu između jezgri u fazi ponika te mlađeg i starijeg pomlatka. Analiza podataka pokazala je da se prirodno pomlađivanje na malim površinama u park-šumi Maksimir odvija uspješno. Broj biljaka po jedinici površine je zadovoljavajući i iznosi 8,3 kom/m2. Prema vrsti smjese to je mješovita sastojina hrasta lužnjaka i običnoga graba s manjim udjelom divlje trešnje (PrunusaviumL.), klena (Acer campestreL.), lipe (Tiliasp.) i mliječa (A. platanoidesL.). Prednost mješovitih sastojina ogleda se u biološkoj i ekološkoj ravnoteži, a to su glavni ciljevi gospodarenja u park-šumi Maksimir. No, kvaliteta mladog na raštaja hrasta lužnjaka je upitna. Posljedica visoke gustoće biljaka na pom-lad noj površini je visok prosječni koeficijent vitkosti mladog hrastovog naraštaja. Velik udio deformiranih debala, loše razvijenih krošnji i prevelika zastupljenost korovske vegetacije posljedica su nenjegovanja pomlatka. Utvrđene su prosječne godišnje relativne vrijednosti difuznog i izravnog svjetla u pojedinim razvojnim stadijima hrasta lužnjaka. Ovisnost broja biljaka u različitim razvojnim stadijima o svjetlosnim uvjetima pojedinog mikrostaništa potvrđena je ?2testom. Dobivena je jaka pozitivna linearna ko re lacija između prosječnog visinskog prirasta hrasta lužnjaka i vrijednosti izravnog svjetla (r = 0,5809)., In a forest park Maksimir, in a mixed forest stand of Pedunculate Oak and Common Hornbeam (Carpino betuli-Quercetum roboris/Anić 1959/ Rauš 1969), influence of light conditions on number and quality of young oak growth was investigated. Experimental plot covered two regeneration gaps and the space between, including the trees in a different stage of development (seedlings, saplings and young trees). Measurements were taken in the winter 2006 and spring 2007 in a single plot within the stand. The plot was divided in 105 sub-plots of 1.5 m x 1.5 m and on each sub-plot height (cm), tree length (cm), ground level diameter (mm) and last five height increments (cm) were measured. Parallel to the measurement, evaluation of stem quality, crown form and tree health state was conducted. Spatial distribution of old grown trees at the plot area, together with crown projections, was recorded. At each sub-plot a hemispherical photograph was taken. Average annual relative values of diffuse and direct light for different development stages of Pedunculate Oak were determined. Depending on the values of diffuse and direct light, four microsites (marked: A – D) with different light conditions were defined. Results indicate that natural regeneration in naturally occurring gaps could be considered successful. Average number of trees per square meter was 8.3. Species composition of naturally occurring young trees in the gap indicates a continuation of the same forest community, namely mixed forest stand of Pedunculate Oak and Common Hornbeam with a smaller share of Wild Cherry (Prunus aviumL.), Hedge Maple (Acer campestreL.), Norway Maple (A.platanoidesL.) and Lime (Tiliasp.). Mixed forest stands are of great biological and ecological value, but also attractive to the park visitors. Maintaining them and their stability is a main management goal in this forest park. However, in naturally occurring gaps in the absence of silvicultural treatments the quality of young trees is questionable. High density of young growth at our plot resulted with high tree slenderness coefficient of 97,7. Share of deformed tree stems was significant (30.3 %), as well as share of badly developed tree crowns (44.3 %). Great abundance of weed vegetation was recorded and can be attributed to the lack of silvicultural treatments during regeneration. Chi-square test showed statistically significant dependence of number of young oak growth in different development stages with respect to the light conditions at microsite. Lower values of direct and diffuse light (microsite C) correspond with great number of oak seedlings. Surviving of oak seedling in low light conditions confirms the fact that in first few years oak is shade tolerant. However, great abundance of oak saplings at microsites A (lower values of direct and higher values of diffuse light) and D (higher values of direct and lower values of diffuse light) indicates that oak, when it arrives to the stage of saplings, favours higher light conditions. This is further corroborated at microsite B (with high values of direct and diffuse light) where young oak trees were most abundant. Quality of oak saplings and young trees was better at microsite B. Young oak trees grown in high light conditions obtained greater height increment and stem verticality. High positive correlation is obtained between Pedunculate Oak average height increment and average values of direct light (r = 0,5809).