Nutritional status and defoliation of common beech (Fagus sylvatica L.) in changed climate conditions

Globalno zagrijavanje je neosporno uzrokovalo klimatske promjene koje su vjerojatno najveća prijetnja postojećim šumskim ekosustavima u Europi. S obzirom na ekološki i gospodarski značaj obične bukve u Europi i Hrvatskoj, cilj ovog istraživanja bio je odrediti utjecaj izmijenjenih klimatskih uvjeta na osutost krošanja i stanje ishrane obične bukve, kao i kakav je međuodnos ova dva indikatora vitaliteta. Istraživanje je provedeno na 28 istraživačkih ploha koji su dio UNECE ICP Forests infrastrukture u Hrvatskoj. Utjecaj klime na osutost proučavan je na podacima osutosti prikupljenim u sklopu programa motrenja oštećenosti šumskih ekosustava u razdoblju od 1996. do 2017. godine. Podaci su obračunati kao osutost u trenutnoj godini, kao i razlika u odnosu na prethodnu godinu (promjena osutosti). Procjena je na istim plohama obavljena u razdoblju 2018 – 2020. radi određivanja stabala za uzorkovanje biljnog materijala (lišća). Uzorci lišća obične bukve za analizu koncentracija biogenih elemenata prikupljani su jednom godišnje u razdoblju od 2018. do 2020. godine, odvojeno za stabla do 25 % i iznad 25 % osutosti. Osutost krošanja stabala obične bukve pokazuje značajan trend povećanja na koji suša ima značajan iako slab utjecaj. Nedostatak jasnog trenda promjene osutosti kao i izražen utjecaj sušeu prethodnojgodini indicirakako je promjenaosutosti odraz intenzivnog stresa, dok pozitivan trend razvoja osutosti predstavlja akumulirani utjecaj lokaciji specifičnih stresnih okolišnih uvjeta na vitalitet stabala. Rezultati ostvareni ovim istraživanjem omogućili su prvi uvid u stanjeishraneobičnebukvena razinicijele Hrvatskete ukazuju na zadovoljavajuću ishranu u usporedbi s graničnim vrijednostima. Proučavanjem odnosa osutosti i ishrane nije utvrđena povezanost kategorije osutosti i ishrane bukovih stabala. Uočene su značajne razlike u koncentracijama P, Ca i Mgu odnosu na osutost, ali koje vrijede samo za pojedine godine istraživanja. Oborine imaju pozitivan utjecaj na koncentracije N i K. Povećanje SPEI rezultira višim koncentracijama Mg, a smanjenim koncentracijama Ca i N, dok povećanje SPEI u prethodnoj godini uzrokuje povećane koncentracije N, P i K. Pozitivna odstupanja temperatura od klimatske normale utječu na smanjenje P, K i Ca, dok se povećanjem prosječne godišnje temperature povećava koncentracija N.Global warming has indisputably caused climate change, which is probably the largest threat to existing forest ecosystems in Europe. Given the ecological and economic importance of beech in Europe and Croatia, the aim of this study was to determine the impact of changed climatic conditions on crown defoliation and nutrition of beech, as well as the relationship between these two vitality indicators. The research was conducted on 28 research plots that are part of the UNECE ICP Forests infrastructure in Croatia. The impact of climate on defoliation was studied on the basis of defoliation data collected as part of the program for monitoring the damage of forest ecosystems in Croatia in the period from 1996 to 2017. Data were calculated as the defoliation in the current year, as well as the difference compared to the previous year (defoliation change). The assessment was performed on the same plots in the period 2018 - 2020 in order to determine the trees for sampling of plant material (leaves). Samples of beech leaves for the analysis of nutrient concentrations were collected once a year in the period from 2018 to 2020, separately for trees up to 25 % and above 25 % of defoliation. The defoliation of beech trees shows a significant positive trend on which drought has a significant, although weak impact. The lack of a clear trend of defoliation change as well as the pronounced impact of drought in the previous year indicates that defoliation change is a reflection of intense stress, while the positive trend of defoliation shows the accumulated impact of location-specific stressful environmental conditions on tree vitality. The results of this research provides the first insight into the nutritional status of beech at the level of the whole of Croatia and indicate a satisfactory beech nutrition in comparison with limit values. The study of the relationship between defoliation and nutrition did not determine the relationships between the defoliation categoryand nutrition of beech trees. Significant differences were observed in the concentrations of P, Ca and Mg in relation to defoliation, but which are valid only for individual years. Precipitation has a positive effect on N and K concentrations. An increase in SPEI results in higher Mg concentrations and reduced Ca and N concentrations, while an increase in SPEI in the previous year causes increased N, P and K concentrations. Positive temperature deviations from climatic normal affect P, K and Ca concentrations, whi increasing average annual temperature increases the concentration of N