| Abstract | Klimatske promjene, osobito učestalije suše, predstavljaju ozbiljnu prijetnju opstanku šumskog drveća, uključujući običnu bukvu. Dosadašnja istraživanja ukazuju na to da sušni uvjeti negativno utječu na usvajanje vode i hraniva, što ograničava rast i vitalitet mladih stabala. Poznato je da gnojidba može poboljšati fotosintezu i rast kod šumskih sadnica, ali interakcija suše i gnojidbe u nije dovoljno istražena. Cilj ovog istraživanja bio je ispitati utjecaj suše, gnojidbe i njihove interakcije na ishranu, fotosintezu i rast sadnica obične bukve, s hipotezom da će visoka doza gnojidbe povećati koncentracije makroelemenata u lišću i ublažiti negativne učinke suše. U tu svrhu, proveden je plastenički pokus na Hrvatskom šumarskom institutu u Jastrebarskom s jednogodišnjim sadnicama bukve. Istraživanje je uključivalo različite tretmane navodnjavanja i gnojidbe: redovito navodnjavanje s visokom dozom gnojiva (WH), neredovito navodnjavanje s visokom dozom gnojiva (DH), redovito navodnjavanje s niskom dozom gnojiva (WL) i neredovito navodnjavanje s niskom dozom gnojiva (DL). Istraživanje je trajalo od početka lipnja do kraja listopada i uključivalo je tri razdoblja: pred-sušno razdoblje u kojem su sve sadnice bile redovito navodnjavane jednakom količinom vode, sušno razdoblje u kojem je polovici sadnica u DH i DL tretmanu uskraćeno navodnjavanje u trajanju od 21 dan i post-sušno razdoblje u kojem su sadnice u DH i DL tretmanu ponovno redovito navodnjavane kao i sadnice u WH i WL tretmanu. Jednom tjedno praćen je vodni potencijal u lišću, parametri fluorescencije klorofila a i izmjene plinova. U sva tri razdoblja uzeti su uzorci lišća za analize koncentracija N, P, K, Ca, Mg i fotosintetskih pigmenata. Na kraju istraživanja uzorkovane su cijele biljke sa svrhom određivanja sadržaja N, P, K, Ca, Mg u lišću, stabljici, krupnom i sitnom korijenu i produkcije biomase. Brz oporavak vodnog potencijala i provodljivosti puči nakon razdoblja suše sugerira otpornost bukovih sadnica na kratkotrajni sušni stres bez obzira na primijenjenu dozu gnojiva. Visoka doza gnojidbe pozitivno je utjecala na koncentracije biogenih makroelemenata, ukupnih klorofila i ukupnu fotosintetsku učinkovitost, čime je ublažila negativne učinke suše na fotosintezu. S druge strane visoka doza gnojiva potaknula je produkciju biomase lišća i smanjila omjer podzemne i nadzemne biomase kod sadnica u DH tretmanu, što može negativno utjecati na otpornost na sušu. Također sadnice u DL tretmanu zadržale su veći omjer podzemne i nadzemne biomase, što može pridonijeti boljoj otpornosti na sušne uvjete nakon presadnje. Rezultati ovog istraživanja pokazuju na koji način gnojidba ublažava negativan utjecaj suše na bukove sadnice, što je važno za njihovu prilagodbu na klimatske promjene. |
| Abstract (english) | Climate change, particularly the increasing frequency of droughts, poses a serious threat to the survival of forest trees, including common beech. Previous research indicates that drought conditions negatively affect water and nutrient uptake, limiting the growth and vitality of young trees. While fertilization enhances photosynthesis and growth in forest seedlings, the interaction between drought and fertilization has not been sufficiently studied. The objective of this research was to examine the effects of drought, fertilization, and their interactions on the nutrition, photosynthesis, and growth of common beech seedlings, with the hypothesis that a high dose of fertilization would increase foliar concentrations and mitigate the negative effects of drought. A greenhouse experiment was conducted at the Croatian Forest Research Institute in Jastrebarsko using one-year-old beech seedlings. The study involved various irrigation and fertilization treatments: regular irrigation with a high fertilizer dose (WH), irregular irrigation with a high fertilizer dose (DH), regular irrigation with a low fertilizer dose (WL), and irregular irrigation with a low fertilizer dose (DL). The experiment lasted from early June to late October and included three periods: a pre-drought period during which all seedlings received regular irrigation with equal amounts of water; a drought period in which half of the seedlings in DH and DL treatments were deprived of irrigation for 21 days; and a post-drought period where seedlings in DH and DL treatments were again regularly irrigated alongside those in WH and WL treatments. Weekly measurements of pre-dawn leaf water potential, chlorophyll fluorescence parameters, and gas exchange were conducted. Foliar samples were collected during all three periods for analyses of N, P, K, Ca, Mg concentrations, and photosynthetic pigments. At the end of the study, whole plants were sampled to determine N, P, K, Ca, and Mg content in leaves, stems, coarse and fine roots, as well as biomass production. The rapid recovery of leaf water potential and stomatal conductance after the drought period suggests that beech seedlings are resilient to short-term drought stress regardless of the applied fertilizer dose. High fertilizer doses positively influenced foliar concentrations, total chlorophyll concentrations, and photosynthetic efficiency, thereby alleviating the negative effects of drought on photosynthesis. Conversely, high fertilizer doses stimulated leaf biomass production but reduced the root-to-shoot ratio in seedlings from the DH treatment, which could negatively impact drought resistance. Seedlings in the DL treatment maintained a higher root-to-shoot ratio, potentially contributing to better resilience under drought conditions post-transplanting. The results indicate how fertilization mitigates the adverse effects of drought on beech seedlings, which is crucial for their adaptation to climate change. |
