Dynamics of nitrogen and phosphorus in needles of silver fir (Abies alba mill.) trees of different defoliation classes

Dinamika du{ika i fosfora u jedno- i dvogodi{njim iglicama obične jele (Abies alba Mill.) pra}ena je tijekom dvije vegetacijske sezone. Istra`ivanje je provedeno na pet ploha koje pru`aju različite edafske i klimatske uvjete za ishranu obične jele, a uzorkovanjem su obuhvaćena stabla različitog stupnja osutosti krošanja s ciljem utvr|ivanja stanja ishrane obi~ne jele, odnosa ishrane i oštećenosti obične jele te utjecaja karakteristika tla i klimatskih prilika na koncentracije dušika i fosfora u iglicama. Utvr|ena je općenito slaba opskrbljenost stabala tim elementima. Koncentracija dušika i fosfora u iglicama obične jele razlikuje se prema vremenu uzorkovanja, godini i plohi. Fiziološki oslabljena stabla manje uspješno reguliraju svoj status ishrane. Poremečaji u ishrani rezultirali su i progresivnim smanjenjem mase suhe tvari iglica u odnosu na povećanu osutost krošanja. Klimatski uvjeti utjeću na ishranu obične jele, a njihov negativan utjecaj izražen je kroz deficijencije u ishrani jele koje nastaju kao posljedica sušnih perioda.The dynamics of nitrogen and phosphorus in current and one-year old needles of Silver fir (Abies alba Mill.) has been monitored during two vegetational seasons. The research was conducted on five plots marked by different edaphic and climatic conditions, and sampled trees had different defoliation degrees. The aim was to determine the nutritional status of Silver fir, the relations of crown condition and nutrition, and the influence of soil and climate properties on the concentration of nitrogen and phosphorus in needles. Overall, the level of these elements in fir needles is low. The concentration of nitrogen and phosphorus in Silver fir needles depends on the sampling period, sampling year and research plot. Physiologically weakened trees are less able to control their nutritional status. The disturbances in nutrition result in the progressive lowering of needle mass in regards to increased crown defoliation. Climate properties have a pronounced effect on the nutrition of Silver fir trees. Their negative influence is expressed through nutritional deficiencies as a result of periods of drought