DIEBACK, LEAF AREA INDEX AND YIELD OF YOUNG EUCALYPT CLONES PLANTATION IN THE BRAZILIAN SAVANNAH REGION

ABSTRACT Eucalypt has been widely planted in Brazil, in the savannah region, which is characterized by high soil water deficit and low fertility. Dieback, leaf area index (LAI) and yield of young stands of 16 eucalypt clones were studied in Vazante, MG, Brazil (17º36’09"S and 46º 42’02"W). It was determined for each clone: a) the proportion of the tree height with dieback symptoms in the apical terminal (HWD%) and the proportion of trees with dieback (NWD%), at 13 months (end of the first dry season); b) the LAI at 13 and 21 months, and c) the yield at the age of 13, 19 and 25 months. HWD% reached 5-9%, and NWD%, 50-80%, for the five most susceptible clones, when the soil water deficit reached 508 mm in the year. LAI varied from 0.61 to 1.56, at 13 months, and from 2.31 to 3.48 at 21 months, presenting inverse relationship with dieback. The least susceptible clones to dieback achieved the highest yield up to 25 months of age. There was interaction between dieback and fertilizer levels only for three clones. There was a positive correlation (p < 0.001) between the LAI at the age of 13 months and the periodic monthly increment from 0 to 11 months, and from 11 to 19 months. The difference in dieback susceptibility among clones allows the selection of genotypes for regions where the soil water deficit is a major limiting factor. RESUMO Eucalipto tem sido plantado, no Brasil, na região de cerrado, caracterizado por elevado défice hídrico no solo e baixa fertilidade. A seca de ponteiros, o índice de área foliar (IAF) e a produção de povoamentos jovens de 16 clones de eucalipto foram estudados em Vazante, MG (17º36’09"S e 46º42’02"W). Foram determinados para cada clone: a) a proporção da altura da árvore com sintomas de seca de ponteiro (HWD%) e a proporção de plantas com seca de ponteiros (NWD%), aos 13 meses (final da primeira estação seca); b) o IAF, aos 13 e 21 meses e, c) a produção de cada clone aos 13, 19 e 25 meses de idade. HWD% atingiu 5-9%, e NWD%, 50-80%, para cinco clones mais susceptíveis, tendo ocorrido défice hídrico de 508 mm no ano. O IAF variou de 0.61 a 1.56, aos 13 meses, e de 2.31 a 3.48 aos 21 meses de idade, apresentando relação inversa com a seca de ponteiros. Os clones menos susceptíveis exibiram elevada produção até 25 meses de idade. Houve correlação positiva (p < 0.001) entre o IAF aos 13 meses e o incremento periódico mensal entre 0 e 11 meses e entre 11 e 19 meses de idade. A susceptibilidade diferenciada à seca de ponteiros entre c