Trade-off between stem growth and acorn production in holm oak

Abstract

Reproduction in trees often requires significant resources, and previous studies have 28 documented trade-offs between reproduction and growth in numerous tree species. In the 29 present study, we assessed the relationships of acorn production with annual and intra-annual 30 stem growth of Quercus ilex L. (holm oak) at the level of the individual tree over six years 31 (2006-2011) at two study sites in southwestern Spain. There were negative correlations between 32 acorn production and annual and late summer-autumn stem growth during masting years. In 33 other words, the growth rates were lower in trees that had greater acorn production. These 34 results suggest the existence of trade-offs between growth and reproduction in Q. ilex. However, 35 there was no relationship between acorn production and winter-spring growth. Moreover, the 36 costs of reproduction varied between the two study sites. There were negative correlations 37 between acorn production and late summer-autumn growth in both study sites, but there were 38 only negative correlations between acorn production and annual growth in one study site. Trade-39 offs appear to be greater in smaller trees living under more stressful conditions. These results 40 show the importance of making intra-annual measurements of tree growth for appropriate 41 interpretation of potential trade-offs.