Clonal development of Maianthemum dilatatum in forests of differing age and structure

The development of a dense tree layer in young coniferous stands can suppre ss understory plants, leading to very low herb abundance and diversity. In this study, clonal development of the rhizomatous herb Maianthemum dilatatu m (Wood) Nels & Macbr. was compared among four types of coniferous forest ( young, closed canopy; young, silviculturally thinned; mature; and old growt h) on the western Olympic Peninsula, Washington. We predicted that (i) rame t turnover would be lowest, (ii) clonal fragment size would be smallest, an d (iii) allocation of resources to leaves would be greatest in young, close d-canopy forests, and that these traits would increase (or decrease for lea ves) as understory conditions became more favorable with stand development or thinning. The low frequency of new ramets in young, closed-canopy stands supported the first prediction. The second prediction was also supported: lateral spread and rhizome mass were smallest in these stands. However, all ocation to leaves was not higher in dense young stands, indicating that Mai anthemum does not respond to stress by increased investment in leaves. Clon al fragments in thinned, mature, and old stands showed no differences in tr aits, suggesting that once tree canopies rise, canopy gaps form, or young s tands are thinned, resource levels are favorable for clonal growth. Maianth emum appears to persist in dense, young stands by maintaining long-lived ra mets that produce leaves annually, rather than by increasing rhizome spread , rhizome storage, or allocation to leaves.