Temporal changes in height and diameter growth for two Nothofagus species in New Zealand

Abstract. We examined whether the growth dynamics of two species can explain their coexistence. In particular, we exam-ined New Zealand forests dominated by Nothofagusfusca and N. menziesii to determine whether both species can reach the canopy in tree-fall gaps. Stems in a gap and other stems (in pairs: one of each species, close together) were destructively sampled and aged at their bases and at heights of 1.4 m and 3 m, and at 2 m intervals thereafter as high as possible. For additional pairs of adjacent, similarly sized stems, one of each species, ring widths were analyzed for responsiveness to envi-ronmental changes. In general the faster growth rates of N. fusca were sufficient to balance the greater abundance of N. menziesii in the understory, such that both species were able to reach the canopy. Stems of both species grew at similar rates for decades. Both species were able to tolerate some periods of suppression and to respond to opportunities (climatic or due to mild disturbances)