Studies on the vegetation of Mount Colenso, New Zealand 2. The population dynamics of red beech.

The population structure of red beech (Nothofagus fusca) is described for four forest stands situated at different altitudes on Mount Colenso. Data on red beech seedling densities and frequency distributions of living and dead tree diameters (d.b.h.) are presented. Red beech seedlings are shown to be more numerous, and on average larger, on decaying red beech logs than elsewhere. This seedling site preference could lead to, a 'regeneration cycle', and explain the 'regeneration gaps' and bimodal d.b.h. frequency distributions commonly found in red beech forest in the Ruahine ranges. A comparison of the population structure in the four stands suggests that the red beech population may be undergoing a slow downhill migration. However, the apparent scarcity of saplings at higher altitudes does not necessarily imply a declining population in that area; it may be due to the long-term cyclic nature of population replacement following a catastrophe. Past browsing by deer and periodic mast production are thought to have had little effect on the population structure of red beech trees on Mount Colenso.