Studies on the vegetation of Mount Colenso, New Zealand. 4. An assessment of the processes of canopy maintenance and regeneration strategy in a red beech (Nothofagus fusca) forest

Information on diameter frequency distributions and spatial patterns, together with estimates of diameter growth and mortality, are used to draw up regeneration balance sheets for three stands of red beech (Nothofagus fusca) on Mount Colenso, New Zealand. Because large canopy gaps are a feature of these forests, attention is directed particularly to their future status. It is concluded that, in the short-term, a further opening of the canopy is likely in the higher altitude forest. This forest appears to have developed following catastrophic destruction, and its predominantly even-aged red beech population may be still undergoing competitive thinning. At lower altitudes uneven-aged forest is likely to maintain its present canopy structure. Simple mathematical predictions based on the Leslie Matrix Model indicate that, in the longer term, the present population has the potential to colonize the larger gaps in all the stands. However, such predictions do not take account of the observed lack of suitable micro sites for seedling survival in the centres of large gaps.Small canopy gaps created by the fall of one or two trees are a consequence of the regeneration strategy in uneven-aged stands. The varying ages and spatial distributions of such gaps lead to considerable variation in size class frequency distribution from place to place. The strategy of individual replacement in "stable" forests, which generates small gaps of varying duration, may render such forests particularly susceptible to invasion by other species.