Changes in structure and composition over fifteen years in a secondary kauri (Agathis australis)-tanekaha (Phyllocladus trichomanoides) forest stand, Coromandel Peninsula, New Zealand.
The stand in the North Island was assessed in 1971 and again in 1986. Stand structure was intermediate between previously described young and mature A. australis stands. A. australis, mostly 100-200 yr old, had the fastest diam. increment (4.3 mm/yr in trees ≥25 cm d.b.h) and contributed almost all the stand b.a. increment; its seedling population contracted and larger trees were developing mature crowns. P. trichomanoides, also mostly 100-200 yr old, had slower diam. increment (2.2 mm/yr) and contributed most of the remaining stand b.a. increment; its seedling population also contracted. Weinmannia silvicola, probably of similar age, incurred mortality at all sizes while Kunzea ericoides var. ericoides, 40-80 yr old, incurred most mortality in large saplings and small trees. Stand b.a. increased rapidly (0.6 m2/ha p.a.) and total density decreased slightly. Spatial patterns of stems over 5 cm d.b.h. largely reflected topographic variation, with A. australis, smaller P. trichomanoides and K. ericoides tending to occur on ridges and upper slopes, and Cyathea dealbata, the main understorey plant, and smaller W. silvicola tending to occur on lower slopes. Larger P. trichomanoides and W. silvicola were randomly distributed. Several successional pathways (replacement patterns) are evident, with P. trichomanoides replacing K. ericoides, and A. australis replacing W. silvicola and likely to replace P. trichomanoides in the future. A. australis thus appears set to become dominant over most of the stand, largely at the expense of the sizeable suppressed component of its own population, temporarily prominent P. trichomanoides, Knightia excelsa and W. silvicola, and ephemeral K. ericoides. Canopy diversity is likely to be enriched slightly by a few podocarps (Dacrydium cupressinum, Podocarpus hallii, Prumnopitys ferruginea) and broadleaves (Elaeocarpus dentatus, Dysoxylum spectabile) with moderately shade-tolerant seedlings which have probably been present for at least 100 yr.