Forest succession on landslides in the Fiord Ecological Region, southwestern New Zealand

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Abstract
Primary succession to montane rain forest on the bare slip faces of landslides is described from three variously aged slides with plot and plotless data, 24 years after a previous study, and is related to adjacent mature forest. Over a 15-102 yr period striking successional changes occurred in both vegetation and flora. The dominant pioneer, Leptospermum scoparium, persists with decreasing importance in the canopy beyond a century, with regeneration failing completely from the seventh decade. Metrosideros umbellata, Weinmannia racemosa, and Nothofagus solandri var. cliffortioides establish early and dominate the mid-successional stages but only W. racemosa maintains a major role in the mature forest, chiefly beneath a canopy of No thofagus menziesii at c. 26 m. Although some species persist throughout the succession and into the mature forest most characterise particular stages and several were recorded only in the mature forest. Among the 90 vascular plant taxa recorded, richness was variable (38-46 taxa) throughout the serai stages and greatest (52) in the mature forest. A total of 118 bryophyte taxa and 26 lichens were recorded from the succession. Bryophyte richness varied from 54 to 66 taxa, the highest being recorded from late seral (102 yr) forest. Ten to 15 species of lichen were recorded per sere with the greatest number in the youngest (39 yr) stage. Tree basal area increased while that of small-trees declined after 40 yr. Tree and small-tree densities generally declined after c. 70 yr to values similar to those in the mature forest. Densities of shrubs, sub-shrubs, and herbs showed no consistent trends with time. The successional pattern can be explained by the facilitation (relay floristics, or autogenic) model. It also conforms with the recently proposed resource-ratio model although more data are needed for its substantiation.