Factors Involved in the Recent Mortality of Plants from Forest and Scrub along the Lake Te an Au Shoreline, Fiordland

Mortality of forest and scrub species from most deltas of the Lake Te Anau shoreline is described following unnaturally prolonged flooding during 1975. Despite a high incidence of pinhole borer in the affected beech trees there is conclusive evidence that the mortality in most species was due to prolonged high water tables that exceeded the tolerances of many important shoreline species. Differential mortality in Leptospermum scoparium (manuka) apparently depended on whether or not plants were totally submerged for substantial periods-their root systems appear to be tolerant of indefinite flooding. The results have substantiated previous predictions on submergence tolerance of species from lake-shore forest and scrub communities. These tolerance values had been derived by indirect methods and form the basis of the high-level operational guidelines for use of the lake waters for hydro-electric generation.