Forest Vines to Snow Tussocks: The Story of New Zealand Plants
Holloway69 suggested that the general lack of regeneration of podocarps since the time when the present mature to aging emergents established is due to a climate change to colder and drier conditions from about 1300 A. D.
Holloway based his climate change hypothesis on forest patterns in western Southland, in which he saw evidence of a downward movement of vegetational zones, and on historical and other evidence of a worldwide colder interval, the 'Little Ice Age', during the last millenium.
Wardle70 investigated a number of podocarp-dominated stands on the west and east of the South Island and in Stewart Island. He supported Holloway's hypothesis but concluded that the 'regeneration gap' started later than Holloway suggested, from about 1600-1800 A. D., and that it was most marked in the drier eastern South Island and least marked on the wetter west and in Stewart Island. Since about 1800 the regeneration of podocarps has resumed at some localities.