A post-fire succession in the northern Urewera forests North Island, New Zealand

Abstract

Where fire has destroyed podocarptawa forest in the northern Urewera Ranges, dense pole stands of Leptospermum ericoides are characteristic of the early stages of the succession. Although young Leptospermum stands contain many woody seedlings (< 50 cm) of Weinmannia racemosa, seedlings > 50 cm and saplings of species other than Leptospermum ericoides, are almost completely absent. Where fire occurred 60–80 years ago, however, Weinmannia racemosa is either the dominant canopy species or is co-dominant with Leptospermum ericoides. The understoreys in these stands are typically open, and woody seedlings (> 50 cm) and saplings are rare. Where localised mortality has occurred in Weinmannia stands, succession is similar to that on recent bum sites, with Leptospermum ericoides the dominant canopy species. Older stands of this type show no evidence of re-invasion by Weinmannia racemosa and few seedlings (> 50 cm) or saplings of other woody species. The absence of regeneration suggests suppression of Weinmannia within the study area has closely followed the introduction and establishment of ungulates, principally red deer (Cervus elaphus). The localised Weinmannia mortality within these seral forests, which has been attributed to browsing by brush-tailed possums (Trichosurus vulpecula) is shown to have occurred before colonisation by possums.

Key Words:

• Cervus elaphus
• charcoal
• fire
• forest
• Leptospermum ericoides
• podocarp-tawa
• succession
• Trichosurus vulpecula
• Urewera Ranges
• Weinmannia racemosa