The tolerance of Sequoia sempervirens to sedimentation, East Coast Region, New Zealand

Authors: M. Marden
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 1993, Issue N.Z.J.For. 38(3) 1993, pp 22-24, Nov 1993
Publisher: New Zealand Institute of Forestry

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Abstract: The health of three redwood {Sequoia sempervirens) stands on alluvial terraces at Waipare, East Coast Region, New Zealand, was monitored for three years after flooding during Cyclone Bola in March 1988. Overall, 27 trees of a population of 402 died, all in the stand where sediment deposits were the thickest and the most extensive.
Anaerobic conditions developed where 60-90 cm of sediment was deposited, causing death of some trees within 10 months. Where sediment depth was 30-60 cm, many trees had unhealthy crowns after the first year and some of these subsequently died. However, where less than 20 cm of sediment was deposited, trees were unaffected.
In contrast, redwood trees in hillside plantations were unaffected by the aggradation of landslide-derived materials around their base. Landslide deposits rarely exceeded 50 cm depth, and materials remained loosely compacted and free-draining. Redwoods may therefore be suitable for planting on free-draining eroding hillslopes in the East Coast Region, but not on terrace sites where deep sediment deposits may lead to anaerobic conditions.

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