Successful season for rare coastal plant Popular Article
- Author
- Smith, C.
- Year
- 2005
- Summary
- Exclosure plots established in three separate areas of kanuka forest on south Kaipara spit in 1983 to assess the impact of introduced fallow deer were remeasured in 1993. Kanuka shared canopy dominance with mapou, houpara and mahoe in forest estimated to be over 100 years old in Lookout Bush, Woodhill, and dominated exclusively in two younger stands at South Head; Coprosma rhamnoides dominated understories throughout. At Lookout Bush cohort senescence, already underway in 1983, continued in kanuka and mapou and began in houpara. Massive recruitment Of mahoe occurred inside the exclosure, and continued in houpara (mostly outside); seedling thickets of kanuka self-thinned, particularly inside the exclosure, where they were also smothered by faster-growing species. Mahoe and another generation of houpara are replacing the existing canopy in the absence of deer, and another generation of kanuka and houpara elsewhere in a partially stalled succession. Canopies are still intact at South Head, and there were no major changes in populations of canopy species. However, similar successional pathways are likely to occur there in future. An influx of highly palatable shrubs, e.g., Coprosma macrocarpa and hangehange into collapsing forest at Woodhill in the absence of deer, and their scarcity or absence elsewhere, indicates continuing impoverishment of the understorey as well by deer. In the long term it is likely that a variety of broadleaved trees will invade these stands and that tall semi-coastal forest, similar to extant relics on the dunes, will develop. In the meantime, the high conservation value of these stands suggests that a major reduction in the deer population - sufficient to allow natural successional changes to proceed unhindered - should be a conservation priority for the region. Of the three methods suggested for achieving this (deer extermination, deer reduction, deer fencing), fencing is considered the most satisfactory.
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