Restoration of the Clanwilliam cedar Widdringtonia cedarbergensis: the importance of monitoring seedlings planted in the Cederberg, South Africa

Published source details Mustart P., Juritz J., Makua C., van der Merwe S.W. & Wessels N. (1995) Restoration of the Clanwilliam cedar Widdringtonia cedarbergensis: the importance of monitoring seedlings planted in the Cederberg, South Africa. Biological Conservation, 72, 73-76.
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Summary

A decline of Clanwilliam cedar Widdringtonia cedarbergensis (an endemic conifer of the fynbos of the Cederberg mountains) led to a restoration programme to bolster the wild population. Adult trees are easily killed by higher intensity fire and a lack of sufficient seed-bearing trees after a wildfire in December 1989/January 1990 has resulted in low seedling recruitment. This project investigated the effects of several microhabitat factors on the survival of transplanted seedlings.

Short-frequency (every 4-6 years), low-intensity patch-burning in autumn/winter (to reduce fuel loads in order to prevent high intensity fires) was combined with large-scale planting of nursery-reared seedling in newly burnt areas. In November 1992, seedling survival at two seedling plantation sites (about 1 km apart), each burnt just before seedlings were transplanted, was recorded:

Site 1 - several thousand 1-year old seedlings transplanted in May 1991; survival (alive/dead) recorded for 69 randomly chosen seedlings (i.e. 18 months after planting);

Site 2 - fifty, 3 year-old seedlings planted in May 1987.

Four microhabitat factors associated with each seedling were recorded: shade, aspect, competition from other plants and soil depth.

Seedling survival was considered high at both sites: site 1, 39.1% and 2, 61.2%. At site 2 seedlings were on average over twice the height (19.4 cm) of those at site 1 (7.8 cm), and had about 21 times the canopy volume (1,021.3 cm³ compared with 48.7 cm³).

No microhabitat variable measured had a significant effect on height or canopy volume at either site. Shade was the only variable showing significant effects on seedling survival at site 1. Increased shade led to greater survival probability: no shade 0% (0/7); partial shade 42% (25/59); complete shade 75% (3/4).

Transplanting of seedling was more efficient (greater seedling survival) than (earlier reported) seed sowing. Ongoing monitoring is needed to assess longer-term survival.

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