A study of a silver beech stand in the Silver Peaks State Forest
INTRODUCTION The distribution of Silver Beech (Nothofagus menziesii (Hook f) Oerst) in New Zealand is noted for gaps and discontinuities (Wardle 1964). These have been hypothesised to be due to extinction of the beech during one or more of the Fleistccene glaciations. The very slow re-invasion of beech back into these areas has been accounted for by the heaviness of the seed and its inability to cross long distances or salt water gaps. However beech seeds can migrate rapidly via running fresh water (Holloway, 1954, Preest 1961). Smaller distribution discontinuities pose interesting problems as to the status of certain beech stands; are they relic stands or young invading stands? Around the Dunedin District several small isolated stands of silver beech occur. Studies on most of these stands were first initiated by Simpson and Scott Thompson in 1928. They recorded twelve isolated stands of this species in the District, one of which, at Bethunes Gully on the slopes of Mt Cargill, has been restudied (Wardle 1953, West 1968). Wardle (1953) also restudied several other stands including an extensive one along the Waikouaiti River. West (1968) restudied the Bethune's Gully stand to determine its status in relation to the surrounding coniferous-broadleaf forest. She investigated the age structure and regeneration of the silver beech trees and compared her results with those obtained by Wardle (1953) and the detailed study of Simpson and Thompson. From this she concluded the stand was probably relic and contained the first beech trees to cover this area. While the stand continued to be maintained, it was failing to encroach on the surrounding coniferous-broadleaf forest. The stand described in this study is a small and again isolated stand of silver beech beside Carey's Creek, within the Silver Peaks State Forest. This stand was missed by Wardle and Simpson and Thompson, and is the only known stand of beech east of the Waikouaiti River. An indigenous forest survey at Silver Peaks State Forest carried out in 1977 by D. Hunt and I. Greenhall brought attention to the existence of this small isolated stand. Until this survey, very little study had been done on the native bush area. The vegetation of the area around Carey's Creek consists mainly of kanuka (Leptospermum ericoides), which has attained or is past its age limit and is starting to collapse. This collapse is visible especially on the ridges. Associated with the kanuka are young, regenerating hardwood species. These are mainly Fuchsia excorticata, Pseudowintera colorata, Pittosporum tenuifolium along with several Pseudopanax species (P. crassifolius, P. simplex and P. colensoi). Hunt and Greenhall considered browsing by stock and feral animals has caused considerable damage to the understorey of this area. Occasional isolated podocarp trees occur, with few associated seedlings. The area of Nothofagus menziesii is beside Carey's Creek, south of the Honeycomb Ridge at an altitude of 60m (Fig. 1). A track has been cut down this ridge and joins with the very old track following the stream from Evansdale Glen, that was constructed about 1906 (?) in conjunction with the water supply for the Orokonui Hospital. Access to the stand can be therefore gained from both these tracks. Hunt and Greenhall made a brief note of the stand, estimated its area (30m x 30m) and measured the diameters of the two largest trees. They considered the stand could have been initiated from one or two trees, since beech is self-fertile, and seed could have been “thrown” a short distance uphill. The stand consists of approximately twenty-seven silver beech trees emergent from a discontinuous kanuka canopy (=10m). The largest trees tend to occur near the stream bed. These have an open grown form with large spreading branches originating relatively low on the trunks, and large spreading canopies. The rest of the stand consists of smaller diameter stems with longer boles, indicating they have grown up through the kanuka canopy. The ground and shrub layers show disturbance by sheep and pigs and are consequently rather open ln places. The object of this study was to investigate the age structure of the stand and the vegetation associated with the stand in an attempt to understand its dynamics and possibly its origins.
Advisor: Mark, Alan
Degree Name: Bachelor of Science with Honours
Degree Discipline: Botany
Research Type: Dissertation
20 leaves : ill., map ; 32 cm. Unpublished material. Research paper (B. Sc. (Hons.)) -- University of Otago, 1979.