Hakea sericea: Seed production and role in succession in golden bay, nelson

Abstract

Seed production and role in succession of Hakea sericea are examined in relation to its status as a weed in Abel Tasman National Park and the Aorere Valley, and compared with the results of a previous study of H. salicifolia. Vegetation composition was assessed within plots, and 42 bushes were felled and their follicles counted and classified according to maturity. Bushes begin to produce follicles when they are 1 m tall. When taller than 2 m they have 300–400 closed follicles, amounting to 260 per m2 of ground surface. This is about half the load borne by H. salicifolia stands. Both species release abundant seeds during their lives but H. salicifolia has a potentially longer establishment period after a fire. H. sericea possibly tolerates poorer soils and greater exposure than H. salicifolia, but their present distribution patterns may also reflect differences in historical use and dissemination.H. sericea does not produce annual growth rings, and the proportion of closed, open, and green follicles was used as an indicator of relative age-state (e.g., whether reproductive) of the bush. H. sericea reaches its maximum height of c. 7 m in 15–20 years. At this point it becomes susceptible to wind throw, although its age-state may not indicate senility. When growing in mixed stands with Leptospermum scoparium and Kunzea ericoides, H. sericea gives way to these species. In contrast, dense stands of tall H. sericea lack a developing subcanopy layer of broadleaved species; after collapse of the H. sericea, the gaps are occupied initially by Pteridium esculentum. In conservation areas, H. sericea need not be controlled where it will be replaced by indigenous forest, but it should be controlled where fires would encourage its spread into herbaceous vegetation of high conservation value. © 1992 Taylor and Francis Group Ltd.