Forestcheck: the response of vascular flora to silviculture in jarrah (Eucalyptus marginata) forest

Abstract

Summary Forest understorey vascular plants were monitored across a sequence of time since treatment to assess the effects of silviculture (timber harvesting and regeneration systems) in jarrah (Eucalyptus marginata) forest in south-west Western Australia. Species richness, abundance and structure were assessed at 48 sites in four jarrah forest ecosystems. Monitoring grids in reference forest, which was either uncut or had not been harvested for at least 40 y, were compared to grids in forest that had undergone shelterwood/selective cut and gap release silvicultural treatments. A total of 446 plant species was recorded of which 68, 22 and 35 species were recorded on only one grid within the reference, shelterwood/selective cut and gap release treatments respectively. Silvicultural treatments had no significant long-term effect on mean species richness and abundance of understorey plants, but had a distinct influence on plant community composition. Reference forest had more species of small and medium shrubs compared with silvicultural treatments. Xanthorrhoea preisii (a grass tree) was significantly less common in silvicultural treatments compared with reference forest and Allocasuarina fraseriana (a small to medium tree) and Kennedia coccinea (a vine) were more common on harvested grids. The mean number of plant species per grid was not significantly different between treatments or forest ecosystems. There was, however, strong regional variation in plant community composition, especially in the Jarrah Blackwood Plateau and Jarrah South forest ecosystems and which probably reflects the influence of climatic and edaphic factors on jarrah forest species composition. Dominance-diversity curves for each treatment showed that ranking of species with high abundance was similar in all treatments, but varied between treatments for species with very low abundances. There was no significant relationship between species richness and time since last fire because field assessments were carried out at least 3–13 y after disturbance, by which time species assemblages had stabilised.