Soil-mediated effects on germination and seedling growth of coastal wattle(Acacia sophorae) by the environmental weed, bitou bush (Chrysanthemoides monilifera ssp rotundata)

Bitou bush (Chrysanthemoides monilifera ssp. rotundata; Asteraceae) is a ma jor woody weed that competes with the native legume Acacia sophorae in coas tal ecosystems of eastern Australia. Three glasshouse experiments examined whether litter or soil from beneath bitou bush or Acacia plants could influ ence seed germination and seedling growth of A. sophorae. The presence of l itter decreased seed germinability and this effect was greater for bitou bu sh litter than for Acacia litter. Shoot growth was increased by the additio n of Rhizobium after 40 days, irrespective of soil type. After 78 days, sho ot and root biomass were significantly lower for seedlings grown in bitou b ush soil than for those grown in Acacia soil. There was a non-significant t rend towards a lower median population of Rhizobium in the soil beneath bit ou bush than in that beneath Acacia. The results demonstrated a slight effe ct of bitou bush on the growth of A. sophorae, which could, however, be ove rshadowed by the judicious use of herbicides or fire for weed control and r evegetation.