Germinable soil seed banks in native pastures in north-eastern Australia

Abstract

Germinable soil seed banks were determined in 20 native pasture communities of widely varying composition (dominated by native tussock grasses, Bothriochloa pertusa, or forbs) near Collinsville (20¦34'S, 147¦51'E). Samples of surface soil (0-10 cm) were taken during the late dry season, seeds were germinated in a shadehouse, and seedlings were identified and counted. Over all pastures there were seeds of 100 species in the seed banks, including 29 grasses (14 perennial), 11 legumes, 8 sedges, and 52 forbs. Total seed numbers varied among pastures from 210 to 9770/m2. Forbs were the most numerous component, followed in order by sedges, perennial grasses, annual grasses, and legumes. Of the 790 seeds/m2 of perennial grasses, the naturalised species B. pertusa contributed 620/m2. Even though the native perennial grasses were prominent in these pastures, they had few seeds in the soil, especially when the pastures had been heavily grazed. To maintain these grasses in pastures, management should aim to prevent excessive mortality of the perennial plants as seedling regeneration could be limited by the small seed numbers available.