Separation of dead and live fine mangrove roots in core samples from Hinchinbrook Island, north Queensland

The dead and live fine root content of mangrove soils was analysed from cores taken from Rhizophora stylosa and Ceriops tagal forests in Missionary Bay, Hinchinbrook Island.One metre long sediment cores, 6cm in diameter, were taken in mangrove forests in the high, mid and low inter-tidal zones. Cores were cut into 10 cm segments and sediment was removed from the roots by wet sieving in the field. Roots were stored in plastic bags at -18°C for up to 3 months until live and dead fine roots were separated using a technique involving solutions of colloidal silica (LUDOX). The method is based on separating roots on the basis that live roots have a lower specific gravity than dead roots. Optimal results were achieved when samples were first mixed in a 11% LUDOX solution. The top layer was then decanted off and further separated by mixing in a 6% LUDOX solution.The efficiency of the method was quantified by staining and examining all roots from separated samples microscopically, to identify dead and live roots not separated by the process. This research was undertaken to develop a rapid, highly efficient method for separating dead and live fine roots to enable investigation of fine root mass and the role of fine root dynamics in plant community materials budgets in tropical mangrove forests.