Cambridge Journals Online

Research Article

Temporal and spatial variation of fine roots in a northern Australian Eucalyptus tetrodonta savanna

David P. Janosa1 c1, John Scotta1 and David M. J. S. Bowmana1 p1 a1 Cooperative Research Centre for Tropical Savannas, Parks and Wildlife Commission of the Northern Territory, PO Box 496 Palmerston, Northern Territory 0831 Australia

Article author query janos dp   scott j   bowman dm

Abstract:

Six rhizotrons in an Eucalyptus tetrodonta savanna revealed seasonal changes in the abundance of fine roots (≤ 5 mm diameter). Fine roots were almost completely absent from the upper 1 m of soil during the dry season, but proliferated after the onset of wet-season rains. At peak abundance of 3.9 kg m⁻² soil surface, fine roots were distributed relatively uniformly throughout 1 m depth, in contrast with many tropical savannas and tropical dry forests in which fine roots are most abundant near the soil surface. After 98% of cumulative annual rainfall had been received, fine roots began to disappear rapidly, such that 76 d later, less than 5.8% of peak abundance remained. The scarcity of fine roots in the upper 1 m of soil early in the dry season suggests that evergreen trees may be able to extract water from below 1 m throughout the dry season. Persistent deep roots together with abundant fine roots in the upper 1 m of soil during the wet season constitute a ‘dual’ root system. Deep roots might buffer atmospheric CO₂ against increase by sequestering carbon at depth in the soil.

(Accepted January 16 2008)

Key Words: open forest; rhizotron; root depth profile; root-length density; root phenology; savanna woodland; small roots; traced root abundance

Correspondence:

^c1 Corresponding author: Department of Biology, University of Miami, P.O. Box 249118, Coral Gables, Florida 33124-0421, USA; email: davidjanos@miami.edu

^p1 Current address: School of Plant Science, The University of Tasmania, Private Bag 55, Hobart Tas. 7001, Australia