Effect of Fertilizer on Fine Root Density and Shoot Growth in Chilean Matorral

Abstract

The effect of a fertilizer dose of 20 g nitrogen (N), 16 g phosphorus (P), and 20 g N + 16 g P m-2 on fine root growth and shoot development of four common shrubs was tested in the Chilean matorral, a typical mediterranean-type shrub vegetation. The fine root density (root diameter ~< 2 mm) was highest in late spring and lowest in late summer. The mean fine root length for the 6 mo research period reached 2 km m-2 in Lithraea caustica in the unfertilized controls and 7 km m-2 with N fertilization. Colliguaya odorifera responded similarly. In Cryptocarya alba, fertilizer reduced total fine root length. The fine roots of Trevoa trinervis, a N2-fixing shrub, did not respond to N addition, but enhanced fine root growth with P was observed. The effect of P and N + P on the other shrubs was erratic. In general, fertilizer application shifted the time of the peak of fine root biomass production from spring toward summer. Shoot response to fertilizer became visible only in the second growing season. Nitrogen enha...