Fine root density and root biomass of two Douglas-fir stands on sandy soils in the Netherlands. 2. Periodicity of fine root growth and estimation of belowground carbon allocation

Abstract

Number of Pseudotsuga menziesii white root tips was used as an indication of periodicity of fine root growth. In the first year the number of white root tips peaked just before budbreak, and then decline gradually towards autumn. Despite a fairly high soil temperature in the winter, few white root tips developed between October-April. In both stands, most fine roots died during the dry spring of the second year. Many fine roots apparently died at bulk soil water pressure heads of around -0.08 MPa. Due to dry periods in the second year of observation, the periodicity of fine root growth showed a different pattern, especially in the stand with lower water holding capacity in the soil. In the less productive stand more carbon per surface area is allocated to the fine roots than in the more productive stand, but the carbon allocation to the coarse roots is greater in the more productive stand. -from Authors