there is increasing interest to develop quantitative approaches to carbon accounting and determine carbon sequestration potential at both the site and landscape scales. currently, our lack of understanding of fine root dynamics in northern temperate forest systems has hampered efforts to accurately parameterize any of the existing c budget models (e.g. , cbm-cfs3). the objectives of this study were to: 1) describe the various approaches most commonly used to estimate fine root biomass, highlighting their strengths and limitations, 2) develop species- and diameter class-specific standard root lengths (i.e. , factor for converting measured root lengths to biomass when using minirhizotron technologies) for selected northern temperate tree species, and 3) compare/contrast the estimates of fine root biomass, productivity, and turnover rates derived from the commonly applied indirect (i.e. , used in most carbon accounting models) and direct ( i.e., in situ stand-level measurements) methods. this study was conducted for three distinct northern temperate forest/stand types (i.e. , northern hardwoods - sugar maple; northern coniferous - jack pine; and boreal mixedwood - aspen, spruce, balsam fir).