This study investigated root biomass and productivity in dominant plantation populations in western Sichuan, China. A total of 4 plots (Picea balfouriana plantation population for 28 age in Maerkang, 9 trees, mean DBH of population for 10.4 cm and height for 10.5m; Larix maxteriana plantation for 22 age in Wolong, 9 trees, mean DBH of population for 17.0cm and height for 13.8
m; Abies fabri plantation for 35 age in Ebian, 18 trees, mean DBH of population for 14.1cm and height for 11.9m; Larix kaempferi plantation for 23 age in Miyaluo, 8 trees, mean DBH of population for 17.4 cm and height for 14.5m; a 20 m×25 m plot located on each of the 4 types in western Sichuan, China) were randomly selected and excavated to a depth of 60cm for each of the 4 plantation population types. To estimate the root biomass of an individual tree using D2H, an exponential model was selected with the highest coefficient ranging from 0.94 to 0.99. The total root biomass per hm2 varied among plantation population types following the order: Larix kaempferi (37.832 t/hm2)>Abies fabri(24.907t/hm²)>Larix maxteriana(18.320 t/hm²)>Picea balfouriana population(15.982t/hm2). The biomass fractions of a given root size class compared to the total root biomass differed among plantation population types. For all 4 studied plantation types, the majority of the roots were distributed in the top 40 cm of soil, e.g. 97.88% for Picea balfouriana population, 96.78% for Larix maxteriana, 95.65% for Abies fabri, and 99.72% for Larix kaempferi population. The root biomass fractions distributed in the top 20 cm of soil were 77.13% for Picea balfouriana，77.13% for Larix maxteriana，65.02% for Abies fabri and 80.66% for Larix kaempferi, respectively. The root allocation in the 0～20, 20～40, and 40～60 cm soil layers gave ratios of 34∶12∶1 for Picea balfouriana, 24∶6∶1 for Larix maxteriana, 15∶7∶1 for Abies fabri, and 64∶4∶1 for Larix kaempferi populations. The root biomass density of dominant plantation population was 10.782 t/(hm²•m) (for Picea balfouriana)，8.230 t/(hm²•m)(for Larix maxteriana)，14.546 t/(hm²•m) (for Larix maxteriana),，13.211 t/(hm²•m) (Larix kaempferi population), respectively. The root biomass productivity was found to be 0.57 t/(hm²•a) (for Picea balfouriana), 0.83 t/(hm²•a) (for Larix maxteriana), 0.71 t/(hm2•a) (for Abies fabric) and 1.64 t/(hm²•a) (Larix kaempferi population), respectively.