Abstract: The forest coarse root biomass is an important part of forest ecosystem. In this paper,we talk about coarse root biomass about natural Larix gmelinii forest,use the average standard tree and all mining method to determinate different age coarse root biomass and distribution pattern of larch forests,and build the coarse root biomass regression model.The results showed that with the increasing of stand age,stand coarse root biomass increased.The root biomass of young forest(26 years,38 years)was 7.92 t/hm²,middle-aged forest(49 years,68 years)was 39.77 t/hm²,near mature forest(96 years)was 49.80 t/hm² and mature forest(132 years)was 74.11t/hm².In Larix gmelini individual biomass,the root biomass accounted for 16.40 ~ 27.25%.More than 65% of root biomass concentrated in the 0~20 cm soil layer.Root biomass increased, with soil depth power function decreased.Established DBH-coarse root biomass model B=0.011314D^2.7629 reached significant levels(R²=0.97).

Key words: Larix gmelini, coarse root biomass, root distribution