Influence of Two Fire Intensities on Coarse Woody Debris in Pinus pumila-Larix gmelini Forests in Greater Hinggan Mountains

Pinus pumila-Larix gmelini forests are the typical vegetation on Greater Hinggan Mountains and were disturbed for a long time by fire.This study compared CWD volume and composition of natural Pinus pumila-Larix gmelini forest and two types of burned forests(lightly burned forest,heavily burned forest).The results showed that:The average volume of CWD was 59.92m3/hm2,199.77 m3/hm2,217.73 m3/hm2 in natural forest,lightly burned forest and heavily burned forest respectively.The volume of natural forest between burned forest was different,but no difference between lightly burned forest and heavily burned forest,which showed the fire disturbance changed the volume and altered the composition of coarse woody debris,but no big impact on the composition of CWD.The CWD diameter class was 2-20cm in natural forest and heavily burned forest,standing dead trees,fallen trees and stumps,each accounting for 34%,64% and 2% and 94%,5% and 1% of the total volume respectively.The CWD was diameter class 2-10 cm in lightly burned forest,standing dead wood,fallen trees and stumps,each accounting for the 47%,50% and 3% of the total volume respectively.It can be seen that the three types of forest of CWD were concentrated in small diameter of standing dead wood and fallen trees,that is,the small diameter of standing dead wood and fallen trees are the major source of CWD in the three types of forests.The volume of forests were increased after forests were disturbed by fire,and the fire may increase the CWD inputs.