Abstract:In order to find the best way of managing shelterbelts,5 poplar tree species were selected from shelterbelts for studying fiber length.Based on the relationships between the fiber length and tree species,fiber length and site conditions,and fiber length and ages,the following results were obtained:the fiber length is determined mainly by species and age,and it is not significantly related to special site conditions of shelterbelts.Based on the distribution of fiber length, and the relationship between fiber length and age,a series of models about fiber length-age were established, and the relatively stable ages of fiber length were also obtained,the height of tree at the relatively stable ages can be considered as Hi(L=n*Hi)during designing shelterbelts.The above results can provide feasible evidence for shelterbelt management.