Growing demand and limited resources have encouraged industries to search for sustainable sources of raw materials. Different companies in wood industries are focusing on short and medium rotation plantations as their primary source of wood and fibers. This has led to substantial growth in the total areas of these plantations worldwide. It is predicted that more industries will change their production lines to fit this sustainable new resource. These plantations produce large quantities of by-products which is mostly in the form of bark chips. The sustainability in the production will be only met when the cascade utilization of the by-products is considered.\nIn this work bark of poplar trees as the most common trees in plantations, in Germany, was characterized to provide information for the possible applications in the manufacturing of various fiber-based materials. Furthermore, bark fibers were used in the production of natural fiber polymer composites as the most flexible and youngest industry in wood and fiber related industries. Natural fiber polymer composites have already created substantial commercial markets in different sectors, such as in structural applications (decking, fencing, etc.) as well as automotive interior parts \nThe structure of the bark of poplar trees (Max hybrid) from short rotation plantations were studied and bark fibers were extracted. The essential properties of the fibers including chemical composition, thermal behavior, fiber dimensions with the two mentioned industrial fiber production methods, density, and microfibril angle were investigated and reported in this research.\nBark fiber polymer composites (BFPC) were produced, as the second and most important aim of the presented work. Two bio-based polymer matrices of polylactic acid (PLA) and cellulose propionate (CP) and a commodity polymer (polypropylene (PP)) were used in the production of the samples. Various properties of the produced composite, with regard to the potential application areas in indoor and outdoor products, were investigated. The studied properties included: tensile, bending, impact as mechanical properties, as well as melt flow index, water absorption, and fungal resistance.\nRegardless of the matrix polymer, BFPCs showed lower mechanical properties than the reference WPC samples but better water absorption and slower fungal growth rate. Modification with the application of coupling agent (Maleic anhydride grafted polypropylene (MAH-PP)) and mercerization with sodium hydroxide showed positive results in improving the mechanical properties of BFPCs. Overall, this research has provided fundamental information for application of bark of short rotation plantation trees in wood industries.