Review on biomass expansion factors for forest

Forest biomass is an important basic data to study the structure and function of forest ecosystem, Biomass Factors (BEs) is the important method for estimation of forest biomass. And biomass expansion factor (BEF), one of the important estimation parameters, is mainly used for the conversion between the stem biomass and total biomass and other forest dimensions of the biomass. This paper analyzed the research status of BEF, the definition of BEF and its relationship with the forest type, tree size, stand density change and other factors. And some problems were found, such as the inconsistencies between method and definition, the lack of systemic research on influence factors, and the poor applicability of BEF datum. Finally, the research on BEF was prospected.