Abstract: Carbon use efficiency (CUE) is defined as the proportion of carbon (C) received from the environment that is used for growth. As one of the key indicators for the ability of biological carbon sequestration, it is widely implemented in the carbon cycle and process-based models. Research on CUE is carried out by various methods at multiple scales. However, the results of different methods vary greatly because of the scale-dependence of CUE, which makes the results difficult to integrate, becoming a vital factor restricting the research methods and application of CUE. In this review, we classified the common CUE acquisition methods into plot-scale, ecosystem-scale, landscape & regional scale and continental & global scale. We summarized the characteristics, advantages and limitations of each method. The progress of CUE application in research is reviewed at each scale. It is found that CUE is influenced by biotic and abiotic factors, which control CUE at different spatial and temporal scales. Moreover, the value of CUE varies with methods and scales applied in study. In order to deepen the understanding of CUE, future research should comprehensively consider the interactive effects of biological and environmental factors, improve the accuracy of data measurement, and promote model optimization by integrating multi-scale results.

Key words: carbon use efficiency (CUE), acquisition method, multi-scale, multi-source data.