Abstract: Radiation use efficiency (RUE) is one of the most useful parameters in crop growth models, and widely used in the remote sensing estimation of net primary productivity. Due to the effects of environmental factors, RUE varies with crop growth. The inaccurate estimation of RUE will lead to large errors in the simulation of net primary productivity. This paper analyzed the determination methods of cropland RUE and the variation characteristics of RUE, discussed the factors controlling RUE (e.g. solar radiation, temperature, vapor pressure deficit, leaf nitrogen content, and crop species), and pointed out the problems in current RUE studies. It was suggested that when using RUE as a parameter to simulate crop production, the variation of RUE with crop growth should be considered. Further works should be enhanced on the relationship between crop biomass and its intercepted radiation, and hotspot would be the study of RUE variation over short period of time scale (hours or days) by using micrometeorological methods such as the eddy covariance technique to provide reliable parameter for constructing carbon cycle models.

Key words: Wolong, Subalpine dark coniferous forests, Gap features