“…Net primary productivity (NPP), defined as the amount of organic matter photosynthetically fixed by vegetation per unit area and time (Field, Behrenfeld, Randerson, & Falkowski, 1998; Gang et al, 2015; Imhoff et al, 2004), is the material basis of numerous ecosystem functions (Song, Dannenberg, & Hwang, 2013; Zhang, Wang, Wang, Yang, & Li, 2020b; Zhao, Liu, Zhang, Cui, & Zhao, 2019). As an effective indicator of environment changes, the variation of NPP over a range of time intervals can well reflect ecological status (Guo et al, 2020; Jenkins, Fleenor, & Dietz, 2019; Zhao et al, 2018).…”