Quantitative Assessment of NPP Changes in the Yellow River Source Area from 2001 to 2017

Abstract It is of great significance to quantitatively evaluate the ecological degradation and restoration Yellow River source area from 2001 2017. Net primary productivity (NPP) core indicator used indicate health terrestrial ecosystems. Based on improved CASA (Carnegie-Ames-Stanford Approach) model MOD17A3 NPP products, 174 measured sample sites were validate simulation results, select with higher accuracy as actual simulation, using Theil-Sen median trend analysis Mann-Kendall test investigate dynamics changes. The results are follows: (1) than that product, it more suitable for in River; (2) Source region has shown a fluctuating upward net over past 17 years, 50% showing slight improvement, 36% significant 13% decline, only 1% average annual growth rate 2.6 g C/yr-1. Compared 2001, 2017 increased by 5.24×10 12 C.