| Popis: |
Evaluation and quantification of vegetation photosynthetic activity (VPA) can provide crucial information for regional ecological environment management, especially in fragile ecosystems, such as the Yellow River Basin (YRB). In this research, MODIS products, solar-induced chlorophyll fluorescence (GOSIF), ChinaFLUX GPP and meteorological datasets were employed to explore the spatiotemporal dynamics of land use types, GOSIF and climate factors in the YRB during 2001-2021. Moreover, the partial derivative method was adopted to quantify the contributions of climate change (CC) and human activities (HA) to GOSIF trends. Results shown that: GOSIF data is applicable in China and can be used to evaluate the VPA in the YRB. The area of cropland, forest, built-up land and water bodies exhibited significant increasing trends, with that of grassland and other lands on the opposite. During 2001-2021, GOSIF and precipitation (Pre) exhibited significant increasing trends at a rate of 0.0014 W $\cdot $ m $^{-2}\cdot \mu $ m $^{-1}\cdot $ sr $^{-1}\cdot $ a−1 and 4.85 mm $\cdot $ a−1, respectively. Temperature (Tem) showed a fluctuating and insignificant upward trend at a rate of 0.0232°C $\cdot $ a−1, while solar radiation (Rad) exhibited an insignificant decreasing trend at a rate of 7.13 MJ $\cdot $ m $^{-2}\cdot $ d $^{-1}\cdot $ a−1. The proportion of climate factors with a significant partial correlation coefficient (PCC) with GOSIF follows the order: Pre (43.92%) > Rad (22.10%) > Tem (17.93%). For climatic factors, the area proportion of GOSIF trends dominated by Tem, Pre, and Rad were 24.36%, 29.89%, and 45.75%, respectively, with the dominance areas of Rad and Pre mainly distributed in most upper and middle YRB. The dominant climatic factor in GOSIF trends was generally consistent with the significance of climatic factors in spatial. For CC and HA, HA was the leading factor in GOSIF trends, accounting for 72.02% areas of the YRB. Combined effects of CC and HA promoted vegetation growth significantly in 85.92% areas of the YRB. The decreasing GOSIF in southwestern upper YRB and parts of northern upper YRB and southern middle YRB were attributed to the single effect of HA (1.83%) and combined effects of HA and CC (1.41%). Results of this study will provide an important reference for promoting ecological protection and high-quality development in the YRB. |
