Effects Of Climate And Land Cover Change On NPP Of Terrestrial Ecosystem In The Yellow River Basin From 2000 To 2020

As an important ecological security barrier in China,the Yellow River Basin（YRB）is the focus of population activities and economic development,and plays an important role in the overall development of the country.Ecological protection and high-quality development of the YRB has become an important national strategy.In recent years,with the acceleration of urbanization in the YRB and the implementation of ecological projects,such as returning farmland to forest（grass）and three-north shelterbelt,the pattern of land cover in the YRB has changed significantly.However,previous studies have paid more attention to the effects of LUCC（Land Use and Land Cover Change）or climate change on vegetation productivity in the YRB.Therefore,this study used WRF（Weather Research and Forecasting Model）and IBIS（Integrated Biosphere Simulator）to quantify the impact of LUCC,climate change and their coupling effect on the net primary productivity（NPP）of terrestrial ecosystem in the YRB from 2000 to 2020.This study provides a scientific basis for ecological protection of the YRB.The main contents and findings of this paper are as follows:（1）The localization of physical parameter scheme of WRF and the localization of soil texture parameters and vegetation functional parameters of IBIS were realized.Different physical parameter configurations,as well as simulation experiments on soil and vegetation parameter configurations,were conducted for the WRF and IBIS.Remote sensing data and observation data were combined to evaluate the WRF and IBIS.The WRF model was used to simulate the temporal and spatial process of climate change in the YRB.Based on the land cover data of the YRB from 2000 to 2020,the temporal and spatial process of climate change in the YRB was simulated.The results show that the spatial distribution of annual average temperature in the YRB decreases from east to west,and the average annual temperature in the south is higher than that in the north.The spatial distribution of precipitation decreases gradually from south to north.The interannual variations of air temperature and precipitation show an upward trend,and the overall climate of the YRB tends to be warm and humid.（2）From 2000 to 2020,the interannual variation of NPP in the YRB showed a significant upward trend and had obvious correlation with LUCC.The IBIS was used to quantify the impact of LUCC on the NPP of terrestrial ecosystem in the YRB.The LUCC led to an average increase of 2.00 g C m^-2 of NPP in the YRB in the past 20 years.From 2000 to 2020,the change of NPP caused by LUCC increased from 0.82 g C m^-2 to2.51 g C m^-2.The change of NPP showed a consistent spatial distribution pattern with LUCC,which showed that the NPP decreased obviously in the areas with the growth of construction land,while the NPP generally increased in the areas with the growth of grassland and woodland.From 2000 to 2020,the change of NPP in the YRB caused by LUCC showed a fluctuating upward trend,and the growth rate of NPP change from 2000to 2010 was higher than that from 2011 to 2020,which was consistent with the interannual change characteristics of intensity of LUCC in the YRB.（3）From 2000 to 2020,the change of NPP in the YRB caused by climate change showed a significant downward trend and then an upward trend.Based on the WRF,the climate data under different land cover scenarios were simulated,and the IBIS was used to quantify the impact of climate change on the NPP of the terrestrial ecosystem in the YRB.It is found that the change of climatic conditions caused by LUCC in the past 20 years has led to an average decrease of 0.07 g C m^-2 of NPP in the YRB.However,from 2000 to 2010,the change of NPP caused by climate change has decreased from 1.64 g C m^-2 to-1.56 g C m^-2,showing a significant downward trend,and increased to 1.19 g C m^-2 from 2010 to 2020.On the seasonal scale,the influence of the climate change in summer and autumn on the NPP of terrestrial ecosystem in the YRB is more obvious than that in other seasons.（4）From 2000 to 2020,the change of NPP in the YRB was more sensitive to climate change,and the LUCC made a greater contribution to the change of NPP in the YRB.Based on the climate data under the coupling effect of LUCC and climate change,the study quantified the impact of coupling effect on the NPP of terrestrial ecosystem in the YRB combined with the IBIS.The results showed that the coupling effect increased the NPP of terrestrial ecosystem in the YRB by an average of 2.07 g C m^-2 from 2000 to 2010.The change of NPP caused by coupling effect decreased from 1.83 g C m^-2 to-0.11 g C m^-2,showing a downward trend,and showed an obvious fluctuating upward trend from 2010 to 2020,increasing to 1.82 g C m^-2.The interannual change of NPP caused by coupling effect and the interannual change of NPP caused by climate change both showed a trend of decreasing at first and then fluctuating upward,and the growth of the change of NPP caused by coupling effect was closer to that caused by LUCC.The response of the change of NPP in the YRB from 2000 to 2020 was more sensitive to climate change than that to LUCC,and the contribution of LUCC to the growth of the change of NPP in the YRB was greater than that of climate change.