Simulation And Estimation Of Net Primary Productivity Of Forest Ecosystem In Qinling Mountains

Net Primary Productivity?NPP?refers to the difference between fixed carbon in plant photosynthesis and carbon consumed by autotrophic respiration,and is one of the important indicators for measuring the impact of climate change on ecosystems.NPP can not only reflect the growth of vegetation in the ecosystem,but also be an important part of the terrestrial carbon cycle.The main methods of NPP estimation include two methods:actual measurement method and model simulation method.At present,the more commonly used model simulation method can estimate NPP at regional or global scale efficiently and accurately,which is the most important means to study NPP at regional or global scale.Qinling is an important natural geographical indication in China.It is not only the north-south boundary line of China,but also contains abundant animal and plant resources.Exploring the trend of NPP in Qinling Mountain is crucial for studying the impact of climate change and regional ecosystem management.Based on the meteorological data,NDVI data,global climate model data and NCEP reanalysis data of the Qinling Mountains,this study first used the C-FIX model to simulate the NPP of the Qinling Mountains from2000 to 2015 and studied its relationship with climatic conditions,and constructed NPP.The auxiliary model with climatic conditions;the ASD statistical downscaling model is used to estimate the climate change of the Qinling Mountains in 2016-2100;finally,the climatic conditions of 2016-2100 are brought into the auxiliary model to simulate the Qinling Mountains in 2016-2100.The change in NPP.The research results are as follows:?1?The NPP range of forest ecosystems in Qinling Mountains in Shaanxi Province from 2000 to 2015 is 0-1253.73 gC·m^-2·a^-1,with an average of 1019.46gC·m^-2·a^-1.The distribution is mainly reflected in the south slope.Above the north slope,the west is higher than the east,the high-altitude forest land is lower than the middle-low-altitude forest land,and the population gathering area is lower than the natural forest land.In terms of interannual variation,the NPP value fluctuated greatly from year to year from 2000 to2015,but the growth trend is very obvious.From the perspective of the trend of NPP,it can be roughly divided into two stages:the inter-annual fluctuation of NPP between 2000 and2010 Large,the upward trend is not obvious;in 2010-2015,except for 2014,NPP showed a rapid upward trend.?2?The NPP change from 2000 to 2015 is strongly consistent with temperature changes:as the temperature rises,NPP continues to rise.Similarly,NPP gradually decreases as the temperature decreases.There is a significant correlation between temperature and NPP in the current month,and there is a certain hysteresis effect.There is also a certain consistency between precipitation changes and NPP changes,but the consistency is not high.The precipitation changes have certain influence on NPP,but it is not the most important influencing factor.Precipitation changes have a strong influence on NPP in the month,but the hysteresis effect is weak,or there is no obvious hysteresis effect.?3?In the future,the NPP changes in the 21st century,from the annual scale,in the RCP4.5 scenario,the increase of the NPP in the Qinling Mountains in the next three periods is 53.36gC·m^-2,75.35 gC·m^-2,79.93 gC·m^-2,indicating that the NPP of Qinling Mountain has the largest growth in the early 21st century,and the medium-term growth begins to slow down.The change of NPP in the later period is minimal;under the RCP8.5scenario The increase of NPP in the Qinling Mountains in the next three periods compared with the baseline period is 55.06 gC·m^-2,94.54 gC·m^-2,132.61 gC·m^-2,respectively.It shows that the NPP of Qinling Mountain has gradually increased,and there is a trend of increasing growth rate.?4?In the NPP change regional scale in the 21st century,in the RCP4.5 scenario,the distribution pattern of NPP in the early 21st century is higher than that in the base period:the negative growth rate is distributed in the higher altitude region,the central growth rate is lower,and the northwest growth rate is lower.The highest medium-term distribution pattern is:the northwest region has a higher growth rate,and the southern region and the high-altitude region have lower growth rates.The latter distribution pattern is:the middle-high altitude region in the central region and the northern region have higher growth rates,and the high-altitude region has a lower growth rate.In the RCP8.5 scenario,the main distribution pattern of NPP growth rate in the Qinling Mountains in the early 21st century is:the growth rate is highest in the northwest and northeast regions,and the growth rate in the central region is relatively low;the medium-term distribution pattern is:the growth rate is low(The<10%area is mainly distributed in the south and the west.The growth rate in the central region is relatively high,and the growth rate in the northwest region is the highest.The distribution pattern in the late 21st century is:the overall distribution pattern shows a distinct step-like distribution:From south to north,the growth rate from east to west is gradually increasing.