Study on spatiotemporal difference and influencing factors of grassland yield in sunan county of Gansu province

Grassland ecosystem is the most important terrestrial ecosystem. Only by accurately estimating grassland yield and productivity can we effectively protect the ecosystem. This thesis is based on 323 monitoring data and MODIS-NDVI and MODIS-EVI vegetation index corresponding to the same period from 2012 to 2016, Based on the establishment of grassland yield estimation model, the grassland yield of Sunan County was estimated. The results show that: (1) After validating the model equations corresponding to the five production areas through the reserved precision verifying points, the model accuracy is higher than 90%, and it is feasible to estimate production by remote sensing.(2) From 2012 to 2016, the average yield of grass in Sunan County was 89.92 million tons, and the average yield per unit area was 524.12 kg/h m2.(3) Grass yield in Sunan County decreased from southeast to northwest during 2012-2016, and the overall grass yield showed a slow downward trend.(4) The annual grass yield in the study area is directly proportional to the annual precipitation and average annual temperature, and the annual precipitation has a greater impact on the annual grass yield.