Estimate Of Saline-alkali Region Grassland Npp In West Of Jilin And Spatial-temporal Characteristics Research

The green vegetation net primary productivity refers to the surface of the earth in unit time and per unit total accumulation of dry matter of organic matter.Use mutual matching of remote sensing data,meteorological data,ground experimental data,set up CASA model estimation west jilin farming-pastoral area grassland NPP take Da'an as an example.The research results can provide reference for the estimation of grassland productivity in western Jilin and even the same latitude area,and provide reference for the study of the multi-temporal NPP estimation,The main research results are as follows:1.Based on the field data,the optimal value of the maximum energy utilization rate of the three main grassland types in Da'an is determined by using the least squares method.:Normal grassland 0.415 MJ·m^-2? Light salt strong alkaline grassland 0.105 MJ ? m^-2?Herbal marsh 5.005 MJ ? m^-2.The maximum light utilization rate obtained from the measured sample data is more regional representation and authenticity,and it is better to estimate the NPP of the study area2.The changes in NPP in Da'an are mainly affected by the amount of solar radiation and temperature.The average temperature of 0 ? is the critical temperature of grass growth and dormancy.When the average temperature is greater than 0?,the plant began to turn green,NPP began to increase;When the average temperature in the late autumn and early winter is lower than 0?,the plants began to enter the hibernation state,NPP is in the very low level range of 0-1g C ? m^-2? ?^-1;The fluctuation of solar radiation in the growing season directly affects the accumulation process of organic matter in the plant,which in turn affects the value of NPP.3.Da'an 2005-2009-2016 year total NPP in order: 10824×108g C ? m^-2? ?^-1?18849×108g C ? m^-2? ?^-1?34238×108g C ? m^-2? ?^-1,Among them,the Sikeshu town's total amount NPP and the NPP are far ahead in the townships of the city,and the Unite town's total NPP and NPP is at the end of the township.High NPP total area is mainly concentrated in the Chagan Lake,Cattle-heart Moisturizing,New-wasteland,Jiangjiadian Grassland and Five-room Reservoirs of these locations.4.The annual period of March to October is NPP changes in the period of time,during this period NPP parabola in the form of change.The NPP of Light and alkali alkaloid grassland varies from 1 to 35 g C ? m^-2? ?^-1,Normal grassland varies from 1 to 130 g C ? m^-2? ?^-1,Herbal marsh varies from 1 to 1779 g C ? m^-2? ?^-1.Different vegetation types basically peaked in early August.