The Temporal-Spatial Changes Of Vegetation Npp In The Main Forest Areas Of Henan Province Based On CASA Model

Vegetation net primary productivity(NPP)to a certain extent reflects namely vegetation growth and health status of vegetation generating capacity under natural conditions.It is an important indicator of vegetation’s ability to accumulate organic matter and an important parameter for evaluating the quality of terrestrial ecosystems.In 2014,the“Henan Provincial Main Research Area Plan”determined to establish the province’s ecological security strategic pattern with“four areas and three belts”as the main body.Taihang Mountain Ecological Area,Funiu Mountain Ecological Area and Tongbai-Dabie Mountain Ecological Area are the key forest ecology in Henan research area.In this paper,the main forest area in Henan Province is used as the research area.The CASA model is used to estimate the NPP from April to September of 2000-2018in the research area.The correlation between NPP and meteorological factors in the area,and a comprehensive evaluation index can be constructed to assess the quality of the ecological quality of the study area.The main findings are as follows:(1)By comparing the NPP estimated by the CASA model based on the modified parameters with the MOD17A3 product,it is found that R~2 is above 0.6.(2)The spatial distribution of NPP in the study area has its own characteristics in the horizontal direction due to the different geographical environment of each ecological area within the study area.The altitude in the vertical direction has become one of the factors limiting the growth of NPP in the Taihang Mountain Ecological Area and the Tongbai-Dabie Mountain Ecological Area.From 2000 to 2018,the NPP in the Taihang Mountain Ecological Region and the Tongbai-Dabie Mountain Ecological Region showed an upward trend,but the NPP in the Funiu Mountain Ecological Region showed a downward trend in the past 19 years.(3)On the annual scale,the NPP in the Funiu Mountain ecological zone is mainly affected by temperature and precipitation,while the NPP in the Taihang Mountain ecological zone and the Tongbai-Dabie Mountain ecological zone are mainly affected by temperature and precipitation,respectively.With the changes in the month,the meteorological factors that affect the NPP in each ecological zone are also constantly changing.(4)Through the construction of the comprehensive evaluation index,it was found that the annual average comprehensive evaluation indexes of Funiu Mountain Ecological Area,Taihang Mountain Ecological Area and Tongbai-Dabie Mountain Ecological Area on the annual scale were 0.53,0.43,0.45.On the monthly scale,the three ecological zones within the study area all achieved the best ecological quality in July and August.The ecological quality within the study area from high to low is the Funiu Mountain Ecological Area,Tongbai-Dabie Mountain Ecological Area,and Taihang Mountain Ecological Area.