Study On Regional Vegetation Chlorophyll Based On The Change Of Environmental Factors

Chlorophyll directly or indirectly participates in the photosynthetic process of plants,absorbing light energy into chemical energy.In this study,ACRM model and Landsat 8 satellite images were used to analyze the spatial and temporal characteristics of chlorophyll content.The spatialization of environmental factors was realized by combining Landsat 8 satellite image data.The response of chlorophyll content to environmental factors in the study area was analyzed by generalized additive model(GAM),Person correlation analysis and path analysis.The main research contents and results are as follows:(1)Accuracy verification and spatial-temporal distribution characteristics of chlorophyll content inversion.In this study,based on the ACRM model and Landsat 8satellite image data,the chlorophyll content of the turning green period,the grassy period,and the yellowing period in the study area from 2013 to 2022 was retrieved,and the accuracy was verified by the measured chlorophyll content on the ground.The correlation coefficient R2 between the inversion result and the measured chlorophyll content is 0.658 in the turning green period(May),0.589 in the grassy period(July),and 0.658 in the yellowing period(September),indicating that the ACRM model can invert the chlorophyll in the Xilinhot area.The maximum and average values of chlorophyll content in the returning green period,grassy period and withered yellow period in the study area showed an upward trend;during the whole growing season,the annual maximum of monthly chlorophyll content showed the peak period > regreening period > withering period.In terms of spatial distribution,the chlorophyll content in the study area showed a distribution pattern of high in southeast and low in northwest.(2)Accuracy verification and spatial-temporal distribution characteristics of environmental factors spatialization.The inverse distance weighted interpolation method was used to realize the spatialization of atmospheric environmental factors(atmospheric temperature,atmospheric pressure,light hours,atmospheric relative humidity,cumulative precipitation)from 2013 to 2022.The Landsat8 image was used to invert the soil environmental factors(surface temperature,soil total nitrogen content,soil phosphorus content,soil nitrogen content,soil potassium content,soil moisture,soil p H,soil organic carbon content)and biological environmental factors(vegetation coverage,grassland carrying capacity)from 2013 to 2022,and the accuracy was verified by the measured environmental factor data.The correlation coefficient R2 between the measured value and the simulated value of each environmental factor is greater than 0.400,indicating that the spatialized environmental factors can be used for the study of relevant content in this area.From 2013 to 2022,the atmospheric temperature,atmospheric relative humidity and cumulative precipitation showed a significant upward trend,which was consistent with the temporal variation of plant chlorophyll content.Soil moisture showed an upward trend,and other soil environmental factors generally changed little,and the fluctuation was not obvious.Vegetation coverage showed an upward trend,and the change of livestock carrying capacity was not obvious.(3)The response of regional vegetation chlorophyll content to environmental factors.a)Based on the spatial distribution characteristics of vegetation chlorophyll content and the distribution characteristics of spatial environmental factors in the study area from 2013 to 2022,the single factor generalized additive model was used to analyze the response of regional vegetation chlorophyll content to various environmental factors.The results showed that the environmental factors that contributed more to the chlorophyll content of vegetation in the regreening period were cumulative precipitation,surface temperature and soil moisture.The environmental factors that contribute more to the effect of vegetation chlorophyll content in the grass period are vegetation coverage,atmospheric relative humidity,and sunshine hours.The environmental factors that contribute more to the effect of vegetation chlorophyll content during the withering period are vegetation coverage,atmospheric temperature and cumulative precipitation.b)Based on the annual average vegetation chlorophyll content and annual average environmental factors in the study area from 2013 to 2022,the response degree of regional vegetation chlorophyll content to various environmental factors was analyzed by using the multi-factor generalized additive model.The results show that the environmental factors that contribute greatly to the annual average vegetation chlorophyll content are cumulative precipitation,atmospheric temperature,and vegetation coverage.c)Based on the average chlorophyll content and environmental factors in the study area from 2013 to 2022,the direct response of chlorophyll content to environmental factors was analyzed by Person correlation analysis and path analysis.The influencing factors of vegetation chlorophyll content in regreening stage: cumulative precipitation >surface temperature > soil moisture > vegetation coverage > soil total nitrogen content >soil total potassium content > soil total phosphorus content > soil p H > atmospheric temperature > atmospheric pressure > sunshine hours > atmospheric relative humidity >soil organic carbon content.The influencing factors of vegetation chlorophyll content in full grass period: vegetation coverage > cumulative precipitation > atmospheric relative humidity > soil total nitrogen content > surface temperature > sunshine hours >atmospheric temperature > atmospheric pressure > soil total phosphorus content > soil moisture > grassland carrying capacity > soil total potassium content > soil p H > soil organic carbon content.The influencing factors of vegetation chlorophyll content in the yellowing period: vegetation coverage > atmospheric temperature > cumulative precipitation > atmospheric relative humidity > soil moisture > surface temperature >sunshine hours > soil total nitrogen content > soil total potassium content > soil total phosphorus content > atmospheric pressure > soil pH > soil organic carbon content.