Dynamic monitoring of straw burned area using multi-source satellite remote sensing data

Abstract: As a general definition, open field burning is the burning of living and dead vegetation. An annual average amount of 730 Tg biomass was burnt in Asia, out of which 250 Tg came from agricultural burning. Burning straw after harvest was common, and it was a significant seasonal source of air pollution, which should not be ignored in China. In recent years, straw combustion was serious in Henan Province in autumn, where mechanized farming was practiced, for the farmers were more inclined to burn the crop residues. At present, remote sense monitoring is a practical solution for detection and assessment of this burning. Many researchers used MODIS (moderate resolution imaging spectroradiometer) and FY data to monitor the straw combustion, but the spatial resolution of these data was low and cannot satisfy the requirement of high frequency and high precision monitoring. Especially, many mixed pixels exist in MODIS and FY remote sensing data, which aggrandized the difficulties to get the spatial distribution with high frequency and precision. So, effective and quick means were necessary to deal with this key problem. Generally, high frequency satellite observations could inverse the changing process of straw burned areas. In the present study, Landsat8, GF-1 and HJ-1A/B data were used comprehensively to improve the remote sensing spatial resolution, while the overlay analysis and the object-oriented image analysis (OOIA) methods were adopted to extract the straw burned areas in Taikang County. Based on the OOIA, the remote sensing interpretation sign was established through the ground investigation, and the straw burned area was extracted with a multi-term single-day form. Straw burned areas of 8 stages were extracted using the full-coverage remote sensing images. With the changing detection at the township scale, the temporal change trend of cumulative straw burned area, new added straw burned area and new added farmland plowing area after straw burned were calculated. The spatiotemporal spreading trend of straw burning showed that after the maize harvest, straw burned started at a certain point in time after a large area of crop was harvested, and spread from a number of fire points to a main direction with the time. The new added straw burned area changed with a wavy pattern, due to that intermittent large-scale plowing occurred subsequently in the added burned area. The rate of plowing was beyond the rate of straw burned, and the incineration activity tended to end. Compared with field observed data, the calculated area extraction accuracy was above 93.89%, and the calculated change trend of new straw burned area was basically consistent with the monitoring results of the Ministry of Environmental Protection. Experiment results have indicated that the method presented in this study is timely and accurate, which can reveal more details and regularities than traditional large-scale application of low spatial resolution satellite remote sensing data.