The Study On Burned Area Mapping And Vegetation Regeneration Based On Remote Sensing Data In Heilongjiang Basin

Heilongjiang Basin, which is located in both ecotones of the east of temperatesteppe in Eruasia and the south of boreal forest, is across over China, Mongolia andRussia. High vegetation cover and inherent climate conditions make it become one ofthe most effected regions by forest fire. Especially in Russia, the regeneration ofvegetation in burned area is mainly a natural process and makes it a representativeregion for forest fire study. Therefore, we chose Heilongjiang basin as the study area,extracted the burned area information of it from2000to2011, and analyzed thevegetation regeneration process of the burned area by both qualitative and quantitativemethods.Based on remote sensing data, we firstly proposed a burned area extractingalgorithm using MODIS time series data, and extracted the burned area information ofHeilongjiang basin from2000to2011. Based on it, we took remote sensingphonological parameters as the evaluation indexes for qualitative analysis of thevegetation regeneration. Then, we used vegetation index and NPP quantitativeanalyzed the vegetation regrowth process. Finally, based on TM/ETM remote sensingdata, we analyzed the vegetation regeneration process under different fire severity.The main conclusions were as follows:1. Under the regional scale, MODIS data can be used to extract the burned areawith higher accuracy. We took Heilongjiang province as the example to validate thealgorithm based on MODIS time series data. The result showed that the total accuracywas71%which is higher than other burned area mapping algorithm under regionalscale.2. Heilongjiang basin was seriously affected by fire. From2000to2011, theannual average value of burned area was0.53million ha. The most affected year was2003with the burned area of14.68million ha. And the least affected year was2010,the burned area just0.18million ha. The forest fire mainly distributed in Russia andHeilongjiang province of China, which has higher vegetation cover. 3. The vegetation dynamic change of burned area was slowly, especially in thehigh burn severity region, and it took a long time of the vegetation phenology featuresreflected a forest’ characters. We chose seven phonological parameters as theevaluation index including EVI maximum value, minimum value, mean value andamplitude, the start time of growing season, the end time of the growing season andthe growing season length. The result showed that there was a obviously decline ofEVI value between pre-and post-fire. The vegetation regrowth would more fast wherethe burn severity was lighter. But in high burn severity area, the regeneration processwas slow.4. The recovery of vegetation index of burned area was similar with the NPPrecovery process, both were a slow process. Fire had a serious effect on vegetationindex in forest covered area, would cause it a significant decline. The first yearpost-fires, vegetation index was the minimum value, and after it the value started toincrease. In the initial several years, the increase rate was fast and gradually decrease.It took7-8years of the vegetation index value recovery to the level of pre-fire.Moreover, the analysis of NPP recovery in burned area showed that it has a similarprocess with vegetation. The process might be found a fluctuation state, but thegeneral trend was increase. The recovery would take about7years.There a different of the regeneration speed under different forest types. Thespeed under coniferous forest was relatively slow and which was faster underbroadleaf forest and mixed-forest.5. There is a obviously difference of the regeneration process among differentburn severity. Based on the burn severity map, we analyzed the vegetation regrowthprocess under five severity grades. The result showed that, in the eleven years afterfire happened, the vegetation was a continuous increase trend, but had not beenachieve the level of pre-fire. In the first five years stage (2001-2006) of vegetationregeneration, the vegetation increase speed was fast. Under every burn severity grade,the area of vegetation increase80%were the predominance one. In the second fiveyears (2006-2011), the increase speed was relatively slow, and there was a differencebetween different burn severity grades.