Journal of Geo-information Science >
Precise Extraction of Damaged Forest Range Caused by Ice-snow Frozen Disaster Based on the NDVI Threshold Method
Received date: 2016-09-12
Request revised date: 2016-12-14
Online published: 2017-04-20
Copyright
Extraction of damaged forest range caused by ice-snow frozen disaster is good for knowing the relevant regional disaster information in time, and it can provide scientific support for disaster prevention and protection of forest resources and ecosystem. We extract pre-disaster plant NDVI reference value and the threshold of normal change with the time series data of 2001-2008. We attained the results of the spatial distribution of Hunan forest disturbed by ice-snow frozen disaster with NDVI data in 2008. The NDVI threshold method can make up for the defect of traditional method based on single-temporal images, which doesn’t take the normal change of vegetation index into consideration. The NDVI threshold method helps extracting different normal change threshold for each pixel, causing the results extracted by NDVI threshold method is more objective and reasonable. Contrasted with the results extracted by the traditional method, the percentage of damaged forest according to two methods have significant difference at county level, although the rates forest disasters with two methods are all 34.74% (the real rate of forest disaster is 35.3%) at provincial level. The forest snow disaster is mainly distributed in southern Hunan province and less in northern Hunan province using the NDVI threshold method, but the results using traditional method is contrary compared to the NDVI threshold method. According to field survey data, the spatial distribution of forest snow disaster using the method of NDVI threshold is more closed to real results compared to traditional method and its extracting accuracy is higher. Therefore, the NDVI threshold method is more suitable for extracting the spatial distribution information of forest snow disaster at large regional scale.
Key words: forests; snow disaster; NDVI threshold; information extraction; Hunan province
WANG Xuecheng , YANG Fei , GAO Xing , LI Li . Precise Extraction of Damaged Forest Range Caused by Ice-snow Frozen Disaster Based on the NDVI Threshold Method[J]. Journal of Geo-information Science, 2017 , 19(4) : 549 -558 . DOI: 10.3724/SP.J.1047.2017.00549
Fig.1 Statistical distribution of NDVI variation ratios of forest pixels图1 森林像元NDVI变化率统计分布 |
Fig.2 The flow chart of extraction of forest ice-snow disaster area图2 森林冰雪受灾区域提取流程 |
Fig.3 Spatial distribution of MaxBias图3 NDVI正常波动范围(MaxBias)空间分异规律示意图 |
Fig.4 The results of forest snow disaster area图4 森林冰雪受灾面积提取结果 |
Fig. 5 Spatial distribution of verification units图5 验证单元空间分布 |
Tab.1 The statistics of snow disaster area extracted by the new algorithm表1 新算法提取冰雪受灾面积统计 |
森林受灾面积/万hm2 | 森林未受灾面积/万hm2 | 林地面积/万hm2 | 受灾面积理论值/万hm2 | 森林受灾率/% | 参考资料受灾率/% | 变化率N/% | |
---|---|---|---|---|---|---|---|
湖南省 | 415.967 | 781.997 | 1197.964 | 422.881 | 34.72 | 35.30 | 1.64 |
郴州市 | 59.049 | 73.664 | 132.713 | 58.924 | 44.49 | 44.40 | 0.21 |
衡阳市 | 30.556 | 40.634 | 71.190 | 42.429 | 42.92 | 59.60 | 27.98 |
衡东县 | 4.280 | 6.385 | 10.666 | 7.707 | 40.13 | 72.26 | 44.46 |
浏阳市 | 9.924 | 26.381 | 36.305 | 8.568 | 27.33 | 23.60 | 15.83 |
江永县 | 6.205 | 3.036 | 9.241 | 5.160 | 67.15 | 55.84 | 20.25 |
道县 | 7.155 | 6.523 | 13.679 | 8.358 | 52.31 | 61.10 | 14.39 |
新田县 | 1.513 | 2.770 | 4.283 | 2.743 | 35.32 | 64.05 | 44.86 |
Tab.2 The statistics of snow disaster area extracted by the traditional method表2 传统方法提取冰雪受灾面积统计 |
森林受灾面积/万hm2 | 森林未受灾面积/万hm2 | 林地面积/万hm2 | 受灾面积理论值/万hm2 | 森林受灾率/% | 参考资料受灾率/% | 变化率N/% | |
---|---|---|---|---|---|---|---|
湖南省 | 373.206 | 701.739 | 1074.945 | 379.456 | 34.72 | 35.30 | 1.65 |
郴州市 | 46.444 | 73.902 | 120.345 | 53.43 | 38.59 | 44.40 | 13.08 |
衡阳市 | 34.238 | 33.351 | 67.589 | 40.283 | 50.66 | 59.60 | 15.01 |
衡东县 | 3.431 | 6.996 | 10.427 | 7.535 | 32.90 | 72.26 | 54.46 |
浏阳市 | 20.491 | 14.115 | 34.606 | 8.167 | 59.21 | 23.60 | 150.90 |
江永县 | 3.602 | 4.968 | 8.570 | 4.785 | 42.03 | 55.84 | 24.73 |
道县 | 3.461 | 8.906 | 12.367 | 7.556 | 27.99 | 61.10 | 54.19 |
新田县 | 0.996 | 1.921 | 2.917 | 1.868 | 34.14 | 64.05 | 46.70 |
Tab.3 The statistical results of forest land area表3 林地面积提取结果统计(万hm2) |
湖南省 | 郴州市 | 衡阳市 | 衡东县 | 浏阳市 | 江永县 | 道县 | 新田县 | |
---|---|---|---|---|---|---|---|---|
林地面积(新) | 1197.97 | 132.713 | 71.190 | 10.666 | 36.305 | 9.241 | 13.679 | 4.283 |
林地面积(旧) | 1074.95 | 120.345 | 67.589 | 10.427 | 34.606 | 8.570 | 12.367 | 2.917 |
The authors have declared that no competing interests exist.
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