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    天然林资源保护工程区植被覆盖度遥感估算及变化分析

    Remote sensing estimation and change analysis of fractional vegetation coverage in Natural Forest Resource Protection Project area

    • 摘要:
        目的  天然林资源保护工程(简称“天保工程”)实施20多年来有效保护和恢复了工程区的森林资源。工程实施成效除了森林覆盖面积增加,更多的表现为森林资源质量持续提升。为了更好地评估天保工程建设成效,利用植被覆盖度作为定量评价指标,分析天保一期(2000—2010年)、天保二期(2011—2020年)工程实施期间的森林质量变化。
        方法  综合年度植被指数合成策略、优化纯植被像元和纯裸土像元值域的动态确定方法,构建改进的像元二分模型,生产天保工程区时间序列的植被覆盖度产品。基于森林资源一类清查郁闭度数据、森林生态系统定位研究网络郁闭度数据、机载高光谱植被覆盖度数据,验证该植被覆盖度产品的精度。在此基础上,分析天保工程林区植被覆盖度的时空变化趋势。
        结果  天保一期植被覆盖度均值为0.68,天保二期植被覆盖度均值为0.71,增加了4.41%;工程区植被覆盖度呈现增加趋势的面积占林区总面积的78.22%,而呈减小趋势的面积仅占林区总面积的9.56%。
        结论  在中国天保工程森林地区,基于MODIS 植被指数产品和改进的像元二分模型生产的植被覆盖度产品的精度高于MODIS产品的精度。自天保工程实施以来,林区植被覆盖度总体上呈现出明显的增加趋势,说明天保工程实施效果显著,森林资源质量持续提升。

       

      Abstract:
        Objective  The forest resources have been effectively protected and restored with the implement of Natural Forest Resource Protection Project (NFPP) in recent twenty years. In addition to a slight increase in forest coverage, effects of the project are mainly the continuous improvement of forest resource quality. To quantitatively assess the effects of NFPP, the fractional vegetation coverage (FVC) was used as the indicator to demonstrate the forest quality during the first stage (2000−2010) and second stage (2011−2020) of NFPP.
        Method  A modified dimidiate pixel model was proposed based on the new vegetation index composition strategy and the dynamically determination method of the pure vegetation and soil pixels, and time series FVC was generated in the project area. FVC was then validated by forest resource inventory data, Chinese forest ecosystem research network data and airborne hyperspectral data. At last, the spatial and temporal variation of FVC was analyzed in NFPP area of China.
        Result  FVC increased from 0.68 to 0.71 since the implement of the project. Area with increased FVC trend was about 78.22% of the total forest area, while area with decreased FVC trend only accounted for 9.56% of the total forest area.
        Conclusion  Accuracy of the estimated FVC was higher than that of MODIS product. An obviously increasing trend of FVC could be found in the NFPP area, which indicates that the quality of forest is increasing since the implement of NFPP.

       

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