Quantifying small‐scale deforestation and forest degradation in African woodlands using radar imagery
Quantifying small‐scale deforestation and forest degradation in African woodlands using radar imagery
复制标题
使用雷达图像量化非洲林地的小规模森林砍伐和森林退化
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
M. Williams
中科院分区：
文献类型：
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作者：
C. Ryan;T. Hill;E. Woollen;C. Ghee;E. Mitchard;G. Cassells;J. Grace;I. Woodhouse;M. Williams
热带土地利用变化产生的碳排放是全球碳循环的一个主要不确定性因素。在非洲林地，小规模耕作和对燃料的需求被认为减少了植被碳储量，但由于光学遥感的局限性和缺乏地面数据，对这些过程的量化受到阻碍。在这里，我们提出了一种以0.06公顷分辨率绘制莫桑比克中部100万km2区域3年植被碳储量及其变化的方法。L波段合成孔径雷达图像和96个地块的库存结合使用回归和自举来生成具有已知不确定性的生物量图。所得到的地图具有足够的精度，能够以95%的置信度检测3年内森林碳储量的变化，最小可达12 MgC ha - 1。这样就可以在一个新的详细水平上描述毁林和森林退化造成的生物量损失。3年间研究区地上总生物量减少了6.9±4.6%，从2007年的2.13±0.12 TgC减少到2010年的1.98±0.11 TgC，减少了0.15±0.10 TgC。降解可能贡献了67%（96.9±91.0 GgC）的生物量净损失，但与高度不确定性相关。碳储量变化的详细地图量化了小规模农业的性质。新清拆面积平均较小（中位数为0.2公顷），而且往往是在已清拆土地的基础上增加的。毁林事件使生物量平均从33.5 MgC ha - 1减少到11.9 MgC ha - 1。与预期相反，我们没有发现证据表明砍伐是针对高生物量地区的。我们的方法具有可扩展性，适用于监测林地生态系统中的土地覆盖变化和植被碳储量，并且可以支持减少森林砍伐和退化（REDD）排放的政策方法。
Carbon emissions from tropical land‐use change are a major uncertainty in the global carbon cycle. In African woodlands, small‐scale farming and the need for fuel are thought to be reducing vegetation carbon stocks, but quantification of these processes is hindered by the limitations of optical remote sensing and a lack of ground data. Here, we present a method for mapping vegetation carbon stocks and their changes over a 3‐year period in a > 1000 km2 region in central Mozambique at 0.06 ha resolution. L‐band synthetic aperture radar imagery and an inventory of 96 plots are combined using regression and bootstrapping to generate biomass maps with known uncertainties. The resultant maps have sufficient accuracy to be capable of detecting changes in forest carbon stocks of as little as 12 MgC ha−1 over 3 years with 95% confidence. This allows characterization of biomass loss from deforestation and forest degradation at a new level of detail. Total aboveground biomass in the study area was reduced by 6.9 ± 4.6% over 3 years: from 2.13 ± 0.12 TgC in 2007 to 1.98 ± 0.11 TgC in 2010, a loss of 0.15 ± 0.10 TgC. Degradation probably contributed 67% (96.9 ± 91.0 GgC) of the net loss of biomass, but is associated with high uncertainty. The detailed mapping of carbon stock changes quantifies the nature of small‐scale farming. New clearances were on average small (median 0.2 ha) and were often additions to already cleared land. Deforestation events reduced biomass from 33.5 to 11.9 MgC ha−1 on average. Contrary to expectations, we did not find evidence that clearances were targeted towards areas of high biomass. Our method is scalable and suitable for monitoring land cover change and vegetation carbon stocks in woodland ecosystems, and can support policy approaches towards reducing emissions from deforestation and degradation (REDD).
影响因子：
13.5
作者：
Le Toan, T.;Quegan, S.;Ulander, L.
通讯作者：
Ulander, L.