Applicability of synthetic aperture radar (SAR) to evaluate leaf area index (LAI) and its growth rate of rice in farmers' fields in Lao PDR
Applicability of synthetic aperture radar (SAR) to evaluate leaf area index (LAI) and its growth rate of rice in farmers' fields in Lao PDR
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DOI：
10.1016/j.fcr.2015.02.022
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发表时间：
2015-05
影响因子：
5.8
通讯作者：
Y. Hirooka;K. Homma;M. Maki;Kosuke Sekiguchi
中科院分区：
文献类型：
--
作者：
Y. Hirooka;K. Homma;M. Maki;Kosuke Sekiguchi
水稻是老挝人民民主共和国(老挝人民民主共和国)最重要的农作物。由于合成孔径雷达(SAR)不受云和太阳光照的影响，被认为是一种更适合于该地区水稻生长的方法。分析了水稻后向散射系数(BSC)与叶面积指数(LAI)之间的关系。在这里，我们讨论了SAR在估计老挝人民民主共和国农民土地上的叶面积指数及其增长率的适用性。在2013年丰水期，选取30块农户水田进行全生育期观测，在抽穗期前4个时段测定每块田的LAI和归一化植被指数(NDVI)。本研究使用的是COSMO-SkyMed系统(SAR)的X波段合成孔径雷达图像。生物量与LAI、NDVI呈显著正相关。30个田中有28个田的生物量与移栽后天数呈正相关，其中10个田的生物量呈显著正相关。在BSC与DAT显著相关的区域，BSC的增加率与LAI显著相关。这一发现表明，如果SAR图像显示BSC相对于DAT显著增加，则增加的速度也可能代表LAI增长速度，尽管无法控制的水位和杂草偶尔会中断观察。这项研究证明了特别工作组评估发展中国家水稻生产的能力。
Rice is the most important crop in Lao People's Democratic Republic (Lao PDR). Synthetic aperture radar (SAR) is proposed as a more suitable method to evaluate rice growth in this area because it is independent from cloud and solar illumination. This study analyzed the relationship between the back scattering coefficient (BSC) in SAR images and leaf area index (LAI) of rice. Here, we discuss the applicability of SAR to estimate LAI and its growth rate in farmers’ fields in Lao PDR. 30 farmers’ paddy fields were selected for surveying throughout the growth period in the wet season of 2013, and both LAI and normalized difference vegetation index (NDVI) were measured at 4 time periods before the heading period for each field. X-band SAR images from the COSMO-SkyMed system (SAR) were used in this study. BSC was significantly correlated with LAI and NDVI. BSC at 28 of 30 fields was positively correlated with days after transplanting (DAT), and 10 of these results were significant. The increased rate in BSC obtained at the fields where BSC and DAT had a significant correlation, were significantly correlated with that in LAI. This finding suggests that if SAR images demonstrate significant increases of BSC against DAT, the increased rate may also represent LAI growth rate, although uncontrollable water levels and weeds occasionally interrupt observation. This study demonstrates the capacity of SAR to evaluate rice production in developing countries.