Department of Earth and Ecosystem Sciences, Lund University, Sölvegatan 12, Lund SE-223 62, Sweden.
Sensors (Basel). 2011;11(8):7678-709. doi: 10.3390/s110807678. Epub 2011 Aug 4.
We present a network of sites across Fennoscandia for optical sampling of vegetation properties relevant for phenology monitoring and satellite data calibration. The network currently consists of five sites, distributed along an N-S gradient through Sweden and Finland. Two sites are located in coniferous forests, one in a deciduous forest, and two on peatland. The instrumentation consists of dual-beam sensors measuring incoming and reflected red, green, NIR, and PAR fluxes at 10-min intervals, year-round. The sensors are mounted on separate masts or in flux towers in order to capture radiation reflected from within the flux footprint of current eddy covariance measurements. Our computations and model simulations demonstrate the validity of using off-nadir sampling, and we show the results from the first year of measurement. NDVI is computed and compared to that of the MODIS instrument on-board Aqua and Terra satellite platforms. PAR fluxes are partitioned into reflected and absorbed components for the ground and canopy. The measurements demonstrate that the instrumentation provides detailed information about the vegetation phenology and variations in reflectance due to snow cover variations and vegetation development. Valuable information about PAR absorption of ground and canopy is obtained that may be linked to vegetation productivity.
我们展示了一个横跨芬诺斯堪的纳维亚地区的网络站点，用于对与物候监测和卫星数据校准相关的植被属性进行光学采样。该网络目前由五个站点组成，分布在瑞典和芬兰的 N-S 梯度上。其中两个站点位于针叶林，一个位于阔叶林，两个位于泥炭地。该仪器包括双光束传感器，以 10 分钟的间隔全年测量入射和反射的红、绿、近红外和 PAR 通量。传感器分别安装在单独的桅杆或通量塔上，以捕获当前涡度相关测量通量足迹内反射的辐射。我们的计算和模型模拟证明了使用离轴采样的有效性，并展示了第一年的测量结果。计算并比较了 NDVI 与搭载在 Aqua 和 Terra 卫星平台上的 MODIS 仪器的结果。将 PAR 通量分为地面和冠层的反射和吸收分量。测量结果表明，该仪器提供了有关植被物候和由于积雪变化和植被发育引起的反射率变化的详细信息。获得了有关地面和冠层 PAR 吸收的有价值信息，这些信息可能与植被生产力有关。
