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iForest -Biogeosciences and Forestry
IntroductionThe assessment of wind-caused forest damage includes some specifics that distinguish it from other tasks of detection and measuring of forest changes, at least in the context of Lithuanian forestry conditions. Fast and accurate determination of affected areas of forest and the severity of the damage are essential to enable forest managers to take immediate action on sanitary felling, timber processing and reforestation. Damage is usually geographically concentrated, some areas being difficult to access and measure in the field; however, all forests in Lithuania are precisely mapped and attributed by stand-wise forest inventories .This paper introduces a method of assessing the forest damage caused by a wind storm on August 8, 2010, in Lithuania. The introduced method may also be useful for solving other remote sensing based change detection tasks. The solution is based on integrating methodological approaches originating from two areas of satellite image usage related to the forest inventory: (i) forest change detection, and (ii) the nearest neighbor technique.The process of analyzing image data from two or more periods for the purpose of mapping cover change is commonly referred to as change detection (McRoberts et al. 2010). The principles of satellite image-based forest change detection were first discussed in detail more than a decade ago (Häme 1991, Olsson 1994, Varjo 1997 and are still a subject of current research and interest (Kennedy et al. 2009, McRoberts et al. 2010. Forests can be considered to grow at a constant rate of change, divided into long-term, short-term and rapid change (Häme 1991). Long-term change is usually connected to the growth of the stand, and even that can be monitored using state-of-the-art remote sensing techniques such as aerial imaging and laser scanning (Hyyppa et al. 2008). Satellite remote sensing can be considered to be a practical technique for long-term change observations, in particular because data with image characteristics suitable for monitoring forest changes are available for most of the Earth's surface for the past 40 years (e.g., the Landsat program -Wulder et al. 2008, McRoberts et al. 2010). Short-term or seasonal changes, usually related to reforestation, defoliation etc. can be monitored by satellite image-based remote sensing (Vogelmann et al. 2009, McRoberts & Walters 2012. The main challenge for foresters, however, is the detection and measuring of rapid changes such as tree felling, wind damage and so on. Satellite image-based remote sensing has become an essential data source for assessing rapid or abrupt changes, being low cost, easily and readily accessible, yet it still provides adequate information