Mapping stand age dynamics of the Siberian larch forests from recent Landsat observations

The Siberian larch forests are a major and unique component of the circumpolar boreal biome. However, because of their large extent, remote location, and lack of consistent satellite data coverage prior to 2000, comparatively little is known about their disturbance and recovery patterns at the regional scale beyond the past 15 years. Spatial distribution of recovering forests in the boreal zone is highly important for quantifying the feedback of forest cover to the climate system through carbon cycling and surface albedo which are strongly related to stand age. This paper presents a new method to map stand age distribution of young recovering forests that are primarily dominated by larch in Siberia using Landsat data acquired during the data-rich post-2000 era. This approach is based on the assumption that the relationship between the spectral signature of a forest stand acquired by Landsat ETM + and TM sensors and stand age before and after the year 2000 is similar thus allowing for training the algorithm on the data from the post-2000 era and applying the algorithm to infer stand age for the pre-2000 era. The output map combines the modeled forest disturbances before 2000 (56% producer's and 81% user's accuracy for disturbances) and direct observations of forest loss after 2000 (80% producer's and 92% user's accuracy for disturbances) to deliver a 24-year stand age distribution map at 30-m resolution for the Siberian larch forests. This is the first dataset that focuses specifically on the mid-term stand age dynamics of these forests at the regional scale. Our results show that >10% of the forested area in the Siberian larch forests has experienced stand-replacing fires in the past 24 years. (C) 2016 Elsevier Inc. All rights reserved.