Abstract
Forest growth estimation is important in forest research and forest management, but complex to analyze in diverse forest stands. Twelve summertime TanDEM-X acquisitions from the boreal test site, Krycklan, in Sweden, with a known digital terrain model, DTM, have been used to study phase height and aboveground biomass change over 3.2 years based on the Interferometric Water Cloud Model, IWCM. The maximum phase height rate was determined to 0.29 m/yr, while the mean phase height rate was 0.16 m/yr. The corresponding maximum growth rate of the aboveground dry biomass, AGB, was 4.0 Mg/ha/yr with a mean rate of 1.9 Mg/ha/yr for 27 stands, varying from 23 to 183 Mg/ha. The highest relative AGB growth was found for young stands and high growth rates up to an age of 150 years. Growth rate differences relative a simplified model assuming AGB to be proportional to the phase height were studied, and the possibility to avoid a DTM was discussed. Effects of tree species, thinning, and clear cutting were evaluated. Verifications using in situ data from 2008 and a different in situ dataset combined with airborne laser scanning data from 2015 have been discussed. It was concluded that the use of multi-temporal TanDEM-X interferometric synthetic aperture radar observations with AGB estimates of each individual observation can be an important method to derive growth rates in boreal forests.
Highlights
Thirty percent of the forested area in the world consists of boreal forests
Interferometric synthetic aperture radar (InSAR) remote sensing systems offer an opportunity to determine three-dimensional properties of forest stands, such as forest height and aboveground biomass, AGB, of importance for inventory and monitoring purposes
The main goal of this paper is to investigate AGB growth and change of individual stands over a 3.2 year period of TanDEM-X data from Krycklan
Summary
Thirty percent of the forested area in the world consists of boreal forests. In Sweden, 51% of the land area is covered by productive forest of mainly boreal or hemi-boreal type, and plays an important role for the Swedish economy. The bistatic TanDEM-X system has been shown to be able to determine boreal forest properties with very high accuracy [3,4,5,6,7,8,9,10,11,12,13,14], primarily based on information from the interferometric phase height. The latter depends on tree height, as well as forest density, and is closely related to stem volume and AGB
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