Estimating aboveground tree biomass and leaf area index in a mountain birch forest using ASTER satellite data

Abstract

Biomass and leaf area index (LAI) are important variables in many ecological and environmental applications. In this study, the suitability of visible to shortwave infrared advanced spaceborne thermal emission and reflection radiometer (ASTER) data for estimating aboveground tree and LAI in the treeline mountain birch forests was tested in northernmost Finland. The biomass and LAI of the 128 plots were surveyed, and the empirical relationships between forest variables and ASTER data were studied using correlation analysis and linear and non‐linear regression analysis. The studied spectral features also included several spectral vegetation indices (SVI) and canonical correlation analysis (CCA) transformed reflectances. The results indicate significant relationships between the biomass, LAI and ASTER data. The variables were predicted most accurately by CCA transformed reflectances, the approach corresponding to the multiple regression analysis. The lowest RMSEs were 3.45 t ha⁻¹ (41.0%) and 0.28 m²m⁻² (37.0%) for biomass and LAI respectively. The red band was the band with the strongest correlation against the biomass and LAI. SR and NDVI were the SVIs with the strongest linear and non‐linear relationships. Although the best models explained about 85% of the variation in biomass and LAI, the undergrowth vegetation and background reflectance are likely to affect the observed relationships.

Acknowledgements

The author thanks NASA, METI, ERSDAC and LP DAAC for providing the ASTER data. The data provided by Metsähallitus was used in the field work planning and topographic correction. The field work was funded by the Finnish cultural foundation. Mrs Sonja Kivinen kindly assisted in the field work. Prof. Petri Pellikka commented on the manuscript and Mr Barnaby Clark checked the language. Also the comments of the anonymous referees were helpful to finish the paper.