Quantitative analysis of the links between forest structure and land surface albedo on a global scale

• Published in: Remote sensing of environment 2020-09, Vol.246, p.111854, Article 111854
• Main Authors: Alibakhshi, Sara, Naimi, Babak, Hovi, Aarne, Crowther, Thomas W., Rautiainen, Miina
• Format: Article
• Language: English
• Subjects: Albedo; Deciduous forests; Deciduous trees; Density; Earth surface; Forest density; Forest structure; Forests; Geographical locations; Growing season; Leaf area; Leaf area index; Leaves; Links; Near infrared radiation; Pixels; Quantitative analysis; Remote sensing; Short wave radiation; Spatial discrimination; Spatial resolution; Spectroradiometers; Tree cover
• ISSN: 0034-4257; 1879-0704
• DOI: 10.1016/j.rse.2020.111854

Forests are critical in regulating climate by altering the Earth's surface albedo. Therefore, there is an urgent need to enhance our knowledge about the effects of forest structure on albedo. Here, we present a global assessment of the links between forest structure and albedo at a 1-km spatial resolution using generalized additive models (GAMs). We used remotely sensed data to obtain variables representing forest structure, including forest density, leaf area index, and tree cover, during the peak growing season in 2005 with pure forest pixels that cover ~7% of the Earth's surface. Furthermore, we estimated black-sky albedo at a solar zenith angle of 38° using the most recent collection of the moderate resolution imaging spectroradiometer (MODIS; version 6) at shortwave, near-infrared, and visible spectral regions. In addition, for the first time, we mapped the magnitude of the relationship between forest structure and albedo at each pixel with a 0.5-degree spatial resolution. Our results suggested that forest structure may modulate albedo in most of the sub-biomes. The response of shortwave albedo was always positive to the leaf area index and negative to the tree cover (except for deciduous broadleaf forests in mediterranean and temperate regions), while the response to forest density varied across space in 2005. The spatial map affirmed that the links between forest structure and albedo vary over geographical locations. In sum, our study emphasized the importance of forest structure in the surface albedo regulation. This paper provides the first spatially explicit evidence of the magnitude of relationships between forest structure and albedo on a global scale. •Forest structure is important in regulating land surface albedo.•LAI increases SW albedo during the peak growing season in forests globally.•For the first time, the map of albedo-forest structure links is estimated.•Links between albedo and forest structure vary over geographical location.