Forest summer albedo is sensitive to species and thinning: how should we account for this in Earth system models?

Abstract

Abstract. Although forest management is one of the instruments proposed to mitigate climate change, the relationship between forest management and canopy albedo has been ignored so far by climate models. Here we develop an approach that could be implemented in Earth system models. A stand-level forest gap model is combined with a canopy radiation transfer model and satellite-derived model parameters to quantify the effects of forest thinning on summertime canopy albedo. This approach reveals which parameter has the largest affect on summer canopy albedo: we examined the effects of three forest species (pine, beech, oak) and four thinning strategies with a constant forest floor albedo (light to intense thinning regimes) and five different solar zenith angles at five different sites (40During stand establishment, summertime canopy albedo is driven by tree species. In the later stages of stand development, the effect of tree species on summertime canopy albedo decreases in favour of an increasing influence of forest thinning. These trends continue until the end of the rotation, where thinning explains up to 50 % of the variance in near-infrared albedo and up to 70 % of the variance in visible canopy albedo.The absolute summertime canopy albedo of all species ranges from 0.03 to 0.06 (visible) and 0.20 to 0.28 (nearinfrared); thus the albedo needs to be parameterised at species level. In addition, Earth system models need to account for forest management in such a way that structural changes in the canopy are described by changes in leaf area index and crown volume (maximum change of 0.02 visible and 0.05 near-infrared albedo) and that the expression of albedo depends on the solar zenith angle (maximum change of 0.02 visible and 0.05 near-infrared albedo). Earth system models taking into account these parameters would not only be able to examine the spatial effects of forest management but also the total effects of forest management on climate.

Trade‐offs between three forest ecosystem services across the state of New Hampshire, USA: timber, carbon, and albedo

“…, , Otto et al. ) specifically for this purpose. Although a few studies have used similar methods to examine temperate forests (Thompson et al.…”

Quantifying energy use efficiency via maximum entropy production: A case study from longleaf pine ecosystems

“…However, high eff s relative to the intermediate site indicated that the xeric site was using the remaining energy available to the site more efficiently. These results demonstrate that sites with higher biodiversity are better adapted to changes in resource availability by way of how they alter their reflective properties, such that energy partitioning is optimized (i.e., high absorption of solar radiation) and high entropy production can be maintained 5 (Gunawardena et al, 2017;Otto et al, 2014;Taha et al, 1988).…”

A vertically discretised canopy description for ORCHIDEE (SVN r2290) and the modifications to the energy, water and carbon fluxes

“…Forests store almost 50 % of the terrestrial organic carbon and 90 % of vegetation biomass (Dixon et al, 1994;Pan et al, 2011). Globally, 70 % of the forest is managed and the importance of management is still increasing both in relative and absolute terms.…”

“…A more detailed description and evaluation of the new multi-layer energy budget and multi-level radiative transfer scheme is given by Ryder et al (2014), Chen et al (2015) and McGrath et al (2015b). A new forest management reconstruction, which is needed to drive forest management in ORCHIDEE-CAN, is presented in McGrath et al (2015a), and the interactions between forest management and the new albedo scheme have been discussed by Otto et al (2014).…”