A simple grid-based framework for simulating forest structural trajectories linked to transient forest management scenarios in Fennoscandia

Abstract

Forest structural properties largely govern surface fluxes of moisture, energy, and momentum that strongly affect regional climate and hydrology. Forest structural properties are greatly shaped by forest management activities, especially in the Fennoscandia (Norway, Sweden, and Finland). Insight into transient developments in forest structure in response to management intervention is therefore essential to understanding the role of forest management in mitigating regional climate change. The aim of this study is to present a simple grid-based framework – the Fennoscandic Forest State Simulator (F2S2) -- for predicting time-dependent forest structural trajectories in a manner compatible with land models employed in offline or asynchronously coupled climate and hydrological research. F2S2 enables the prescription of future regional forest structure as a function of: i) exogenously defined scenarios of forest harvest intensity; ii) forest management intensity; iii) climate forcing. We demonstrate its application when applied as a stand-alone tool for forecasting three alternative future forest states in Norway that differ with respect to background climate forcing, forest harvest intensity (linked to two Shared Socio-economic Pathways (SSPs)), and forest management intensity. F2S2 captures impacts of climate forcing and forest management on general trends in forest structural development over time, and while climate is the main driver of longer-term forest structural dynamics, the role of harvests and other management-driven effects cannot be overlooked. To our knowledge this is the first paper presenting a method to map forest structure in space and time in a way that is compatible with land surface or hydrological models employing sub-grid tiling.

Representation of tree cover in global land cover products: Finland as a case study area

“…As a result, the vegetation cover fraction and LAI are not constant for each pixel (Zeng et al 2002 ) and thus, the impact of fractional cover (i.e., LC product) on climate simulation outcomes cannot be directly evaluated. More attention should be paid to LC data (and therefore also the underlying forest class definitions) that are being used to parametrize the LSMs, as the expected improvements in predicted surface fluxes will rely on the quality of the employed tree cover mapping (e.g., Bright et al 2018 ; Majasalmi et al 2018 ; Majasalmi et al 2020 ).…”

“…However, while very detailed processes can be represented in site or regional scale simulations, on a global scale, identifying the locations of different vegetation types is of utmost importance. While there have been attempts to represent forest-age structural properties and to account for forest management effects in a climate model simulation, these LC products and models suffice only for regional analyses (see, e.g., Majasalmi et al 2018 , 2020 ).…”

SiTree: A framework to implement single-tree simulators

“…Simulations produced using SiTree are currently and actively being used to inform policy decisions [for example, see 10], as well as in research [for example, see 9,11].…”