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

Titta Majasalmi,Rasmus Astrup,Clara Antón-Fernández,Ryan M Bright,Micky Allen

doi:10.1007/s10584-020-02742-1

Titta Majasalmi, Rasmus Astrup + Show 3 more

Open Access

https://doi.org/10.1007/s10584-020-02742-1

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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.

Highlights

The heightened role of forest management to mitigate regional climate change necessitates a deeper understanding of how forest harvest and management affects regional surface energy and hydrological budgets through modifications to forest composition and structure
The aim of this study is to present a simple grid-based framework – the Fennoscandic Forest State Simulator (F2S2) – that can be applied to update surface data in land models employed in regional climate or hydrological research in Fennoscandia (Norway, Sweden, and Finland)
In 2015 most of its area resides in class c2, and the general trend is that the areas dominated by intermediate classes c2 and c3 decrease steadily towards the end of the century as transitions from class c3 into mostdeveloped class c4 proceeds

Summary

Introduction

The heightened role of forest management to mitigate regional climate change necessitates a deeper understanding of how forest harvest and management affects regional surface energy and hydrological budgets through modifications to forest composition and structure. Various approaches have been developed allowing disturbances to be implemented at the sub-grid-cell level, permitting a more detailed accounting of within-forest differences in forest structure, and improved modeling of successional dynamics in managed forest environments. This is typically done by increasing the number of sub-grid components in the model. In ORCHIDEE-CAN, three tiles per PFT have been used, with tile merging following the exceedance of predefined diameter thresholds (Naudts et al 2015) The drawback of such approaches is that the sub-grid information is lost as soon as tile units are merged, which must be done to constrain the number of age or structural classes to save computation costs. Some have developed separate forest management “modules” to track sub-grid forest structural information outside of the land model (e.g. Organizing Carbon and Hydrology in Dynamic EcosystEms (ORCHIDEE) FMM by Bellassen et al (2010) and Community Atmosphere Biosphere Land Exchange (CABLE) by Haverd et al (2018))

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