Modeling the forest dynamics of the Sierra Nevada under climate change using SORTIE-ND

Key message

Model simulation results suggest that forests in the Sierra Nevada mountains of California will tend to increase in density and basal area in the absence of fire over the next century, and that climate change will favor increases in drought-tolerant species.


Context Climate change is projected to intensify the natural summer drought period for Mediterranean-climate forests. Such changes may increase tree mortality, change species interactions and composition, and impact ecosystem services.
Aims To parameterize SORTIE-ND, an individual-based, spatially explicit forest model, for forests in the Sierra Nevada, and to model forest responses to climate change.
Methods We use 3 downscaled GCM projections (RCP 8.5) to project forest dynamics for 7 sites at different elevations.
Results Basal area and stem density tended to increase in the absence of fire. Climate change effects differed by species, with more drought-tolerant species such as Jeffrey pine (Pinus jeffreyi A.Murray bis) and black oak (Quercus kelloggii Newb.) exhibiting increases in basal area and/or density.
Conclusion Increasing forest density may favor carbon sequestration but could increase the risk of high-severity fires. Future analyses should include improved parameterization of reproduction and interactions of disturbance with climate effects.

Individual-based model; Climate change; Coniferous forest; Pinus; Quercus; Abies

Moran, E.V., Vannest, N. & Aubry-Kientz, M. Modeling the forest dynamics of the Sierra Nevada under climate change using SORTIE-ND. Annals of Forest Science 78, 75 (2021).

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Data availability
Seedling and adult tree data used to parameterize the model are available on, as reported in Moran et al. (2019) (“Seedling and tree data from Sequoia National Park and Yosemite National Park” Seed data are not publicly available, as they are being used by for ongoing analyses, but are available upon reasonable request from corresponding author. Climate projections were obtained from the California Climate Commons (

Code availability
The parameterized model behaviors will be made available on the SORTIE-ND website upon publication of this manuscript New behaviors currently under review by SORTIE-ND team include “ClimateSeedlingHeightGrowth”,“ClimateSeedlingHeightSurvival”, “ClimateNCIGrowth”, and “ClimateNCIMoratality”. Model outputs and the code for making the figures are available through GitHub Tree allometry relationships were calculated from FIA data, using the method developed in the package MakeMyForests

Handling Editor
Andreas Bolte

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