Simulating Growth and Competition on Wet and Waterlogged Soils in a Forest Landscape Model

• Published in: Frontiers in Ecology and Evolution
• Main Authors: Eric J. Gustafson, Brian R. Miranda, Anatoly Z. Shvidenko, Brian R. Sturtevant
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media S.A. 2020
• Subjects: forest landscape modeling; permafrost; forested wetlands; hydrology; LANDIS; Siberia; Evolution; QH359-425; Ecology; QH540-549.5
• Online Access: https://doi.org/10.3389/fevo.2020.598775; https://doaj.org/article/63525f4f33ec4c63b3020eee4e497752

Changes in CO2 concentration and climate are likely to alter disturbance regimes and competitive outcomes among tree species, which ultimately can result in shifts of species and biome boundaries. Such changes are already evident in high latitude forests, where waterlogged soils produced by topography, surficial geology, and permafrost are an important driver of forest dynamics. Predicting such effects under the novel conditions of the future requires models with direct and mechanistic links of abiotic drivers to growth and competition. We enhanced such a forest landscape model (PnET-Succession in LANDIS-II) to allow simulation of waterlogged soils and their effects on tree growth and competition. We formally tested how these modifications alter water balance on wetland and permafrost sites, and their effect on tree growth and competition. We applied the model to evaluate its promise for mechanistically simulating species range expansion and contraction under climate change across a latitudinal gradient in Siberian Russia. We found that higher emissions scenarios permitted range expansions that were quicker and allowed a greater diversity of invading species, especially at the highest latitudes, and that disturbance hastened range shifts by overcoming the natural inertia of established ecological communities. The primary driver of range advances to the north was altered hydrology related to thawing permafrost, followed by temperature effects on growth. Range contractions from the south (extirpations) were slower and less tied to emissions or latitude, and were driven by inability to compete with invaders, or disturbance. An important non-intuitive result was that some extant species were killed off by extreme cold events projected under climate change as greater weather extremes occurred over the next 30 years, and this had important effects on subsequent successional trajectories. The mechanistic linkages between climate and soil water dynamics in this forest landscape model produced tight links between climate ...