Physiological Processes

iLand models the continuous physiological processes that govern energy capture, resource competition, and biogeochemical cycling at individual tree and landscape levels.

Resource Availability and Competition

Spatially explicit competition among individual trees for above- and belowground resources:

• Light Competition: 3D canopy light absorption based on Light Influence Patterns (LIPs).
• Belowground Competition: Competition for soil water and nitrogen mediated by root distribution and soil properties.

Primary Production

Radiation absorption and gross primary production calculated using a hierarchical approach derived from the 3-PG model:

• Environmental Modifiers: Response functions modulating productivity based on temperature, vapor pressure deficit, atmospheric CO₂, soil water, and soil nitrogen.
• Phenology: Seasonal dynamics of foliage flush, senescence, and growing season length.

Carbon Allocation & Stem Growth

Partitioning of net primary production (NPP) into foliage, fine roots, and woody biomass pools based on pipe-model allometry and resource limitations.

Water Cycle

Canopy interception, evapotranspiration, snowpack accumulation/melt, and soil water percolation:

• Landscape Soil Water Dynamics: Lateral redistribution of soil water across topography on landscape scales.

Soil Dynamics & Biogeochemical Cycling

Litter decomposition, soil organic matter turnover, and nutrient mineralization based on the Century/ICBM soil models.