Demographic Processes

Demographic processes in iLand simulate the continuous life-cycle transitions of trees: established trees grow in diameter and height, environmental stress triggers tree mortality, and mature trees produce and disperse seeds to establish forest regeneration.

Growth

Simulates annual diameter and height increment, crown architecture, and allometric relationships of established trees (>4m height) based on allocated carbon.

Regeneration

Models the establishment and early development of new tree cohorts:

• Seed Dispersal: Spatially explicit dispersal of seeds from mature trees and external seed sources using species-specific seed kernels.
• Establishment: Germination and survival of seeds on suitable seedbeds subject to environmental filters.
• Sapling Growth and Competition: Growth of sapling cohorts (<4m height) competing for light and belowground resources.
• Recruitment: Transition of saplings exceeding 4m height into individual trees in the core model.
• Sprouts: Vegetative regeneration via coppicing and resprouting after harvesting or disturbance.
• Serotiny: Canopy seed banking and post-fire seed release.

Mortality

Simulates tree mortality:

• Stress-induced mortality: Carbon starvation and hydraulic failure resulting from negative annual carbon balance or acute stress.
• Base Mortality: Background age- and size-dependent mortality probability.