sgam.pft

Physiological parameters for a Plant Functional Type.

This dataclass defines carbon allocation fractions and turnover rates for different plant tissues (leaf, stem, root). These parameters are used in the SGAM to model plant growth and competition dynamics.

Attributes:

• leaf_base_allocation (float) –

  Fraction of new carbon allocated to leaves during growth. Represents the leaf mass fraction (LMF).

• stem_base_allocation (float) –

  Fraction of new carbon allocated to stems during growth. Represents the stem mass fraction (SMF).

• root_base_allocation (float) –

  Fraction of new carbon allocated to roots during growth. Represents the root mass fraction (RMF).

• leaf_turnover_rate (float) –

  Fraction of leaf biomass replaced per week (weeks^-1).

• stem_turnover_rate (float) –

  Fraction of stem biomass replaced per week (weeks^-1).

• root_tunover_rate (float) –

  Fraction of root biomass replaced per week (weeks^-1).

• leaf_maint_coeff (float) –

  Fraction of leaf carbon respired per week (weeks^-1) for maintenance metabolism. This is the highest cost across all PFTs as leaves require constant enzyme maintenance. Crops have the highest values (0.14) meaning 14% of leaf carbon is burned weekly without GPP.

• stem_maint_coeff (float) –

  Fraction of stem carbon respired per week (weeks^-1) for maintenance metabolism. Lower for trees and shrubs due to lignified, metabolically inactive wood; higher for grasses and crops with succulent, active stems.

• root_maint_coeff (float) –

  Fraction of root carbon respired per week (weeks^-1) for maintenance metabolism. Reflects the metabolic cost of maintaining fine root systems for water and nutrient uptake.

• lue_max (float) –

  Maximum light use efficiency (gC MJ^-1). Represents the maximum rate of carbon gain per unit of absorbed light. Crops have the highest values due to C4 photosynthesis and optimized agricultural conditions; shrubs have the lowest, reflecting adaptation to resource-poor environments.

• iwue_max (float) –

  Maximum intrinsic water use efficiency (μmol mol^-1). Represents the maximum ratio of photosynthesis to stomatal conductance. Shrubs have the highest values to maintain photosynthesis under extreme water tension.

• leaf_carbon_area (float) –

  Specific leaf area expressed as carbon content per unit leaf area (gC/m²).

• wilting_point (float) –

  Soil moisture (fraction, 0.0-1.0) at which plant water stress reaches maximum (f_sm = 0).

• field_capacity (float) –

  Soil moisture (fraction, 0.0-1.0) at which plant water stress is minimum (f_sm = 1).

• vpd_threshold (float) –

  Vapor Pressure Deficit (Pa) above which stomatal conductance begins to decline.

• vpd_sensitivity (float) –

  Rate of decline in stomatal conductance with increasing VPD (Pa^-1). Used in f_vpd = exp(-gamma * (VPD - threshold)).

Bases: StrEnum

Plant Functional Type (PFT) classification.

Represents different categories of plants based on their growth form and ecological characteristics. Each PFT has associated physiological parameters that define carbon allocation and turnover rates.

Attributes:

• TREE –

  Woody perennial plants with a single main stem or trunk.

• GRASS –

  Herbaceous plants with narrow leaves and short lifespan.

• SHRUB –

  Woody perennial plants with multiple stems, smaller than trees.

• CROP –

  Cultivated plants grown for agricultural purposes.