pyfvs-fia 0.2.3

Forest growth modeling in Python

Part of the FIAtools Python Ecosystem
pyFIA · gridFIA · pyFVS · askFIA

A Python implementation of the Forest Vegetation Simulator (FVS) Southern variant. Simulate growth and yield for loblolly, shortleaf, longleaf, and slash pine from age 0 to 50 years.

Supported Species

Quick Start

pip install pyfvs

from pyfvs import Stand

# Initialize a planted stand
stand = Stand.initialize_planted(
    species="LP",
    trees_per_acre=500,
    site_index=70
)

# Simulate 50 years of growth
stand.grow(years=50)

# Get results
metrics = stand.get_metrics()
print(f"Final volume: {metrics['volume']:.0f} ft³/acre")

Growth Models

pyFVS implements individual tree growth models from FVS documentation:

Height-Diameter (Curtis-Arney)

height = 4.5 + p2 × exp(-p3 × DBH^p4)

Large Tree Diameter Growth

ln(DDS) = β₁ + β₂×ln(DBH) + β₃×DBH² + β₄×ln(CR) + β₅×RH + β₆×SI + ...

Small Tree Height Growth (Chapman-Richards)

height = c1 × SI^c2 × (1 - exp(c3 × age))^(c4 × SI^c5)

Architecture

Tree Initial State
       │
       ▼
   DBH >= 3.0? ──No──► Small Tree Model
       │                    │
      Yes                   ▼
       │            Height Growth
       ▼                    │
  Large Tree Model          ▼
       │            Height-Diameter
       ▼                    │
  Predict ln(DDS)           ▼
       │              Update DBH
       ▼                    │
  Calculate DBH Growth      │
       │                    │
       └────────┬───────────┘
                ▼
        Update Crown Ratio
                │
                ▼
        Crown Competition
                │
                ▼
        Updated Tree State

Configuration

Species parameters are stored in YAML configuration files:

# cfg/species/lp_loblolly_pine.yaml
species_code: "LP"
common_name: "Loblolly Pine"
height_diameter:
  p2: 243.860648
  p3: 4.28460566
  p4: -0.47130185
bark_ratio:
  b1: -0.48140
  b2: 0.91413

Output

pyFVS generates yield tables with standard forest metrics:

Integration with pyFIA

from pyfia import FIA
from pyfvs import Stand

# Get current stand conditions from FIA
with FIA("database.duckdb") as db:
    db.clip_by_state(37)
    stand_data = db.get_stand_summary(plot_id="123")

# Initialize pyFVS with FIA data
stand = Stand.from_fia_data(stand_data)
stand.grow(years=30)

The FIAtools Ecosystem

pyFVS is part of the FIAtools Python ecosystem - a unified suite of open-source tools for forest inventory analysis:

Explore the full ecosystem at fiatools.org

References

• FVS Southern Variant Documentation
• Bechtold & Patterson (2005) "The Enhanced Forest Inventory and Analysis Program"

Citation

@software{pyfvs2025,
  title = {pyFVS: Python Implementation of the Forest Vegetation Simulator},
  author = {Mihiar, Christopher},
  year = {2025},
  url = {https://fiatools.org}
}