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pyfia.estimation.estimators.volume

Volume estimation for FIA data. Simple, straightforward implementation for calculating tree volume without unnecessary abstractions.

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Functions

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volume

Estimate tree volume from FIA data. Calculates volume estimates using FIA’s design-based estimation methods with proper expansion factors and stratification. Automatically handles EVALID selection to prevent overcounting from multiple evaluations. Args:
  • db: Database connection or path to FIA database. Can be either a path string to a DuckDB/SQLite file or an existing FIA connection object.
  • grp_by: Column name(s) to group results by. Can be any column from the TREE, COND, and PLOT tables. Common grouping columns include:
Tree Characteristics:
  • ‘SPCD’: Species code (see REF_SPECIES table)
  • ‘SPGRPCD’: Species group code (hardwood/softwood groups)
  • ‘DIA’: Diameter at breast height (continuous, use with caution)
  • ‘HT’: Total tree height in feet
  • ‘CR’: Crown ratio (percent of bole with live crown)
  • ‘CCLCD’: Crown class code (1=Open grown, 2=Dominant, 3=Codominant, 4=Intermediate, 5=Overtopped)
  • ‘TREECLCD’: Tree class code (2=Growing stock, 3=Rough cull, 4=Rotten cull)
  • ‘DECAYCD’: Decay class for standing dead trees
Ownership and Management:
  • ‘OWNGRPCD’: Ownership group (10=National Forest, 20=Other Federal, 30=State/Local, 40=Private)
  • ‘OWNCD’: Detailed ownership code (see REF_RESEARCH_STATION)
  • ‘ADFORCD’: Administrative forest code
  • ‘RESERVCD’: Reserved status (0=Not reserved, 1=Reserved)
Forest Characteristics:
  • ‘FORTYPCD’: Forest type code (see REF_FOREST_TYPE)
  • ‘STDSZCD’: Stand size class (1=Large diameter, 2=Medium diameter, 3=Small diameter, 4=Seedling/sapling, 5=Nonstocked)
  • ‘STDORGCD’: Stand origin (0=Natural, 1=Planted)
  • ‘STDAGE’: Stand age in years
Site Characteristics:
  • ‘SITECLCD’: Site productivity class (1=225+ cu ft/ac/yr, 2=165-224, 3=120-164, 4=85-119, 5=50-84, 6=20-49, 7=0-19)
  • ‘PHYSCLCD’: Physiographic class code
  • ‘SLOPE’: Slope in percent
  • ‘ASPECT’: Aspect in degrees (0-360)
Location:
  • ‘STATECD’: State FIPS code
  • ‘UNITCD’: FIA survey unit code
  • ‘COUNTYCD’: County code
  • ‘INVYR’: Inventory year
Disturbance and Treatment:
  • ‘DSTRBCD1’, ‘DSTRBCD2’, ‘DSTRBCD3’: Disturbance codes
  • ‘TRTCD1’, ‘TRTCD2’, ‘TRTCD3’: Treatment codes
For complete column descriptions, see USDA FIA Database User Guide.
  • by_species: If True, group results by species code (SPCD). This is a convenience parameter equivalent to adding ‘SPCD’ to grp_by.
  • by_size_class: If True, group results by diameter size classes. Size classes are defined as: 1.0-4.9”, 5.0-9.9”, 10.0-19.9”, 20.0-29.9”, 30.0+”.
  • land_type: Land type to include in estimation:
  • ‘forest’: All forestland (COND_STATUS_CD = 1)
  • ‘timber’: Timberland only (unreserved, productive forestland with SITECLCD < 7 and RESERVCD = 0)
  • ‘all’: All land types including non-forest
  • tree_type: Tree type to include:
  • ‘live’: All live trees (STATUSCD = 1)
  • ‘dead’: Standing dead trees (STATUSCD = 2)
  • ‘gs’: Growing stock trees (live, TREECLCD = 2, no defects)
  • ‘all’: All trees regardless of status
  • vol_type: Volume type to estimate:
  • ‘net’: Net cubic foot volume (VOLCFNET) - gross minus defects
  • ‘gross’: Gross cubic foot volume (VOLCFGRS) - total stem volume
  • ‘sound’: Sound cubic foot volume (VOLCFSND) - gross minus rot
  • ‘sawlog’: Sawlog board foot volume (VOLBFNET) - net board feet
  • tree_domain: SQL-like filter expression for tree-level attributes. Examples:
  • “DIA >= 10.0”: Trees 10 inches DBH and larger
  • “SPCD IN (131, 110)”: Specific species (loblolly and Virginia pine)
  • “DIA BETWEEN 10 AND 20”: Mid-sized trees
  • “HT > 50 AND CR > 30”: Tall trees with good crowns
  • area_domain: SQL-like filter expression for COND-level attributes. Examples:
  • “STDAGE > 50”: Stands older than 50 years
  • “FORTYPCD IN (161, 162)”: Specific forest types
  • “OWNGRPCD == 40”: Private lands only
  • “SLOPE < 30 AND ASPECT BETWEEN 135 AND 225”: Gentle south-facing slopes
  • totals: If True, include total volume estimates expanded to population level. If False, only return per-acre values.
  • variance: If True, return variance instead of standard error.
  • most_recent: If True, automatically select the most recent evaluation for each state/region. Equivalent to calling db.clip_most_recent() first.
  • eval_type: Evaluation type to select if most_recent=True. Options: ‘ALL’, ‘VOL’, ‘GROW’, ‘MORT’, ‘REMV’, ‘CHANGE’, ‘DWM’, ‘INV’. Default is ‘VOL’ for volume estimation.
Returns:
  • Volume estimates with the following columns:
  • YEAR : int Inventory year
  • [grouping columns] : varies Any columns specified in grp_by parameter
  • VOLCFNET_ACRE : float (if vol_type=‘net’) Net cubic foot volume per acre
  • VOLCFGRS_ACRE : float (if vol_type=‘gross’) Gross cubic foot volume per acre
  • VOLCFSND_ACRE : float (if vol_type=‘sound’) Sound cubic foot volume per acre
  • VOLBFNET_ACRE : float (if vol_type=‘sawlog’) Net board foot volume per acre
  • VOLCFNET_ACRE_SE : float (if variance=False) Standard error of per-acre volume estimate
  • VOLCFNET_ACRE_VAR : float (if variance=True) Variance of per-acre volume estimate
  • N_PLOTS : int Number of plots in estimate
  • N_TREES : int Number of trees in estimate
  • AREA_TOTAL : float Total area (acres) represented by the estimation
  • VOLCFNET_TOTAL : float (if totals=True) Total volume expanded to population level
  • VOLCFNET_TOTAL_SE : float (if totals=True and variance=False) Standard error of total volume
Examples: Basic net volume on forestland:
from pyfia import FIA, volume with FIA(“path/to/fia.duckdb”) as db: … db.clip_by_state(37) # North Carolina … results = volume(db, land_type=“forest”, vol_type=“net”) Volume by species on timberland: results = volume( … db, … by_species=True, … land_type=“timber”, … tree_type=“gs” # Growing stock only … )

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Find top species by volume

if not results.is_empty(): … top_species = results.sort(by=‘VOLCFNET_ACRE’, descending=True).head(5) Large tree volume by ownership: results = volume( … db, … grp_by=“OWNGRPCD”, … tree_domain=“DIA >= 20.0”, … variance=True … ) Sawlog volume by forest type: results = volume( … db, … grp_by=“FORTYPCD”, … vol_type=“sawlog”, … tree_type=“gs”, … tree_domain=“DIA >= 11.0” # Hardwood sawtimber size … ) Volume by multiple grouping variables: results = volume( … db, … grp_by=[“STATECD”, “OWNGRPCD”, “STDSZCD”], … land_type=“forest”, … totals=True … ) Complex filtering with domain expressions:

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High-value timber on productive sites

results = volume( … db, … grp_by=“SPCD”, … land_type=“timber”, … tree_domain=“DIA >= 16.0 AND TREECLCD == 2”, … area_domain=“SITECLCD <= 3 AND SLOPE < 35” … ) Dead tree volume assessment: >>> results = volume( … db, … tree_type=“dead”, … by_species=True, … tree_domain=“DIA >= 10.0 AND DECAYCD IN (1, 2)” # Sound dead trees … )

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Classes

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VolumeEstimator

Volume estimator for FIA data. Estimates tree volume (cubic feet) using standard FIA methods. Methods:

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get_required_tables

Volume estimation requires tree, condition, and stratification tables.

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get_tree_columns

Required tree columns for volume estimation. Uses centralized column resolution from columns.py to reduce duplication. Volume estimation requires volume columns based on vol_type configuration.

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get_cond_columns

Required condition columns. Uses centralized column resolution from columns.py to reduce duplication. Volume estimation needs PROP_BASIS for area adjustment calculations.

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calculate_values

Calculate volume per acre. Volume calculation: VOLUME * TPA_UNADJ

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aggregate_results

Aggregate volume with two-stage aggregation for correct per-acre estimates. CRITICAL FIX: This method implements two-stage aggregation following FIA methodology. The previous single-stage approach caused ~22x underestimation by having each tree contribute its condition proportion to the denominator. Stage 1: Aggregate trees to plot-condition level Stage 2: Apply expansion factors and calculate ratio-of-means Returns:
  • Bundle containing results, plot_tree_data, and group_cols for explicit variance calculation.

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calculate_variance

Calculate variance for volume estimates using domain total variance formula. Uses the stratified domain total variance formula from Bechtold & Patterson (2005): V(Ŷ) = Σ_h w_h² × s²_yh × n_h This matches EVALIDator’s variance calculation for tree-based estimates.

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format_output

Format volume estimation output.