> ## Documentation Index
> Fetch the complete documentation index at: https://pyfia.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Basic tree counts

> EVALIDator-style tree enumeration with diameter-based adjustment factors and population expansion.

Tree-counting queries that demonstrate the core EVALIDator pattern: `TPA_UNADJ` × diameter-based adjustment factor × `EXPNS`, filtered to live trees on forest conditions.

## Oregon — total live trees

<Info>**EVALID:** 412101 (Oregon 2021) · **Result:** 10,481,113,490 live trees (357.8 trees/acre) on 29,292,380 forest acres · [source](https://github.com/mihiarc/pyfia/blob/main/reference/queries/basic_tree/oregon_total_live_trees.sql)</Info>

The canonical template: it counts every live tree on forest land, applying the right adjustment factor for each tree's diameter and expanding to the population.

<Accordion title="View SQL">
  ```sql theme={null}
  SELECT
      SUM(
          TREE.TPA_UNADJ *
          CASE
              WHEN TREE.DIA IS NULL THEN POP_STRATUM.ADJ_FACTOR_SUBP
              WHEN TREE.DIA < 5.0 THEN POP_STRATUM.ADJ_FACTOR_MICR
              WHEN TREE.DIA < COALESCE(CAST(PLOT.MACRO_BREAKPOINT_DIA AS DOUBLE), 9999.0) THEN POP_STRATUM.ADJ_FACTOR_SUBP
              ELSE POP_STRATUM.ADJ_FACTOR_MACR
          END * POP_STRATUM.EXPNS
      ) AS total_live_trees
  FROM POP_STRATUM
  JOIN POP_PLOT_STRATUM_ASSGN ON (POP_PLOT_STRATUM_ASSGN.STRATUM_CN = POP_STRATUM.CN)
  JOIN PLOT ON (POP_PLOT_STRATUM_ASSGN.PLT_CN = PLOT.CN)
  JOIN COND ON (COND.PLT_CN = PLOT.CN)
  JOIN TREE ON (TREE.PLT_CN = COND.PLT_CN AND TREE.CONDID = COND.CONDID)
  WHERE
      TREE.STATUSCD = 1            -- Live trees
      AND COND.COND_STATUS_CD = 1  -- Forest conditions
      AND POP_STRATUM.EVALID = 412101;
  ```
</Accordion>

## North Carolina — live trees by species

<Info>**EVALID:** 372301 (North Carolina 2023) · **Result:** 13,541,944,859 trees across 129 species (729.1 trees/acre) · [source](https://github.com/mihiarc/pyfia/blob/main/reference/queries/basic_tree/north_carolina_trees_by_species.sql)</Info>

The same pattern, grouped by species with common/scientific names joined from `REF_SPECIES`.

<Accordion title="View SQL">
  ```sql theme={null}
  SELECT
      t.SPCD,
      rs.COMMON_NAME,
      rs.SCIENTIFIC_NAME,
      SUM(
          t.TPA_UNADJ *
          CASE
              WHEN t.DIA IS NULL THEN ps.ADJ_FACTOR_SUBP
              WHEN t.DIA < 5.0 THEN ps.ADJ_FACTOR_MICR
              WHEN t.DIA < COALESCE(CAST(p.MACRO_BREAKPOINT_DIA AS DOUBLE), 9999.0) THEN ps.ADJ_FACTOR_SUBP
              ELSE ps.ADJ_FACTOR_MACR
          END * ps.EXPNS
      ) AS total_trees_expanded
  FROM POP_STRATUM ps
  JOIN POP_PLOT_STRATUM_ASSGN ppsa ON ppsa.STRATUM_CN = ps.CN
  JOIN PLOT p ON ppsa.PLT_CN = p.CN
  JOIN COND c ON c.PLT_CN = p.CN
  JOIN TREE t ON t.PLT_CN = c.PLT_CN AND t.CONDID = c.CONDID
  LEFT JOIN REF_SPECIES rs ON t.SPCD = rs.SPCD
  WHERE
      t.STATUSCD = 1
      AND c.COND_STATUS_CD = 1
      AND ps.rscd = 33            -- North Carolina
      AND ps.evalid = 372301
  GROUP BY t.SPCD, rs.COMMON_NAME, rs.SCIENTIFIC_NAME
  ORDER BY total_trees_expanded DESC
  LIMIT 10;
  ```
</Accordion>

<Tip>The Python equivalent is [`tpa()`](/api/pyfia-estimation-estimators-tpa) with `by_species=True`.</Tip>