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

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Oregon — total live trees

EVALID: 412101 (Oregon 2021) · Result: 10,481,113,490 live trees (357.8 trees/acre) on 29,292,380 forest acres · source
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. 
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;

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North Carolina — live trees by species

EVALID: 372301 (North Carolina 2023) · Result: 13,541,944,859 trees across 129 species (729.1 trees/acre) · source
The same pattern, grouped by species with common/scientific names joined from REF_SPECIES. 
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;
The Python equivalent is tpa() with by_species=True.