Procedimiento para prevención de ruido Contenido

4.3.2.1 The Statistical Summary Table

The Statistical Summary Table (figure 4-4) displays a statistical description of the input (inventory) data. This table is printed as part of the main FVS output file when the STATS keyword record is included in the keyword set. The upper portion of this table contains per acre estimates of trees, basal area, and volumes broken down by species. The lower portion of the table contains statistics for these same attributes for all species combined. Reported statistics are based on total stand area.

GENERAL SPECIES SUMMARY FOR THE CRUISE

SPECIES BOARD FEET CUBIC FEET TREES PER ACRE BA PER ACRE --- WL = WL 2018.6 396.4 40.5 14.5 DF = DF 1540.2 366.2 188.1 17.7 GF = GF 448.9 305.8 161.7 18.2 WH = WH 0.0 49.6 15.8 3.6 RC = RC 0.0 112.1 101.0 8.8 LP = LP 1797.4 445.1 28.9 14.5

DISTRIBUTION OF STAND ATTRIBUTES AMONG SAMPLE POINTS

STANDARD COEFF OF SAMPLE 95% SAMPLING ERROR IN CHARACTERISTIC MEAN DEVIATION VARIATION SIZE CONFIDENCE LIMITS PERCENT UNITS --- --- --- --- --- --- --- TREES/ACRE 536.05 561.86 1.05 11 158.48 913.61 70.4 377.6 CUBIC FEET/ACRE 1675.30 1216.39 0.73 11 857.90 2492.70 48.8 817.4 BOARD FEET/ACRE 5805.14 5567.12 0.96 11 2064.10 9546.18 64.4 3741.0 BASAL AREA/ACRE 77.39 45.39 0.59 11 46.89 107.90 39.4 30.5

Figure 4-4 — Example of the Statistical Summary Table from the Forest

Vegetation Simulator.

4.3.2.2 The Structural Statistics Table

Descriptors of stand structure have become an increasingly important consideration in prescribing management actions to preserve wildlife habitat and watershed values. FVS will search for up to three distinct canopy strata. For each significant stratum, the canopy cover corrected for crown overlap, major species, ranges of diameters, tree heights, and heights to crown base are displayed. From these data a structural class is assigned. Per acre values are calculated for the stockable area of the stand only.

The Structural Statistics Table (figure 4-5) (Crookston and Stage 1999) displays a description of the number of valid strata, percent canopy cover, and structural class for the stand. Included for each stratum are: the nominal diameter and height, the heights of the tallest and shortest trees, the crown base height, percent canopy cover, major species, and a code indicating if the stratum is invalid, valid, or the uppermost valid stratum. These statistics are output for the stand before simulated harvests and are repeated for post-harvest conditions. This table is printed as part of the main FVS output file when the STRCLASS keyword record is included in the keyword set.

Stand percent canopy cover (PCC) is the percentage of the ground area that is directly covered with tree crowns and is calculated based on the methodologies presented in

Crookston and Stage (1999). Generally the crown area of a tree is computed using the formula for a circle as a function of crown radius. Crown radius is estimated using formulae that are different for each FVS geographic variant. Percent canopy cover may be obtained for the entire stand or based on species, tree value class, DBH, or height categories. All percent cover estimates computed in FVS are corrected for canopy overlap.

Percent canopy cover is computed by calculating the projected crown area represented by each tree record. This is adjusted to a percent using equation {4.3.2.2.1} and summed over all tree records in the grouping for which the percent canopy cover is being calculated. The sum is then corrected for canopy overlap using equation {4.3.2.2.2}. {4.3.2.2.1} C = 100 · • (0.00001803 · FCW2 · TPA)

{4.3.2.2.2} PCC = 100 · [1 – e (-.01 · C)] where:

C is uncorrected percent canopy cover for a given species/tree value class/DBH/height category

FCW is estimated tree crown width

TPA is trees per acre represented by each tree

PCC is percent canopy cover corrected for canopy overlap

0.00001803 is a factor used to convert crown width in feet to the percent of an acre covered by the crown

• is summation over all trees in the stand

Canopy strata are initially defined by naturally occurring gaps in the distribution of tree heights. The gaps are found when the heights of two trees in a list sorted by height differ by more than 30 percent of the height of the taller tree and at least 10 feet. The two largest gaps define three potential strata. If there is only one gap, two potential strata are defined and if there are no gaps, one potential stratum is defined.

Initially defined strata must have over 5 percent canopy cover or they are rejected. Nominal stratum diameter and height are computed by averaging the nine sample trees centered on the 70th percentile tree. Once the strata are defined, the stand is classified as bare ground (BG), stand initiation (SI), stem exclusion (SE), understory reinitiation (UR), young forest multistrata (YM), old forest single stratum (OS), or old forest multistrata (OM) as a function of the number of strata, the nominal diameter of trees in the strata, and stocking.

Several features in FVS relate to the percent canopy cover and stand structure statistics. The classification logic can be tuned to achieve specific goals using the STRCLASS keyword. The Event Monitor contains pre-defined variables relating to the structural class, nominal diameter of the uppermost stratum, and percent canopy cover, and the SPMCDBH function allows the computation of percent canopy cover for any subset of the trees in the stand (see section 5.5.2.2). The THINCC keyword record allows users to

thin stands to a specified percent canopy cover within a specified diameter range (see section 5.2.4.2.3).

The classification can vary between runs of FVS with different starting values of the random number generator (see section 6.4.2). This behavior is inherent in any

classification system based on statistics sensitive to random variation such as average diameter of a subset of trees. When the stratum average diameter is near the class boundary, the classification of the stand in one class versus another is sensitive to the interaction between the arbitrary rules and the variation inherent in the sample data and in the processes of growth and regeneration.

Structural statistics for stand: S248112 MgmtID: NONE

--- Stratum 1 --- --- Stratum 2 --- --- Stratum 3 ---

Rm ---Height-- -Crown- -Major- C ---Height-- -Crown- -Major- C ---Height-- -Crown- -Major- C N Tot Struc Year Cd DBH Nom Lg Sm Bas Cov Sp1 Sp2 D DBH Nom Lg Sm Bas Cov Sp1 Sp2 D DBH Nom Lg Sm Bas Cov Sp1 Sp2 D S Cov Class ---- -- --- --- --- --- --- --- --- --- - --- --- --- --- --- --- --- --- - --- --- --- --- --- --- --- --- - - --- --- 1990 0 9.8 66 75 55 43 26 DF WL 2 5.8 30 38 2 7 40 GF RC 1 0.0 0 0 0 0 0 -- -- 0 2 56 3=UR 1990 1 9.7 67 75 59 43 21 DF WL 2 5.8 30 38 2 13 35 GF RC 1 0.0 0 0 0 0 0 -- -- 0 2 49 3=UR 2000 0 8.8 48 91 29 28 55 GF RC 2 0.1 2 4 1 0 2 WH GF 0 0.0 0 0 0 0 0 -- -- 0 1 56 2=SE 2000 1 8.8 48 91 29 28 55 GF RC 2 0.1 2 4 1 0 2 WH GF 0 0.0 0 0 0 0 0 -- -- 0 1 56 2=SE 2010 0 12.6 59 101 36 34 60 GF RC 2 0.2 5 11 1 0 6 WH GF 1 0.0 0 0 0 0 0 -- -- 0 2 62 3=UR 2010 1 12.6 59 101 36 34 60 GF RC 2 0.2 5 11 1 0 6 WH GF 1 0.0 0 0 0 0 0 -- -- 0 2 62 3=UR 2020 0 14.4 76 109 41 39 64 GF RC 2 0.8 11 18 2 1 14 WH RC 1 0.0 0 0 0 0 0 -- -- 0 2 69 3=UR 2020 1 13.2 73 99 39 31 57 GF WH 2 0.0 0 0 0 0 0 -- -- 0 0.0 0 0 0 0 0 -- -- 0 1 57 1=SI 2030 0 13.8 77 108 49 35 60 GF WH 2 0.1 1 4 1 0 3 WH GF 0 0.0 0 0 0 0 0 -- -- 0 1 61 2=SE 2030 1 13.8 77 108 49 35 60 GF WH 2 0.1 1 4 1 0 3 WH GF 0 0.0 0 0 0 0 0 -- -- 0 1 61 2=SE 2040 0 16.5 101 117 57 40 63 GF WH 2 0.1 3 7 1 0 5 WH DF 1 0.0 0 0 0 0 0 -- -- 0 2 65 3=UR 2040 1 16.5 101 117 57 40 63 GF WH 2 0.1 3 7 1 0 5 WH DF 1 0.0 0 0 0 0 0 -- -- 0 2 65 3=UR 2050 0 19.0 113 125 63 46 65 GF WH 2 0.6 8 11 1 1 8 WH RC 1 0.0 0 0 0 0 0 -- -- 0 2 68 3=UR 2050 1 20.7 113 117 80 75 14 DF -- 2 0.9 10 11 10 1 0 DF -- 0 0.0 0 0 0 0 0 -- -- 0 1 14 1=SI 2060 0 21.7 118 122 90 79 16 DF -- 2 2.6 22 22 22 2 0 DF -- 0 0.7 5 7 1 0 4 WH DF 0 1 19 1=SI 2060 1 0.7 6 22 1 0 0 WH DF 2 0.7 5 7 3 0 4 WH DF 0 0.0 0 0 0 0 0 -- -- 0 1 4 1=SI 2070 0 10.0 63 63 63 6 2 DF -- 0 2.8 24 40 1 1 46 DF WH 2 0.0 0 0 0 0 0 -- -- 0 1 47 1=SI 2070 1 10.0 63 63 63 6 2 DF -- 0 2.8 24 40 1 1 46 DF WH 2 0.0 0 0 0 0 0 -- -- 0 1 47 1=SI 2080 0 8.8 53 77 1 2 85 DF WH 2 0.0 0 0 0 0 0 -- -- 0 0.0 0 0 0 0 0 -- -- 0 1 85 2=SE 2080 1 8.8 53 77 1 2 85 DF WH 2 0.0 0 0 0 0 0 -- -- 0 0.0 0 0 0 0 0 -- -- 0 1 85 2=SE 2090 0 12.6 71 89 2 4 93 DF WH 2 0.0 0 0 0 0 0 -- -- 0 0.0 0 0 0 0 0 -- -- 0 1 93 2=SE

Figure 4-5 — Example of the Structural Statistics Table from the Forest

Vegetation Simulator

The Database Extension can be used to send Structural Class output directly to a database (see section 8.11).

4.3.2.3 Outputs from Extensions

Several extensions to FVS produce special reports. These tables are printed as part of the main FVS output file when the appropriate keyword records are included in the keyword set (see section 8).