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Calculate stand height metrics from tree list data

Source: R/calc_ht_metrics.R
calc_ht_metrics.Rd

These functions compute several stand height metrics from tree list data.

Usage

calc_ht_metrics(tree_list, digits = 1)

calc_landfire_stand_ht(
  subp_overlay_mean,
  micr_overlay_mean,
  numTrees,
  meanTreeHtDomBAW,
  meanTreeHtBAW,
  meanSapHt
)

Arguments

tree_list

A data frame with tree records for one FIA plot. Must have columns DIA (tree diameter), HT (tree height), ACTUALHT (tree actual height, ACTUALHT < HT indicating a broken top), CCLCD (FIA crown class code), TPA_UNADJ (trees per acre).

digits

Optional integer indicating the number of digits to keep in the return values (defaults to 1).

subp_overlay_mean

A numeric vector, value(s) of subp_overlay_mean from the output of calc_tcc_metrics().

micr_overlay_mean

A numeric vector, value(s) of micr_overlay_mean from the output of calc_tcc_metrics().

numTrees

A numeric vector, value(s) of numTrees from the output of calc_ht_metrics().

meanTreeHtDomBAW

A numeric vector, value(s) of meanTreeHtDomBAW from the output of calc_ht_metrics().

meanTreeHtBAW

A numeric vector, value(s) of meanTreeHtBAW from the output of calc_ht_metrics().

meanSapHt

A numeric vector, value(s) of meanTreeHmeanSapHttBAW from the output of calc_ht_metrics().

Details

calc_ht_metrics() computes several stand height metrics for a given tree list. The return value is a named list as described below.

calc_landfire_stand_ht() computes LANDFIRE stand height. This metric is computed separately since it depends on canopy cover estimates for the sapling and overstory layers derived by overlaying modeled crowns. The input data are given as vectors of values for one or more plots (all input vectors must have the same length). The return value is a numeric vector of stand heights, with length equal to the number of elements in each of the input vectors.

Stand height metrics are based on live trees (STATUSCD == 1), and are are assigned 0 by definition if no live trees are present. calc_ht_metrics()returns a named list with the following elements:

  • $numTrees: number of live trees >= 5.0 in. (12.7 cm) diameter

  • $meanTreeHt: mean height of trees >= 5.0 in. (12.7 cm) diameter

  • $meanTreeHtBAW: basal-area weighted mean height of trees >= 5.0 in. (12.7 cm) diameter

  • $meanTreeHtDom: mean height of canopy dominant/co-dominant trees >= 5.0 in. (12.7 cm) diameter

  • $meanTreeHtDomBAW: basal-area weighted mean height of canopy dominant/co-dominant trees >= 5.0 in. (12.7 cm) diameter

  • $maxTreeHt: height of the tallest tree >= 5.0 in. (12.7 cm) diameter

  • $predomTreeHt: predominant tree height, as the mean height of the tallest trees >= 5.0 in. (12.7 cm) diameter comprising up to 16 trees per acre (39.5 trees per hectare)

  • $numSaplings: number of live saplings (trees >= 1.0 in. but < 5.0 in. diameter, i.e., >= 2.54 cm but < 12.7 cm)

  • $meanSapHt: mean height of saplings

  • $maxSapHt: height of the tallest sapling

For the purpose of height calculations, metrics based on "canopy dominant/co-dominant" include open grown trees, i.e., include trees with FIA crown class codes CCLCD of 1 (open grown), 2 (dominant) or 3 (co-dominant), but exclude trees with CCLCD of 4 (intermediate) or 5 (over-topped).

LANDFIRE stand height is a metric computed for FIA plots used as reference data supporting development of the Existing Vegetation Height (EVH) raster product (https://www.landfire.gov/vegetation/evh). It is generally the basal-area weighted mean height of canopy dominant/co-dominant trees (i.e., meanTreeHtDomBAW). However, this metric attempts to identify plots that may be best characterized as sapling stage, in which case stand height is the mean height of saplings (meanSapHt). Sapling-stage plots are defined using arbitrary thresholds of canopy cover, estimated separately for the sapling layer based on microplot data, and the overstory tree layer based on subplot measurements. See calc_tcc_metrics() for variable definitions. A plot is considered sapling stage if subp_overlay_mean <= 10 and micr_overlay_mean >= 3 * subp_overlay_mean.

Examples

calc_ht_metrics(plantation)
#> $numTrees
#> [1] 89
#> 
#> $meanTreeHt
#> [1] 44.8
#> 
#> $meanTreeHtBAW
#> [1] 45.3
#> 
#> $meanTreeHtDom
#> [1] 44.8
#> 
#> $meanTreeHtDomBAW
#> [1] 45.3
#> 
#> $maxTreeHt
#> [1] 51
#> 
#> $predomTreeHt
#> [1] 50.7
#> 
#> $numSaplings
#> [1] 2
#> 
#> $meanSapHt
#> [1] 34.5
#> 
#> $maxSapHt
#> [1] 43
#>