knfi (version 1.0.2)

summary_nfi: Calculate descriptive statistics for National Forest Inventory Data

Description

summary_nfi() is a function that calculates comprehensive descriptive statistics for National Forest Inventory (NFI) data. It can provide summaries for individual plots, the entire study area, or specific groups within the study area using parameters byplot or plotgrp. Users have flexibility in specifying data inclusion criteria and analysis levels using parameters clusterplot, largetreearea, stockedland, and talltree. These parameters determine whether to treat cluster plots as single plots, to include large tree survey plots, and to focus only on Stocked land and tall trees.

Usage

summary_nfi(
  data,
  byplot = FALSE,
  plotgrp = NULL,
  continuousplot = FALSE,
  clusterplot = FALSE,
  largetreearea = TRUE,
  stockedland = TRUE,
  talltree = TRUE
)

Value

A data.frame that includes summary statistics. The structure depends on the input parameters:

• If byplot = TRUE, each row represents a plot.

• If byplot = FALSE, each row represents the entire dataset or a group specified by plotgrp

Arguments

data

: A list containing 'plot' and 'tree' data frames, typically generated by read_nfi.

byplot

: A logical flag (default FALSE); if TRUE, calculates statistics for each plot separately. If FALSE, calculates for the entire dataset.

plotgrp

: A character vector; specifies variables from 'plot' table to use for grouping. Use c() to combine multiple variables.

continuousplot

: A logical flag (default TRUE); if TRUE, includes only plots that have been measured at the exact same location across all NFI cycles (5th, 6th, etc.). If FALSE, includes all plots regardless of location changes or missing cycle measurements.

clusterplot

: A logical flag (default FALSE); if TRUE, treats each cluster plot as a single unit. If FALSE, calculates for each subplot separately.

largetreearea

: A logical flag (default TRUE); if TRUE, includes large tree survey plots in the analysis. If FALSE, only uses standard tree plots.

stockedland

: A logical flag (default TRUE); if TRUE, includes only stocked land. If FALSE, includes all land types.

talltree

: A logical flag (default TRUE); if TRUE, includes only tall trees. If FALSE, includes both trees and shrubs.

Details

The function calculates the following statistics: Plot-related statistics:

• Number of cluster plots

• Number of subplots

• Number of subplots with large trees (\(\geq\) 30cm) observed

Tree-related statistics:

• Number of individual trees

• Number of large trees

• Number of dominant trees

• Number of tree species

Tree measurements and stand statistics (mean and standard deviation):

• DBH (Diameter at Breast Height)

• Tree height

• Height of dominant trees

• Number of trees per hectare

• Basal area per hectare

• Volume per hectare

The largetreearea parameter affects calculations differently:

• For per-hectare statistics (trees per hectare, basal area per hectare, volume per hectare), setting largetreearea = TRUE includes data from large tree survey plots.

• For all other statistics, trees from large tree survey plots are always excluded, regardless of the largetreearea setting.

Examples

data("nfi_donghae")

# Basic usage
summary_stats <- summary_nfi(nfi_donghae, continuousplot = TRUE)

# Summarize by the group, including all land types
grouped_stats <- summary_nfi(nfi_donghae, plotgrp = "OWN_CD", 
                              stockedland = FALSE, continuousplot = TRUE)

# Summarize by individual plots, including both trees and shrubs 
plot_summaries <- summary_nfi(nfi_donghae, byplot = TRUE, talltree = FALSE)