Add Tree with Nurse Tree Effect

Adds a new tree to the stand. If adding a pinyon pine (PIED), places it near an existing juniper to reflect nurse tree facilitation. Other species are placed randomly.

Usage

perturb_add_with_nurse(
  trees,
  plot_size,
  species_names,
  species_probs,
  dbh_mean,
  dbh_sd,
  nurse_distance = 3
)

Arguments

trees

Data.table. Current tree data

plot_size

Numeric. Plot dimension in meters

species_names

Character vector. Available species codes

species_probs

Numeric vector. Target species proportions (must sum to 1)

dbh_mean

Numeric. Mean DBH for new tree (cm)

dbh_sd

Numeric. Standard deviation of DBH (cm)

nurse_distance

Numeric. Target distance to place PIED near juniper (m). Actual distance is drawn from normal distribution with mean = nurse_distance and SD = 0.3 * nurse_distance.

Value

Data.table. Updated tree data with new tree added

Details

New tree species is selected based on species_probs. If PIED is selected and junipers exist, tree is placed at distance ~ N(nurse_distance, 0.3*nurse_distance) from a randomly selected juniper. Position is constrained within plot bounds. DBH is drawn from N(dbh_mean, dbh_sd) and constrained to minimum 5cm.

Examples

# \donttest{
trees <- data.table::data.table(Number = 1:10, x = runif(10, 0, 100), 
                    y = runif(10, 0, 100), 
                    Species = sample(c("PIED", "JUSO"), 10, replace = TRUE),
                    DBH = rnorm(10, 20, 5))
trees_new <- perturb_add_with_nurse(trees, 100, c("PIED", "JUSO"),
                                    c(0.7, 0.3), 20, 5, 2.5)
# }