R/drought.r

In nuaquilue/medLDM: Mediterranean Landscape Dynamic Model

#' Drought mortality
#'
#' Determines the dieback of forest areas due to drought-induced mortatlidy
#' 
#' @param land A \code{landscape} data frame with forest stand records and land-cover types in rows
#' @param decade A number indicating the decade of the current time step
#' @param step The curretn time step
#' 
#' @return A vector with the \code{cell.id} of the killed locations 
#' 
#' @export
#' 
#' @examples
#' data(landscape)
#' drought(landscape, decade=10, step=1)
#' 

drought <- function(land, decade, step){
  
  ## Count how many ha to kill, totally and this time step
  ## Those forest species out of its climatic range and not burnt the current time step
  to.kill <- land %>% filter(spp<=13, sdm==0, tsdist>0)
  nkill <- round(table(to.kill$spp) / (10 - (step-1 - (decade-10)) ) )
  
  ## Tracking
  if(sum(nkill)>0)
    cat("Drought", "\n") 
  
  ## Kill randomly as many cells per spp
  killed.cells <- integer()
  for(i in names(nkill)){
    if(nkill[i]>1)
      killed.cells <- c(killed.cells, sample(to.kill$cell.id[to.kill$spp==i], nkill[i], replace=F))
    if(nkill[i]==1)
      killed.cells <- c(killed.cells, to.kill$cell.id[to.kill$spp==i])
  }
  # sample(x,1) returns a number in range [1, x], instead of x itself.
  
  return(killed.cells)
}