R/aphidsBACI.R

In ecostats: Code and Data Accompanying the Eco-Stats Text (Warton 2022)

#' Aphid data as a BACI design
#'
#' @description
#' A subset from a study of the effects of bird exclusion on biological control of aphids in a German oat
#' field (Grass \emph{et al.} 2017). Many thanks to Ingo for providing the raw data. The full data are
#' in \code{\link{aphids}}, here we provide just two sampling times, 3 days and 30 days after netting.
#' OK, this is not quite a BACI design, 3 days after netting is not quite "before" but effects at this 
#' point should be negligible...
#' 
#' There were eight plots, four with plastic netting to exclude birds, and four without. Aphid abundance 
#' was counted on 5 shoots per plot. The expectation was that aphid numbers would decrease on bird 
#' exclusion, because an important food source to tree sparrows is aphid predators, hoverflies and 
#' ladybird beetles, so presence of birds may be limit the effectiveness of a biological control of aphids.
#'
#' @docType data
#'
#' @usage data(aphidsBACI)
#'
#' @format A dataframe containing:\describe{
#' \item{Plot}{The plot ID, a factor with eight levels}
#' \item{Treatment}{A factor indicating whether birds were excluded, \code{excluded} or \code{present}.}
#' \item{Time}{The data of sampling (June 18th or July 15th, 3 and 30 days after netting, respectively)}
#' \item{counts}{Aphid abundance (counts)}
#' \item{logcount}{log(y+1)-transformed aphid abundance}
#' }
#'
#' @keywords datasets
#'
#' @references Grass \emph{et al.} (2017) Insectivorous birds disrupt biological control of cereal aphids.
#' Ecology, \bold{98} 1583-90.
#'
#' @examples
#' data(aphidsBACI)
#' plot(logcount~interaction(Treatment,Time),data=aphidsBACI,col=c("lightgreen","pink"))
"aphidsBACI"