R/grassmapr-package.R

In rebeccalpowell/grassmapr: Predict C3/C4 Grass Distribution

#' grassmapr: A package to map C3/C4 grass distribution and model terrestrial
#'   d13C isoscape
#'
#' \pkg{grassmapr} provides functions (1) to predict C3 and C4 grass cover based
#'   on climate constraints; and (2) to generate stable carbon (d13C) isoscapes
#'   for terrestrial vegetation.
#'
#' @docType package
#'
#' @name grassmapr
#'
#' @author Rebecca L. Powell, Daniel M. Griffith, Sydney M. Firmin
#'
#' \emph{Maintainer:} Rebecca L. Powell <\email{rebecca.l.powell@du.edu}>
#'
#' @section
#' \strong{1. Mapping C3/C4 grass distribution}:
#'
#' To predict and map the C3/C4 distribution of grasses, the following functions
#'   should be applied sequentially. Minimum inputs required are gridded climate
#'   data for temperature and precipitation. Each function returns a new Raster*
#'   object:
#'
#' \tabular{lll}{
#'   \code{mask_climate} \tab .... \tab To generate climate masks based on
#'     two climate variables, usually temperature and precipitation\cr
#'   \code{calc_C4_ratio} \tab .... \tab To predict the C4 proportion of
#'     grasses for each grid cell\cr
#' }
#'
#' @section
#' \strong{2. Modeling d13C isoscape for terrestrial vegetation}:
#'
#' To predict and map the d13C isoscape for terrestrial vegetation, the
#'   following steps should be applied sequentially. First, the C4 proportion of
#'   grasses is converted to C3 and C4 percent cover layers. The user may
#'   optionally incorporate other vegetation layers (e.g., \% woody
#'   cover, \% crop cover, etc.). Second, a simple mixing model weights d13C
#'   endmembers based on relative cover of each plant functional type:
#'
#' \tabular{lll}{
#'   \code{calc_pft_cover} \tab .... \tab To generate percent cover layers\cr
#'   \code{calc_del13C} \tab .... \tab To generate stable carbon isoscape\cr
#' }
#'
#' @references Still, C. J. et al. 2003. Global distribution of C3 and C4 vegetation:
#'   carbon cycle implications. -- Global Biogeochemical Cycles 17:1006.
#'
#' Still, C. J. and Powell, R. L. 2010. Continental-scale distributions of vegetation
#'   stable carbon isotope ratios. In: West, J. B. et al. (eds). Isoscapes:
#'   understanding movement, pattern, and process on earth through isotope
#'   mapping -- Springer, pp.179-193.
#'
#' Powell, R. L. et al. 2012. Vegetation and soil carbon-13 isoscapes for South
#'   America: integrating remote sensing and ecosystem isotope measurements. --
#'   Ecosphere 3:109.
#'
#'
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