C4 Grass Distribution

Description 1. Mapping C3/C4 grass distribution 2. Modeling d13C isoscape for terrestrial vegetation Author(s) References

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.

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:

`mask_climate`	....	To generate climate masks based on two climate variables, usually temperature and precipitation
`calc_C4_ratio`	....	To predict the C4 proportion of grasses for each grid cell

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:

`calc_pft_cover`	....	To generate percent cover layers
`calc_del13C`	....	To generate stable carbon isoscape

Rebecca L. Powell, Daniel M. Griffith, Sydney M. Firmin

Maintainer: Rebecca L. Powell <rebecca.l.powell@du.edu>

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.

rebeccalpowell/grassmapr documentation built on June 20, 2019, 8:07 p.m.