DESCRIPTION

Isolation or connectivity of singular patches of a defined landcover class using individual-based dispersal models. This function is based on a maximum amount of energy for each individuals dispersing through the landscape which is deminished by a fricition or cost map. Unlike the related function r.pi.energy does this function allows individuals to stay or move within a patch until the energy is depleted.

NOTES

Amount of successful immigrants or emigrants are not taken individual into account which emigrated from and immigrated into the same patch (pseudo immigration).

The suitability matrix impacts the step direction, while the costmap relates to the depletion of assigned energy.

If individuals are moving beyond the mapset borders the indivuals are set back to their original source patches.

EXAMPLE

An example for the North Carolina sample dataset: The amount of successful emigrants (*_emi), immigrants (*_imi), the percentage of immigrants per patch (*_imi_percent), the amount of lost indivuals (*_lost), the amount of migrants (*_mig), successful (*_mig_succ) and unsuccessful migrants (_mig_unsucc) can be retrieved using this command: 
r.pi.energy input=landclass96 output=energy1 keyval=5 n=1000 step_length=5 energy=10 percent=80
introducing costs for movement results in different immigration counts: 
r.mapcalc "cost_raster = if(landclass96==5,1,if(landclass96 == 1, 10, if (landclass96==3,2, if(landclass96==4,1,if(landclass96==6,100)))))"
r.pi.energy input=landclass96 output=energy1 keyval=5 n=1000 step_length=5 energy=10 percent=80 costmap=cost_raster
introducing a suitability for the movement: 
# the suitability for the next step selection is defined as: class 5 
# and 3 (forest and grassland) have a high suitability, while shrubland 
# (class 4) only a moderate and water and developed areas (class 6 and 1) 
# have a very low suitability:

r.mapcalc "suit_raster = if(landclass96==5,100,if(landclass96 == 3, 100, if (landclass96==1,1, if(landclass96==6,1,if(landclass96==4,50)))))"
r.pi.energy input=landclass96 output=energyiter3 keyval=5 n=1000 step_length=5 energy=10 percent=80 suitability=suit_raster
further settings can be changed and information retrieved: setting the perception range to 10 pixel: 
r.pi.energy input=landclass96 output=energyiter keyval=5 n=1000 step_length=5 energy=10 percent=80 perception=10
increasing the attraction to move towards patches to 10: 
r.pi.energy input=landclass96 output=energyiter keyval=5 n=1000 step_length=5 energy=10 percent=80 stats=average multiplicator=10
output of each movement location for a defined step frequency. Here every 10th step is provided as output raster: 
r.pi.energy input=landclass96 output=energyiter keyval=5 n=1000 step_length=5 energy=10 percent=80 stats=average out_freq=10

SEE ALSO

r.pi.energy.pr, r.pi.energy, r.pi

AUTHORS

Programming: Elshad Shirinov
Scientific concept: Dr. Martin Wegmann
Department of Remote Sensing
Remote Sensing and Biodiversity Unit
University of Wuerzburg, Germany

Port to GRASS GIS 7: Markus Metz

Last changed: $Date$