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Limited filling of the potential Pinus cembra range


Pinus Cembra (Pinaceae L.) or Swiss Stone Pine is a localised and endemic tree species that occurs in the alpine timberline. We are going to calculate the realized / potential range size ratio (range filling R/P) for the alpine Pine Pinus cembra as a measure of how well this species fulfills its potential range Gaston 2003. We use the Pinus cembra habitat suitability modeling Casalegno et al., 2010 and the Pinus cembra distribution map euforgen database to estimate R/P ratio.

  • P is the total number of Pinus cembra suitable pixels within the study area.
  • R is the number of Pinus cembra suitable pixels within the Pinus cembra distribution maps pixels.

This will quantify the extent to which Pinus cembra fulfills its modelled suitability range in the Alps. We computed the realized / potential range size ratio (R/P) across the Alpine and Carpathian mountains area.

Start a new GRASS project and define a region of analysis

We open a terminal and go to the directory corresponding to our GRASS LOCATION.

cd ~/ost4sem/grassdb/europe

We copy the PERMANENT MAPSET and rename it PCEM. PCEM will be our new MAPSET and grass project where we store maps for calculating the R/P ratio.

rm -r PCEM

We start grass in the newest PCEM mapset

grass -text  ~/ost4sem/grassdb/europe/PCEM

Look at the default g.region and redefine a study area including the Carpathian and Alpine mountain ranges. Set the new working region at 1km resolution and call it alpine:

g.region -d
g.region -p
g.region --o n=3070000 s=2270000 w=3900000 e=5660000 res=1000 save=alp_car
g.region -p

Pinus Cembra distribution map: data preparation

Import and reclass distribution map

Import the Euforgen Pinus cembra distribution map from the euforgen web page and convert it from a shape file to a raster file : dsn=~/ost4sem/exercise/rp_ratio/pcem_euforgen/Pinuscembra_LAEA.shp output=pcem_euforgen --overwrite

Convert the vector file to a raster file, look at the pixels values and reclass this map into a binary presence and absence of Pinus cembra distribution.

You can open Qgis within the grass section and continue to work with grass using the following command
qgis &

Once you have opened Qgis, load the pcem_euforgen@PCEM vector map and check which source of raster values you have to use for the conversion from vector to raster. You have the choice between: attr,cat,val,z,dir. --o input=pcem_euforgen@PCEM output=pcem_euforgen use=cat pcem_euforgen pcem_euforgen

The raster we generate has values running from 1 to 14 but we need a presence-absence map so we have to reclassify the pcem_euforgen raster into 0 - 1 map values.

r.mapcalc pcem_euforgen = "if(pcem_euforgen > 0 , 1 ,0 )"

Pinus Cembra suitability map: data preparation

Import and resize suitability map

Import the random forest model of suitability for Pinus cembra -o -e input=~/ost4sem/exercise/rp_ratio/pcem_randomforest/gdwarp_PRESENT.tif output=pcem_potential --o

Visualise the actual suitability of Pinus cembra acccording to the Random Forest Model

d.mon start=x3
d.rast pcem_potential

Calculate the realised range of Pinus Cembra suitability

The Potential distribution map or suitability map pcem_potential has values equal to:

  • 1 : No suitable or no potential
  • 2 : Suitable or Potential
  • 20: Sea

The distribution map pcem_euforgen has values equal to:

  • NoData: absence
  • 1: presence

If we sum the two maps we will be able to generate a realized range map. This is done by selecting class 3 from the sum of the two maps. Class 3 represents suitable pixels within the presence of distribution.

r.mapcalculator amap=pcemeuforgen bmap=pcempotential formula=A+B outfile=pcemrealized –overwrite r.mapcalc pcemrealized = “if(pcem_realized == 3 , 1 ,0 )”

You visualize and save results for the Realized area in a text file with the following commands: -n map=pcem_realized units=k -n map=pcem_realized units=k > ~/ost4sem/exercise/rp_ratio/results/R_value.txt

The R (realised distribution range) is equal to 24,606 square Kilometres.

You visualize and save results for the Potential area in a text file with the following commands: -n map=pcem_potential units=k -n map=pcem_potential units=k > ~/ost4sem/exercise/rp_ratio/results/P_value.txt

The P (potential distribution range) is equal to 32,538 square Kilometres.

The RP ratio ⇒ 24,606 / 32,538 % 100 = 75 %


wiki/exercise_rp_ratio.txt · Last modified: 2021/01/20 20:36 (external edit)