Hi

I have to model the deposition of water dispersed seed. My basic idea is to
let them flow from the location of the seed source via the flowpath
downhill, and deposit a certain percentage of seeds depending on the slope.

So what I did in R was to

1) for each seedsource
2) determine adjacend cell of flow and the slope
3) reduce the number of seeds
4) go back to 2 if there are still seeds left

As I am working on a large grid, this takes a long time --- to long
actually.

So I started porting these calculations to GRASS. I now have calculated the
flowpaths from each cell, and can also convert the 2d lines into 3d lines
with the deposit rate (based on the slope) as the 3rd dimension.

Now my problem is, how can I calculate the number of seeds deposited in each
cell?

I would have to identify the floodline for a given seedsource by the start
of the flowline, and iterate through it to calculate the number of seeds
deposited, and add them to a new grid containing the deposited seeds.

Is there an easy way to put these steps together? I could import the
floodlines and do everything in R, but the amount of data to import would be
quite large.

Any suggestions how I could tackle this problem to get a fast algorythm?

Thanks,

Rainer


-- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology,
UCT), Dipl. Phys. (Germany)

Centre of Excellence for Invasion Biology
Stellenbosch University
South Africa

Tel :       +33 - (0)9 53 10 27 44
Cell:       +33 - (0)6 85 62 59 98
Fax (F):       +33 - (0)9 58 10 27 44

Fax (D):    +49 - (0)3 21 21 25 22 44

email:      Rainer@krugs.de

Skype:      RMkrug

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