Kelp data processing

[brunj7]

We decided to produce our own gridded product of maximum Kelp extent for habitat analysis.

I found this data set on EDI: https://portal.edirepository.org/nis/mapbrowse?packageid=knb-lter-sbc.74.17

Note:

• the data do not have gridded dimensions as normally in a netcdf file
• the dimensions are time and stations
• The station locations are stored in a different grid

Here is the workflow attempted so far:

1. Import the grid as a data frame using tidync package; this data frame will have time x stations nrow
2. group_by station taking the max value since it is what we are interested in (max biomass); this results in a data frame having one row per station
3. transform the station location grid into a data frame
4. join the two data frames on station
5. create a point sf object
6. rasterize to any grid we want

Here is the script: https://github.com/NCEAS/ca-mpa/blob/main/analyses/7habitat/code/kelplter_data.R

[brunj7]

It seems that the central stations do not have data at all.

Cori suggested it might be because the data is just Giant kelp, however, the metadata mentions that this data set should include both giant kelp, Macrocystis pyrifera, and bull kelp, Nereocystis luetkeana.

I need to check my code and if correct reach out to know if it is expected

[brunj7]

Looking at area instead of biomass, I do have values for all stations:

I am reaching out to the email listed to know if it is expected

[brunj7]

Actually looking more carefully at the metadata I found this statement:

Biomass data (wet weight, kg) are given for individual 30 x 30 meter pixels in the coastal areas extending from near Ano Nuevo, CA through the southern range limit in Baja California (including offshore islands), representing the range where giant kelp is the dominant canopy forming species.

So We will have to use the maximum area