Considering the magnitude of variation of the following environmental variables:
-sea surface temperature (SST; °C)
-chlorophyll-a (Chl-a; mg/m3)
-salinity (pss)
-pH
-currents velocity (m/s)
-dissolved oxygen (mol/m3), and
-seabed features (depth and slope, m)
Should I normalize them before attempting a ENM?
Cheers
Dear Bernabé:
It all depends on the purpose you are trying to deal with. However, it is always necessary to have dimensionless values reflecting your main variables. Of course it is widely reccomended.
Niche model refers to the range of dispersion, abundance, or presence of species. For example, any plant species have its lower minumum, its lower optimum, its maximum, its upper optimum, and its upper minumum. This tendency mimics a normal distribution of the species for example its abundance as a function of the environmental variable(s) that control the abundance of the species. When you sample across the full range of the environmental variable of interest, the species abundance or its presence should follow a normal distribution. Then the enviornmental variable distributes normally as well. No need to transform to normalize. When You sample only in a small range of the full distribution range, it depends on what part of the normal distribution range you are sampling. If it is on the lower or upper level of the dsitribution range the normalization would not help. If the sampling is conducted withing the maximum and optimums, no need to normalize, the env variable distributes normal.
Hope this explanation would help.
Kind Regards
Sincerely
Jose Navar, Ph.D
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