Serpentine Soils Poster Design

I need a detailed and informative A1 poster about serpentine soils in California and Oregon.

Requirements:
- Types of serpentine soils
- Key land uses in different colors
- Slope gradients

Additional Elements:
- Scale and compass rose
- Cited sources

Ideal Skills & Experience:
- Proficiency in graphic design
- Experience with geographical information systems (GIS)
- Attention to detail and accuracy