What would the effects be on mountains, deserts, and grasslands? I know about the effects of a planet with no tilt, but I was curious about a 10 degree tilt. I am thinking the seasons would still be there but much less evident.
Earth's axial tilt is 23.5°. Assuming the orbital eccentricity is similar or identical to Earth's, you'd get cooler summers, warmer winters, and an easier transition between them (spring and fall) than we do here on earth. At least, the temperate and polar regions would have that. Effects on equatorial regions wouldn't be all that noticeable.
The effect on mountains would be negligible. Deserts are more a function of geography, rather than seasons, so they likely wouldn't be changed all that much, either. Grasslands might be more lush and stay green longer because of the milder winters where they'd be getting more rain instead of snow, but that's only one possible factor in what could happen to them.