Is there a Minecraft command for changing biomes?

If you are on a server, you can use WorldEdit (the plugin).

SPC, short for Single Player Commands, is a mod that allows you to use WorldEdit on singleplayer and LAN.

When you do //biome with WorldEdit, all other articles will be explained.

Short answer:

No, there isn't, and I don't think any mod can do this.

The biomes are generated by the world seed and the current generation rules. So to re-generate a chunk delete the exact save file, then go to a old version (like 1.3), open the world, generate the deleted chunks and then switch to 1.9

The other way is to make the biome look like another biome by replacing the dirt by sand or oak wood to some other wood.

Example of "changing" a forest to a desert:

/fill ~-25 ~-5 ~-25 ~+25 ~+5 ~+25 minecraft:sand 0 replace minecraft:dirt
/fill ~-25 ~-5 ~-25 ~+25 ~+5 ~+25 minecraft:sand 0 replace minecraft:grass
/fill ~-25 ~-5 ~-25 ~+25 ~+5 ~+25 minecraft:air 0 replace minecraft:leaves
/fill ~-25 ~-5 ~-25 ~+25 ~+5 ~+25 minecraft:cactus 0 replace minecraft:wood

Example of "changing" a desert biome to plains:

/fill ~-25 ~-5 ~-25 ~+25 ~+5 ~+25 minecraft:grass 0 replace minecraft:sand
/fill ~-25 ~-5 ~-25 ~+25 ~+5 ~+25 minecraft:stone 0 replace minecraft:sandstone
/fill ~-25 ~-5 ~-25 ~+25 ~+5 ~+25 minecraft:air 0 replace minecraft:cactus  
/fill ~-25 ~-5 ~-25 ~+25 ~+5 ~+25 minecraft:air 0 replace minecraft:dead_bush  

These commands will, if executed, "replace" the surrounding biome with another. You can fiddle with the numbers to get a bigger part filled, and you can set up command blocks getting activated every ~10 seconds (~40 Repeaters) with these commands:

/execute @a ~ ~ ~ fill <yourFillCommand>