Described by Land Rover:

Spiked Tires

Further allowing the concepts to adjust to changing conditions is a driver-deployable spiked tire system. This is operated by an electro-mechanical system mounted within the tire; activation of the technology permits air to inflate a secondary air chamber, filling pods moulded into the tread of the tire and which contain the spikes. The spikes rise just above the tread surface and fix into place for driving on packed snow and ice. When conditions have eased, the spikes can be retracted, obviating the need to carry two sets of tires or snow chains.

While all they’re showing now is some CG video, it’s exciting to see the things they’re thinking up!  Below you can see the shots showing a normal looking tire which instantly gets snow cleats!