How is intensive subsistence agriculture distinguished from extensive subsistence cropping?

Subsistence agriculture is that in which the farmers use or consume most of what they produce, rather than selling it in a market (commercial agriculture).

Intensive subsistence agriculture refers to subsistence agriculture that supports a large number of people on a relatively small parcel of land (i.e., high physiological density). The primary example of intensive subsistence agriculture would be rice growing, such as that found in East, South and Southeast Asia.

Extensive subsistence agriculture, on the other hand, is that which requires a lot of land to support relatively few people (i.e., low physiological density). Examples of this type include shifting cultivation/swidden agriculture (or slash and burn) and pastoral nomadism.