The 'adret'( borrowed from French or Occitan) is the Sun-facing side of a mountain valley. The reverse side or antonym is ubac.

A sunny slope is the most important natural factor in the cultivation. The advantages of 'adret' slopes, which are usually drier and more protected, are evident and of paramount importance. Adret aspects receive much higher levels of direct sunlight, which produces higher soil and plant temeratures.

The vegetation of Bachelard Valley (Alps, France) mainly consists of forests and alpine pastures, and bare rock outcrops dominate the lanscape. The location of the tree limit depends on some factors.

On south-facing slopes (adrets pl.) the tree limit of the vegetation can reach as high as 2400m, but on the shadowy north-facing slopes (ubac) it is usually near 2200m.

More Info: en.wiktionary.org