 The ecoregion is bounded on the east by the humid Oaxacan montane forests, which lie below elevation.To the east, the xeric Tehuacan Valley matorral occupies the Tehuacan valley to the northwest, the Jalisco dry forests occupy the upper basin of the Santo Domingo River, which lies in the rain shadow of the Sierra, and the Southern Pacific dry forests lie to the south along the Pacific coast, extending into the upper basin of the Tehuantepec River and the Valley of Oaxaca.The dry forests separate the Sierra Madre de Oaxaca pine–oak forests from the Sierra Madre del Sur pine–oak forests to the southwest.