It has been estimated that more than 90% of poplar cultivation throughout the world is concentrated on species and hybrids in section Aigeiros (Thielges 1985). This is due to the ease of intrasectional hybridisation and intersectional crosses with species in the Tacamahaca section, the broad adaptability of these species and hybrids in the temperate and sub-tropical zones, and the ease of vegetative propagation. Section Turanga has been increasing in importance, and the scale of some planting programs is enormous: the Three North Shelterbelt System is a 35.6 million hectare shelterbelt project across the desert border in northern China, where poplars make up 60% of the effort, much of it P. euphratica and hybrids Populus simonii × P. nigra (Weisberger et al. 1995, Wang 1996).