Afforestation Technique fo Short-rotation Industrial Timber Poplar Plantation on the Edge of Tenggeli Desert in Ningxia Multi-species Design in Planting Industrial Forests by Genetic Algorithm Cultivation trial of Michelia hedyosperma Techniques for Afforestation in the Extremely DegenerativeMountainous Land of Dry and Hot Areain Nanjian,Yunnan Province The Silviculture of Calophyllum polyanthum (Guttiferae)in China STUDIES ON THE AFFORESTATION TECHNIQUES FOR THREE OAK SPECIES INTHE SEMIARID AREAS OF WESTERN LIAONING PROVINCE