An Analysis and Inquiry into the Wild Apple Trees in Iri
Liu Xinshi (Chengdu Geology College,Chengdu,610000) Lin Peijun (Iri Gardening Institute,Irin,835000) Zhong Junping ("August First" Agriculture College,Urumqi,830052)
Researchers from China and abroad generally thought that the wild apple trees in Iri was the relic species of the Tertiary period and was kept till now because of its distribution in the valley which was free from the coverery of the Quatenary glacier. According to the authors'on-the-spot investigation of the Cast and west parts of Iri Valley, It was clear that three glaciations had once taken place in the valley, under the frequent Quatenary glaciation, especially in the prosperous high-land ice age of middle pleistocene epoch, the temperate broad-leaf trees including wild apple tree were difficult to be kept in the either side of Iri valley, so the valley was not the shelter for wild apple trees of the Tertiary period. A more reasonable conclution should be the following one: with the advance and retreat of the Quatenary glacier,the wild apple trees once transported back and forth more times along the broad middle Asian plain (including Iri valley),migrated from west to east at the last ice age and gradually developed into what it is now. The reason why the wild apple trees only grow in some parts of the valley mainly depends on the microclimate determined by the local topography and human being's damage.