Abstract: Based on the 1961~2004 observation data of temperature, precipitation, humidity, wind, and solar radiation from 52 weather stations, and by using revised Penman formula, this paper calculated the potential evapotranspiration in Liaoning Province during the past 40 years, with its temporal and spatial distribution and representativeness discussed and the aridity index and water budget in surface soil computed. According to the aridity index, Liaoning Province was compartmentalized into three climatic regions, i.e., semi-arid region, semi-humid region, and humid region. The analysis of the inter-decadal fluctuation of dry and wet climate boundary in Liaoning Province showed that during the past 40 years, the dry and wet climate boundary fluctuated markedly and differentiated greatly, but the semi-humid and humid and the semi-arid and semi-humid climate boundaries did not move forward east and back west synchronously on the interdecade scale. In 1990’s, the dry and wet climate had an abrupt change. The semi-humid and humid climate boundary moved toward east, and the semiarid and semi-humid climate boundary moved toward west. The semi-arid and humid areas were reduced, while the semi-humid area was enlarged markedly. The main factors affecting the fluctuations of dry and wet climate boundary and the variations of dry and wet climate in Liaoning Province should be the Southeast Monsoon, Southwest Monsoon, and West Pacific Subtropical High. In western Liaoning, West Pacific Subtropical High and Southeast Monsoon mainly controlled the dry and wet climate status; while in eastern Liaoning, the factor topography precipitation should also be considered.

Key words: Larix olgensis, Population, Geographic variation