Dewfall Variation by Large-Scale Reclamation in Sanjiang Plain

Over the past decades, the area of the cultivated land in Sanjiang Plain has increased at the cost of wetland shrinkage. In order to reveal the change in dewfall brought about by large-scale wetland reclamation, dew was monitored by woodstick made from poplar tree, and the annual factual dewfall per unit area was calculated by the leaf area index (LAI) in wetland, soybean land, paddy land, and residential land from May to October 2010 in Sanjiang Plain. The results showed that dewfall levels in wetland, soybean land, paddy land, and residential land were (11.12, 11.98, 30.18, and 4.25) mm, respectively. When wetland changed into soybean land, dewfall did not have significant variation. While, when soybean land was reclaimed into paddy land, dewfall increased to about twice the initial value. Dewfall in the residential land was the least, accounting for only about 1/7 of that in the paddy. LAI was the main factor that affected dewfall in different ecosystems. Relative humidity and air temperature were the main factors that affected dew formation. Monitoring of the dew intensity can reveal wetland adjustments in the local space micro-climate and determine how changes in land-use and land-cover by humans transform the water cycle.