Abstract: A sample plot of Pinus sylvestris var. mongolica (MP) savanna (SMP) in Daqinggou (42°52′N, 122°55′E) where no large scale disturbances such as afforestation and farmland development were experienced, and the sample plots of grassland (GR), clearcut of declined MP sandfixation forest (CMP), and pure MP sand-fixation forests (MPP) with different ages in Zhanggutai (42°43′N, 122°22′E) where large scale afforestation and farmland development were conducted since the 1950s, were selected to monitor the variations of groundwater table (GT) from May to October 2005. The seasonal variation of the GT exhibited four types, i.e., linear, “V”, “N”, and “M” curves. The GT value in SMP plot in Daqinggou had lesser variation in growth season, with an average of 1.88 m, while the GT values in GR and CMP plots in Zhanggutai increased from May to July, and then fell down. The 23 year old MPP plot had a larger variation of GT in growth season, with a difference of 4.30 m, but the elder (33-, 42-, and 45-year old) MPP plots had a fluctuation of GT, with its variation range differed. As a whole, the GT value ranked in the order of SMP in Daqinggou < GR and CMP in Zhanggutai < 23-year old MPP < 33-years old MPP < 42-year old MPP < 45-year old MPP. These results suggested that large-scale afforestation and agricultural development were the major causes inducing the differences of groundwater table between Daqinggou and Zhanggutai, and the different types of vegetation cover and stand age in Zhanggutai also affected the groundwater table.

Key words: Hormone, Wheat, Photosynthesis rate, Regulation and control