Abstract: Base on the observations at 24 meteorological stations in the Dongting Lake area during 1960-2012, the variation characteristics of sunshine duration and its impact factors were analyzed by linear trend analysis, MannKendall test, and wavelet analysis. The results showed that the sunshine hours had a significant decrease trend of 46.0 hours per decade, being most notable in summer (29.5 hours per decade), followed by winter (14.6 hours per decade), and no obvious change in spring and fall. The decrease rate in the northern part of the Lake was higher than in the south, and the greatest decrease rate was observed at the Jianli Station (97.8 hours per decade). The annual sunshine hours during the 1960s to 1970s were higher than the normal, and the turn point was in 1980; thereafter, the annual sunshine hours were below the normal. The annual sunshine hours had three variation cycles of 2, 6 and 10-11 years. The decrease of annual sunshine hours might be caused by the decrease of wind speed and increase of precipitation, cloud amount and foggy days in the Dongting Lake area.

Key words: maize, mulching, drip irrigation, Hetao Irrigation District., photosynthetic characteristics