Abstract: Habitat suitability assessment provides scientific basis for protecting rare waterfowl habitat and preserving biodiversity. In this study, habitat suitability of redcrowned crane in the west Songnen Plain during 1980 to 2010 was performed by the maximum entropy (MaxEnt) model. This model was implemented using Landsat TM image data, measured waterfowl distribution points, as well as selected environmental characteristics including land use type, vegetation coverage, density of rivers, density of lakes, density of residents, density of roads and density of croplands. Finally, we could get the suitability hierarchical graph of the redcrowned crane habitat suitability. The results showed that: (1) Suitable habitat for the redcrowned crane in the study area was mainly distributed in marsh wetlands and grasslands surrounded by rivers or lakes with high coverage of vegetation and a low degree of human disturbance. (2) The area of most suitable region and moderately suitable region during the four periods (1980, 1995, 2000 and 2010) were all gradually decreased. The most suitable area was decreased from 7536.38 km² in 1980 to 3762.50 km² in 2010. The unsuitable area was increased year by year. (3) The transformation among different habitat suitable grades conformed to the principle of proximity and reversibility. Thus the most area of most suitable region turned into moderately suitable region and the most area of moderately suitable region turned into marginally suitable region. On the contrary, the area of unsuitable region turned into most suitable region was small. This study offers a significant basis for wetland development planning, nature reserve conservation and reasonable layout, biological resource sustainable development and biodiversity conservation in the future.

Key words: residual nitrate-N, summer fallow, leaching, winter wheat, nitrogen mineralization.