Abstract: Based on remote sensing and the nonlinear theories of entropy and catastrophe, the spatiotemporal variation of ecoenvironmental frangibility in Kenli County of Yellow River Delta was analyzed through the installation of sampling plots. The methods of analyzing and estimating ecoenvironmental frangibility were also established. The results indicated that in 1987-2005, the environment of Kenli County tended to deteriorating, and two catastrophes of environmental frangibility occurred, one in 1997, and the other in 2004. The former catastrophe was mainly caused by storm tide and the water shortage from Yellow River, with the main appearance characteristics being habitat change and dominant species substitution, while the latter one was mainly from the water shortage from Yellow River, increase of evaporation-precipitation ratio, a great deal construction of reservoir, and increases of traffic road and population density, with the main appearances of the changes in vegetation type and coverage ratio. The analysis on the spatial variations of the environmental frangibility along the directions of different distances to the Yellow River and to the ocean testified the spatial gradual change pattern of the frangibility. This research was a new attempt, and provided an effective way for the quantitative easurement of environmental frangibility.

Key words: salt stress, maximum electron transport rate, mesophyll conductance, maximum carboxylation rate, FvCB model