The land of fractal dimension value is vary from 1 to 2.When the value of D is 1.5,namely D is critical value,the change mode of land types is Brown random movement.

• 斑块的分维数介于1到2之间,当分维数D为1·5时,是斑块的临界值点,代表斑块处于布朗随机运动状态。