processes of physiographic change cause change in plants. 1. Tendency to fill in low places + tear off high places. 2. Base level may be established - penepplain - new valley older valley penepplain - 1st effect of physiographic change is to intensify differences. B. A. / extreme difference between points. development usually tends to make conditions more uniform. A penepplain is an expression of diminished differences. vegetation has a profound effect on topography and habitat factors. 4. Soil development: soil is result of long slow change. addition of humus or dead plant material. one of the greatest effects is to increase the water holding capacity of the soil.