A BRIEF REVIEW OF STUDIES ON DIFFERENTIATION OF VEGETATION PATTERN ALONG A TOPOGRAPHIC GRADIENT IN HILLY REGIONS

Abstract

The relationship between plants and environmental conditions is one of the most basic characteristics of plant communities. The humid hilly regions are a complex habitat that has various degrees of disturbance related to water erosion. At an intermediate_scale level, the region can be divided into an upper and lower hillslope area divided by an erosion front. At a more detailed_scale, the sections can be divided further into micro_scale geomorphological units. The upper hillslope area contains a crest slope, upper sideslope and head hollow etc. and the lower hillslope contains a lower sideslope, foot slope, flood terrace and river bed etc. The upper and lower hillslopes are two basic functional land area types for assessing species composition and forest structure. On the upper hillslope area, the vegetation changes gradually and continuously from the crest slope, to upper sideslope and head hollow. On the lower hillslope, however, the micro_landform units have little effect on vegetation structure as disturbance plays the most important role in regulating vegetation patterns. The lower hillslope area is characterized by active soil erosion, landslides and slope failures. Thus, the plant communities that develop on it are early successional communities, and their regeneration depends on active surface disturbance. However, the plant communities that develop on the upper hillslope areas are climate climax communities as it has been stable for a long time, and their regeneration can be explained based on the gap dynamic theories. Topography is the most basic and important habitat factor affecting vegetation patterns. Habitat niche differentiation related to topographic variation supports the coexistences of species and results in high species diversity at small spatial scales.