Vegetation of the woodland-steppe transition at the southeastern edge of the Inner Mongolian Plateau

The vegetation of the woodland-steppe transition in southeastern Inner Mongolia, where the East Asian monsoon climate reaches its northwestern edge, is described and analysed in this paper. The communities are classified in a phytocoenological way. 12 major types of woodland, shrubland, meadow, fen, open woodland and steppe are differentiated and described on the basis of 133 phytosociological releves. Detrended Correspondence Analysis shows that precipitation plays a crucial role in the distribution of grassland communities while woodland and shrubland communities are controlled by both warmth and humidity conditions. Four vegetation zones can be distinguished. From the woodland to the woodland-grassland zone, the temperature decreases and the precipitation increases with increasing altitude, which leads to the conditions suitable for the meadow and fen communities. In the direction of the woodland-steppe zone the temperature increases while the precipitation decreases with the gradual lowering of the altitude; the steppe communities form a matrix while the woodlands have a patchy distribution. From the woodland-steppe to the steppe zone, the precipitation rather than temperature decreases; as a result the woodland communities disappear gradually. On a local scale, geomorphologic conditions determine the vegetation pattern of the study area. Due to the existence of a sandy substrate different woodland types occur together in the woodland-steppe transition. The local distribution of woodland and steppe communities is dependent on slope conditions. In addition, human disturbance has also influenced the composition of plant communities.