As a result of the broken nature of much of Nyasaland and the diversity of its climate there is a correspondingly wide range of vegetation offering very varied habitats to wild life. From an alpine zone, containing giant lobelias on the Nyika Plateau and mountain grasslands with residual patches of broadleaved evergreen forest, occurring over all the plateaux above about 6,000 feet, the country drops into the Brachystegia woodland. This in its many forms covers most of the main watersheds of the country. The alluvial soils lying along the larger rivers on the plain of Lake Nyasa and down the Shire valley are characterized by mixtures of Acacia and Combretum species growing in grass which is long and intensely thick. Copaifera mopane woodland covers parts of the floor of the Shire valley, whilst on the poor sandy soils of the Lower Shire there are a number of patches of deciduous forests and thickets, some of which are virtually impenetrable except along paths made by the larger game animals. The only approach to open plains is found in the region of Lake Chilwa.