Riparian Vegetation of Gravel-bed Rivers : a Global Review

Kurzfassung/Abstract

Aim: This chapter provides a global review of the riparian vegetation of the major mountain regions and includes a high proportion of the worldwide braided rivers. The focus is on characteristic and frequent native and invasive non-native plants in the different geomorphological phases of the riparian vegetation communities.

Main methods: Nine global areas were defined as reference mountain regions to cover the wide range of abiotic factors and human impacts. Each area is considered as representative of the regional mountain ranges for analyzing their characteristics in terms of the associated riparian vegetation. For the subdivision of the riparian vegetation we extended the ‘fluvial biogeomorphic succession concept’, which differentiates floodplains into the geomorphic, pioneer, biogeomorphic, early and late successional ecologic phases.

Conclusion: The majority of the investigated reference mountain regions that include a high proportion of braided rivers are in the boreal zone of the Northern Hemisphere. They are characterized by common characteristics, with all succession stages occupied by a number of widespread, floodplain-typical plant species. In contrast to riparian forests of the boreal zone, the mainly continental floodplains of the mountain ranges of Central Asia largely lack riparian forests due to drought.

In the Southern Hemisphere, fast growing native pioneer shrubs and trees are nearly absent. These open niches can be colonized by Northern Hemisphere pioneer shrubs and trees, especially at the lower reaches of braided river corridors, where adjacent agricultural and urban areas are increasing.

Two mountain regions differ substantially from the global scheme. These are the geologically young Glacier Forelands of the Arctic Tundra of the Vatnajökull (Iceland), and the Wadis in the Mountain Ranges of the Middle East with extremely dry floodplains and only periodic to episodic stream flow.