Vegetation-Erosion Dynamics - River Dynamics and Integrated River Management - page 67

perennial stream becoming intermittent or ephemeral. Restoration of vegetation in the watershed has
become one of the main tasks of management of the river ecosystem.
Basically, vegetation development needs water, soil, and suitable temperatures. In nature, vegetation
develops almost everywhere, on the mountains and in river valleys, even deserts and glaciers. Figure. 2.18(a)
shows the vegetation on the glacier near Banff in Canada. The trees may grow in only 1-2 months in
summer, when the soil temperature is over 0 ć . Most of the trees have an age over 1,000 years although
the trunk diameter of the trees is only several tens of centimeters. Figure 2.18(b) shows the trees in the
Sinai Peninsula in Egypt, where the climate is very dry and rain several years.
(a)
(b)
Fig. 2.18 (a) Vegetation in the glacier near Banff in Canada. Most of the trees have an age over 1,000 years; (b) Trees
in the Sinai Peninsula in Egypt, where the climate is very dry and rain several years
Development of the vegetation cover in mountainous or hilly areas depends on the local climate,
precipitation, soil texture, parent material, topography, soil erosion, types of land-use, and human
activities. Among them, soil erosion is the most important natural factor and human activities are the
most vital non-natural factor affecting the vegetation. Kosmas et al. (2000) studied the effect of land
parameters on vegetation and erosion on the island of Lesvos, Greece. The island is divided into
semi-arid and sub-humid zones. Low rainfall combined with high evapotranspiration demands in the
semi-arid zone has significantly affected vegetation performance and the degree of erosion.