back to Panorama content

Floodplain primary succession

Unlike the majority of rivers in the United States, this section of the Middle Fork River, Montana is not regulated by a dam allowing nature to continually reshape this floodplain and provide an example of primary succession. The Nyack floodplain is positioned between Glacier National Park (GNP, northeast) and Flathead National Forest (FNF, southwest). High water created by snow melt in the spring drive primary succession in this riparian system (vegetation growing along river's edge). These pictures were taken in late May after much of the snow had melted and the river was relatively low. In photograph below right, the gravel/cobble bar is disturbed annually and new recruits of willow (Salix spp.) and cottonwood (Populus sp.). These seedlings are only about 1 foot tall. These two genera of plants can be found across the globe. Behind the bar is a pole stand of cottonwood (see white arrow). This raised area experiences flooding less frequently allowing primary succession to progress. Trees in this stand and others like it are often a cohort of trees with identical ages that established after an episodic flooding event. A number of forest patches of different age and successional status (successional sere) can be found in this area.

This is an interactive panorama represented as a QuickTime VR movie. Click and drag the mouse to pan and tilt the view. Depress the shift and control keys to zoom in or zoom out.

Below is a deciduous forest growing along a river at Shades State Park in central Indiana. Less severe shoreline disturbance along this river likely represents cases of secondary succession. The distinction between the two types of succession in the context of riparian disturbance is subtle and potentially confusing. A key criteria differentiating the two relates to the degree of substrate disturbance. Severe riparian disturbance will remove all the topsoil substrate and expose mineral soils that are relatively infertile and lacking signs of life (e.g. seedbank, organic matter, etc.). This represents a scenario of primary succession where all recruits must re-colonize an area that is deplete of propagules and developed soils.