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Primary succession of coastal dunes

The sand dunes of Lake Michigan helped inspire Henry Chandler Cowles, one of North America's greatest ecologists, and his landmark ideas as a plant ecologist regarding predictable and orderly patterns in vegetation in the late 1900's which we now refer to as primary succession. He worked in and around Chicago, Illinois. He sampled vegetation along a geologic chronosequence with young dunes near the shore and old dunes more inland. The dunes where he performed his seminal research were unfortunately destroyed for industrial development. However, various groups were inspired to preserve some of the remaining dunes. The pictures below are from the Indiana Dunes National Lakeshore and nearby Nature Conservancy land in Indiana. The dramatic variation in environmental gradients makes these areas hotspots for plant diversity. Although relatively small, the Indiana Dunes National Lakeshore (~15,000 acres) is ranked 7th among U.S. National Parks for plant diversity with an estimated 1,418 vascular plant species. In comparison the Great Smoky Mountains National Park (over 500,000 acres) has more than 4,000 plant species.

The above picture shows the beach and foredune area. Plants such as marram grass (Ammophila spp.) and cottonwood trees (Populus spp.) help to stabilize dunes and facilitate primary succession.

The above picture shows the area behind the foredune. Ponds and other wetland areas are common behind dunes also referred to as intradunal ponds.

Although some dunes are relatively small in stature, even modest changes in topography affect soil moisture and helps produce such great amounts of plant diversity. For example, the picture to the left shows prickly pear cactus (Opuntia sp.)[yellow flowers] a xeric species (arid) growing next to horsetail (Equisetum sp.) [segmented plant with a prehistoric appearance and a cone like top] a species common in mesic areas (wet). I was certainly surprised to find a cactus growing at such a high latitude and even more surprised to see it growing next to a species generally restricted to very moist habitats. 

Ancient dunes can be found ~2 miles inland from the shore of Lake Michigan. To the left is an aerial photograph (Google Earth image) of ancient dune remnants located to the left of a residential street near Cary, Indiana (suburb of Chicago). This area has experienced considerable development so ancient dunes are relatively scarce. The brown banded areas represent upland dunes about 1-2 meters taller than the lower more wet areas appearing dark green. If you are lucky, then you may get to see some of the lady's slipper orchids growing in the dunes including the Showy lady's slipper orchid (Cypripedium reginae).

Above is a panorama showing the ancient dune area during a summer shower. The changes in topography are not as striking as in the aerial photograph above but still present. This plant community also looks completely different from the dune communities shown near the top.