Habitats

1. Habitats Definition: types of places where specific kinds of plants and animals live. Within biomes, a variety of habitats exist where the physical environment shapes the biological environment. Concepts: • Niche- the range of conditions that species tolerate (or prefer). It may be thought of as an n-dimensional (more than 3-dimension) space. • Community- a group of species found in a particular habitat. The species may or may not interact. • Diversity- a term that refers to the number of species in a community (species richness) and the relative population density (evenness) of these species.

2. Southern New England Habitats I: Barrier Beach • Definition: areas of wind- and current-deposited sand that act as barriers between the ocean and upland. Much of the high energy (wind and wave action) of the coastal environment is dissipated on the barrier beach. • Physical environment: This is an extreme and ephemeral, dynamic environment, in that it possesses difficult conditions for organisms to live in, and in that it continually changes shape and may disappear and reappear over time. Physical environmental features that organisms face include, wind, wave action, highly saline water, wind-borne salt spray, tidal fluctuation and shifting sands. • Diversity: The richness of terrestrial species may be low, because few species possess the adaptations necessary to survive this extreme environment. The density of these species may be high, however. In contrast, the richness of marine species in the near-shore environment may be comparatively high.

3. Topography: Intertidal Zone • The intertidal zone is the region between high and low tide; that place where the ocean meets the land and expends much of its energy. • At the upper end of the intertidal zone, algae and other debris carried by wave action are deposited at the wrack line.

4. The Berm • The berm is the low region above high tide that is largely devoid of vegetation. Sea rocket and beach clotbur are among the few plant species that can colonize the upper reaches of the berm. • It is characterized by wind-blown (aeolian) sand deposits that changes in profile from summer (more gently sloping) to winter (steeper profile).

5. Primary Dunes • The primary dunes are wind-formed deposits of sand that are the first beach environment extensively colonized by terrestrial plants. • This environment is characterized by wind-borne salt spray and shifting sands. • The principal plant species of the primary dunes is dune grass- a species that produces a network of rhizomes (underground stems) that stabilizes the plant and the sand it occupies. • Other common herbaceous species include seaside goldenrod and beach pea.

6. Back Dunes • The back dunes are further from the ocean, and are less affected by wind and salt spray. • With a less extreme environment, the diversity of plant species increases. Low woody species like beach heather and beach plum (present in foreground) also appear.

7. Dune Forest • Still further back from the ocean, the extreme effects of the coastal environment subside to the point where salt-tolerant trees can become established. • Pitch pine, eastern redcedar, American holly, black cherry and shadbush are typical members of the dune forest.

8. Bay Edge • The low energy and quiet water of the inland (bay) edge of the beach permits the development of a marsh fringe. • This marsh is vegetated by grasses and other herbaceous species that can tolerate inundation by saline tidal waters.

9. Profile of a Southern New England Barrier Beach

10. Adaptations • Plants and animals must have adaptations to survive the high salinity, high energy, often dry environments of the beach. • Plants have adaptations such as waxy coatings (prickly pear cactus at left) on leaves to reduce evaporation of water, salt glands to remove excess salt from tissues, and net-like rhizomes to help anchor them to the shifting sands. • Animals such as the herring gull (above) also have salt glands at the base of the beak to remove excess salts from tissues.