Jenny, You might look up the word prairie on a web search. There are many areas of prairie across the east coast. They typically form where there is a soil type that is not good for tree growth. At Jennings Environmental Education Ceneter in western PA the site says "The Jennings prairie remains due to a thick layer of impermeable clay that prevents most tree species from becoming established. Plants and animals that do live on the prairie must tolerate shallow soils, fluctuating periods of drought and saturation, and fire. Even under these harsh conditions, this ecosystem teems with life." Other ones exist at places like serpentine barrens where the soil is poisonous to trees but grass and some herbs can establish. Another area is along flood plains frequently flooded. Some trees can establish there, like sycamore and silver maple, but often frequent harsh flooding will create an area that is occupied by grasses because they replenish faster than trees. Finally there are grass areas in environments that are frequently burned. Many of these are reverting to scrub oak and pine forests as people have messed with the fire cycle. To some degree many of these pockets of grasslands are on a very long term transient, but they can exists for thousands of years at a locality before transitioning to another ecotype, but they can also form in new areas as well.
Ed Frank --~--~---------~--~----~------------~-------~--~----~ Eastern Native Tree Society http://www.nativetreesociety.org Send email to [email protected] Visit this group at http://groups.google.com/group/entstrees?hl=en To unsubscribe send email to [email protected] -~----------~----~----~----~------~----~------~--~---
