 The sixth and seventh ecological zones are characterized by their shrubs and trees , and Presque Isle State Park is home to 633 plant species ( 195 monocotyledons , 410 dicotyledons , 5 gymnosperms , 5 horsetails , 13 ferns , and 5 mosses ) . The sixth zone , thicket and sub @-@ climax forest , forms when shrubs grow on dying marshes , followed by small trees . The trees shade and thin out the thickets of shrubs , leading to a sub @-@ climax forest . The seventh and final stage is climax forest , where many large trees form a canopy . If left undisturbed , this ecological succession is believed to take between 500 and 600 years , although visitors to parts of Presque Isle State Park can walk through all of these zones in 5 miles ( 8 km ) . 
