What is a Savanna?

 The most basic definition is “an open landscape with scattered trees.”  Of course it’s much more complicated than that.  For most people, their image of a Savanna probably resembles that of a park in an urban area.  Sturdy trees randomly clustered together along with open spaces dotted with individual trees randomly spaced throughout the landscape.  Savanna as a biome is generally the transition zone between the open prairie and some form of woodland, whether it be a northern Boreal or a southern hardwood deciduous forest.  The natural forces and physical boundaries that combine to act on a prairie and maintain the openness; fire, low precipitation infrequent lakes and rivers, becomes less common as the prairie approach the woodlands.  The lower occurrence of these forces or land forms, forge a new landscape, a mosaic of open prairies, tightly clustered woodlands and scattered trees. It becomes a sort of hybrid of prairie and woodland, bringing with it the full compliment of species found in both ecosystems along with unique species exclusive to the savanna.

Savanna’s can be found along the entire border or transition zone of the woodlands and prairies, fromCanadato theGulf of Mexico.  A transitional ecosystem running longitudinally through a continent will be highly diverse in terms of species composition, but the physical appearance remains constant; a mosaic of random openness and closed canopy forests.

The Savanna ecosystem is not only found on the borders of large contiguous plant communities like Prairies and Forests, but inside the plant communities as well.  For instance; a south facing slope on a lake, river or wetland in the heart of a great hardwood forest will have elements of a savanna.  Because of the well drained nature of the soils and slope, fire tolerant species may take hold and become dominant.  The frequent fires will create more openings in the canopy, in turn creating less leaf litter and more grasses in the understory.  Grasses will encourage more prairie plants and less woodland species that tend to be ephemeral in the spring.

In contrast, north facing slopes around lakes and rivers within the prairie ecosystem may be more savanna than prairie.  The cool environment slows the intensity of the wildfires, allowing  trees to survive to create a mixed ecosystem.  In northern boreal forests, vast wet grassy meadows will create Savanna type woods on their periphery because of the frequent fires that rip across the meadows in periods of dry conditions. Species like scrubby Jack Pine and Bur Oak become more dominant than the less fire tolerant large stately Pines and Maple species. Proximity to the the meadow or the dry slope and the natural forces that act upon them, will determine the species success and thus the composition of the plant community.

When evaluating a site, MNL staff always takes into account soils, geographic relief, surrounding plant communities and the history of the property.  The gathered information will help us design a project installation that is ecologically sound and self sustaining.