Tunica Hills, Louisiana, landscape components include flat surfaces dissected by steep sided, but plant covered, ravines; trees, vines, shrubs and herbaceous plants; and small mammals, birds and insects. There are always dead trees or snags in these landscapes. Water is normally intermittent but does collect in small depressions and pools along a water course.
Landscape structure is how the parts go together. The Tunica Hills forest usually has about seven layers of plants from ground surface to canopy. Through observation we find that the distribution of elements is not random and the composition of plants is in patterns. Patterns are related to soil, moisture, solar orientation, wind exposure or other factors.
Understanding function , or what things do in the landscape, may be somewhat more difficult. Besides observation, detailed study of elements may be necessary. In the example landscape, it is easy to see that the pools provide collection and slow release of water back to the areas around them, that the snags are providing a home for insects and decomposers, that the leaf layer on the ground is serving as a mulch and composter and that the small borrowing animals are serving to mix and aerate the soil. Further study might show us which plants are companions, nitrogen fixing, attracting birds and beneficial insects, or serving other roles.
There is little chance of our being able to pattern our design
on natural systems unless we take the time to observe and study
landscapes in our region. Through an understanding of our bioregion
we can accelerate succession and change by "using what is
already growing to build soil fertility," "introducing
plants that will easily survive on the site and which will help
build soil fertility," "raising organic levels artificially
by using mulch, green manure crops, compost and fertilizer to
change the soil environment," and "substituting our
own herb, pioneer, and climax species which are of more use to
us than the existing natural or disturbed vegetation." (Bill Mollison and Reny Mia
Slay, Introduction to Permaculture, pg. 24)