EPOW - Ecology Picture of the Week

Trees of the Past, Trees of the Future

Tropical Forest Profiles
San Blas, Nayarit, Mexico

Explanation:  Enjoy these profiles a tropical forest, here just outside the town of San Blas in the state of Nayarit along the west coast of Mexico.  

Tropical forests are amazing structures ... with overlapping ("imbricate") tree crowns, a diversity of tree growth forms and species, multiple layers, tangling vines, and so much more.

My favorite way to view tropic forests, however, comes from a textbook from the late 1970s, that describes tropical forests in terms not of space but of time.  
  

  
The authors describe the dynamic, changing composition and structure of tropical forests in terms of three sets of trees:  trees of the past, trees of the present, and trees of the future.

Trees of the past are those trees that once lived and occupied various positions and layers in the forest canopy.  Those trees are now dead and gone, but their influence is still prevalent.  When they died and fell, they left holes in the canopy that now have become occupied by early succession, fast-growth plants ... including herbs and shrubs on the forest floor, as sunlight finally penetrated, and late including fast-growing trees that quickly take advantage of the opportunity to seek the sun.

Trees of the present are, well, what we see today.  In this week's photos, the trees of today are a combination of recent and older establishments.  With some experience, and an eye to time, one can read today's jungle like a book of many chapters.  

Trees of the future are the most interesting set.  They are the trees and other plants yet to come, yet to establish, yet to take root and grow.  They can be dense lianas (climbers, vines) that take advantage of sunlit openings, such as the vine growths along the roadside in these photos.  They can also be those large, old, mature trees that thrive more in the dense shade, although they might not appear for many years into the future. 

So with this understanding of how time plays out in the history, current growth, and future development of forests, one can peer back in time and forward in time, to see the jungle as a living, developing, ever-changing entity.

  
Information:
     Halle, F., R. A. A. Oldeman, and P. B. Tomlinson. 1978. Tropical trees and forests: an architectural analysis (Chapter 5, Forests and vegetation). Springer-Verlag, Berlin. 441 pp.