Forests and Succession

N.R.Fuller, www.SayoStudio.com

In a previous post, "The Nature You Know," I touched on an idea that I think is important to keep in mind while writing.  So many of the images that we have of the natural world have been shaped by the way humans impact their surroundings that many of us have difficulty envisioning a truly natural environment.  Even those of us who spend our leisure time walking in the woods, climbing mountains, or fly fishing usually experience nature as guided by human hands.  While using these images in your story may be perfectly appropriate in many instances, it can be useful to know what our characters would actually encounter when they head out into the wilds.  Most of our parks are not the pristine habitat we imagine them to be.
    Succession is the idea that an area of cleared forest land (because of fire, high winds, etc.) will regrow in a predictable pattern.  During this process not only the plants, but the animals who inhabit the area will change.  These changes are brought about due to the changes in the availability of sunlight, nutrients, and water.  The specific species taking part in this process will differ depending upon local climatic conditions (temperature, elevation, latitude).  Early stage plant species are grasses and shrubs which thrive in bright sunlight.  Following this, trees begin to sprout and competition really kicks into gear as species fight each other for resources.  Eventually (presuming no catastrophic events) a mature forest will develop.  At this stage, the leaf litter of the forest floor has decreased because the canopy has solidified, killing off the spreading lower branches you see on those solitary trees in farmers' fields.  When a new area of the forest is cleared (due to fire, winds, insects, disease, etc.) the process begins anew.
    Not all open ground will complete the cycle of succession.  Plant populations are limited by the quantity and quality of the soil that is beneath them.  While this seems like a simplistic statement, you'll want to keep it in mind.  There is a significant reason why the NJ Pine Barrens don't have farms, and it isn't because we didn't try.  The sandy acidic soil of this region is not so friendly.  Similarly, grasslands remain grasslands mostly because of the poor quality (I'm not judging them, I promise) of the soil beneath them.  While thin soils may change radically from one inch to another (due to a change in underlying rock type), the thicker soils underlying mature forests are less likely to have radical divisions.  Consequently, many unaltered forests play out the gradations of succession on their fringes as the soil decreases in quality. 


So, how do humans impact forests?

1) We fight fires.  While controlled burns of public lands have long been advocated for as a more natural and cost effective way to manage our forests, we keep dumping chemicals on these massive tinderboxes to delay the inevitable.  Consequently, forest fires tend to be more destructive, though less frequent.  Natural forests would generally have more clearings (undergoing succession) and less accumulated litter (leaf and branch).  Additionally, some species thrive specifically in the aftermath of fires.

2) Humans clear forests to provide farmland and to build roads.  This creates that weird effect of having a stand of really tall straight trees next to open ground.  Fresh cut stands are really obvious because there are no branches on the exposed sides of those trees, or they have those sad little branches sticking out from the otherwise barren trunk.  Unless there is a significant change in the soil quality/thickness at that line, this is the result of a catastrophic event (human interaction included).  Oh, this also includes clear-cutting to put up power lines and the like.

3) Logging has an impact on the forest for a variety of reasons.  Obviously, the largest trees tend to be targeted, which impacts the animals that live in and around them (remember the spotted owl fiasco?).  Modern techniques also tend to clear an area, instead of taking only the most desirable trees (which was more economically viable when being done by hand). Some forms will take only the trunk of the tree, leaving behind all of the scraps, making great tinder.  Cable logging leaves long scars in the earth where logs were dragged en route to the trucks waiting below.

4) Paths that we cut through Parkland give a false sense of reality.  These pathways are often leveled, widened, and cleared to make a more pleasant experience for the hikers.  Secondly, pathways are often curved into switchbacks to decrease erosion.  I'm going a little off topic here, but I'm pretty sure our predecessors didn't bother with this.  Paths would most likely follow the shortest route, leading to rocky washed out trails in dry times, or swampy morasses in the rainy season.

5) Rerouting and damming rivers has a pretty obvious impact on forests.  Most trees don't sprout when they're submerged in water (some coastal species like mangroves do weird things), so those barren trunks sticking up in the middle of the pond might not have gotten there naturally (though there are ways to do it).  Take a look next time you see one and check if there is a dam or a road blocking the natural drainage.

I hope you enjoyed this little peek at the world around you.  As always, let me know if you have something to add, or you think I screwed something up.  Check out the links below for more detailed info on what I covered.





http://forest.wisc.edu/sites/default/files/pdfs/publications/78.PDF
http://www.envirothonpa.org/documents/ForestSuccession.pdf
http://www.georgian.edu/pinebarrens/
http://www.privatelandownernetwork.org/pdfs/benefits_of_prescribed_burning_low-res.pdf
http://www.bigskyfishing.com/National_parks/glacier/logging-lake-galleries/near-burn-area.php
http://www.ecofootage.com/vs0259.html
http://www.irishtimes.com/news/ireland/irish-news/storms-reveal-7-500-year-old-drowned-forest-on-north-galway-coastline-1.1715303