Why do some forests have undergrowth so thick you can’t get through it, and others are just tree trunk after tree trunk with no undergrowth at all?
In: Biology
The amount of underbrush is determined by the amount of natural light available at lower levels and by grazing patterns of wild life. And by forest fire patterns.
In places in the pacific coastal rainforest (west coast of bc), there is a big difference between old growth forests and “reforested” areas post -clearcutting.
In old growth forests, trees are regularly being knocked and branches broken off in the wind. This creates a lot of patches of light that filter down to ground level. So there is a lot of underbrush, but the density of underbrush varies quite a bit. Most of the time, there’s lots of ferns and spindly bushes. But anytime there is a decent patch of light, salal, salmonberry, maple and many other bushes take off- if a plant was well established in a shady environment and a tree toppled over creating a patch of light, all those established plants and trees grow madly as soon as the sun hits them.
In an artificially reforested (tree planted) all of the preexisting Forest is eliminated. Seedlings are planted the same age and spacing and variety so they grow at approximately the same rate. There are fewer wind falls and so the area at ground level is really consistently dark. Once the trees are taller than the normal bushes, the bushes are strangled by lack of light, resulting in almost no undergrowth.
Some organizations that rehabilitate forests intentionally go through and fall trees, kill and leave standing dead wood, and top trees to bring more diversity to the undergrowth. Essentially more light means more plant diversity means more animal diversity
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