The Forest Is Not A Pastoral Landscape

We like to think of the forest as a pastoral paradise with elk, deer and moose sipping water from a lake by the narrows. Birds and quail chipper in the background and an occasional bear with her cubs stroll by. Cottage lots and chalets as well as a golf course may be nearby. This is all far away from the crowded city, its heat and population, commercial buildings and houses.

However the truth about forests with their idyllic lakes is not a true and actual one. The forest ecosystem is actually one major struggle for survival where chemical and biological warfare exists. Trees actually try to attack and kill their so called competitors with horribly toxic chemicals all the time. In other words trees actually produce herbicides to kill their competitors. Conversely other trees show an incredible hypersentivity to the herbicidal concoctions of certain trees and plants.

This all makes for better landscaping of the forest and its environs. You cannot expect to plant an oak tree in the middle of a farm field and expect it to grow well.

And why is it that nothing except grow can grow on a prairie field. Can these questions be answered differently from the standard answer of “competition for light, water and minerals” explanation that our forestry or high school biology textbooks repeatedly mention?

The sad fact is that some trees have evolved to actually exude poisons to kill other plants to ensure their own survival. And it is this phenomenon that plant physiologists give the wonderful descriptive term allelopathy. The best example of this in Canada is black walnut ( Julans nigra). Increasing with maturity, the chemical juglone is released from the trees leaves, fruit and roots where it concentrates in the soil making it very difficult for other trees (especially garden plants) to grow in their immediate vicinity.

The endangered butternut (Juglans cimera) also exhibits this phenomenon to a much lesser extent. The same has been reported for sycamore (Platanus occidentalis), another tree of Southwestern Manitoba whose decaying leaves reportedly cause significant reductions in seed germination and seedlings growth and render their understory sterile of any herbaceous plants.

Sugar maple (Acer saccharum) is another case in point. Unlike shade intolerant (sun loving) trees like poplar, the shade tolerant (shade loving) sugar maple tree has difficulty growing amidst the residues of typical old field plants such as goldenrod and mullein. However in a forest situation, sugar maples themselves are thought to exude a mild allelochem which excludes the growth of many other plants.

We all knew that “competitive forces” were at work in our forests – that there exists a “battle for resources – for light, water and nutrients between tree seedlings of various species. What is a marvel is the extent of the tools and tactics of the landscape itself. So much for scenic pastoral scene of our forest – with its lakes, waterfowl and wildlife as a peaceful scene.