Nothing Lives in Isolations-GardeningGirl.com

Nothing lives in isolation.

By Dr Craig Hull.

One of the joys I have during the warmer months is to sit on my back porch and watch the various birds hunt around for caterpillars in an old jacaranda tree. Sometimes the birds come to within just a couple of feet from myself, giving me an indifferent glance as they continue on their branch by branch search.

Whilst the birds seem to catch a decent share of grubs, bashing them against the tree to subdue them before gulping them down, the tree does suffer quite a large leaf loss over the course of a summer. The amount of near-empty branches attests to the supreme appetite of the caterpillars. As if that weren't enough,the jacaranda has to cope with a nearby gum tree, that towers over it.

When I look at that jacaranda tree, I can see that life amongst the greenery is not as simple as I once thought it to be.

And so I was interested to read of a recent experiment from some researchers at the University of Toronto and the University of Alberta. Joshua Haag and his colleagues decided to have a closer look at the interactions between insect attack and competition amongst plants.

Selecting four native species, wild blue flax, June grass, annual sunflower and common tickseed, the scientists set about modifying the levels of competition between plants, as well as the number of insects present. Despite what I may have expected, the insect herbivores had little effect on plant growth.

Plants can be resilient organisms, and have more defenses against insects than we often give them credit for. The largest limiting factor for growth was competition between plants. In fact, having some of the insects around actually increased growth in three out of the four plant species,as the hungry little animals reduced the amount of competition from surrounding plants.

I am certainly not suggesting that we all fill our gardens with insects or pull out every plant in the nearby vicinity. It is how all of these factors work together that keeps a system going. And sometimes,it is just nice to be reminded that the natural world uses many different processes to produce its wonders. Rarely is anything as simple as wewould like it to be.

I know that there is a tendency inside us to 'take over the reins' of nature when we build our gardens and of course there are times when a firm hand is needed to guide a garden in a particular direction. Never the less, whilst we may head outside with the thought of weeding or spraying for a pest, perhaps we should give some thought to how all of these processes come together to shape how plants grow.

I often find that the natural processes can be far more entertaining and stimulating than imposing my own will upon a garden. Perhaps you too may even decide to let some of natures ways work for you. At the very least, a healthy respect for how things work can only ever increase your enjoyment of your own little part of nature.

References.

Haag, J. J., Coupe, M. D, and Cahill, J. F. Jr. 2004. Antagonistic interactions between competition and insect herbivory on plant growth. Journal of Ecology 92: 156-167.

Dr. Craig Hull is a qualified zoologist and entomologist, and has a special
interest in how insects interact with plants. He has spent the last 10 years trying to uncover some of the secrets of insect antennae, but maintains a passion for all aspects of the natural world. Craig was born in what is now Zimbabwe and after spending a few years of his youth in New Zealand, currently resides in Brisbane, Australia.

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