There’s a lot going on in our garden; between the decomposition in the soil to the birds swooping overhead. A food web is a tool that we can use to better understand the many different kinds of organisms that affect our garden and the plants we are trying to grow. In our garden and on earth in general we have 5 major levels of organisms. These are called “trophic levels”, which are defined as the levels comprising organisms that share the same function in the food chain and have the same relationship to the primary sources of energy. There are five main levels:
- Decomposers: These organisms take dead organic matter (such as leaves) and decompose them in the soil to break down the nutrients so that plants can better use them. Examples: snails, red wiggler worms, aspergillus fungi, and other bacteria
- Producers/Autotrophs: Most commonly plants, producers take all their energy from the sun and nutrients that have been broken down in the soil in order to create food for omnivores. Examples: beans, sunflowers, corn, wheat, algae
- Primary Consumers: Organisms that feed directly on autotrophs, also known as herbivores. Examples: bumblebee, cochineal beetle, cottontail, grasshopper, pocket gopher
- Secondary Consumers: Animals that consume primary consumers, which can be either carnivores (eat all animals) or omnivores (eat animals and plants). Examples: coyote, field mouse, lady bug, centipede
- Tertiary Consumers: Animals that consume secondary consumers, which are always carnivores. Examples: bull snake, cooper’s hawk, great horned owl, roadrunner
Of course, all different levels of the food web interact and develop important relationships. For example, the relationship between a plant and the mycorrhiza fungus is essential to maintaining the structure of the soil. All of these relationships affect how well the plants are able to grow, so it is important to understand what’s going on. Food webs can show just how interconnected our ecosystem is, although that does not exhaust the important interactions going on in the garden.
Here is an example of a food web:
Food Web: http://www.dunkirkcsd.org/site/Default.aspx?PageID=1416
As you can see, the arrows denote the organisms that are being consumed. This food web is smaller and less entangled than the 24-organism DOT garden food web that I am creating, although it conveys the same idea. When we take action in the garden, such as our attempt to get rid of gophers, it is important to understand how this will affect other organisms. Are pocket gophers important because they consume pests? Or do they simply destroy plants? Do they have some other role? It turns out that pocket gophers are primary consumers, which means they eat exclusively plants. However, pocket gophers still have a role in the garden; the aerate the soil. Our goal is not to kill all the pocket gophers because they still are an important part of the ecosystem. It is simply to protect our plants and keep our ecosystem healthy. Food webs are great at showing the importance of minding each level when taking drastic action, as well as developing a better understanding of the beauty and intricacy that is our garden.
Resources:
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/F/FoodChains.html
http://science.jrank.org/pages/6974/Trophic-Levels-Primary-consumers.html
Student Investigations in Agro-Ecology 