Insects Cycle Nutrients

Biological Strategy

Insects

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Cycle Nutrients

In ecosystems, there is no such thing as waste. Instead, one organism’s waste can be considered as another organism’s resource, and the cycling of nutrients may be the most important form of recycling in living systems. But sometimes those nutrients are transformed by one organism into a form that isn’t readily used by other organisms. For example, lignin is a complex organic molecule found in the cell walls of plants. In a forest, it’s one of the hardest molecules to break down in woody vegetation. Therefore, ecosystems include organisms that are particularly well-adapted to break down different types of nutrients. In the case of lignin, some fungi and bacteria release lignin-modifying enzymes that can break down the lignin to form carbohydrates and other life-supporting chemicals.

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Generate Soil/Renew Fertility

An ecosystem can’t survive long without building up its soils and preventing them from being depleted of fertility. Organic matter, minerals, and other nutrients in soil support organisms, from microorganisms to the largest mammals. Raw soil consists of weathered minerals, such as silica. But organisms need more than minerals to survive, and minerals alone are poor at storing water needed by organisms. Therefore, soil has organic matter to support an ecosystem of organisms that, in turn, contribute more organic matter, make nutrients more accessible, and hold water. The dung beetle is an organism that enhances soil fertility. This beetle gathers and transports animal dung, feeds on it, buries it in the soil, and lays eggs on it. The dung provides its young with food when they hatch. At the same time, it adds nutrients and organic matter to the soil, benefitting the ecosystem as a whole.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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Bodies of Magicicada cicadas provide mass pulses of nutrients that encourage growth of the forest trees they feed on thanks to their periodical lifecycle.

Introduction

“Forest trees in the eastern USA grow quicker in years after large numbers of cicadas have emerged. Cicadas spend most of their lives underground, where they consume tree root juices, depriving leaves of valuable nutrients. Some periodical species then emerge en masse every 13 or 17 years and feast on tender tree branches before laying their eggs and dying. Now Louie Yang at the University of California at Davis has established that, in dying en masse in this way, the insects provide a deluge of compost that fertilises forest soils and helps trees grow faster.” (Courtesy of the Biomimicry Guild)

The Strategy

“Yang applied various densities of dead cicadas to 1-metre-square forest plots. After a month, plots laden with a typical 240 cicadas contained more microbes, three times the concentration of available ammonium and 2.5 times the concentration of nitrates compared with untreated plots.” (Courtesy of the Biomimicry Guild)

“Resource pulses are occasional events of ephemeral resource superabundance that occur in many ecosystems. Aboveground consumers in diverse communities often respond strongly to resource pulses, but few studies have investigated the belowground consequences of resource pulses in natural ecosystems. This study shows that resource pulses of 17-year periodical cicadas (Magicicada spp.) directly increase microbial biomass and nitrogen availability in forest soils, with indirect effects on growth and reproduction in forest plants. These findings suggest that pulses of periodical cicadas create ‘bottomup cascades,’ resulting in strong and reciprocal links between the aboveground and belowground components of a North American forest ecosystem.” (Yang 2004:1565)

Last Updated August 18, 2016

References

Journal article

Periodical Cicadas as Resource Pulses in North American Forests

Science | 26/11/2004 | L. H. Yang

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