Effect Of Greenhouse Gases On Soil Insects

It is doubtful that soil-inhabiting insects will respond directly to increased levels of CO2 because of existing high concentrations in the soil. However, there are many likely indirect effects of CO2 on soil insects. Light interception by a larger canopy may lower soil temperature and moisture. The most important change, though, is likely to be increased litterfall. Soil organic matter is likely to accumulate, rendering grasslands and forests net sinks of carbon under conditions of elevated CO2. However, before senescence, most leaf nitrogen is reabsorbed by the plant, so that whereas living leaves in elevated CO2 generally have a lower nitrogen content than leaves in ambient CO2 conditions, litter quality remains unchanged. However, the increased volume of litter is likely to increase the number of litter-decomposing insects there.

In addition, increased root production may benefit root-feeding insects. Total numbers of Collembola per kilogram of soil have been shown to be significantly higher in experimental laboratory-based mesocosms where CO2 levels were 60% above ambient. Species composition of Collembola also changed. Part of these increases in Collembola may be due to changes in abundance of mycorrhizal and nonmycor-rhizal fungi on which they feed.

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