Effects of elevated carbon dioxide and ozone on forest insect abundance, diversity, and community composition.

摘要

Elevated concentrations of carbon dioxide and tropospheric ozone pose important threats to the abundance, diversity, and composition of forest arthropod communities. In turn, modification of arthropod communities could alter forest health, productivity, and ecosystem services. I studied the independent and interactive effects of elevated CO2 and elevated O3 on the abundance, species richness, and community composition of arthropods in stands of trembling aspen and paper birch. Sampling occurred at the Aspen Free Air CO2 Enrichment (FACE) site near Rhinelander, WI, USA. I found that elevated CO2 and O3 had strong effects on natural enemy abundance but idiosyncratic and generally weak effects on herbivorous insect abundance. Insect family/species richness was rarely affected by the fumigation treatments. Similar to abundance results, elevated CO 2 and elevated O3 strongly affected natural enemy community composition but rarely altered herbivore community composition. Interactive effects of CO2 and O3 on insects were rare except for on some chewing herbivores. In addition to examining the effects of eCO 2 and eO3 on insects, I also studied how CO2 and O3 altered the quality of herbivore organic inputs to the forest floor. I showed that small changes in green leaf quality, and the quality of herbivore organic inputs to the soil, caused by elevated CO2 and O3 were insufficient to impact soil processes, but increased quantity of organic inputs to the soil significantly altered soil processes. Overall, my data suggest that forest insect communities may not be strongly impacted by concentrations of CO2 and O3 predicted for 2060. However, even small changes in the abundance or community composition of insect herbivores could have impacts on forest processes such as nutrient cycling. Altered forest processes could feed back to enhance environmental change in forest ecosystems and exacerbate the negative consequences of altered forest ecosystems for humans.