Background/Question/Methods Exotic earthworm species are invading many forests in North America, producing profound ecosystem changes. Elimination of forest floor and redistribution of soil organic matter (SOM) between the organic and mineral layers are of particular concern due to the importance of SOM to nutrient supply and carbon sequestration. In 2008 we set up a series of field plots in successional (70 yr) and mature (150 yr) deciduous forest at the Snmithsonian Environmental Research Center, Maryland. The main objective of this project is to assess the effect of earthworms on below- and aboveground biota and processes We manipulated earthworm abundance by removing them using electroshocking from a subset of plots and by adding them to another subset. We also manipulated leaf litter input by regularly adding tulip poplar (high quality litter) and beech (low quality litter) to the plots. A total of 36 1m x 1m plots were established in 2 forest sites. To follow the treatment effects on soil carbon cycling we measured soil respiration every two weeks starting in Nov 2008.
Results/Conclusions

In general, soil respiration rates correlated exponentially with soil temperature (R varied between 0.85-0.95). Q₁₀ calculated varied between 3~3.7 for each treatments. As expected, soil respiration was 10~20% higher in the tulip poplar treatment than in the beech treatment  (P<0.05). Hovewer, plots amended with beech leaves were more sensitive to temperature change: Q₁₀ was higher by 0.2 (P<0.05). Soil respiration was about 5~10% higher in earthworm addition plots than in earthworm removal plots (P<0.05).  Soil respiration in the earthworm manipulation plots was generally higher in the mature forest than successional forest (P<0.001) whereas in control plots the patten is opposite (P<0.001) . We found significant interactions between leaf litter and forest stage (P<0.001), earthworm and forest stage (P<0.001), but not between leaf litter and earthworms. Our results indicated that forest age and tree composition play an important role since both quality and quantity of lea litter input is different in young and old forests. Our results also suggested that earthworm can directly or indirectly increase C turnover, but these effects are confounded  by other factors.