Recent studies have focused on how climate change may impact aboveground communities, but more research is necessary to elucidate how climate change will affect belowground communities and ecosystem functioning, specifically nutrient cycling through decomposition. We used a long-term multi-factor experiment at the Global Change Field Research Facility on the Oak Ridge National Environmental Research Park (25̊54’N; 84̊21’W) to examine the separate and combined effects of elevated CO₂, temperature, and water availability on potential extracellular enzyme activity in soils. In 2002, twelve open-top chambers were established at Oak Ridge National Laboratory. Each chamber is treated with either ambient or elevated (ambient + 300 ppm) CO_2, and ambient or elevated (ambient + 3.5 degrees C) temperature. Each chamber is divided in half and exposed to ±50% water based on mean weekly precipitation records from the Oak Ridge, Tennessee weather station to create ‘wet’ and ‘dry’ irrigation treatments. Treatments consisted of all of the possible combinations of these three variables, with the ambient temperature, ambient CO₂ and wet side of the chambers used as a control. We used methylumbelliferone (MUB)-linked substrates and 3, 4 Dihydroxyphenylalanine (L-DOPA) to determine the potential activity of nine enzymes in the soil that are important in the cycling of nitrogen, carbon, phosphorus, and sulfur.

Results/Conclusions

We demonstrated that soil enzyme activity was most affected by water availability (especially in hemi-cellulose degrading enzymes, P = 0.03). However, interactions among water, temperature, and CO₂ concentration were important in determining the activity of enzymes involved in the degradation of cellulose, lignin, and polyphenols. These data suggest that the direct effects of drought on microbial activity may be mediated by other interacting global change factors, and that short-term microbial community dynamics may affect long-term soil carbon and nutrient cycling. We conclude single factor studies may miss nuances in microbial responses to climate change making more research on these interactive effects important.