Atmospheric CO2 and soil extracellular enzyme activity: a meta-analysis and CO2 gradient experiment

Rising atmospheric CO2 concentrations can alter carbon and nutrient cycling and microbial processes in terrestrial ecosystems. One of the primary ways microbes interact with soil organic matter is through the production of extracellular enzymes, which break down complex organic molecules and release nutrients into the soil. We conducted a meta-analysis of 34 studies that examined responses in microbial enzyme activity to elevated CO2 and a field study of soil enzyme activity in a tallgrass-prairie ecosystem with sandy loam (with lower organic matter content) and clayey soils (with higher organic matter content) exposed to a continuous gradient of 250 to 500 ppm CO2. Of the ten enzyme groups examined in the meta-analysis, including those degrading starch, b-glucan, cellulose, xylan/hemicellulose, lignin, organic P, and organic N, only the activity one enzyme that degrades the C- and N-containing building blocks of chitin (N-acetyl-glucosaminidase) increased consistently at elevated CO2 by 12.6% (p