REFORESTATION OR RESPONSE TO RISING ATMOSPHERIC CO2: INVESTIGATING TWO POSSIBLE MECHANISMS FOR THE INCREASE IN GROUNDWATER CO2 AT THE KONZA PRAIRIE, NORTHEASTERN KANSAS

The Konza Prairie, a National Science Foundation Long-Term Ecological Research site and Biological Station, is an unplowed tallgrass prairie underlain by Early Permian-aged limestone-shale couplets that create sandwich-type aquifers. In an upland watershed at this site, two wells on the edge of the riparian zone on one side of the ephemeral stream draining the watershed show a 15-year increase in groundwater CO₂ (Macpherson et al., 2008). The watershed has experienced invasion of woody species, especially near the riparian zone, and Liu et al. (2008) invoked the reforestation of a watershed in China as an explanation for increasing soil CO₂. Therefore, we tested whether two other wells at the Konza Prairie that have not seen an increase in woody vegetation show changes in groundwater CO₂ or not. Our findings confirm that, because the wells used for this study have experienced an increase in groundwater CO₂ similar to the wells near the increasingly woody riparian zone, the increase in groundwater CO₂ cannot be attributed to a change in vegetation, but may be a response to changing climate.

References

Macpherson G.L., Roberts J.A., Blair J.M., Townsend M.A., Fowle D.A. and Beisner K.R. (2008) Increasing shallow groundwater CO₂ and limestone weathering Konza Prairie, USA. Geochimica et Cosmochimica Acta. 72, 5581-5599.

Liu, Z., Dreybrodt, W. and Wang, H. (2008) A possible important CO₂ sink by the global water cycle. Chinese Science Bulletin. 53, 402-407.