Kammann et al. 2005

Kammann C, Grünhage L, Grüters U, Janze S, Jäger H-J. 2005. Response of aboveground grassland biomass and soil moisture to moderate long-term CO2 enrichment. Basic and Applied Ecology 6: 351-365.

These authors present the results of the first 5 years of the GiFACE experiment in Germany (see Jäger et al. 2003). The major findings, as alluded to in the title, concern the response of aboveground biomass and soil moisture to moderate, year-round (but not 24-hour) CO2 enrichment in a temperate, mesic, semi-natural grassland ecosystem.

Compared to other similar studies, the GiFACE experiment found increased grass biomass under CO2 enrichment, no increase in forbs, and no changes in soil moisture. Other studies found less biomass increase, especially of grasses, generally increased forbs both by measures of diversity and by biomass, and generally increased soil moisture. Differences associated with GiFACE include the low CO2 step increase of 20% compared with much higher in other studies, such as doubling, the cutting frequency that is lower than most other studies, and the year-round CO2 enrichment compared with many studies enriching only during the active growing season. Additionally, the mix of species at Giessen may have been “right” for a strong biomass response, with an interaction from the low cutting frequency allowing these strongly responding grasses to increase above ground biomass to a large degree.

This paper suffers from an irritating flaw – a non-significant difference in annual biomass yield between enriched and control plots is described as “non-significantly higher”, an oxymoron. If it’s not significantly higher, it’s not higher.