Growing biofuels from restored native prairie...

The Konza Prairie owned by The Nature Conservancy and Kansas State University. A native tallgrass prairie in the Flint Hills of Kansas. Image credit, Edwin Olson.A new study in the journal Ecological Applications looks at native prairie hay meadows as a potential system for biofuel production. The study findings suggest that native prairie agriculture might be just as productive for biofuels as more intensively farmed hayfields.

Conservationists have been giving heightened attention to some of the negative consequences of biofuels lately. There's been some concern about biofuel demand spurring conversion of natural habitat to agricultural production. Another concern has arisen about the nitrogen inputs to crop production and subsequent impacts to water (i.e. eutrophication and dead zones).

Native prairie hay meadows involve the planting and harvesting of native grasses. The practice can serve as a quasi-ecological restoration because it can entail returning abandoned or active agricultural lands dominated by a few fast growing exotic grasses to a meadow more closely resembling the historic native prairie. These systems typically do not rely on fertilizer inputs unlike the much more common, intensively farmed hayfields.

From an ecological perspective this practice could help restore native prairie ecosystems. This could be particularly important in central North America where 99% of the historic tallgrass prairie has been converted to farmland but recently there has been an increasing push for largescale restoration.

Researchers from University of Kansas compared native prairie hay meadows versus a fertilizer driven system with respect to species diversity and biomass (an indicator for biofuels production levels). They did this by comparing agricultural plots subject to different treatments: some underwent sowing of native perennial grasses, some received applications of chemical fertilizer, and some saw a combination of treatments.

The study found:

• Sowing native plants on plots not subject to chemical fertilizers resulted in peak biomass that was indistinguishable from fertilized plots. This shows that sowing native plants can compensate for the loss in productivity from not using fertilizers.

• Species richness and diversity were both suppressed significantly by fertilization.  This is consistent with past research findings that nitrogen limits diversity by giving a super-competitive advantage to the few species that can most benefit from high fertility.

• Sown native species were more likely to establish in plots without fertilization.

• Haying increased species diversity somewhat in fertilized plots suggesting that it created an opportunity for plant establishment that otherwise would not have been there.

The researchers write:

This comparison likely underestimates the long-term positive impact of native species restoration on overall ecosystem productivity at our site because (1) we did not account for effects on root biomass, which is typically much greater under native than nonnative grasses at our site; and (2) peak biomass in this study was measured fairly early in the restoration process: four years after sowing. As native species likely increase further in abundance over time we expect to see further increases in production in the restored plots.

  --Reviewed by Rob Goldstein

Foster, B., Kindscher, K., Houseman, G., & Murphy, C. (2009). Effects of hay management and native species sowing on grassland community structure, biomass, and restoration Ecological Applications, 19 (7), 1884-1896 DOI: 10.1890/08-0849.1