PRESIDENT'S LETTER

Cypripedium pubescens. PHOTO BY TONY OMEIS.

Perennialism and Stewardship

As I write this letter it is mid-April in central Pennsylvania, meaning that the threat of snow is (almost) behind us and spring flowers are starting to brighten the landscape. While crocuses, daffodils, and tulips are important to the floriculture industry, perennials of another sort have begun to make a name for themselves as field crops. Specifically, C₄ perennial grasses such as switchgrass and Miscanthus are the focus of much interest as next-generation biofuel crops. These species exhibit high productivity, and their growth habit confers several advantages (1, 2). For example, these species promote soil retention as a result of their permanent root/rhizome systems coupled with reduced tillage requirements, and may exhibit reduced irrigation requirements due both to these deeper root systems and the generally higher water use efficiency of C4 species. Perennial root systems can also sequester significant amounts of atmospheric carbon, e.g., at estimated annual rates for switchgrass of 1 to 10 tons/ha (3, 4). Importantly, these grasses can also thrive on marginal lands not suitable for cultivation of other crops. Thus, even before the focus on energy crops, switchgrass, a native prairie grass, was utilized by farmers participating in the U.S. Conservation Reserve Program (CRP) (5), whereby growers receive a financial incentive to convert highly erodible or environmentally sensitive land to permanent vegetative cover (1, 6).

	Miscanthus at maximum biomass topping 11 feet, shown with Emily Doherty for contrast. PHOTO COURTESY OF STEPHEN LONG LAB, UNIVERSITY OF ILLINOIS, 2006.

A recent five-year study of switchgrass grown on marginal croplands throughout the midwestern United States calculated that these switchgrass monocultures yielded 540% more (renewable) energy than (nonrenewable) energy consumed in their cultivation (7). Biomass yields from Miscanthus have been calculated to be even higher (8). However, this is not to say that these plants will be a panacea for the world’s energy crisis. C₄ perennial grasses are not suitable for all climatic regions, and their rate of establishment is slow, especially compared to annual crops such as corn. Opportunities for improving their genomic makeup have scarcely been touched (9) and will require overcoming barriers to facile transformation as well as natural ploidy and self-incompatibility barriers (2, 9). And the overriding challenge that remains to be addressed for any biofuels program is the fact that technologies for energy extraction and conversion from lignocellulosic tissue are far from optimized. Finally, even post-optimization, biofuels can be expected to meet only a fraction of the world’s energy needs. It is still difficult to estimate what that fraction might be, but one interesting back-of-the-envelope calculation described by Carroll and Somerville in their recent review (2) is that 1% photosynthetic efficiency on 1% of the land could fuel approximately 27% of global human energy use as of 2001.

The point that biofuels can provide a significant—albeit minority—fraction of the “energy pie” was also made in a 2007 ASPB President’s Letter by Rick Amasino (10). In fact, biofuels have been a perennial (!) topic in ASPB President’s Letters, with previous columns on this subject from past presidents Mike Thomashow, Rick Amasino, and Rob McClung (11, 12, 13). It is interesting to look back at these articles and see how concepts and
approaches toward biofuels have evolved. However, it is also interesting to note that the topic of C₄ perennial grasses as crops has a literary history that predates our President’s Letters by at least several decades. My first encounter with this concept was in essays by the American man of letters, Wendell Berry. In a 1981 essay entitled “New Roots for Agriculture” (14), Berry extols many of the virtues of perennial grass species—although his focus in that essay is on the idea of perennials as seed crops rather than as biofuel crops. He writes “Perennial grain crops will greatly reduce expenditures for machinery, energy, labor, chemicals, irrigation, and seed….[Perennials] will permit the safe use of lands now considered marginal because of vulnerability to erosion under present cropping systems.” In other words, Berry enumerates many of the same advantages recognized by present-day plant biologists. In an even earlier essay, “The Native Grasses and What They Mean” (15), Berry describes switchgrass plots analyzed by Tim Taylor, then an agronomist at the University of Kentucky. “The prairie grasses,” Berry writes, “are extremely efficient users of light….This means that their productivity—of pasture, hay, or humus—is spectacularly greater than that of the cool season grasses.” Berry’s essay was written in 1979, but it took until the 21st century, with the confluence of climate, food, and energy concerns—including the imperative that we do not exchange food for fuel—to better appreciate the agronomic potential of these perennial grasses.

Berry is himself a farmer, and his writings are imbued with a sense of the farmer as a caretaker of the land. Perhaps the farming of perennial biofuels may help in the fight against global climate change and for renewable energy by promoting this same sense of stewardship in the non-farmer. An intelligent citizen activist does not need a scientific degree to recognize the losses that come with the clear-cutting of forests in areas where this silvicultural practice is environmentally contraindicated or improperly executed, nor does a gardener have to be a scientist to appreciate the reappearance of spring perennials, whether they be the aforementioned cultivated plants or species such as the lady slipper orchids that bloom in May in the woodlands of Pennsylvania (see cover photo). It will be a valuable if unanticipated benefit if the cultivation of perennial biofuels results in inculcating in the general public a similar sense of stewardship toward agrarian land. Perhaps this hope is not misplaced—after all, as the photo to the left shows, a stand of 11-foot-high Miscanthus x giganteus is a pretty impressive sight!

The concept of stewardship is also of direct relevance to professional societies such as ASPB, because, I believe, the major role of any professional society is to serve as a steward for its members and their interests. It is for this reason that ASPB not only publishes journals and organizes meetings but also provides significant logistical and financial support toward the member-driven activities of 13 ASPB leadership committees. The activities of some of these committees (Minority Affairs, Women in Plant Biology, Education) were described in my March/April newsletter article (16); this month, I’d particularly like to draw your attention to the recent activities of ASPB’s Committee on Public Affairs, which are described in detail in the Public Affairs section of this newsletter.

I was lately reading over a list of anonymous comments from individuals describing why they had elected to renew their membership in ASPB. Some respondents focused on the tangible benefits of membership, such as discounted meeting registrations, print versions of the journals, teaching resources and the like, which is reasonable. However, the types of responses that most resonated with me are exemplified by the response of one individual who wrote, “Because it’s the right thing to do.” This person, it seems to me, recognized the role that ASPB strives to fulfill as a steward of plant biology and plant biologists. S/he was voicing trust in ASPB to do the best job the Society could “to promote the growth and development of plant biology, to encourage and publish research in plant biology, and to promote the interests and growth of plant scientists in general,” as described in the mission statement of ASPB. Whether or not that stewardship resulted in direct benefits to this individual was not as important to him/her as the fact that ASPB was serving the community. And that, in a nutshell, is what stewardship is all about.

Sally Assmann

References

1. Rinehart, L. (2006). Switchgrass as a bioenergy crop.
2. Carroll, A., and Somerville, C. (2009). Cellulosic biofuels. Annual Review of Plant Biology 60: 165–182.
3. Frank, A.B., Berdahl, J.D., Hanson, J.D., Liebig, M.A., and Johnson, H.A. (2004). Biomass and carbon partitioning in switchgrass. Crop Science 44: 1391–1396.
4. McLaughlin, S.B., et al. (2002). High-value renewable energy from prairie grasses. Environmental Science & Technology 36: 2122–2129.
5. U.S. Conservation Reserve Program.
6. Mulkey, V.R., Owens, V.N., and Lee, D.K. (2006). Management of switchgrass-dominated conservation reserve program lands for biomass production in South Dakota. Crop Science 46: 712–720.
7. Schmer, M.R., Vogel, K.P., Mitchell, R.B., and Perrin, R.K. (2008). Net energy of cellulosic ethanol from switchgrass. Proceedings of the National Academy of Sciences 105: 464–469.
8. Heaton, E.A., Dohleman, F.G., and Long, S.P. (2008). Meeting U.S. biofuel goals with less land: The potential of Miscanthus. Global Change Biology 14: 2000–2014.
9. Bouton, J.H. (2007). Molecular breeding of switchgrass for use as a biofuel crop. Current Opinion in Genetics & Development 17: 553–558.
10. Amasino, R. (2007). The energy pie. ASPB News 34(5): 5–6.
11. Thomashow, M. (2006). Plant biologists and the development of renewable energy sources. ASPB News 33(1): 1, 5.
12. Amasino, R. (2007). Energy and plant biology. ASPB News 34(1): 1, 4.
13. McClung, C. R. (2008). Let them eat cake? One dickens of a dilemma. ASPB News 35(3): 1, 4–5.
14. Berry, W. (1981). “New Roots for Agriculture.” Reprinted in The Gift of Good Land: Further Essays Cultural and Agricultural. San Francisco: North Point Press, pp. 238–249.
15. Berry, W. (1979). “The Native Grasses and What They Mean.” Reprinted in The Gift of Good Land: Further Essays Cultural and Agricultural. San Francisco: North Point Press, pp. 77–88.
16. Assmann, S. (2009). Election 2009! ASPB News 36(2): 1, 11–12.