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Global demand for transportation fuels will increase rapidly during the upcoming decades, and concerns about fossil-fuel consumption have stimulated research on renewable biofuels that can be sustainably produced from biological feedstocks. However, if unchecked, pathogens and parasites are likely to infect these cultivated biofuel feedstocks, greatly reducing crop yields and potentially threatening the sustainability of renewable bioenergy production efforts. In particular, clonal biofuel crops grown as monocultures at industrial scales will be confronted both by an accumulation of specialist pathogens over time, and by the rapid evolution of those pathogens. We propose possible solutions to these important sustainability problems, with a focus on managing disease risk through crop rotations and the cultivation of multi-species polycultures.

For millennia, agriculture has been shaping landscapes on Earth. Technological change has increased agricultural productivity dramatically, especially in the past six decades, but also resulted in trade-offs such as land and soil degradation, emission of greenhouse gases (GHGs), and spreading of toxic substances. In this article we review the impacts of agriculture on the world's arable land. We start by synthesizing information on the extent of arable land and associated agricultural practices, followed by a review of the state of the art of soil health and soil carbon. We review processes of land degradation, emission of GHGs, and threats to biodiversity. To conclude, we review key social and economic aspects of arable land and identify some important concerns for the future. The article ends on a positive note describing a potential new pathway for agriculture—to gradually adopt polycultures of novel perennial grain crops. [ABSTRACT FROM AUTHOR]

Restoration quality of native prairie can be improved by reintroducing key organisms from the native plant microbiome such as arbuscular mycorrhizal (AM) fungi. Here, we assess whether the positive effects of a native mycorrhizal inoculation observed during the first growing season remained at the end of the fourth growing season. In 2016, an experiment was initiated that assessed the response of a restored tallgrass prairie to an inoculation density gradient of native mycorrhizal fungi ranging from 0 to 8,192 kg/ha. First year results indicated that native plant establishment benefited from high but not low densities of native mycorrhizal inocula, resulting in improvements in native plant abundance, richness, and diversity. To assess whether these effects persist in later growing seasons, we resampled the prairie restoration in 2020 and analyzed the data similarly. Results from the fourth growing season indicated that the pattern of responses had persisted; the positive effects of inoculation observed during the first growing season remained after four growing seasons as demonstrated by improvements in total and native plant diversity and reduced non‐native abundance. Additionally, the low densities of mycorrhizal amendment that were not initially effective were found to reduce non‐native abundance in the fourth growing season, suggesting that low densities of mycorrhizal amendment can be amplified via positive plant‐AM fungal feedback to suppress weeds following the introduction of lesser amounts of AM fungi. [ABSTRACT FROM AUTHOR]

To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1523-1739.2006.00606.x Byline: MATTHEW R. R. LOESER (*[double dagger]), THOMAS D. SISK (*), TIMOTHY E. CREWS ([dagger]) Keywords: Bromus tectorum; cheatgrass; climatic variation; exotic plants; livestock grazing; plant community; plant cover; short duration grazing Abstract: Abstract: The ecological benefits of changing cattle grazing practices in the western United States remain controversial, due in part to a lack of experimentation. In 1997 we initiated an experimental study of two rangeland alternatives, cattle removal and high-impact grazing, and compared grassland community responses with those with more conventional, moderate grazing practices. The study was conducted in a high-elevation, semiarid grassland near Flagstaff, Arizona (U.S.A.). We conducted annual plant surveys of modified Whittaker plots for 8 years and examined plant composition shifts among treatments and years. High-impact grazing had strong directional effects that led to a decline in perennial forb cover and an increase in annual plants, particularly the exotic cheatgrass (Bromus tectorum L.). A twofold increase in plant cover by exotic species followed a severe drought in the sixth year of the study, and this increase was greatest in the high-impact grazing plots, where native cover declined by one-half. Cattle removal resulted in little increase in native plant cover and reduced plant species richness relative to the moderate grazing control. Our results suggest that some intermediate level of cattle grazing may maintain greater levels of native plant diversity than the alternatives of cattle removal or high-density, short-duration grazing practices. Furthermore, episodic drought interacts with cattle grazing, leading to infrequent, but biologically important shifts in plant communities. Our results demonstrate the importance of climatic variation in determining ecological effects of grazing practices, and we recommend improving conservation efforts in arid rangelands by developing management plans that anticipate this variation. Abstract (Spanish): Impacto de la Intensidad de Pastoreo durante la Sequia en un Pastizal de Arizona Resumen: Los beneficios ecologicos del cambio de practicas de pastoreo de ganado en el oeste de Estados Unidos aun son controversiales, en parte por la falta de experimentacion. En 1997 iniciamos un estudio experimental de dos alternativas, remocion de ganado y pastoreo de alto impacto, y comparamos las respuestas de la comunidad de pastizal con las de practicas de pastoreo moderadas, mas convencionales. El estudio se llevo a cabo en un pastizal semiarido, de alta elevacion, cerca de Flagstaff, Arizona (E.U.A.). Durante 8 anos realizamos muestreos anuales de plantas en parcelas Whittaker modificadas y examinamos los cambios en la composicion de plantas entre tratamientos y anos. El pastoreo de alto impacto tuvo dos efectos direccionales que llevaron a una declinacion en la cobertura de hierbas perennes y al incremento de plantas anuales, particularmente de pasto exotico Bromus tectorum L. Despues de una sequia severa la cobertura de especies exoticas incremento al doble en el sexto ano del estudio, y este incremento fue mayor en las parcelas de pastoreo de alto impacto, en las que la cobertura de especies nativas declino a la mitad. La remocion de ganado resulto en un leve incremento en la cobertura de plantas nativas y redujo la riqueza de especies de plantas en relacion con el control con pastoreo moderado. Nuestros resultados sugieren que algun nivel intermedio de pastoreo puede mantener mayores niveles de diversidad de plantas nativas que las alternativas de remocion de ganado o de practicas de pastoreo de alta densidad y corta duracion. Mas aun, las sequias episodicas interactuan con el pastoreo de ganado, conduciendo a cambios, poco frecuentes pero biologicamente importantes, en las comunidades de plantas. Nuestros resultados demuestran la importancia de la variacion climatica en la determinacion de los efectos ecologicos de las practicas de pastoreo, y recomendamos el mejoramiento de los esfuerzos de conservacion en llanuras aridas mediante el desarrollo de planes de gestion que anticipen esta variacion. Author Affiliation: (*)Center for Environmental Sciences and Education, Northern Arizona University, Box 5694, Flagstaff, AZ 86011-5694, U.S.A. ([dagger])Environmental Studies Program, Prescott College, 220 Grove Avenue, Prescott, AZ 86301, U.S.A. Article History: Paper submitted August 16, 2005; revised manuscript accepted May 15, 2006. Article note: ([double dagger]) Current address: Biology Department, Yakima Valley Community College, P.O. Box 22520, Yakima, WA 98907-2520, U.S.A., email mloeser@ yvcc.edu