• Authors:
    • Regetz, J.
    • Wolkovich, E. M.
    • O'Connor, M. I.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 7
  • Year: 2012
  • Summary: Understanding how species and ecosystems respond to climate change requires spatially and temporally rich data for a diverse set of species and habitats, combined with models that test and predict responses. Yet current study is hampered by the long-known problems of inadequate management of data and insufficient description of analytical procedures, especially in the field of ecology. Despite recent institutional incentives to share data and new data archiving infrastructure, many ecologists do not archive and publish their data and code. Given current rapid rates of global change, the consequences of this are extreme: because an ecological dataset collected at a certain place and time represents an irreproducible set of observations, ecologists doing local, independent research possess, in their file cabinets and spreadsheets, a wealth of information about the natural world and how it is changing. Although large-scale initiatives will increasingly enable and reward open science, we believe that change demands action and personal commitment by individuals - from students and PIs. Herein, we outline the major benefits of sharing data and analytical procedures in the context of global change ecology, and provide guidelines for overcoming common obstacles and concerns. If individual scientists and laboratories can embrace a culture of archiving and sharing we can accelerate the pace of the scientific method and redefine how local science can most robustly scale up to globally relevant questions.
  • Authors:
    • Lindquist, J. L.
    • Drijber, R. A.
    • Bernards, M. L.
    • Francis, C. A.
    • Wortman, S. E.
  • Source: AGRONOMY JOURNAL
  • Volume: 104
  • Issue: 5
  • Year: 2012
  • Summary: Previous studies have demonstrated benefits of individual cover crop species, but the value of diverse cover crop mixtures has received less attention. The objectives of this research were to determine the effects of spring-sown cover crop mixture diversity and mechanical cover crop termination method on cover crop and/or cash crop productivity, soil moisture and N, and profitability in an organic cropping system. An experiment was conducted between 2009 and 2011 near Mead, NE, where mixtures of two (2CC), four (4CC), six (6CC), and eight (8CC) cover crop species, or a summer annual weed mixture were included in a sunflower-soybean-corn rotation. Cover crops were terminated in late May using a field disk or sweep plow undercutter. Undercutting cover crops increased soil NO 3-N (0-20 cm) by 1.0 and 1.8 mg NO 3-N kg -1 relative to disk incorporation in 2010 and 2011, respectively. Cover crop mixtures often reduced soil moisture (0-8 cm) before main crop planting, though cover crop termination with the undercutter increased soil moisture content by as much as 0.024 cm 3 cm -3 compared to termination with the disk during early main crop growth. Crop yields were not influenced by cover crop mixture, but termination with the undercutter increased corn and soybean yield by as much as 1.40 and 0.88 Mg ha -1, respectively. Despite differences in productivity between spring cover crop mixtures and weed communities, crop yield was not different among these treatments; thus, profitability of the weed mixture-undercutter treatment combination was greatest due to reduced input costs.
  • Authors:
    • Lindquist, J. L.
    • Francis, C. A.
    • Wortman, S. E.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 3
  • Year: 2012
  • Summary: Achieving agronomic and environmental benefits associated with cover crops often depends on reliable establishment of a highly productive cover crop community. The objective of this study was to determine if cover crop mixtures can increase productivity and stability compared to single species cover crops, and to identify those components most active in contributing to or detracting from mixture productivity. A rainfed field experiment was conducted near Mead, NE, in 2010 and 2011. Eight individual cover crop species (in either the Brassicaceae [mustard] or Fabaceae [legume] family) and four mixtures of these species (two, four, six, and eight species combinations) were broadcast planted and incorporated in late March and sampled in late May. Shoot dry weights were recorded for sole crops and individual species within all mixtures. Sole crops in the mustard family were twice as productive (2428 kg ha -1) as sole crops in the legume family (1216 kg ha -1), averaged across 2 yr. The land equivalent ratios (LERs) for all mixtures in 2011 were >1.0, indicating mixtures were more productive than the individual components grown as sole crops. Improved performance in mixture may be related to the ecological resilience of mixed species communities in response to extreme weather events, such as hail. Partial LERs of species in the mustard family were consistently greater than those in the legume family, indicating that mustards dominated the mixtures. Results provide the basis for yield-stability rankings of spring-sown cover crop species and mixtures for the western Corn Belt.
  • Authors:
    • Voigt, T. B.
    • David, M. B.
    • Behnke, G. D.
  • Source: BioEnergy Research
  • Volume: 5
  • Issue: 4
  • Year: 2012
  • Summary: Understanding the effects of nitrogen (N) fertilization on Miscanthus x giganteus greenhouse gas emissions, nitrate leaching, and biomass production is an important consideration when using this grass as a biomass feedstock. The objective of this study was to determine the effect of three N fertilization rates (0, 60, and 120 kg N ha(-1) using urea as the N source) on nitrous oxide (N2O) and carbon dioxide (CO2) emissions, nitrogen leaching, and the biomass yields and N content of M. x giganteus planted in July 2008, and evaluated from 2009 through early 2011 in Urbana, Illinois, USA. While there was no biomass yield response to N fertilization rates in 2009 and 2010, the amount of N in the harvested biomass in 2010 was significantly greater at the 60 and 120 kg N ha(-1) N rates. There was no significant CO2 emission response to N rates in 2009 or 2010. Similarly, N fertilization did not increase cumulative N2O emissions in 2009, but cumulative N2O emissions did increase in 2010 with N fertilization. During 2009, nitrate (NO (3) (-) ) leaching at the 50-cm soil depth was not related to fertilization rate, but there was a significant increase in NO (3) (-) leaching between the 0 and 120 kg N ha(-1) treatments in 2010 (8.9 and 28.9 kg NO3-N ha(-1) year(-1), respectively). Overall, N fertilization of M. x giganteus led to N2O releases, increased fluxes of inorganic N (primarily NO (3) (-) ) through the soil profile; and increased harvested N without a significant increase in biomass production.
  • Authors:
    • Leytem, A. B.
    • Venterea, R. T.
    • Fixen, P. E.
    • Snyder, C. S.
    • Liebig, M. A.
    • Del Grosso, S. J.
    • Cavigelli, M. A.
    • McLain, J. E.
    • Watts, D. B.
  • Source: Frontiers in Ecology and the Environment
  • Volume: 10
  • Issue: 10
  • Year: 2012
  • Summary: The use of commercial nitrogen (N) fertilizers has led to enormous increases in US agricultural productivity. However, N losses from agricultural systems have resulted in numerous deleterious environmental impacts, including a continuing increase in atmospheric nitrous oxide (N2O), a greenhouse gas (GHG) and an important catalyst of stratospheric ozone depletion. Although associated with about 7% of total US GHG emissions, agricultural systems account for 75% of total US N2O emissions. Increased productivity in the crop and livestock sectors during the past 30 to 70 years has resulted in decreased N2O emissions per unit of production, but N2O emissions from US agriculture continue to increase at a rate of approximately 0.46 teragrams of carbon dioxide equivalents per year (2002-2009). This rate is lower than that during the late 20th century. Improvements in agricultural productivity alone may be insufficient to lead to reduced emissions; implementing strategies specifically targeted at reducing N2O emissions may therefore be necessary. Front Ecol Environ 2012; 10(10): 537-546, doi:10.1890/120054
  • Authors:
    • Lorenz, N.
    • Saxena, J.
    • Chaudhary, D. R.
    • Dick, R. P.
  • Source: Plant, Soil and Environment
  • Volume: 58
  • Issue: 6
  • Year: 2012
  • Summary: The use of switchgrass (Panicum virgatum L.) as an energy crop has gained great importance in past two decades due to its high biomass yields on marginal lands with low agricultural inputs and low maintenance requirements. Information on the allocation of photosynthetically fixed C in the switchgrass-soil system is important to understand the C flow and to quantify the sequestration of C in soils. The allocation of C-13 labeled photosynthates in shoot, root, soil, and in microbial biomass carbon (MBC) of rhizosphere and bulk soil of 45 days old, greenhouse grown-switchgrass was examined during 20 days C-13-CO2 pulse labeling period. The total C-13 recovered in the plant-soil system varied from 79% after 1 day to 42% after 20 days of labeling. After labeling, 54%, 40%, and 6% excess C-13 resided in shoot, root and soil, respectively on day 1; 27%, 61% and 11%, respectively on day 5 and 20%, 63% and 17%, respectively day 20 after labeling. The maximum incorporation of C-13 from roots into the MB of rhizosphere soil occurred within the first 24 h of labeling. The excess C-13 values of rhizosphere soil and rhizosphere MBC were significantly higher than excess C-13 values of bulk soil and the bulk soil MBC, respectively. The proportion of excess C-13 in soil as MBC declined from 92 to 15% in rhizosphere soil and from 79 to 18% in bulk soil, for 1 day and 20 days after labeling, respectively. The present study showed the effectiveness of C-13 labeling to examine the fate of recently photosynthesized C in soil-plant (switchgrass) system and dynamics of MBC.
  • Authors:
    • Decock, C.
    • Leakey, A. D. B.
    • Gray, S. B.
    • Venterea, R.
    • Chung, H.
    • Six, J.
  • Source: Soil Biology and Biochemistry
  • Volume: 51
  • Issue: August
  • Year: 2012
  • Summary: In order to predict and mitigate future climate change, it is essential to understand plant-mediated effects of elevated CO2 (eCO(2)) and O-3 (eO(3)) on N-cycling, including N2O emissions. This is of particular interest for agroecosystems. since N-cycling and N2O emissions are responsive to adaptive management. We investigated the interaction of soil moisture content with eCO(2) and eO(3) on potential N2O emissions from SoyFACE during a 28-day laboratory incubation experiment. We also assessed field N2O fluxes during 2 soybean-growing seasons. In addition, we sought to link previously observed changes in soybean growth and production to belowground processes over a longer time scale by analyzing changes in natural abundance stable isotope ratios of soil N (delta N-15). This method relies on the concept that soil delta N-15 can only change when inputs or outputs with an isotope signature different from that of soil N are altered. We found no major effects of eCO(2) and eO(3) on laboratory and field measured N2O emissions. Natural abundance isotope analyses suggested, however, a decrease in belowground allocation of biologically fixed N in combination with decreased total gaseous N loss by eCO(2), resulting in a tighter N cycle in the longer-term. In contrast, the isotope data suggested an increase in belowground allocation of biologically fixed N under eO(3), leading to increased gaseous N loss, most likely in the form of N-2. Given that effects of eCO(2) and eO(3) on N pools and instantaneous transformation rates in surface soil layers of this agroecosystem have been minimal, our results illustrate the importance of evaluating longer-term changes in N turnover rates. We conclude that eCO(2) decelerates whereas eO(3) accelerates N-cycling in the longer-term, but feedback through changed N2O emissions is not occurring in this soybean system. (C) 2012 Elsevier Ltd. All rights reserved.
  • Authors:
    • Cavigelli, M. A.
    • Del Grosso, S. J.
  • Source: Frontiers in Ecology and the Environment
  • Volume: 10
  • Issue: 10
  • Year: 2012
  • Summary: Climate stabilization wedges are defined as strategies that contribute to greenhouse-gas (GHG) mitigation that - in aggregate - achieve a particular goal. Wedges have been proposed as a GHG mitigation framework because no single technology or economic sector can sufficiently reduce emissions to acceptable levels. To avoid the most dangerous risks of climate change, we argue that mitigation of similar to 9000 teragrams of carbon equivalents (Tg Ceq) will be required by the year 2030. We estimate that agriculture could provide wedges of 1350 to 3900 Tg Ceq under attainment of technological and human behavior mitigation potentials. Improved agricultural management can decrease nitrous oxide and methane emissions and increase carbon sequestration. Consumption of fewer livestock products along with agricultural intensification through available technologies can result in reduced emissions in both developed and developing countries. Decreasing excess protein and calorie consumption in developed countries improves personal health, while reforestation and avoided deforestation in developing countries help to maintain biodiversity. The mitigation wedges have varying economic costs but also have multiple benefits. Front Ecol Environ 2012; 10(10): 571-578, doi:10.1890/120058
  • Authors:
    • Olander, L. P.
    • Eagle, A. J.
  • Source: Advances in Agronomy
  • Volume: 115
  • Year: 2012
  • Summary: Responsible for 6% of U.S. greenhouse gas (GHG) production, agricultural land use has significant potential to reduce these emissions and capture additional carbon in the soil. Many different activities have been proposed for such mitigation, but assessments of the biophysical potential have been limited and have not provided direct comparison among the many options. We present an in-depth review of the scientific literature, with a side-by-side comparison of net biophysical GHG mitigation potential for 42 different agricultural land management activities in the United States, many of which are likely applicable in other regions. Twenty of these activities are likely to be beneficial for GHG mitigation and have sufficient research to support this conclusion. Limited research leads to uncertainty for 15 other activities that may have positive mitigation potential, and the remaining activities have small or negative GHG mitigation potential or life-cycle GHG concerns. While we have sufficient information to move forward in implementing a number of activities, there are some high-priority research needs that will help clarify problematic uncertainties.
  • Authors:
    • Griffis, T. J.
    • Fassbinder, J. J.
    • Baker, J. M.
  • Source: Agricultural and Forest Meteorology
  • Volume: 153
  • Issue: February
  • Year: 2012
  • Summary: Separation of the photosynthetic (F-P) and respiratory (F-R) fluxes of net CO2 exchange (F-N) remains a necessary step toward understanding the biological and physical controls on carbon cycling between the soil, biomass, and atmosphere. Despite recent advancements in stable carbon isotope partitioning methodology, several potential limitations can cause uncertainty in the partitioned results. Here, we combined an automated chamber system with a tunable diode laser (TDL) to evaluate carbon isotope partitioning under controlled environmental conditions. Experiments were conducted in a climate controlled greenhouse utilizing both soybean (C-3 pathway) and corn (C-4 pathway) treatments. Under these conditions, net exchange of (CO2)-C-13 and (CO2)-C-12 was obtained with an improved signal to noise ratio. Further, the chamber system was used to estimate soil evaporation (E) and plant transpiration (T), allowing for an improved estimate of the total conductance to CO2 (g(c)). This study found that the incorporation of short-term and diel variability in the isotope composition of respiration (delta(R)) caused F-P to nearly double in the corn system while only slightly increasing in the soybean system. Variability in both g(c) and the CO2 bundle sheath leakage factor for C-4 plants (phi) also had a significant influence on F-P. In addition, chamber measurements of F-N and its isotope composition (delta(N)) indicated that post-illumination processes caused a decrease in plant respiration for up to 3 h following light termination. Finally, this study found systematic differences between the isotope and temperature-regression partitioning methods on the diel time scale. Published by Elsevier B.V.