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Hoeksema J.D.,University of Mississippi | Chaudhary V.B.,Northern Arizona University | Gehring C.A.,Northern Arizona University | Johnson N.C.,Northern Arizona University | And 9 more authors.
Ecology Letters | Year: 2010

Mycorrhizal fungi influence plant growth, local biodiversity and ecosystem function. Effects of the symbiosis on plants span the continuum from mutualism to parasitism. We sought to understand this variation in symbiotic function using meta-analysis with information theory-based model selection to assess the relative importance of factors in five categories: (1) identity of the host plant and its functional characteristics, (2) identity and type of mycorrhizal fungi (arbuscular mycorrhizal vs. ectomycorrhizal), (3) soil fertility, (4) biotic complexity of the soil and (5) experimental location (laboratory vs. field). Across most subsets of the data, host plant functional group and N-fertilization were surprisingly much more important in predicting plant responses to mycorrhizal inoculation ('plant response') than other factors. Non-N-fixing forbs and woody plants and C4 grasses responded more positively to mycorrhizal inoculation than plants with N-fixing bacterial symbionts and C3 grasses. In laboratory studies of the arbuscular mycorrhizal symbiosis, plant response was more positive when the soil community was more complex. Univariate analyses supported the hypothesis that plant response is most positive when plants are P-limited rather than N-limited. These results emphasize that mycorrhizal function depends on both abiotic and biotic context, and have implications for plant community theory and restoration ecology. © 2010 Blackwell Publishing Ltd/CNRS. Source

Ciais P.,CEA Saclay Nuclear Research Center | Dolman A.J.,VU University Amsterdam | Bombelli A.,Euro Mediterranean Center for Climate Change | Duren R.,Jet Propulsion Laboratory | And 57 more authors.
Biogeosciences | Year: 2014

A globally integrated carbon observation and analysis system is needed to improve the fundamental understanding of the global carbon cycle, to improve our ability to project future changes, and to verify the effectiveness of policies aiming to reduce greenhouse gas emissions and increase carbon sequestration. Building an integrated carbon observation system requires transformational advances from the existing sparse, exploratory framework towards a dense, robust, and sustained system in all components: anthropogenic emissions, the atmosphere, the ocean, and the terrestrial biosphere. The paper is addressed to scientists, policymakers, and funding agencies who need to have a global picture of the current state of the (diverse) carbon observations. We identify the current state of carbon observations, and the needs and notional requirements for a global integrated carbon observation system that can be built in the next decade. A key conclusion is the substantial expansion of the ground-based observation networks required to reach the high spatial resolution for CO2 and CH4 fluxes, and for carbon stocks for addressing policy-relevant objectives, and attributing flux changes to underlying processes in each region. In order to establish flux and stock diagnostics over areas such as the southern oceans, tropical forests, and the Arctic, in situ observations will have to be complemented with remote-sensing measurements. Remote sensing offers the advantage of dense spatial coverage and frequent revisit. A key challenge is to bring remote-sensing measurements to a level of long-term consistency and accuracy so that they can be efficiently combined in models to reduce uncertainties, in synergy with ground-based data. Bringing tight observational constraints on fossil fuel and land use change emissions will be the biggest challenge for deployment of a policy-relevant integrated carbon observation system. This will require in situ and remotely sensed data at much higher resolution and density than currently achieved for natural fluxes, although over a small land area (cities, industrial sites, power plants), as well as the inclusion of fossil fuel CO2 proxy measurements such as radiocarbon in CO2 and carbon-fuel combustion tracers. Additionally, a policy-relevant carbon monitoring system should also provide mechanisms for reconciling regional top-down (atmosphere-based) and bottom-up (surface-based) flux estimates across the range of spatial and temporal scales relevant to mitigation policies. In addition, uncertainties for each observation data-stream should be assessed. The success of the system will rely on long-term commitments to monitoring, on improved international collaboration to fill gaps in the current observations, on sustained efforts to improve access to the different data streams and make databases interoperable, and on the calibration of each component of the system to agreed-upon international scales. © 2014 Author(s). Source

Duval B.D.,University of Illinois at Urbana - Champaign | Duval B.D.,U.S. Department of Agriculture | Anderson-Teixeira K.J.,University of Illinois at Urbana - Champaign | Anderson-Teixeira K.J.,Smithsonian Conservation Biology Institute | And 6 more authors.
PLoS ONE | Year: 2013

Bioenergy related land use change would likely alter biogeochemical cycles and global greenhouse gas budgets. Energy cane (Saccharum officinarum L.) is a sugarcane variety and an emerging biofuel feedstock for cellulosic bio-ethanol production. It has potential for high yields and can be grown on marginal land, which minimizes competition with grain and vegetable production. The DayCent biogeochemical model was parameterized to infer potential yields of energy cane and how changing land from grazed pasture to energy cane would affect greenhouse gas (CO2, CH4 and N2O) fluxes and soil C pools. The model was used to simulate energy cane production on two soil types in central Florida, nutrient poor Spodosols and organic Histosols. Energy cane was productive on both soil types (yielding 46-76 Mg dry mass{dot operator}ha-1). Yields were maintained through three annual cropping cycles on Histosols but declined with each harvest on Spodosols. Overall, converting pasture to energy cane created a sink for GHGs on Spodosols and reduced the size of the GHG source on Histosols. This change was driven on both soil types by eliminating CH4 emissions from cattle and by the large increase in C uptake by greater biomass production in energy cane relative to pasture. However, the change from pasture to energy cane caused Histosols to lose 4493 g CO2 eq{dot operator}m-2 over 15 years of energy cane production. Cultivation of energy cane on former pasture on Spodosol soils in the southeast US has the potential for high biomass yield and the mitigation of GHG emissions. © 2013 Duval et al. Source

Mattor K.,Colorado State University | Betsill M.,Colorado State University | Huayhuaca C.,Colorado State University | Huber-Stearns H.,Colorado State University | And 5 more authors.
Environmental Science and Policy | Year: 2014

Working effectively across boundaries is a critical skill for researchers focused on environmental governance in complex social-ecological systems, but challenges remain in the acquisition of such skills given the current structure of traditional disciplinary training. In an effort to contribute to improved coordination of research across disciplinary boundaries, we provide an insiders' view based on our experience participating in a two-year transdisciplinary research initiative designed to address the changing nature of environmental governance in the Intermountain West region of the United States. We discuss transdisciplinary research as a promising approach for addressing complex, real-world problems and identify several challenges. We analyze our transdisciplinary research process using the ideas of boundary setting, boundary concepts, and boundary objects. We conclude with reflections and lessons learned, emphasizing the importance of our external boundary setting, the role of funding, and the inexorable link between individual commitment and project success. © 2014 Elsevier Ltd. Source

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