348 research outputs found
Dinitrogen Emissions Dominate Nitrogen Gas Emissions From Soils With Low Oxygen Availability in a Moist Tropical Forest
No full textLowland tropical forest soils are relatively N rich and are the largest global source of N2O (a powerful greenhouse gas) to the atmosphere. Despite the importance of tropical N cycling, there have been few direct measurements of N2 (an inert gas that can serve as an alternate fate for N2O) in tropical soils, limiting our ability to characterize N budgets, manage soils to reduce N2O production, or predict the future role that N limitation to primary productivity will play in buffering against climate change. We collected soils from across macro- and micro-topographic gradients that have previously been shown to differ in O2 availability and trace gas emissions. We then incubated these soils under oxic and anoxic headspaces to explore the relative effect of soil location versus transient redox conditions. No matter where the soils came from, or what headspace O2 was used in the incubation, N2 emissions dominated the flux of N gas losses. In the macrotopography plots, production of N2 and N2O were higher in low O2 valleys than on more aerated ridges and slopes. In the microtopography plots, N2 emissions from plots with lower mean soil O2 (5%–10%) were greater than in plots with higher mean soil O2 (10%–20%). We estimate an N gas flux of ∼37 kg N/ha/yr from this forest, 99% as N2. These results suggest that N2 fluxes may have been systematically underestimated in these landscapes, and that the measurements we present call for a reevaluation of the N budgets in lowland tropical forest ecosystems.This article is published as Almaraz, Maya, Peter M. Groffman, Whendee L. Silver, Steven J. Hall, Yang Lin, Christine O’Connell, and Stephen Porder. "Dinitrogen emissions dominate nitrogen gas emissions from soils with low oxygen availability in a moist tropical forest." Journal of Geophysical Research: Biogeosciences 128 (2023): e2022JG007210. doi:10.1029/2022JG007210. Posted with permission
Crab Burrowing Limits Surface Litter Accumulation in a Temperate Salt Marsh: Implications for Ecosystem Functioning and Connectivity
No full textBurial of aboveground plant litter by animals reduces the amount available for surface transport and places it into a different environment, affecting decomposition rates and fluxes of organic matter to adjacent ecosystems. Here we show that in a Southwestern Atlantic salt marsh the burrowing crab Neohelice granulata buries aboveground plant litter at rates (0.5–8 g m−2 day−1) comparable to those of litter production (3 g m−2 day−1). Buried litter has a low probability (0.6%) of returning to the marsh surface. The formation of burrow excavation mounds on the marsh surface is responsible for most litter burial, whereas litter trapped in burrows was an order of magnitude lower than rates of burial under excavation mounds. Crab exclusion markedly increased surface litter accumulation (3.5-fold in just 21 days). Tides with the potential to transport significant amounts of surface litter are infrequent; hence, most litter is buried before it can be transported elsewhere or decomposes on the surface. Crab litter burial can account for the observed low levels of surface litter accumulation in this ecosystem and likely drives organic matter transformation and export. The impacts of ecosystem engineering by this crab species are therefore substantial and comparable in magnitude to the large effects found for tropical crabs and other litter-burying organisms, such as anecic earthworms.Fil: Gutierrez, Jorge Luis Ceferino. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales; Argentina. Cary Institute of Ecosystem Studies; Estados Unidos. Grupo de Investigación y Educación en Temas Ambientales (GrIETA) - Estación Biológica Las Brusquitas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Jones, Clive G.. Cary Institute of Ecosystem Studies; Estados UnidosFil: Ribeiro, Pablo Damián. Grupo de Investigación y Educación en Temas Ambientales (GrIETA) - Estación Biológica Las Brusquitas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Findlay, Stuart E. G.. Cary Institute of Ecosystem Studies; Estados UnidosFil: Groffman, Peter M.. Cary Institute of Ecosystem Studies; Estados Unidos. City University of New York; Estados Unido
Denitrification Hysteresis During Wetting and Drying Cycles in Soil
No full textIn the drying phase, rates of denitrification decreased dramatically as soils were dried from saturation to field capacity, with further decreases in activity observed at 60 and 20% water-filled porosity. In the wetting phase, denitrification activity sharply increased immediately after rewetting soils from 20-60% water-filled porosity, with only slight increases observed as soils were wet further to field capacity and saturation. The hysteretic response was observed in three soils of markedly different texture. Denitrification dynamics in the wetting phase were strongly correlated with pulses of C and N mineralization caused by stress of microbial biomass by drying and rewetting. -from Author
Ideas and perspectives: biogeochemistry - some key foci for the future
No full text© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bianchi, T. S., Anand, M., Bauch, C. T., Canfield, D. E., De Meester, L., Fennel, K., Groffman, P. M., Pace, M. L., Saito, M., & Simpson, M. J. Ideas and perspectives: biogeochemistry - some key foci for the future. Biogeosciences, 18(10), (2021): 3005–3013, https://doi.org/10.5194/bg-18-3005-2021.Biogeochemistry has an important role to play in many environmental issues of current concern related to global change and air, water, and soil quality. However, reliable predictions and tangible implementation of solutions, offered by biogeochemistry, will need further integration of disciplines. Here, we refocus on how further developing and strengthening ties between biology, geology, chemistry, and social sciences will advance biogeochemistry through (1) better incorporation of mechanisms, including contemporary evolutionary adaptation, to predict changing biogeochemical cycles, and (2) implementing new and developing insights from social sciences to better understand how sustainable and equitable responses by society are achieved. The challenges for biogeochemists in the 21st century are formidable and will require both the capacity to respond fast to pressing issues (e.g., catastrophic weather events and pandemics) and intense collaboration with government officials, the public, and internationally funded programs. Keys to success will be the degree to which biogeochemistry can make biogeochemical knowledge more available to policy makers and educators about predicting future changes in the biosphere, on timescales from seasons to centuries, in response to climate change and other anthropogenic impacts. Biogeochemistry also has a place in facilitating sustainable and equitable responses by society.TSB was supported in part by the Beverly Thompson Endowed Chair in Geological Sciences; MJS acknowledges support from the Natural Sciences and Engineering Research Council via a Tier 1 Canada Research Chair in Integrative Molecular Biogeochemistry
A conceptual assessment of the importance of denitrification as a source of soil nitrogen loss in tropical agro-ecosystems
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