The movement of dissolved organic carbon (DOC) through soils is an important process for the transport of carbon within ecosystems and the formation of soil organic matter. In some cases, DOC fluxes may also contribute to the carbon balance of terrestrial ecosystems; in most ecosystems, they are an important source of energy, carbon, and nutrient transfers from terrestrial to aquatic ecosystems. Despite their importance for terrestrial and aquatic biogeochemistry, these fluxes are rarely represented in conceptual or numerical models of terrestrial biogeochemistry. In part, this is due to the lack of a comprehensive understanding of the suite of processes that control DOC dynamics in soils. In this article, we synthesize information on the geochemical and biological factors that control DOC fluxes through soils. We focus on conceptual issues and quantitative evaluations of key process rates to present a general numerical model of DOC dynamics. We then test the sensitivity of the model to variation in the controlling parameters to highlight both the significance of DOC fluxes to terrestrial carbon processes and the key uncertainties that require additional experiments and data. Simulation model results indicate the importance of representing both root carbon inputs and soluble carbon fluxes to predict the quantity and distribution of soil carbon in soil layers. For a test case in a temperate forest, DOC contributed 25% of the total soil profile carbon, whereas roots provided the remainder. The analysis also shows that physical factors—most notably, sorption dynamics and hydrology—play the dominant role in regulating DOC losses from terrestrial ecosystems but that interactions between hydrology and microbial–DOC relationships are important in regulating the fluxes of DOC in the litter and surface soil horizons. The model also indicates that DOC fluxes to deeper soil layers can support a large fraction (up to 30%) of microbial activity below 40 cm.

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Dissolved Organic Carbon in Terrestrial Ecosystems: Synthesis and a Model

/pdf/conservation-agriculture-and-ecosystem-services-an-overview-5dh4ewvhue.pdf

Conservation agriculture and ecosystem services: An overview

No-till agriculture is generally considered good for soils, and probably also beneficial in relation to climate change adaptation. However, this Perspective argues that the potential for climate change mitigation through soil carbon sequestration that is possible from a change to no-till agriculture has been widely overstated.

Limited potential of no-till agriculture for climate change mitigation

The sources and distribution of anthropogenic nitrogen (N), including N fertilization and N fixed during fossil-fuel combustion, are rapidly becoming globally distributed. Responses of terrestrial ecosystems to anthropogenic N inputs are likely to vary geographically. In the temperate zone, long-term N inputs can lead to increases in plant growth and also can result in over-enrichment with N, eventually leading to increased losses of N via solution leaching and trace-gas emissions, and in some cases, to changes in species composition and to ecosystem decline. However, not all ecosystems respond to N deposition similarly; their response depends on factors such as successional state, ecosystem type, N demand or retention capacity, land-use history, soils, topography, climate, and the rate, timing, and type of N deposition. We point to some of the conditions under which anthropogenic impacts can be significant, some of the factors that control variations in response, and some areas where uncertainty is large due to limited information.

The globalization of nitrogen deposition: consequences for terrestrial ecosystems.

The use of seaweeds has a long history, as does the cultivation of a select and relatively small group of species. This review presents several aspects of seaweed production, such as an update on t...

https://www.tandfonline.com/doi/pdf/10.1080/09670262.2017.1365175

Seaweed production: overview of the global state of exploitation, farming and emerging research activity

Cellulase produced from the marine fungus Cladosporium sphaerospermum through solid state fermentation (SSF) was investigated for its saccharification potential of seaweed biomass using the common green seaweed Ulva fasciata . The seaweed substrate, containing inoculated fungus with 60% moisture content, cultured at 25 °C and pH 4 for four days, showed optimum enzyme production. The enzyme, assayed for carboxymethyl cellulase and filter paper assay, showed an activity of 10.20 ± 0.40 U/g and 9.60 ± 0.64 U/g on a dry weight basis, respectively. Further, ionic liquid tolerance of the enzyme was studied in the presence of 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium trifluoromethanesulfonate and 1-butyl-1-methylpyrrolidinium trifluromethanesulfonate. At 10% v/v concentration, the enzyme retained 72.17 to 85.04% activity in all the ionic liquids. The pre-incubation of enzyme in the same ionic liquids for 24 h, the activity got slightly enhanced and ranged between 73.80 and 93.70%. The hydrolysis of U. fasciata feedstock with enzyme (10 U/g) for 24 h at 40 °C and pH 4 gave maximum yield of sugar 112 ± 10 mg/g dry weight. On fermentation, an ethanol yield of 0.47 g/g reducing sugar was obtained, corresponding to 93.81% conversion efficiency. These findings indicate that cellulase produced from a marine fungus can be employed for saccharification of cellulosic feedstock for the production of renewable biofuels from marine macroalgal feedstock. Since bioethanol yields obtained compare very favorably with those from land crops, the strategy employed in this study warrants further exploration.

Solid state fermentation (SSF)-derived cellulase for saccharification of the green seaweed Ulva for bioethanol production

2037 Soil Sci. Soc. Am. J. 75:2037–2048 Posted online 28 Sept. 2011 doi:10.2136/sssaj2011.0145 Received 18 Apr. 2011. *Corresponding author (baveyp@rpi.edu). © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. From Dust Bowl to Dust Bowl: Soils are Still Very Much a Frontier of Science SSSA 75th Anniversary Paper

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From Dust Bowl to Dust Bowl: Soils are Still Very Much a Frontier of Science

Effects of soil structure on solute transport were studied in a clayey, well-aggregated Oxic Dystropept under grass and secondary forest at La Selva, Costa Rica Both fine pores ( 30 µm) are abundant, as indicated by a water content of 037 m³ m⁻³ at −1500 kPa matric potential, the shape of the moisture release curve, and an initial infiltration rate (at field capacity) averaging 3900 mm hr⁻¹ Field application of Rhodamine B dye without ponding (simulating heavy rainfall) showed preferential flow along decayed-root channels, animal burrows, cracks, and other macropores Dye application to intact cores under conditions of ponded steady-state flow gave a good correlation between flow rate and total stained area (p <001 under forest; p < 005 under grass) Solute (CaCl₂) breakthrough occurred very rapidly, often after < 01 pore volumes had percolated; however, relative concentration of the effluent did not exceed 095 even after five pore volumes had percolated These results indicate that most water flows between aggregates or through macropores (as preferential or channelized flow), even when the fine pores are not fully saturated, and in effect bypasses the fine pore space When solution inflow was interrupted after ∼18 pore volumes, then resumed after 10 min pause, relative concentration of the effluent dropped by 10 to 40%, then rose again This indicates that solute diffused slowly into the aggregates Taken together the results suggest that this soil strongly resists leaching Preferential water flow may serve to prevent nutrient loss from the matrix of all highly aggregated soils and of all noncultivated soils in which animal activity and turnover of woody roots create abundant macropores Research supported by NSF Grants BSR 83-17198 and BSR 86-05047 to the Organization for Tropical Studies, Duke Univ, Durham, NC 27706

Effects of Soil Physical Structure on Solute Transport in a Weathered Tropical Soil

Bypass Water Flow through Unsaturated Microaggregated Tropical Soils

http://www.aquaculturewithoutfrontiers.org/wp-content/uploads/2010/04/Radulovich-tropical-seaweeds-food-biodiversity.pdf

Ricardo Radulovich

Papers

Solid state fermentation (SSF)-derived cellulase for saccharification of the green seaweed Ulva for bioethanol production

From Dust Bowl to Dust Bowl: Soils are Still Very Much a Frontier of Science

Effects of Soil Physical Structure on Solute Transport in a Weathered Tropical Soil

Bypass Water Flow through Unsaturated Microaggregated Tropical Soils

Tropical seaweeds for human food, their cultivation and its effect on biodiversity enrichment