Turnover Of Organic Material Research Articles

Difference of Soil Aggregates Composition, Stability, and Organic Carbon Content between Eroded and Depositional Areas after Adding Exogenous Organic Materials

Black soil in northeastern China has suffered widespread soil degradation due to long-term cultivation while causing eroded–depositional landscapes, leading to soil-associated carbon redistribution. In agricultural systems, adding exogenous organic material to degraded soil is a common measure to improve soil aggregate stability and soil quality. However, differences in soil properties may alter the decomposition and turnover of organic material in aggregates. Using a uniform method to restore the eroded (E) and depositional (D) soils is inefficient. Therefore, an indoor constant temperature and humidity incubation experiment with the addition of three organic materials, namely, straw (S), biochar (B), and swine manure (M), was designed with an equal amount of carbon. Soil aggregate composition, stability, and organic carbon from eroded and depositional soils were analyzed for evaluating the amendment efficiency of soil quality by exogenous organic material addition. The main results were as follows: adding straw and swine manure could effectively promote >2-mm aggregates formation (E: 7.1%, 8.8%; D: 17.3%, 8.6%) and significantly improved the mean weight diameter (MWD) (E: 0.45 mm, 0.52 mm; D: 0.96 mm, 0.54 mm), while the addition of biochar significantly increased the proportion of 0.25–2-mm aggregates (E: 7.9%; D: 10.9%), but the effect of improving MWD was less than straw and swine manure. All the three organic materials could significantly increase soil total organic carbon (TOC) (S, B and M: 1.95, 3.12 and 2.46 g·kg−1) in the eroded area, and the effect of biochar was the best, whereas it was not significant for the soil in the depositional area. Specially, adding swine manure and adding straw is more beneficial to the restoration of eroded areas and depositional areas, respectively.

In situ oxygen dynamics and carbon turnover in an intertidal sediment (Skallingen, Denmark)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 566:49-65 (2017) - DOI: https://doi.org/10.3354/meps12016 In situ oxygen dynamics and carbon turnover in an intertidal sediment (Skallingen, Denmark) Eva Walpersdorf1, Michael Kühl2,3, Bo Elberling1, Thorbjørn J. Andersen1, Birger U. Hansen1, Morten Pejrup1, Ronnie N. Glud4,5,6,* 1Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen K, Denmark 2Marine Biological Laboratory, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark 3Plant Functional Biology and Climate Change Cluster, University of Technology Sydney, Ultimo, NSW 2007, Australia 4University of Southern Denmark, Institute of Biology and Nordic Center for Earth Evolution (NordCEE), Odense M, Denmark 5Department of Ocean and Environmental Sciences, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan 6Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, PA37 1QA Dunbeg, UK *Corresponding author: rnglud@biology.sdu.dk ABSTRACT: Intertidal areas are considered to be productive habitats, but due to the challenging and dynamic environment, in situ assessments of their performance remain scarce. Here, we aimed to quantify the production and turnover of organic material in an intertidal sediment across several consecutive diel/tidal cycles and to evaluate the importance of key drivers affecting the community performance. Time-series measurements of the oxygen (O2) microdistribution across 2 sites at a silty sandflat documented extreme variability, which was mainly driven by light availability and flow conditions. Diffusion dominated the interstitial solute transport, but advective porewater transport was observed during 15% of the 9 d study period. Photosynthetic activity never exhibited light inhibition and average daytime net photosynthesis ranged between 1.01 and 11.15 mmol m-2 d-1 depending on the daily light availability, while the assessed gross primary production was ∼80% higher. When irradiance exceeded 17.2 mol photons m-2 d-1, daytime net autotrophy more than balanced the heterotrophic activity during the night (average night-time respiration, ERn: -4.01 mmol m-2 d-1). However, despite intense primary production, the integrated activity during the target autumn period was net heterotrophic with an average net ecosystem metabolism of -2.21 (span: -7.93 to 1.48) mmol O2 m-2 d-1. This study highlights the extreme temporal and spatial variation of intertidal sediments and the importance of accounting for natural in situ dynamics to correctly assess their performance and contribution to system production. KEY WORDS: In situ O2 dynamics · Transecting microprofiler · Benthic primary production · P/E relation · Flow · Net ecosystem metabolism · Intertidal Full text in pdf format PreviousNextCite this article as: Walpersdorf E, Kühl M, Elberling B, Andersen TJ, Hansen BU, Pejrup M, Glud RN (2017) In situ oxygen dynamics and carbon turnover in an intertidal sediment (Skallingen, Denmark). Mar Ecol Prog Ser 566:49-65. https://doi.org/10.3354/meps12016 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 566. Online publication date: February 27, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Streptomycesas symbionts: an emerging and widespread theme?

Streptomyces bacteria are ubiquitous in soil, conferring the characteristic earthy smell, and they have an important ecological role in the turnover of organic material. More recently, a new picture has begun to emerge in which streptomycetes are not in all cases simply free-living soil bacteria but have also evolved to live in symbiosis with plants, fungi and animals. Furthermore, much of the chemical diversity of secondary metabolites produced by Streptomyces species has most likely evolved as a direct result of their interactions with other organisms. Here we review what is currently known about the role of streptomycetes as symbionts with fungi, plants and animals. These interactions can be parasitic, as is the case for scab-causing streptomycetes, which infect plants, and the Streptomyces species Streptomyces somaliensis and Streptomyces sudanensis that infect humans. However, in most cases they are beneficial and growth promoting, as is the case with many insects, plants and marine animals that use streptomycete-produced antibiotics to protect themselves against infection. This is an exciting and newly emerging field of research that will become increasingly important as the search for new antibiotics switches to unusual and under-explored environments.