Dissolved organic matter (DOM), typically quantified as dissolved organic carbon (DOC), has been hypothesized to play many roles in pedogenesis and soil biogeochemical cycles, however, most research to date concerning forest soils has focussed on the high molecular weight (HMW) components of this DOM. This review aims to assess the role of low molecular weight (LMW) DOM compounds in the C dynamics of temperate and boreal forest soils focussing in particular on organic acids, amino acids and sugars. The current knowledge of concentrations, mineralization kinetics and production rates and sources in soil are summarised. We conclude that although these LMW compounds are typically maintained at very low concentrations in the soil solution (<50μM), the flux through this pool is extremely rapid (mean residence time 1–10h) due to continued microbial removal. Due to this rapid flux through the soil solution pool and mineralization to CO2, we calculate that the turnover of these LMW compounds may contribute substantially to the total CO2 efflux from the soil. Moreover, the production rates of these soluble transitory compounds could exceed HMW DOM production. The possible impact of climate change on the behaviour of LMW compounds in soil is also discussed.
No abstract is provided for this article.
Soil soluble nitrogen (N) is crucial to the N nutrition and productivity of plants. Consequently, understanding the factors that affect its pool size and c
Research Article| November 01 1966 The Location of Chitin in the Yeast Cell Wall J. S. D. Bacon; J. S. D. Bacon Search for other works by this author on: This Site PubMed Google Scholar Elizabeth D. Davidson; Elizabeth D. Davidson Search for other works by this author on: This Site PubMed Google Scholar D. Jones; D. Jones Search for other works by this author on: This Site PubMed Google Scholar Irene F. Taylor Irene F. Taylor Search for other works by this author on: This Site PubMed Google Scholar Biochem J (1966) 101 (2): 36C–38C. https://doi.org/10.1042/bj1010036C Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Cite Icon Cite Get Permissions Citation J. S. D. Bacon, Elizabeth D. Davidson, D. Jones, Irene F. Taylor; The Location of Chitin in the Yeast Cell Wall. Biochem J 1 November 1966; 101 (2): 36C–38C. doi: https://doi.org/10.1042/bj1010036C Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Journal Search Advanced Search This content is only available as a PDF. © 1966 The Biochemical Society1966 Article PDF first page preview Close Modal You do not currently have access to this content.
A sensitive method for the determination of citrate and malate in sub-microliter samples of soil solution is described. The organic acids were derivatized with a pyrene reagent (1-pyrenebutanoic acid hydrazide) and analysed by micellar electrokinetic chromatography separation. The citrate and malate derivatives were detected within 10 min by using a fluorescence detector with a broad excitation wavelength of 240-400 nm and an emission wavelength of 400 nm. The detection limits (noise x 3) were about 0.24 µM for citrate and 0.72 µM for malate. By using internal standardization, this method was applicable to the determination of citrate and malate in soil solution. Furthermore, application of siphon injection with a commercial micropipette enabled the injection of a sub-microliter sample into the analytical system with acceptable reproducibility. When combined with a microsampling method, the method presented here will be useful for the sensitive and selective analysis of citrate and malate in soil solution with high spatial resolution.
The hyperarid core of the Atacama Desert represents one of the most intense environments on Earth, often being used as an analog for Mars regolith. The area is characterized by extremes in climate (e.g., temperature, humidity, UV irradiation) and edaphic factors (e.g., hyper-salinity, high pH, compaction, high perchlorates, and low moisture, phosphorus and organic matter). However, the halophytic C4 plant Distichlis spicata appears to be one of the few species on the planet that can thrive in this environment. Within this habitat it captures windblown sand leading to the formation of unique structures and the generation of above-ground phyllosphere soil. Using a combination of approaches (e.g., X-ray Computed Tomography, TXRF, δ13C/δ15N isotope profiling, microbial PLFAs, 14C turnover, phosphate sorption isotherms) we examined the factors regulating the biogeochemical cycling of nitrogen (N), phosphorus (P) and carbon (C) in both vegetated and unvegetated areas. Our results showed that D. spicata rhizomes with large aerenchyma were able to break through the highly cemented topsoil layer leading to root proliferation in the underlying soil. The presence of roots increased soil water content, P availability and induced a change in microbial community structure and promoted microbial growth and activity. In contrast, soil in the phyllosphere exhibited almost no biological activity. Organic C stocks and recent C4 plant derived input increased as follows: phyllosphere (1941 g C m−2; 85% recent) > soils under plants (575–748 g C m−2; 55–60%) > bare soils (491–642 g C m−2; 9–17%). Due to the high levels of nitrate in soil (>2 t ha−1) and high rates of P sorption/precipitation, our data suggest that the microbial activity is both C and P, but not N limited. Root-mediated salt uptake combined with foliar excretion and dispersal of NaCl into the surrounding area indicated that D. spicata was responsible for actively removing ca. 55% of the salt from the rhizosphere. We also demonstrate that NH3 emissions may represent a major N loss pathway from these soil ecosystems during the processing of organic N. We attribute this to NH3 volatilization to the high pH of the soil and slow rates of nitrification. In conclusion, we demonstrate that the extremophile D. spicata physically, chemically and biologically reengineers the soil to create a highly bioactive hotspot within the climate-extreme of the Atacama Desert.
There is a major knowledge gap concerning the extent of microplastic pollution in agronomic regions of China, which represent a plastic use hotspot. This study investigated the characteristics of microplastics distributed in agricultural soils from three typical regions (Beijing (BJ), Shandong (SD), and Xinjiang (XJ)) with two plastic film mulching modes (greenhouse (G) and conventional field-based film mulching (M)) in China. The average abundance of microplastics under G and M modes was 3.60×104 items kg-1 and 3.01×104 items kg-1, respectively, and the estimated weight of microplastics per kg of dry soils in BJ, SD, and XJ was 3.12 mg kg-1, 5.63 mg kg-1, and 7.99 mg kg-1, respectively. Microplastics in farmland were mainly of small particle size (50 to 250 μm), with their abundance decreasing with increasing particle size. Among the microplastics detected, polyethylene and polypropylene were the two dominant types present, accounting for 50.0% and 19.7%, respectively. In addition, plastic film mulching mode (G vs. M) had a stronger effect on microplastic distribution than agronomic region. This research provides key data for an assessment of the environmental risk of microplastics and supports the development of guidelines for the sustainable use of agricultural plastic film.
Leachate emissions from landfill sites are of concern, primarily due to their toxic impact when released unchecked into the environment, and the potential for landfill sites to generate leachate for many hundreds of years following closure. Consequently, economically and environmentally sustainable disposal options are a priority in waste management. One potential option is the use of soil–plant based remediation schemes. In many cases, using either trees (including short rotation coppice) or grassland, phytoremediation of leachate has been successful. However, there are a significant number of examples where phytoremediation has failed. Typically, this failure can be ascribed to excessive leachate application and poor management due to a fundamental lack of understanding of the plant–soil system. On balance, with careful management, phytoremediation can be viewed as a sustainable, cost effective and environmentally sound option which is capable of treating 250m3 ha−1 yr−1. However, these schemes have a requirement for large land areas and must be capable of responding to changes in leachate quality and quantity, problems of scheme establishment and maintenance, continual environmental monitoring and seasonal patterns of plant growth. Although the fundamental underpinning science is well understood, further work is required to create long-term predictive remediation models, full environmental impact assessments, a complete life-cycle analysis and economic analyses for a wide range of landfill scenarios.
A putative natural inter-specific orchid hybrid between Pterostylis alveata and P. ophioglossa from Fingal Point, New South Wales, Australia, with intermediate morphological characters between the parents was tested using starch gel electrophoresis. Four enzyme systems, glucose phosphate isomerase (GPI), uridine diphosphogluconic pyrophosphatase (UDP), malic enzyme (ME) and leucine amino-peptidase (LAP), exhibited precisely the heterozygote pattern in the hybrid plants demonstrating the presence of alleles from both parents and distinguishing hybrid genotypes from the parental genotype.
The availability of inorganic N has been shown to be one of the major factors limiting primary productivity in high latitude ecosystems. The factors regulating the rate of transformation of organic N to nitrate and ammonium, however, remain poorly understood. The aim of this study was to investigate the nature of the soluble N pool in forest soils and to determine the relative rate of inorganic N production from high and low molecular weight (MW) dissolved organic nitrogen (DON) compounds in black spruce forest soils. DON was found to be the dominant N form in soil solution, however, most of this DON was of high MW of which >75% remained unidentified. Free amino acids constituted less than 5% of the total DON pool. The concentration of NO3 − and NH4 + was low in all soils but significantly greater than the concentration of free amino acids. Incubations of low MW DON with soil indicated a rapid processing of amino acids, di- and tri-peptides to NH4 + followed by a slower transformation of the NH4 + pool to NO3 −. The rate of protein transformation to NH4 + was slower than for amino acids and peptides suggesting that the block in N mineralization in taiga forest soils is the transformation of high MW DON to low MW DON and not low MW DON to NH4 + or NH4 + to NO3 −. Calculated turnover rates of amino acid-derived C and N immobilized in the soil microbial biomass were similar with a half-life of approximately 30 d indicating congruent C and N mineralization.
