Contribution of the vertical movement of dissolved organic carbon to carbon allocation in two distinct soil types under Castanopsis fargesii Franch. and C. carlesii (Hemsl.) Hayata forests

International audienceAbstractKey messageThe vertical transport of dissolved organic carbon (DOC) is an important determinant of carbon distribution across a soil profile. The transport of DOC down a soil profile can be largely influenced by incoming DOC and soil organic carbon (SOC) levels, which insulate DOC from adsorption processes regulated by soil texture and Fe/Al mineralogy.ContextUncertainties about how soil properties affect DOC transport through the soil profile require study because soils can differ strongly with respect to texture or Fe/Al mineralogy and yet retain similar quantities of DOC.AimsThis study aimed to assess the role of incoming DOC and native SOC in regulating DOC migration in soils and investigate the contribution of DOC movement to SOC allocation.MethodsWe leached a standard DOC solution extracted from Castanopsis carlesii litter through two distinct soil types, using two leaching strategies: single leaching and sequential leaching. The two soil types under a natural Castanopsis carlesii (Hemsl.) Hayata forest and a natural Castanopsis fargesii Franch. forest, respectively, differ strongly with respect to soil texture, Fe/Al oxide abundances, and SOC nature.ResultsWith single leaching, where each of six soil layers making up an entire 0–100-cm soil depth profile received single doses of standard DOC solution, deeper soil layers retained more DOC than upper soil layers, with native SOC largely masking the effects of soil texture and Fe/Al mineralogy on DOC migration. Following sequential leaching, where a sixfold larger amount of standard DOC solution sequentially percolated through the six soil layers, the upper soil layers generally retained more DOC than deeper layers. Nevertheless, in sequential leaching, desorption-induced transfer of carbon from upper soil layers to deeper soil layers resulted in greater total carbon retention than in single leaching.ConclusionForest subsoils (40–100 cm) are well below C saturation, but DOC vertical movement from top soils only transfers limited organic carbon to them. However, DOC vertical movement may greatly alter SOC allocation along the top soil profile (0–40 cm), with part of outer sphere native SOC displaced by incoming DOC and migrating downwards, which is a natural way to preserve SOC

Non-Structural Carbohydrate Dynamics in Leaves and Branches of Pinus massoniana (Lamb.) Following 3-Year Rainfall Exclusion

Drought-induced tree mortality is an increasing and global ecological problem. Stored non-structural carbohydrates (NSCs) may be a key determinant of drought resistance, but most existing studies are temporally limited. In this study, a 3-year 100% rainfall exclusion manipulation experiment was conducted to evaluate the response of NSC dynamics to drought stress in 25-year-old Pinus massoniana leaves and branches. The results showed: (1) compared with the control condition, leaf NSC concentration in the drought treatment increased 90% in the early stage (days 115–542) (p < 0.05), and then decreased 15% in the late stage (days 542–1032), which was attributed to water limitation instead of phenology; (2) the response of leaf NSCs to drought was more significant than branch NSCs, demonstrating a time lag effect; and (3) the response of P. massoniana to mild drought stress was to increase the soluble sugars and starch in the early stage, followed by an increase in soluble sugars caused by decreasing starch in the later stress period. Considering these results, mid-term drought stress had no significant effect on the total NSC concentration in P. massoniana, removing carbon storage as a potential adaptation to drought stress

Integration of stable isotope labeling derivatization and magnetic dispersive solid phase extraction for measurement of neurosteroids by in vivo microdialysis and UHPLC-MS/MS

In this work, a novel strategy of stable isotope labeling derivatization (SILD) combined with magnetic dispersive solid-phase extraction (MDSPE), has been proposed for simultaneous monitoring of neurosteroids changes linked to Parkinson's disease (PD) by in vivo microdialysis. The developed method was based on ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) detection using multiple-reaction monitoring (MRM) mode. In this study, a new pair of stable isotope labeling reagents d(0)-/d(3)-3-N-methyl-2'-carboxyl Rhodamine 6G (d(0)-/d(3)-MCR6G), were designed and synthesized for derivatizing neurosteroids in rat blood microdialysates and neurosteroid standards, respectively. d(3)-MCR6G labeled neurosteroids standards were used as internal standard for the following pretreatment and UHPLC-MS/MS quantification to minimize the deviations caused by complex matrix and ion suppression effects in mass spectrometry analysis. Under the optimized derivatization and extraction conditions, good linearities of eight neurosteroids were obtained with correlation coefficients R-2 values > 0.98. The limits of detection (LODs) and quantitation (LOQs) ranged from 0.06 to 0.12 pg/mL and 0.30-0.40 pg/mL, respectively. Taken together, the established method exhibited high sensitivity and selectivity, excellent accuracy, convenience and high efficiency. It was applied for the simultaneous and dynamic measurement of multiple neurosteroids in normal and PD rat blood microdialysates. This method would be expected to be potentially useful for the monitoring and drug treatment of PD and related neurological disorders in the future

Synthesis of thienyl-substituted isochromene derivatives through gold-catalyzed tandem heteroarylation/cycloisomerization of <i>ortho</i>-alkynylbenzaldehydes with thiophenes

<p>We describe herein a gold-catalyzed tandem heteroarylation/cycloisomerization reaction of <i>ortho</i>-alkynylbenzaldehydes with thiophenes. By this reaction, a variety of 1-(thiophen-2-yl)-1<i>H</i>-isochromene derivatives can be obtained in good yield.</p

Silver-Catalyzed Domino Reaction of ortho-Carbonylated Alkynyl-Substituted Arylaldehydes with Conjugated Dienes: Stereoselective Access to Indanone-Fused Cyclohexenes

A silver-catalyzed domino reaction of ortho-carbonylated alkynyl-substituted arylaldehydes with conjugated dienes is described here. Through this reaction, the synthesis of a variety of indanone-fused cyclohexene derivatives can be achieved efficiently. The formation of these tricyclic products could involve a key Diels–Alder reaction of <i>in situ</i> generated indanenone dienophiles with conjugated dienes. Particularly, the products can be accomplished in a high <i>endo</i>/<i>exo</i> selective way

Chemoselective α‑Methylenation of Aromatic Ketones Using the NaAuCl₄/Selectfluor/DMSO System

Gold-catalyzed chemoselective α-methylenation of aromatic ketones was developed through the use of Selectfluor as a methylenating agent. A variety of useful 1,2-disubstituted propenone derivatives can be prepared in good yields via the present protocol. This reaction features a simple operation, good functional group tolerance, and broad scope of substrates

Synthesis of multisubstituted <i>N</i>-(tosylamino)pyrrole derivatives by AuCl₃-catalyzed cycloisomerization of the β-alkynyl hydrazones

<p>A method for preparing multisubstituted <i>N</i>-(tosylamino)pyrrole derivatives through AuCl₃-catalyzed cycloisomerization of the β-alkynyl hydrazone compounds was described. The reaction could be carried out in one pot from the β-ketoesters to give the cyclized products in moderate to excellent yields with low catalyst loadings.</p