[Effects of reductive soil disinfestation and organic fertilizer application on microbial community stability in a facility vegetable soil]. / 强还原处理和施用有机肥对设施蔬菜地土壤微生物群落稳定性的影响.

Reductive soil disinfestation (RSD) is an effective method for remediating degraded facility vegetable soils. However, the effectiveness of RSD using green manure as a carbon source in the field has not yet been clarified. We investigated the effects of RSD and organic fertilizer application on soil microbial community composition, diversity, and stability in a degraded facility vegetable soil. There were six treatments, including no fertilization (CK), no fertilization and soil flooded and mulched with plastic film (FF), soil amended with chicken manure (OM), soil amended with chicken manure and flooded and mulched with plastic film (OMR), soil amended with Sesbania cannabina (TF), and soil amended with S. cannabina and flooded and mulched with plastic film (TR). The results showed that the OMR and TR treatments significantly decreased bacterial Chao1 index, altered bacterial and fungal community structure, and increased the relative abundances of Bacillus, Rhodococcus, Clostridium, and Penicillium. The TR treatment significantly reduced the relative abundance of Fusarium. Results of redundancy analysis and Mantel test analysis suggested that soil ammonium nitrogen and dissolved organic carbon contents were the key factors influencing bacterial community composition, and soil pH was the key factor affecting fungal community composition. Results of cohesion analysis showed that the OMR and TR treatments significantly improved bacterial community stability, and that there was no difference between OMR and TR treatments. The TR treatment enhanced fungal community stability, which was significantly higher than the OMR treatment. Therefore, the RSD with green manure as carbon source could be effective remediation practice to improve soil health.

[Effects of different regeneration patterns on soil dissolved organic matter degradation in Castanopsis carlesii forests of subtropical China]. / äºšçƒ­å¸¦ç±³æ§ æž—ä¸åŒæ›´æ–°æ–¹å¼å¯¹åœŸå£¤å¯æº¶æ€§æœ‰æœºè´¨é™è§£æ€§çš„å½±å“.

Biodegradability of dissolved organic matter (DOM) affects stabilization and mineralization of soil organic matter, which is of great significance to soil nutrient cycling. In order to explore the effects of forest regeneration on soil DOM degradation, soil DOM solution was sampled in a natural Castanopsis carlesii forest (NF), a secondary forest of C. carlesii (SF), and an artificial-assisted regeneration forest of C. carlesii (AR) in a sub-tropical area and conducted 42-day laboratory incubation. The results showed that: 1) both the degradation rate of soil dissolved organic carbon (DOC) and the ratio of labile DOC were as follows: SF>AR>NF; dissolved organic nitrogen (DON) and microbial biomass carbon (MBC) are the factors significantly affecting the ratio of labile DOC; 2) stable DOC accounted for the majority of soil DOC in all the three forest types (72.3%-94.6%), which had long turnover time and contributed to the formation of stable soil organic matter (SOC); 3) the initial humification index in emission mode (HIXem) of soil DOM would affect the turnover time of labile DOC. The spectral structure of DOM changed dynamically during the degradation process, indicating that microorganism would turn to degrade aromatic and hydrophobic fractions for carbon source after the depletion of labile DOM. Overall, the transformation from NF of C. carlesii into SF and AR could increase the proportion of the easily degradable DOC, and enhance the biodegradability of soil DOM, which were not conducive to the accumulation of SOC.

[Effects of rainfall reduction on the quantity and spectroscopic characteristics of soil dissolved organic matter in a subtropical natural Castanopsis carlesii forest.] / éš”ç¦»é™é›¨å¯¹äºšçƒ­å¸¦ç±³æ§ å¤©ç„¶æž—åœŸå£¤å¯æº¶æ€§æœ‰æœºè´¨æ•°é‡åŠå ‰è°±å­¦ç‰¹å¾çš„å½±å“.

The alteration of rainfall pattern under the background of global climate change may affect the quantity and quality of soil dissolved organic matter (DOM). To better understand the responses of soil DOM to rainfall reduction in subtropical forests, we conducted a 6-year rainfall reduction experiment. There were three treatments: control (CK), 30% rainfall reduction (-30%), and 60% rainfall reduction (-60%). With ultraviolet-visible, infrared and three-dimensional fluorescence spectroscopy, we investigated the effects of rainfall reduction on the quantity and structure of DOM from different soil layers of a natural Castanopsis carlesii forest in subtropical China. Rainfall significantly reduced the content of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in the 0-10 cm soil layer. Specifically, less decreases of DOC than DON were found under the -30% treatment, while more reduction of DOC than DON for the -60% treatment. Under each treatment, the contents of DOC and DON were significantly higher in the 0-10 cm soil layer than that in the 10-20 cm soil layer. Relatively more microbial metabolite with complex structures, such as aromatic humus and alkanes, contributed to soil DOM from the -30% treatment than that from the -60% treatment. Beyond water availability, microbial activity was a key factor regulating the quantity and structure of soil DOM in response to rainfall reduction.

[Effects of nitrogen deposition on the concentration and spectral characteristics of dissolved organic matter in soil solution in a young Cunninghamia lanceolata plantation.] / æ°®æ²‰é™å¯¹æ‰æœ¨äººå·¥å¹¼æž—åœŸå£¤æº¶æ¶²å¯æº¶æ€§æœ‰æœºç‰©è´¨æµ“åº¦åŠå ‰è°±å­¦ç‰¹å¾çš„å½±å“.

To study the effects of nitrogen deposition on the concentration and spectral characteristics of dissolved organic matter (DOM) in the forest soil solution from the subtropical Cunninghamia lanceolata plantation, using negative pressure sampling method, the dynamics of DOM in soil solutions from 0-15 and 15-30 cm soil layer was monitored for two years and the spectroscopic features of DOM were analyzed. The results showed that nitrogen deposition significantly reduced the concentration of dissolved organic carbon (DOC), and increased the aromatic index (AI) and the humic index (HIX), but had no significant effect on dissolved organic nitrogen (DON) concentration in both soil layers. There was obvious seasonal variation in DOM concentration of the soil solution, which was prominently higher in summer and autumn than in spring and winter.Fourier-transform infrared (FTIR) absorption spectrometry indicated that the DOM in forest soil solution had absorption peaks in the similar position of six regions, being the highest in wave number of 1145-1149 cm-1. Three-dimensional fluorescence spectra indicated that DOM was mainly consisted of protein-like substances (Ex/Em=230 nm/300 nm) and microbial degradation products (Ex/Em=275 nm/300 nm). The availability of protein-like substances from 0-15 cm soil layer was reduced in the nitrogen treatments. Nitrogen deposition significantly reduced the concentration of DOC in soil solution, maybe largely by reducing soil pH, inhibiting soil carbon mineralization and stimulating plant growth. In particular, the decline of DOC concentration in the surface layer was due to the production inhibition of the protein-like substances and carboxylic acids. Short-term nitrogen deposition might be beneficial to the maintenance of soil fertility, while the long-term accumulation of nitrogen deposition might lead to the hard utilization of soil nutrients.

[Soil microbial community structure of two types of forests in the mid-subtropics of China].

Soil microbial community structures were analyzed by biomarker method of phospholipid fatty acid (PLFA) for a natural forest dominated by Castanopsis fabri (CF) and an adjacent plantation of Cunninghamia lanceolata (CL) in the mid-subtropics of China. The results showed that the amounts of total PLFAs, bacterial PLFAs, fungal PLFAs, gram-positive bacterial PLFAs and gramnegative bacterial PLFAs in the 0-10 cm soil layer were higher than in the 10-20 cm soil layer, and each type of PLFAs in CF were higher than in CL. In either soil layer of the two forest types, the contents of bacterial PLFAs were significantly higher than those of fungal PLFAs. In the two forests, the contents of bacterial PLFAs accounted for 44%-52% of total PLFAs, while the contents of fungal PLFAs just accounted for 6%-8%, indicating the bacteria were dominant in the soils of the two vegetation types. Principal component analysis showed that the influence of vegetation types was greater than soil depth on the microbial community structures. Correlation analysis showed that gram-negative bacterial PLFAs, gram-positive bacterial PLFAs and bacterial PLFAs were significantly negatively correlated with pH, positively with water content, and the PLFAs of main soil microorganism groups were significantly positively correlated with soil total nitrogen, organic carbon, C/N and ammonium.

[Fractionation of dissolved organic carbon along soil profiles during the leaching process].

Two distinct soil types in mid-subtropical China were selected for soil sampling at the depth of 0-10, 10-20, 20-40, 40-60, 60-80, 80-100 cm for soil cores preparation. Dissolved organic carbon (DOC) extracted from recently fallen litters of Castanopsis carlesii with ultrapure water was leached through such soil cores to investigate the fractionation and retention pattern when migrating along the soil layers. The results showed the leachates out of deeper soil cores had lower concentrations and were chemically simpler, the hydrophobic pools contributed to the majority of the retention, but the proportion of retained hydrophilic materials gradually increased with the increasing soil depth. The infrared spectrum suggested that the hydrophobic materials containing aromatic rings could be easily absorbed by soils, but alkanes and simple carbohydrates would transport into subsoils with soil solution. Proportional decrease in the highly sorptive DOC restricted C sorption by subsoils, and thus the adsorption occurred mainly in 0-40 cm soil layers, suggesting that the chemical nature of DOC had a greater influence on sorption capacity of the soils than soil physicochemical properties. The retention amounts of DOC by different soil types differed significantly, which were significantly positively correlated with the contents of clay, iron and aluminum oxides.

Bis(mu4-butane-1,4-dithiolato)bis[hexacarbonyldiiron(II)(Fe-Fe)].

The novel title double-butterfly Fe/S cluster complex, [Fe(4)(C(4)H(8)S(2))(2)(CO)(12)], which is structurally similar to the active site of the Fe-only hydrogenases, contains two inversion-related Fe(2)S(2)(CO)(6) subcluster cores connected by two equivalent butyl chains to afford a 16-membered macrocycle. The formation of the 16-membered macrocycle has an influence on the C-S-Fe angles, while the Fe-Fe and Fe-S bond lengths remain similar to those in related complexes.

Diiron models for the active site of Fe-only hydrogenase with terminal organosulfur ligation: synthesis, structures and electrochemistry.

Diiron model complexes (micro-SCH(2)CH(2)CH(2)S)Fe(2)(CO)(5)L with thioether-substitution, L=S(CH(2)CH(3))(2) (2), S(CH(2)CH(3))(CH(2)CH(2)Cl) (3), S(CH(2)CH(3))(C(6)H(5)) (4), or sulfoxide-substitution, L=SO(CH(2)CH(2)CH(3))(2) (5), SO(CH(3))(2) (6), were synthesized as active site analogues of Fe-only hydrogenase. The organosulfur ligands were introduced into the diiron centers via moderately stable intermediates following two routes. The X-ray crystallographic structures of complexes 2-6 show the apical positions of terminal organosulfur ligands. The electrochemical behaviors of the model complexes were investigated, especially for the interesting properties of the derivative of 6 which is proposed to be the first model with weak donor ligand similar to CO.