[Stability characteristics of soil organic carbon pool following development of sand-fixing forest in Mu Us sandy land, China]. / æ¯›ä¹Œç´ æ²™åœ°å›ºæ²™æž—å‘è‚²è¿‡ç¨‹ä¸­åœŸå£¤æœ‰æœºç¢³åº“ç¨³å®šæ€§ç‰¹å¾.

The study aimed to reveal the cumulative effects and stability characteristics of soil organic carbon (SOC) during forest development at the Mu Us sandy land, China. Using space for time substitution, surface soil samples were collected from semi-fixed sandy lands and restored arbor and shrub lands with the ages of 22, 32 and 53 years in the Yulin sand control region in Northern Shaanxi Province. The content of total organic carbon (TOC), oxidizable labile organic carbon, and resistant carbon and the characteristics of mineralized carbon emission and decomposition ratio were analyzed. The results showed that the increment of TOC for 22 to 53 years shrub and arbor lands from resistant carbon were 3.5-6.2 g·kg-1 and 3.2-7.7 g·kg-1, and from oxidized labile carbon were 2.8-3.4 g·kg-1 and 1.3-2.8 g·kg-1, respectively, compared with semi-fixed sand land. The ratio of soil oxidizable labile carbon in shrub land and arbor land were stable and maintained at 37.0% and 26.8%, respectively. However, the ratio decreased to 25.7% and 17.4% after incubated at a constant temperature for 60 days. The mineralization rate of shrub and arbor lands with 22-53 years was not significant at the ending of soil incubation. Carbon losses from oxidized liable carbon were 76.9%-98.7%, and only 1.3%-23.5% from resistant carbon in all sand-fixing forest plots. Compared with the maximum carbon emission rate, the soil cumulative carbon release exhibited a higher correlation with soil enzyme activities of ß-glucosidase and dehydrogenase, but the enzyme activities did not change from 32-53 years. In conclusion, SOC pool showed stable characteristics of lower emission and higher sequestration with the increases of sand-fixing forest stand age. The carbon fixation effect of arbor sand-fixing forest was better than that of shrub sand-fixing forest.

[Carbon sequestration in soil particle-sized fractions during reversion of desertification at Mu Us Sand land.] / æ¯›ä¹Œç´ æ²™åœ°æ²™æ¼ åŒ–é€†è½¬è¿‡ç¨‹åœŸå£¤é¢—ç²’å›ºç¢³æ•ˆåº”.

The aim of this study was to investigate the effects of carbon sequestration in soil particle-sized fractions during reversion of desertification at Mu Us Sand Land, soil samples were collected from quicksand land, semifixed sand and fixed sand lands that were established by the shrub for 20-55 year-old and the arbor for 20-50 year-old at sand control region of Yulin in Northern Shaanxi Province. The dynamics and sequestration rate of soil organic carbon (SOC) associated with sand, silt and clay were measured by physical fractionation method. The results indicated that, compared with quicksand area, the carbon content in total SOC and all soil particle-sized fractions at bothsand-fixing sand forest lands showed a significant increasing trend, and the maximum carbon content was observed in the top layer of soils. From quicksand to fixed sand land with 55-year-old shrub and 50-year-old arbor, the annual sequestration rate of carbon stock in 0-5 cm soil depth was same in silt by 0.05 Mg·hm-2·a-1. The increase rate of carbon sequestration in sand was 0.05 and 0.08 Mg·hm-2·a-1, and in clay was 0.02 and 0.03 Mg·hm-2·a-1 at shrubs and arbors land, respectively. The increase rate of carbon sequestration in 0-20 cm soil layer for all the soil particles was averagely 2.1 times as that of 0-5 cm. At the annual increase rate of carbon, the stock of carbon in sand, silt and clay at the two fixed sand lands were increased by 6.7, 18.1 and 4.4 times after 50-55 year-old reversion of quicksand land to fixed sand. In addition, the average percentages that contributed to accumulation of total SOC by different particles in 0-20 cm soil were in the order of silt carbon (39.7%)≈sand carbon (34.6%) > clay carbon (25.6%). Generally, the soil particle-sized fractions had great carbon sequestration potential during reversion of desertification in Mu Us Sand Land, and the slit and sand were the main fractions for carbon sequestration at both fixed sand lands.

Alkaloids and sesquiterpenoids from Acorus tatarinowii.

The rhizome of Acorus tatarinowii is a well-known traditional Chinese medicine. Our extensive investigation on this plant material afforded two new compounds, including a cadinane-type sesquiterpenoid and a pyrazine derivative, along with seven known compounds. The structures of the new compounds, tatarinowin B and tatarinine A, were elucidated as 2-oxocadinan-1(10),3-dien-5-ol (1) and 2-(3',4'-dihydroxy-1'-butylenyl)-5-(2'',3'',4''-trihydroxybutyl)-pyrazine (2), respectively, by means of spectral methods.

A new pregnane steroid from Poria cum radix pini.

A new pregnane steroid and eight known compounds were isolated from Poria cum radix pini. Their structures were identified by spectroscopic data. All the known compounds were isolated from this species for the first time.

Compounds from Acorus tatarinowii: determination of absolute configuration by quantum computations and cAMP regulation activity.

A new cadinane-type sesquiterpenoid, tatarinowin A (1), two phenylpropanoids, tatarinoids A (2) and B (3), and a trinorlignan, tatarinoid C (4), along with 15 known compounds including two pairs of mixtures were isolated from the rhizome of Acorus tatarinowii. The absolute configurations of 1-4 were established by computation of specific rotation values. The isolated compounds were evaluated for their cAMP regulatory activity by the AlphaScreen assay.

[Content and evolution characteristics of organic carbon associated with particle-size fractions of grey desert soil under long-term fertilization].

Physical fractionation technique was used to analyze the content, distribution, and temporal evolution of organic carbon associated with particle-size fractions of grey desert soil under long-term (1990-2007) fertilization. Compared with no fertilization, a combined application of manure and chemical fertilizers increased the organic carbon associated with particle-size fractions significantly, with the highest increment (0.34 g x kg(-1) x a(-1)) in sand. Following also increased the organic carbon associated with clay and silt significantly. Straw return to cropland only maintained the organic carbon content in different particle-size fractions, while long-term application of chemical fertilizers was not beneficial to the organic carbon increase in particle-size fractions. Coarse silt and coarse clay had the highest distribution rates of organic carbon (27.9% and 27.1%, respectively), being the important fractions in sequestrating organic carbon. When manure was applied with chemical fertilizers, the organic carbon in sand was significantly increased by 119.4%, while that in fine silt and coarse clay was significantly decreased by 40.3% and 37.9%, respectively, which resulted in the increase in the ratio of particulate organic carbon content (W(POC)) to mineral-associated organic carbon content (W(MOC)), and improvd soil carbon property. Long-term application of manure combined with chemical fertilizers was the best mode to increase the organic carbon content in particle-size fractions and improve the fertility of grey desert soil.

Acortatarins A and B, two novel antioxidative spiroalkaloids with a naturally unusual morpholine motif from Acorus tatarinowii.

Acortatarins A (1) and B (2), two novel spiroalkaloids with a naturally unusual morpholine motif, were isolated from the rhizome of Acorus tatarinowii. Their structures with absolute configuration were determined by spectroscopic methods, X-ray diffraction analysis, and Mosher's method. Importantly, compound 1 could significantly inhibit reactive oxygen species production in high-glucose-stimulated mesangial cells in a dose- and time-dependent manner.