Wyniki wyszukiwania - Biblioteka Nauki

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Triterpenoid Acids from Kadsura ananosma

100%

Chen Y. , Song X. , Hai N. , Fang A. , Bi Y. , Liao X.

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2006

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tom Vol. 80, nr 10

1677-1681

EN

Ananosic acid D, a new 18 (1312) abeo lanostane triterpenoid acid was isolated from the stem barks of Kadsura ananosma and assigned the structure 3-hydroxy-18 (1312) abeo lanost-7 (8), 12 (18), 24 (Z)-trien-26-oic acid (1) by spectroscopic analysis including HR-ESI-MS and 2D-NMR. In addition, known lanostane triterpenoid acids 24(E)-3-oxo- lanosta-8, 24-dien-26-oic acid (2) and anwuweizic acid (3) were also obtained from this species. 2 was obtained as a new natural product and 3 was isolated from the plant for the first time.

2

Biomass fraction of graminoids and forbs in N-limited alpine grasslands: N:P stoichiometry

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Zhang R. , Gou X. , Bai Y. , Zhao J. , Chen L. , Song X. , Wang G.

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2011

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tom Vol. 59, nr 1

105-114

EN

It is known that the dominance of graminoid species is promoted by N addition; however, there has been relatively little effort to examine the pattern induced by natural N fertility. Since nutriet use efficiency (NUE) is an important trait determining plant competitive ability, we expected that the species guild with higher NUE (lower nutrient content) may be more competitive on infertile soils. We explored the relationships between relative forbs biomass share, soil N and productivity by the linear regressi on analysis on a natural alpine meadow in northeast of Qinghai Tibetan Plateau (3600 m a.s.l.). To test the variety of leaf N:P stoichiometry, paired t test and general linear model multivariate (GLM) analysis were also used. We found that the leaf N:P ratios of the whole community were below 13 in studied sites, which may be consistent with the N limitation on the vegetation. Graminoids retained lower concentrations of leaf N and P than forbs in community on the N limited grassland. Consistent with our prediction, we found that the biomass fraction of graminoids declined with soil N content and aboveground production on the grassland. Different from the pattern along fertility gradients induced by N fertilization, our results showed that gr aminoids with lower internal nutrient content were able to resist low levels of nutrient availability on the natural alpine grassland when compared to forbs.

3

Potential risk of Mesodinium rubrum bloom in aquaculture area of Dapeng'ao cove, China: diurnal changes in the ciliate community structure in the surface water

100%

Liu H. , Song X. , Huang L. , Tan Y. , Zhong Y. , Huang J. R.

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2012

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tom No. 54 (1)

109-117

EN

Diurnal changes in the structure of the ciliate community in surface waters were studied in the aquaculture area of Dapeng'ao cove, China. Two periods of heavy rainfall occurred during the study period, intensifying water column stratification and influencing the water's properties. A total of 21 ciliate taxa from 15 genera were identified; the dominant species was Mesodinium rubrum. The maximum abundance of M. rubrum reached 3.92 × 104 indiv. dm-3, contributing 95.1% (mean value) to the total ciliate abundance. Diurnal changes in M. rubrum abundance were highly variable, the driving force probably being irradiance and food availability. The results suggest that M. rubrum may form blooms in aquaculture areas when there is a suitable physical regime with enriched nutrients, which is potentially harmful to the fish-farming industry.

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Leaf litter decomposition along the temperate - tropical transect (East China) : the influence of stand succession, litter quality and climate

84%

Song X. , Jiang H. , Peng C. , Zhou G. , Chang S. , Yu S. , Ma Y. , Peng S. , Wei X.

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2012

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tom Vol. 60, nr 2

265-276

EN

The relationship between litter decomposition and forest succession in addition to the influence of climate variables on the rate of litter decomposition in forest ecosystems are poorly understood. In this study, the effects of forest successional stages, climate, and litter quality on litter decomposition rates were investigated in five sites located in China. The selected sites cover 29 degrees of latitude from 18[degrees]N to 47[degrees]N and spans more than 5,000 km in length along a temperature gradient that transverses across eastern China. This zonal gradient includes five climate zones from temperate to subtropical to tropical zones. Forest types include broad-leaved Korean pine, deciduous broad-leaved, evergreen broad-leaved, monsoon evergreen broad-leaved, and tropical rain forests. The North-South Transect of Eastern China (NSTEC) is one of fifteen international standard transects setup by Global Change and Terrestrial Ecosystems (GCTE). NSTEC is a key component of the International Geosphere-Biosphere Programme (IGBP). The litterbag method was used in this study to determine mass loss and annual decomposition rates of eight tree species (Pinus massoniana Lamb., Cunninghamia lanceolata (Lamb.) Hook., Schima superba Gardn. et Champ., Cinnamomum camphora (L.) Presl., Cyclobalanopsis glauca (Thunb.) Oerst., C. gracilis (Rehd. et Wils.) Cheng et T. Hong, Michelia chapensis Dandy, and Castanopsis eyeri (Champ.) Tutch. through a timeframe starting in May, 2006, and ending in May, 2008. Litterbags 15 x 15 cm and 0.5 x 1.0 mm mesh were filled with 10 g of leaf litter collected from the subtropical forest region and then placed onto the forest floor in triplicate samples for each eight species in all five sites. Three litterbags per species were retrieved from each of the five sites at two month intervals during the two year experimental period. Results suggest that species litter in the climax stage (C. glauca, C. gracilis, and M. chapensis) tended to decompose faster than those in the pioneer stage (P. massoniana and C. lanceolata). Initial phosphorous (P) and nitrogen (N) concentrations of leaf litter were the most critical variables of litter quality in relation to the impact on the rate of litter decomposition. Litter decomposition at different successional stages was found to be directly related to climatic variables such as mean annual precipitation (MAP) and mean annual temperature (MAT). MAP and initial P and N concentrations could therefore be considered good indicators of rates of decomposition.