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991.
Quantification of soil organic carbon sequestration potential in cropland: A model approach 总被引:4,自引:0,他引:4
Agroecosystems have a critical role in the terrestrial carbon cycling process. Soil organic carbon (SOC) in cropland is of
great importance for mitigating atmospheric carbon dioxide increases and for global food security. With an understanding of
soil carbon saturation, we analyzed the datasets from 95 global long-term agricultural experiments distributed across a vast
area spanning wide ranges of temperate, subtropical and tropical climates. We then developed a statistical model for estimating
SOC sequestration potential in cropland. The model is driven by air temperature, precipitation, soil clay content and pH,
and explains 58% of the variation in the observed soil carbon saturation (n=76). Model validation using independent data observed in China yielded a correlation coefficient R
2 of 0.74 (n=19, P<0.001). Model sensitivity analysis suggested that soils with high clay content and low pH in the cold, humid regions possess
a larger carbon sequestration potential than other soils. As a case study, we estimated the SOC sequestration potential by
applying the model in Henan Province. Model estimations suggested that carbon (C) density at the saturation state would reach
an average of 32 t C ha−1 in the top 0–20 cm soil depth. Using SOC density in the 1990s as a reference, cropland soils in Henan Province are expected
to sequester an additional 100 Tg C in the future. 相似文献
992.
Background
Accurate classification of microarray data is critical for successful clinical diagnosis and treatment. The "curse of dimensionality" problem and noise in the data, however, undermines the performance of many algorithms. 相似文献993.
Predators influence the phenotype of prey through both natural selection and induction. We investigated the effects of grazers
and nutrients on chain formation in a dinoflagellate, Cochlodinium polykrikoides, which forms dense blooms and has deleterious effects on marine ecosystems around the world. Field populations of C. polykrikoides formed longer chains than laboratory cultures without grazers. In the field, chain length of C. polykrikoides was positively correlated with the abundance of the copepod Acartia tonsa. Chain length of C. polykrikoides increased when exposed to live females of A. tonsa or its fresh (<24 h post-isolation) exudates for 48 h. These results suggest that dissolved chemical cues released by A. tonsa induce chain formation in C. polykrikoides. Ingestion rate of A. tonsa on four-cell chains of C. polykrikoides was lower than on single cells, suggesting that chain formation may be an effective anti-grazing defense. Finally, nutrient
amendment experiments demonstrated that vitamins (B1, B7, and B12) increased the chain length of C. polykrikoides both singly and collectively, while trace metals and inorganic nutrients did not, showing that vitamins may also influence
chain formation in this species. 相似文献
994.
Zhengquan Yao Guoqiao Xiao Haibin Wu Yukun Chen 《Palaeogeography, Palaeoclimatology, Palaeoecology》2010,297(2):502-510
The Plio-Pleistocene history of C4 plant biomass in northwestern China has been documented from the loess-soil sequences of the Loess Plateau region. However, how C4 plants evolved in the warmer and low-elevation eastern China monsoon zone is still poorly known mainly because of the unavailability of well-dated geological records. In this study, a 203.6-m core of floodplain deposits was recovered from the North China Plain near Tianjin and dated magnetostratigraphically. The results define a chronosequence for the last 3.3 Ma. The late Quaternary portion of the core consists of fluvio-marine sediments while the rest of the section (3.3-0.6 Ma) contains abundant paleosols formed on the floodplain, as confirmed by soil micromorphological evidence. The stable carbon and oxygen isotopic composition of pedogenic carbonates was measured to document vegetation and climate changes. The results reveal mixed C3 and C4 vegetation with an estimated C4 abundance of ~ 40-60% from ~ 3.1 to ~ 2.2 Ma, and a subsequent gradual decline to ~ 25% until ~ 0.6 Ma. This trend is consistent with the data from the loess-soil sequences further west on the Loess Plateau, suggesting they are regionally significant changes. The lowering of growing-season temperature and/or drier conditions induced by global cooling would explain this overall decline. 相似文献
995.
Qun Dong Xuan Liu Jian Yao Xiaotang Dong Chao Ma Yuxia Xu Jinian Fang Kan Ding 《Phytochemistry》2010,71(11-12):1430-1437
A polysaccharide fraction, J6, was isolated from the hot-water extract of flowers of oleander Nerium indicum Mill., using ethanol precipitation, cetyltrimethylammonium bromide (CTAB) complexing, anion-exchange chromatography and gel permeation chromatography. J6 was found to contain l-rhamnose, l-arabinose, d-galactose, and d-galacturonic acid, in the ratio of 10.1:49.8:30.1:10.0. Its structure was investigated by methylation analysis, periodate oxidation, Smith degradation, partial acid hydrolysis, electrospray ionization mass spectrometry and NMR spectroscopic methods. It was found that J6 is an RG-I type polysaccharide, which contains a rhamnogalacturonan backbone, with various branches attached to O-4 of l-rhamnose. The branches probably involve (1 → 4)-β-d-galactan, branched l-arabino-(1 → 3)(1 → 6)-β-d-galactan, and (1 → 5)-α-l-arabinan. J6 stimulated NO production of macrophage RAW264.7 cells in a preliminary test. 相似文献
996.
Effects of organic matter incorporation on nitrous oxide emissions from rice-wheat rotation ecosystems in China 总被引:8,自引:0,他引:8
Zhisheng Yao Zaixing Zhou Xunhua Zheng Baohua Xie Baoling Mei Rui Wang Klaus Butterbach-Bahl Jianguo Zhu 《Plant and Soil》2010,327(1-2):315-330
Organic matter addition is thought to be an important regulator of nitrous oxide (N2O) emissions from croplands. Contradictory effects, however, were reported in previous studies. To investigate the effects of crop residue management on N2O emissions from rice-wheat rotation ecosystems, we conducted field experiments at three sites (Suzhou, Wuxi and Jiangdu) in the Yangtze River Delta, using static chamber and gas chromatography methods. Our data show that N2O emissions throughout the rice season from plots treated with wheat straw application at a high rate (WS) prior to rice transplanting (1.1–2.0 kg N ha?1) were significantly lower (P?<?0.05) than those from the control plots without organic matter addition or added with wheat straw at a moderate rate (1.6–2.9 kg N ha?1). Furthermore, the WS treatments had a residual inhibitory effect on N2O emissions in the following non-rice season, which consistently resulted in significantly lower emissions (P?<?0.05) compared to the control treatments (2.2–3.1 vs. 3.9–5.6 kg N ha?1). In comparison to the control treatments, the WS treatments reduced both the seasonal and annual direct emission factors of the applied nitrogen (EFd) by 50–68% (mean: 57%). The addition of compost (aerobically composted rice or wheat straw harvested in the last rotation) reduced the seasonal and annual EFds by 29–32%. Over the entire rice-wheat rotation cycle, annual N2O emissions from the fertilized fields at the three sites ranged from 3.3?±?0.3 to 16.8?±?0.6 kg N ha?1, with a coefficient of variation (CV) of 61%. Similarly, the EFds during the rice-wheat rotation cycle ranged from 0.4% to 2.5%, with a CV of 67%. These high spatial variations might have been related to: variations in soil properties, such as texture and soil organic carbon; management practices, such as straw treatments (i.e., compost versus fresh straw) and weather conditions, such as precipitation and rainfall distribution. Our results indicate that the incorporation of fresh wheat straw at a high rate during the rice season is an effective management practice for the mitigation of N2O emissions in rice-wheat rotation systems. Whether this practice is also effective in reducing the overall global warming potential of net N2O, CH4 and CO2 emissions needs to be seen through further studies. 相似文献
997.
998.
999.
Mingming Xin Yu Wang Yingyin Yao Chaojie Xie Huiru Peng Zhongfu Ni Qixin Sun 《BMC plant biology》2010,10(1):123
Background
MicroRNAs (miRNAs) are a class of small non-coding regulatory RNAs that regulate gene expression by guiding target mRNA cleavage or translational inhibition. MiRNAs can have large-scale regulatory effects on development and stress response in plants. 相似文献1000.
Thomas M Davis Melanie E Shields Qian Zhang Denise Tombolato-Terzić Jeffrey L Bennetzen Ana C Pontaroli Hao Wang Qin Yao Phillip SanMiguel Kevin M Folta 《BMC plant biology》2010,10(1):81