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961.
Energy balance and partition in Inner Mongolia steppe ecosystems with different land use types 总被引:3,自引:0,他引:3
Shiping Chen Jiquan Chen Guanghui Lin Wenli Zhang Haixia Miao Long Wei Jianhui Huang Xingguo Han 《Agricultural and Forest Meteorology》2009,149(11):1800
Land use change and grassland degradation are two of the most critical problems ubiquitously found in arid and semi-arid areas in Northern China. Energy fluxes, including net radiation (Rn), latent heat flux (LE), sensible heat flux (H) and soil heat flux (G), were examined over an entire year (December 2005 to November 2006) in different steppe ecosystems – the steppe and cropland in Duolun and the fenced and grazed steppe in Xilinhot – in Inner Mongolia based on direct measurements from four eddy-covariance flux towers. The seasonal changes in Rn, LE, H and G of the four sites were similar, with very low values during the period of snow cover from December to February, followed by a gradual increase in the growing season. The opposite seasonal patterns of the LE and H fraction resulted in significant seasonal changes in Bowen ratio (β). Human activity in cropland ecosystems not only resulted in a rapidly shift between LE and H, but also triggered a decrease in latent heat fraction because of a shortened growing season of crop plants. The significantly positive relationships between canopy surface conductance (gc) and LE/LEeq of all of the study sites suggested that a lack of precipitation coupled with high VPD conduced remarkable decreases of stomatal conductance. This could impede the latent heat partitioning of available energy (Rn − G) in semi-arid ecosystems, Inner Mongolia. The obvious decrease in the values of gc and the decoupling factor (Ω) in both the cropland and the degraded steppe suggested that land use change could depress latent flux fraction and increase its sensitivity to air and soil drought. 相似文献
962.
Cultivation and grazing altered evapotranspiration and dynamics in Inner Mongolia steppes 总被引:2,自引:0,他引:2
Haixia Miao Shiping Chen Jiquan Chen Wenli Zhang Ping Zhang Long Wei Xingguo Han Guanghui Lin 《Agricultural and Forest Meteorology》2009,149(11):1810
To examine the effects of cultivation and grazing on evapotranspiration (ET), continuous measurements of ET were conducted over almost two years, from December 2005 to September 2007, using the eddy-covariance technique in two paired ecosystems: a steppe and a cropland in Duolun and a fenced and a degraded steppe in Xilinhot, Inner Mongolia, China. The ET of the four ecosystems approached or exceeded precipitation in both years. During the growing season (May–September), cultivation reduced the ecosystem ET in Duolun by 15% in the wet year (2006) and 7% in the dry year (2007). Grazing reduced the ET of the steppe in Xilinhot by 13% during the growing season of 2006, while there was similar ET between the degraded and fenced steppes in 2007. The low soil moisture in the cropland and the degraded steppe compared with the steppe at each area was the reason for the decrease in ET of the steppe ecosystems. In addition, a shorter growing period during the growing season, due to the changes in type and phenology characteristics of the vegetation associated with cultivation, was suspected for the reduction in ET in Duolun. The low soil moisture, due to the low precipitation in the dry year, limited vegetation growth and decreased canopy surface conductance (gc), resulting in reduced plant transpiration. In addition, cultivation and grazing increased the sensitivity of ET to soil moisture in the dry year, suggesting that future changes in precipitation would not only affect ET by changing soil moisture directly, but would also influence the relationship between ET and soil moisture. 相似文献
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966.
猪细小病毒SYBR Green Ⅰ模式实时定量PCR检测方法的建立 总被引:1,自引:0,他引:1
根据GenBank猪细小病毒(PPV)的NS1基因序列,设计一对特异性引物,采用SYBR Green Ⅰ随机结合渗入法,建立实时定量PCR检测方法,构建了检测PPV的标准DNA模版,循环阈值(Ct)与标准质粒DNA模板在7.8×101~7.8×108拷贝/μl浓度范围内呈良好的线性关系,相关系数为0.997。该方法用于猪细小病毒的检测具有很高的特异性,其敏感性与常规PCR相比可以提高100倍,可以用于猪细小病毒的快速检测。 相似文献
967.
Determination of isoflavones in red clover by capillary electrophoresis with electrochemical detection 总被引:5,自引:0,他引:5
Capillary electrophoresis with electrochemical detection (CE-ED) was employed to analyze isoflavones in red clover (Trifolium pratense). The effects of potential of working electrode, pH and concentration of running buffer, separation voltage and injection time on CE-ED were investigated. Operated in a wall-jet configuration, a 300 microm diameter carbon-disk electrode was used as the working electrode, which exhibits a good response at +0.85 V (versus saturated calomel electrode) for the analytes. The analytes could be separated in a 50 mmol/l borate buffer (pH 9.5) within 25 min. The response was linear over three orders of magnitude with detection limit (S/N=3) ranging from 2x10(-5) mg/ml to 5x10(-5) mg/ml for the analytes. This method has been used for the determination of daidzein, genistein and biochanin A in red clover with satisfactory results. 相似文献
968.
969.
Ye Tingqi Wu Jiayan Mu Cuimin Pan Guangchen Chen Jiakang Wang Xuepeng 《Aquaculture International》2021,29(3):1233-1243
Aquaculture International - Edwardsiella piscicida (E. piscicida) is a common pathogen in freshwater and marine environments and an important intestinal pathogen of fish. Fucose large presence in... 相似文献
970.