Twenty-six stocker cattle (286.1 ± 25.7 kg) were used to quantify the effect of commercial plant tannin extracts (control vs. mimosa and chestnut tannins) on animal performance, gastrointestinal parasites control...Twenty-six stocker cattle (286.1 ± 25.7 kg) were used to quantify the effect of commercial plant tannin extracts (control vs. mimosa and chestnut tannins) on animal performance, gastrointestinal parasites control and plasma metabolite changes in heifers grazing winter wheat forage (Triticum aestivum L. var. “cutter”). The forage biomass and crude protein content were generally similar among treatments. Initial live-weight (LW) was similar among treatments, although final LW (P = 0.1) and average daily gain (ADG;P P Ostertagia was lower (P P P < 0.02) for chestnut tannins group than for control, and intermediate for mimosa tannins. However, cholesterol level was similar among treatment after 20 days cessation of tannins treatments. Our data suggest that heifers grazing winter wheat forage supplemented with plant tannins rather than control (non-tannins group) increased ADG (8% to 19%) for mimosa and chestnut tannins groups, respectively with no detectable detrimental effects on animal health. The increase in ADG may be due to decrease fecal parasites infections.展开更多
To identify the main sources responsible for soil heavy metal contamination, 70 topsoils were sampled from the Daxing County in the urban-rural transition zone of Beijing. The concentrations of heavy metals Cu, Zn, Pb...To identify the main sources responsible for soil heavy metal contamination, 70 topsoils were sampled from the Daxing County in the urban-rural transition zone of Beijing. The concentrations of heavy metals Cu, Zn, Pb, Cr, Cd, Ni, As, Se, Hg, and Co; the soil texture; and the organic matter content were determined for each soil sample. Descriptive statistics and geostatistics were used to analyze the data, and Kriging analysis was used to estimate the unobserved points and to map the spatial patterns of soil heavy metals. The results showed that the concentrations of all the soil heavy metals exceeded their background levels with the exception of As and Se. However, only the Cd concentration in some areas exceeded the critical value of the national soil quality standard. The semivariance analysis showed that the spatial correlation distances for soil Cu, Zn, Cr, Cd, As, Ni, and Co ranged from 4.0 to 7.0 km, but soil Se, Pb, and Hg had a larger correlation distance. Soil Co, Se, Cd, Cu and Zn showed a strong spatial correlation, whereas the other soil heavy metals showed medium spatial correlation. Soil heavy metal concentrations were related to soil texture, organic matter content, and the accumulation of heavy metals in the soils, which was because of air deposition and use of water from the Liangshui, Xinfeng, and Fenghe rivers that are contaminated by wastewater and sewage for the purpose of irrigation of fields. Hence, a comprehensive treatment plan for these rivers should be formulated.展开更多
Field studies were conducted at Bushland, Texas, USA, in 2004 to examine usefulness of canopy temperature depression (CTD), the difference of air-canopy temperature, in screening wheat (Triticum aestivum L.) genot...Field studies were conducted at Bushland, Texas, USA, in 2004 to examine usefulness of canopy temperature depression (CTD), the difference of air-canopy temperature, in screening wheat (Triticum aestivum L.) genotypes for yield under dryland and irrigated. Forty winter wheat genotypes were grown under irrigation and dryland. CTDs were recorded after heading between 1 330 and 1 530 h on 6 clear days for dryland and 9 days for irrigation. Drought susceptible index (DSI) for each genotype was calculated using mean yield under dryland and irrigated conditions. Genotypes exhibited great differences in CTD under each environment. The dryland CTDs averaged 1.33℃ ranging from -0.67 to 2.57℃, and the average irrigation CTD were 4.59℃ ranging from 3.21 to 5.62℃. A low yield reduction was observed under dryland conditions relative to irrigated conditions for high-CTD genotypes. CTD values were highly negatively correlated with DSI under dryland, and genotypes of CTDs = 1.3℃ in dryland condition were identified as drought resistant. For 21 genotypes classified as drought resistant by DSI, their CTDs were 1.68℃ for dryland and 4.35℃ for irrigation on average; for 19 genotypes classified as drought susceptible by DSI, average CTD was 0.94℃ in dryland and 4.85℃ in irrigation. The high-yield genotypes consistently had high CTD values, and the low-yield ones had low CTD values for all measurements in dryland. After heading, genotypes maintained consistent ranking for CTD. Regression results for CTD and yield suggested that the best time for taking CTD measurement was 3-4 weeks after heading in irrigation but any time before senescence in dryland. Crop water stress index (CWSI) calculated from CTD data was highly correlated with CWSI calculated from yield, which suggesting traditional costly CWSI measurement may be improved by using portable infrared thermometers. Most importantly, grain yield was highly correlated with CTD under dryland (R^2 = 0.79-0.86) and irrigation (R^2 = 0.46-0.58) conditions. These results clearly indicated grain yield and water stress can be predicted by taking CTD values in field, which can be used by breeding programs as a potential selection criterion for grain yield and drought resistance in wheat, but a second study year is needed to confirm further.展开更多
The functional response of Cydonia vicina nilotica Muls. (Coleoptera: Coccinellidae) to six densities of Aphis craccivora Koch (Homoptera: Aphididae) nymphs on broad bean (Viciafaba Linn.) was investigated in ...The functional response of Cydonia vicina nilotica Muls. (Coleoptera: Coccinellidae) to six densities of Aphis craccivora Koch (Homoptera: Aphididae) nymphs on broad bean (Viciafaba Linn.) was investigated in the laboratory. A linear relationship between the rate of consumption and prey density was observed with r^2 values between 0.58 and 0.97. Plotting prey density against prey killed by four larval instars, and adult males and females of C. vicina nilotica fit well with the type Ⅱ model of Holling' s disc equation. Adult females consumed the highest number of prey, followed by fourth instars and adult males. Based on the functional response data, the model predicts a maximum of 144.9, 116.3, 86.2, 80.0, 72.5 and 20.0 nymphs to be consumed per day by an individual adult female, fourth instar, adult male, third, second and first instars, respectively. The differences in the responses of the predator to aphid densities are discussed.展开更多
The pine caterpillar, Dendrolimus tabulaeformis is one of the most important pests on Pinus tabulaeformis and other pine species in North China. In the present study, effects of relative humidity (RH) on the develop...The pine caterpillar, Dendrolimus tabulaeformis is one of the most important pests on Pinus tabulaeformis and other pine species in North China. In the present study, effects of relative humidity (RH) on the development and survival of pine caterpillars and soil moisture (SM) on their diapausing larvae were investigated. Low RH (20%) deferred the development of eggs and larvae, reduced egg hatching and larval surviving compared to 40%, 60% and 80% RH. Both low (20%) and high (100%) RH reduced egg hatching, but only 20% RH deferred the development of larvae, prolonged developmental duration and reduced the body mass and body length of larvae. The SM influenced the survival of diapausing larvae significantly. The dry treatment significantly reduced the supercooling points (SCPs), whereas increased the mortality and reduced body mass from 56.9 to 36.5 mg and body water content from 78% to 63% after 2 weeks' exposure. Therefore, higher RH is more favorable for the development of early instars and survival of diapausing larvae of the pine caterpillars.展开更多
文摘Twenty-six stocker cattle (286.1 ± 25.7 kg) were used to quantify the effect of commercial plant tannin extracts (control vs. mimosa and chestnut tannins) on animal performance, gastrointestinal parasites control and plasma metabolite changes in heifers grazing winter wheat forage (Triticum aestivum L. var. “cutter”). The forage biomass and crude protein content were generally similar among treatments. Initial live-weight (LW) was similar among treatments, although final LW (P = 0.1) and average daily gain (ADG;P P Ostertagia was lower (P P P < 0.02) for chestnut tannins group than for control, and intermediate for mimosa tannins. However, cholesterol level was similar among treatment after 20 days cessation of tannins treatments. Our data suggest that heifers grazing winter wheat forage supplemented with plant tannins rather than control (non-tannins group) increased ADG (8% to 19%) for mimosa and chestnut tannins groups, respectively with no detectable detrimental effects on animal health. The increase in ADG may be due to decrease fecal parasites infections.
基金Project supported by the National Natural Science Foundation of China (Nos. 40401025 and 49871005)the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT0412)
文摘To identify the main sources responsible for soil heavy metal contamination, 70 topsoils were sampled from the Daxing County in the urban-rural transition zone of Beijing. The concentrations of heavy metals Cu, Zn, Pb, Cr, Cd, Ni, As, Se, Hg, and Co; the soil texture; and the organic matter content were determined for each soil sample. Descriptive statistics and geostatistics were used to analyze the data, and Kriging analysis was used to estimate the unobserved points and to map the spatial patterns of soil heavy metals. The results showed that the concentrations of all the soil heavy metals exceeded their background levels with the exception of As and Se. However, only the Cd concentration in some areas exceeded the critical value of the national soil quality standard. The semivariance analysis showed that the spatial correlation distances for soil Cu, Zn, Cr, Cd, As, Ni, and Co ranged from 4.0 to 7.0 km, but soil Se, Pb, and Hg had a larger correlation distance. Soil Co, Se, Cd, Cu and Zn showed a strong spatial correlation, whereas the other soil heavy metals showed medium spatial correlation. Soil heavy metal concentrations were related to soil texture, organic matter content, and the accumulation of heavy metals in the soils, which was because of air deposition and use of water from the Liangshui, Xinfeng, and Fenghe rivers that are contaminated by wastewater and sewage for the purpose of irrigation of fields. Hence, a comprehensive treatment plan for these rivers should be formulated.
基金This study was financially supported by the China National 863 Program(2002AA2Z4011)the China National R&D Program(2004BA508B09)Texas wheat breed and physiology program.These assistances are gratefully acknowledged.We also thank Gail Petersion and Melanie Allred for their assistance when the study was going on.
文摘Field studies were conducted at Bushland, Texas, USA, in 2004 to examine usefulness of canopy temperature depression (CTD), the difference of air-canopy temperature, in screening wheat (Triticum aestivum L.) genotypes for yield under dryland and irrigated. Forty winter wheat genotypes were grown under irrigation and dryland. CTDs were recorded after heading between 1 330 and 1 530 h on 6 clear days for dryland and 9 days for irrigation. Drought susceptible index (DSI) for each genotype was calculated using mean yield under dryland and irrigated conditions. Genotypes exhibited great differences in CTD under each environment. The dryland CTDs averaged 1.33℃ ranging from -0.67 to 2.57℃, and the average irrigation CTD were 4.59℃ ranging from 3.21 to 5.62℃. A low yield reduction was observed under dryland conditions relative to irrigated conditions for high-CTD genotypes. CTD values were highly negatively correlated with DSI under dryland, and genotypes of CTDs = 1.3℃ in dryland condition were identified as drought resistant. For 21 genotypes classified as drought resistant by DSI, their CTDs were 1.68℃ for dryland and 4.35℃ for irrigation on average; for 19 genotypes classified as drought susceptible by DSI, average CTD was 0.94℃ in dryland and 4.85℃ in irrigation. The high-yield genotypes consistently had high CTD values, and the low-yield ones had low CTD values for all measurements in dryland. After heading, genotypes maintained consistent ranking for CTD. Regression results for CTD and yield suggested that the best time for taking CTD measurement was 3-4 weeks after heading in irrigation but any time before senescence in dryland. Crop water stress index (CWSI) calculated from CTD data was highly correlated with CWSI calculated from yield, which suggesting traditional costly CWSI measurement may be improved by using portable infrared thermometers. Most importantly, grain yield was highly correlated with CTD under dryland (R^2 = 0.79-0.86) and irrigation (R^2 = 0.46-0.58) conditions. These results clearly indicated grain yield and water stress can be predicted by taking CTD values in field, which can be used by breeding programs as a potential selection criterion for grain yield and drought resistance in wheat, but a second study year is needed to confirm further.
文摘The functional response of Cydonia vicina nilotica Muls. (Coleoptera: Coccinellidae) to six densities of Aphis craccivora Koch (Homoptera: Aphididae) nymphs on broad bean (Viciafaba Linn.) was investigated in the laboratory. A linear relationship between the rate of consumption and prey density was observed with r^2 values between 0.58 and 0.97. Plotting prey density against prey killed by four larval instars, and adult males and females of C. vicina nilotica fit well with the type Ⅱ model of Holling' s disc equation. Adult females consumed the highest number of prey, followed by fourth instars and adult males. Based on the functional response data, the model predicts a maximum of 144.9, 116.3, 86.2, 80.0, 72.5 and 20.0 nymphs to be consumed per day by an individual adult female, fourth instar, adult male, third, second and first instars, respectively. The differences in the responses of the predator to aphid densities are discussed.
基金This research was supported in part by the Key Program of National Natural Science Foundation of China (30330490) and China Spark Program (2006EA740049).
文摘The pine caterpillar, Dendrolimus tabulaeformis is one of the most important pests on Pinus tabulaeformis and other pine species in North China. In the present study, effects of relative humidity (RH) on the development and survival of pine caterpillars and soil moisture (SM) on their diapausing larvae were investigated. Low RH (20%) deferred the development of eggs and larvae, reduced egg hatching and larval surviving compared to 40%, 60% and 80% RH. Both low (20%) and high (100%) RH reduced egg hatching, but only 20% RH deferred the development of larvae, prolonged developmental duration and reduced the body mass and body length of larvae. The SM influenced the survival of diapausing larvae significantly. The dry treatment significantly reduced the supercooling points (SCPs), whereas increased the mortality and reduced body mass from 56.9 to 36.5 mg and body water content from 78% to 63% after 2 weeks' exposure. Therefore, higher RH is more favorable for the development of early instars and survival of diapausing larvae of the pine caterpillars.