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Browsing by Author "Zhang, C."

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    Application of Radarsat imagery on grassland heterogeneity assessment
    (2005-02-17) Zhang, C.; Guo, X.; Wilmshurst, J.; Sissons, R.
    Heterogeneity, the degree of dissimilarity, is one of the most important and widely applicable concepts in ecology. It is highly related to ecosystem condition and wildlife habitat. In this study, the feasibility of applying Radarsat-1 HH polarization Synthetic Aperture Radar (SAR) image on heterogeneity study is tested on the Grasslands National Park (GNP) and surrounding pastures. GNP is located in southern Saskatchewan along the international boundary of Canada and the United States, which represents northern mixed grasslands. Fieldwork was conducted at GNP and surrounding pastures from June to July, 2003. Biophysical variables including species composition, cover, biomass, and canopy height were collected from 10 sites. Height heterogeneity index, Shannon’s index, and standard deviation were calculated based on field data. One standard mode Radarsat-1 HH image acquired on August 1, 2003 was used for this study. Parameters from texture analysis and standard deviation of the backscatters are correlated with biophysical parameters to measure grasslands heterogeneity. Results showed that different parameters had various abilities to detect field heterogeneity. Correlation showed the highest ability to explain variation of bareground cover (79%). Mean and contrast can also be utilized to explain the variation of grass biomass and standing dead cover (59% and 56% respectively).
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    Enhanced UV-B effects on wheat under different temperature, solar light, and soil moisture
    (2004-02-19) Zheng, Y.; Guo, X.; Zhang, C.
    Ultraviolet radiation-B (UV-B) will increase in the future due to the Ozone depletion; global climatic factors, such as temperature, precipitation, evapotranspiration, soil moisture and CO2 content, are changing because of the increase of greenhouse emission and the destruction of ecosystems. Both of them have effects on crop production. Many studies have assessed the effects of enhanced UV-B on crops and impacts of global climatic change on crops separately. However, when UV-B effects were discussed, other environmental factors were generally neglected. It is well-known that crops in nature are seldom affected by only a single stress factor, such as UV-B radiation. The impacts of elevated UV-B radiation can be greatly increased or decreased by other environmental factors. In this paper, through field and plant growth chambers experiments, interactional effects of enhanced UV-B radiation with other environmental factors including solar visible light, temperature and soil moisture content were investigated on wheat fields. The experimental results show that increased UV-B can restrain growth and development of wheat, which leads to shortening plant height, reducing leaf area, slowing physiological activity and decreasing biomass and yield of wheat. The response of wheat to enhanced UV-B varied with UV-B intensity and climatic conditions. While in stress, some of the climatic factors cause screening or weaken effects of UV-B on wheat to some extent.
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    Implementation of marker-assisted selection for lodging resistance in pea breeding
    (2003-02-18) Zhang, C.; Tar’an, B.; Warkentin, T.
    Lodging resistance is a key criterion in pea breeding programs. In traditional breeding, a large number of lines are discarded in F3 or later generations, because of susceptibility to lodging and much labor and other costs are wasted. Implementation of selection using molecular markers for lodging resistance at earlier generations will significantly enhance the efficiency of the pea breeding process. Ten F2 populations consisting of a total of 869 plants were grown in the field in Saskatoon in the summer of 2002. These 10 populations were derived from crosses between the lodging susceptible variety Carrera, crossed with ten other lodging resistant lines. DNA samples were extracted from each individual plant. Each plant was scored for the presence of coupling phase linked SCAR markers A001 and A002, as well as a repulsion phase linked SCAR marker A004. The results showed that the frequency of marker presence is similar to the estimated frequency, obeying the rule of independent single gene segregation. Chi-Square analysis showed that the combination of A001 and A004 markers also followed a two gene model (P>0.05) in 8 populations. Due to linkage between A001 and A002 markers, population No. 3 and No. 4 did not follow the two or three independent gene segregation model. F3 populations will be planted in the field in 2003 to evaluate the effectiveness of Marker Assist Selection for lodging resistance in pea.