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RISS 인기검색어
- 검색키워드
- 저자 : Nadar, Madhumalini Muralikrishnan (검색결과 3 건)
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Estimation of methane and nitrous oxide emission from rice paddies and forest land
Khokhar, Nadar Hussain 한양대학교 대학원 2019 국내박사
Methane (CH4) and nitrous oxide (N2O) are important greenhouse gases after carbon dioxide (CO2), but there global and regional budgets are not well known. Rice paddies and forest land are two major land use systems of South Korea. In this thesis, we discussed CH4 emission in rice paddies, CH4 uptake and N2O emission in forest land. Beside CH4 estimation we proposed new simplified sampling scheme for estimation of CH4 emission in rice paddies. Instead of weekly or biweekly CH4 sampling throughout the season, we proposed five times one hourly samplings only in a season. We also monitored physical effect of precipitation on CH4 uptake in temperate forest soil. CH4 uptake increased with precipitation intensity. We measured N2O emission in forest from different leaflitter applications in (IN) and on (ON) soil. Leaf litter incorporation into soil exhibited higher N2O emission than leaf litter on soil, in this study. In chapter 2, We monitored CH4 emission from rice paddies for one complete rice-growing season. Daytime CH4 emission increased from 08:00 h, and maximal emission was observed at 12:00 h. Daily averaged CH4 flux increased during plant growth or fertilizer application and decreased upon drainage of plants. CH4 measurement results were linearly interpolated and matched with the daily averaged CH4 emission calculated from the measured results. The time when daily averaged emission and the interpolated CH4 curve coincided during the daytime was largely invariant within each of the five distinctive periods. One-hourly sampling during each of these five periods was utilized to estimate the emission during each period, and we found that five one-hourly samples during the season accurately reflected the CH4 emission calculated based on all 136 hourly samples. In chapter 3, we measured CH4 flux in a temperate forest soil immediately after variable volume of water applications equivalent to 10, 20 40, and 80 mm m-2 day-1 precipitation. CH4 uptake was significantly higher when the water was not applied. The CH4 uptake decreased significantly with increasing water application. CH4 uptake was linked with air filled porosity and water filled porosity. CH4 uptake response to actual precipitation intensity was in agreement with CH4 uptake results in this study. CH4 uptake decreased 55% at highest precipitation intensity. Since annual CH4 flux is calculated with interpolation of weekly or biweekly field observations, instant effect of precipitation can mislead the interpolated annual results. In chapter 4, N2O emission in temperate deciduous forest was monitored for one year. In this study, the effect of variations in leaf litter mass on N2O emission was observed. We measured N2O emission from different leaf litter applications: 0 (control), 370, 730, and 1009 g dry weight m-2 IN and ON soil. N2O emission decreased with leaf litter removal and increased with soil tilling. N2O emission increased significantly with increasing leaf litter mass from 370 to 730 g m-2 in both IN and ON treatments. N2O emission decreased in IN and ON treatments with leaf litter application of 1009 g m-2 due to high soil water content and carbon to nitrogen ratio. Soil temperature was weakly correlated with cumulative N2O emission in both IN and ON treatments. Average N2O emission in IN treatments was higher than ON treatments. Average N2O emission measured in temperate deciduous forest in this study was 752.4 g ha-1 y-1, which is 13.4% higher than the World average.
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Charting the Volunteering Characteristics of College Students In a Land-Grant University
Nadar, Madhumalini Muralikrishnan ProQuest Dissertations & Theses Auburn University 2019 해외박사(DDOD)
Volunteerism in the undergraduate years can be a predictor highly correlated with remarkable increase in social integrity, civic-mindedness, (Astin & Sax, 1998; Eyler & Giles, 1999; Pascarella & Terenzini, 2005; Vogelgesang & Astin, 2000; Cruce & Moore, 2007, 2012; Johnson, 2014; Plante & Halman, 2016), continued participation after college (Astin et al., 2000) and selecting service-oriented careers (Astin et al., 1999), which are attributes for accomplishing the land-grant university service mission. Distinguishing these environmental characteristics that influence volunteering will substantially benefit universities and colleges in concentrating on these measures to increase student participation.This quantitative study was conducted to understand the volunteering characteristics of college students in a land-grant university. Participants of this study were 8,318 college students enrolled from 2013-2018, that completed the National Survey of Student Engagement questionnaire. The research model controlled for the demographic characteristics and examined the college experience measures that influenced the intensity of volunteering in college students. Data analysis was conducted using descriptive statistics, Pearson Correlation and Multinomial regression analysis. Results from the logistic regression analysis validated that the suggested set of predictors considerably increased the odds of predicting volunteerism in college students of a land-grant university.Among the study sample 50.5% students had volunteered 1-5 hours during college in a land-grant university. The environmental characteristic variables that demonstrated higher likelihood to volunteering were athletic involvement and membership in a social organization. The demographic variables that presented greater likelihood to volunteering were gender, age, and race. The current study results were consistent with previous findings that majors like engineering, physical science and mathematics were constantly challenged to incorporate service into the curriculum in ways that provided applicable and meaningful learning for the college students (Felder & Silverman, 1988).The land-grant university being predominantly white, with a majority of traditional age group students enrolled full-time has multiple student groups volunteering 1-5 hours per week, suggesting that the institution has an established inclusive volunteering program on campus. Generally, integrating volunteering into the academic curriculum among all majors, that are practical and applicable can substantially increase student engagement and support land-grant universities in effectively achieving their service mission.
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