Hari Ram Shrestha
Department of Forest and Ecosystem Science
The University of Melbourne, Creswick Campus
Water Street, Creswick, VIC, 3363, Australia
Email: h.shrestha@pgrad.unimelb.edu.au
Phone: +61 03 5321 4130, 0412 341 165(M)
Fax: +61 03 5321 4166
Degree
M For.Sc. by Research
Duration - Two years (Aug., 2007- 2009)
Thesis title
Biological nitrogen fixation by legumes in an alpine ecosystem in south eastern Australia
Supervisors
Project Rationale and Description
Biological Nitrogen Fixation by Legumes in an Alpine Ecosystem
Biological Nitrogen Fixation (BNF) is one of the fundamental processes to life in Earth and it has been estimated that about 108 tones of nitrogen are annually added to the soil by BNF. In addition, it is widely believed that 75% of total BNF is contributed by root nodules of legumes. The measurement of N2 fixation is important to understand the relative contribution of N2 fixing component to the N-cycle.
In Australia, wildfires are very common in alpine and subalpine areas during summer months and South-eastern Australia is known to be one of the most fire-prone environments in the world. For example, Bogong High Plains in Victorian Alps were repeatedly burnt by extensive and severe wildfires in 1926, 1939, 1985, 1998, 2003 and most recently in 2006.
Wildfires affect the physical, chemical and biological properties of soil and nitrogen is lost through volatilization and soil leaching which greatly alters the N budget of plant community. Despite this nitrogen loss, soil ammonium (NH4+) pool may be increased in recently burnt sites and considerable organic N may be present in the ash which could provide an important source of N after fire.
In Eucalyptus forests, leguminous species such as Acacia spp. and Davesia spp. germinate in large numbers after fire. After landscape scale wildfire in 2003, there was massive regeneration of Mountain Hickory Wattle (Acacia obliqunervia) with the density in 2005 up to 3, 00,000 seedlings per hectare in mature Alpine Ash forests near Falls Creek, Victoria. Though Acacia spp. are common understory layer in Eucalyptus forests in alpine region, their contribution to soil fertility by atmospheric nitrogen fixation and their role to replace the N lost due to fire in alpine ecosystem are poorly documented.
There are both direct and indirect methods for measuring BNF but no one technique will provide an accurate measure of nitrogen fixation for all legumes growing under diverse environmental conditions as each technique has its own advantages and limitations. In natural forest ecosystem, the 15 N natural abundance method is the only suitable method available for quantitative estimations for symbiotic nitrogen fixation and has been used by many researchers. This method is based on small differences in the natural abundance of 15 N between atmospheric nitrogen and other nitrogen sources available to nitrogen fixing systems. In general, soil nitrogen is usually more abundant in 15 N than in atmospheric nitrogen. Soil nitrogen is most often more abundant in 15 N than atmospheric nitrogen. Non- nitrogen fixing plants, whose primary source of nitrogen is soil derived nitrogen, would be expected to be more abundant in 15 N than nitrogen fixing plants which take nitrogen from the atmosphere as well as from the soil. This method assumes that isotopic fractionation during nitrogen fixation is nil or a known constant value. The major advantage of the natural abundance technique is that no pre-treatment with 15 N salts is required and can be applied to existing experiments or a tree growing in plantations or forests and this method doesn’t disturb the natural system. However, this method can only be used when certain conditions are met as there should be sufficiently large difference in the 15 N values between soil nitrogen and atmospheric nitrogen.
This study aims to quantify the biological nitrogen fixation by several legume species in sub-alpine and alpine regions in South-eastern Australia. Field works will be done in study sites established in 2002; Falls Creek Road, Switch Back and Buckety Plains in Alpine Ash forests and Transect 1, 3 and 5 in Bogong High Plains. Foliage samples of legumes and reference plants (non-legume species) as well as soil samples have been collected from all sites with different depths (0-5 cm; 5-10 cm; 10-15 cm and 15-20 cm). Collected field samples have been analyzed at Department of Forest and Ecosystem Science laboratory, Creswick. Primary data like concentration of 15N, 13C, total N, C etc in foliage samples and concentration of 15N, Nitrate, Ammonium, total N, C, soil MC, soil pH and EC etc of soil samples will be analyzed. On the basis of concentration of 15N in foliage of both legume and reference plants as well as in soil, 15N natural abundance method will be used to quantify the BNF by legume species. Then, above ground biomass of legume species will be measured in field to calculate the N productivity of legumes for the estimation of seasonal and/or annual input of fixed N per hectare in study sites.
The finding of the study will be presented in a seminar and research findings will be disseminated in the form of research report.
Interests and Background
I am broadly interested on nutrient cycling in forest ecosystems, especially nitrogen cycle and nitrogen fixing species and their input of N to forest ecosystems. I am also interested in microbial activities in soil and fluxes of greenhouse gases e.g. methane, carbon dioxide and nitrous oxide from forest ecosystems.
I have received B.Sc. Forestry Degree in 2003 from Institute of Forestry, Tribhuvan University, Pokhara, Nepal. Then, I joined Department of Forests, Government of Nepal as Forest Technician and involved in Planning, Implementation; Monitoring and Evaluation of Community Forestry Programs. Community Forestry is one of the most successful people based program in Nepal and the motto of this program is ‘By the people, for the people, of the people’.
Scholarships for M.Sc. Degree
Melbourne International Fee Remission Scholarship (MIFRS), University of Melbourne
Melbourne International Research Scholarship (MIRS), University of Melbourne
Qualifications
2005 - Masters Degree in Rural Development, Department of Humanities and Social Sciences, Tribhuvan University, Nepal
2003 - B.Sc. Forestry, Institute of Forestry, Tribhuvan University, Nepal
Project Paper – ‘An Assessment of Sustainability of Community Development Groups (CDGs) from Financial Perspective’ (A case study from Paudi-Khola sub-watershed area in Lamjung District, Western Nepal), submitted for the partial fulfillment of the B.Sc. Forestry degree to Institute of Forestry in 2003, Pokhara, Nepal.
1997- I. Sc. Forestry, Institute of Forestry, Tribhuvan University, Nepal
Work Experience
1998-1999 Forest Technician (Ranger), Department of Forests, Government of Nepal
2003-2007 Forest Technician (Ranger), Department of Forests, Government of Nepal
Training
- Initial Environment Examination (IEE) and Environment Impact Assessment(IEA)
- GIS for Forest Data Management
- Non-Timber Forest Products (NTFPs) Management
- Community Forest Resources Inventory
- Training of Trainers (TOT)
Professional Affiliations
Institute of Foresters of Australia (IFA)
Nepalese Foresters Association (NFA)
Ranger’s Association of Nepal (RAN)
Nepal GIS Society (NGS)
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