UNIVERSITY GRADUATE SCHOOL
BULLETIN
Doctoral Dissertation
Defense
Vegetation Dynamics and
Their Implications for the Management of Wetlands in the Lowlands of Nepal
by
The maintenance of species richness on a local scale
is often a priority in the management of nature reserves, where consumptive use
of resources is generally prohibited. The purpose of this research was to
improve management by understanding the dynamics of subtropical wetland systems
in the lowlands of Nepal. The objectives were to determine vegetation
associations in relation to physical environments and human-induced
disturbances that affect diversity and vegetation dynamics on floodplains, where
periodic flooding and associated fluvial
processes have been altered by dams and barrages, and consumptive use of
plant resources is an integral and unavoidable factor influencing natural
processes.
Floodplain vegetation in relation to physical environments
and disturbances were studied in a series of 20m x 20m quadrats along transects, laid perpendicular to the
course of the Mahakali River in the western Terai of Nepal. Forest structural
changes in relation to flooding and livestock grazing were studied for three
years in ten 0.75 ha permanent plots. A randomized split-block
experiment with nine treatments resulting from combinations of burning
(unburned, early-burned, and late-burned) and grazing (ungrazed, lightly-grazed
and heavily-grazed) treatments was performed in seasonally flooded Imperata cylindrica-Vetiveria
zizanioides grasslands. A semi-structured questionnaire was used to
assess local people’s socio-economic status, natural resource utilization
patterns and conservation attitudes. Two-way species indicator analysis and ordination
techniques were applied to identify vegetation assemblages in relation to
environmental factors. Statistical differences among treatments were analysed
using analysis of variance (ANOVA) and Tukey’s test for pair-wise comparisons.
Categorical socio-economic data were analysed using non-parametric tests. Logistic regression was used to determine
whether demographic and economic variables explained conservation attitudes.
Elevation, soil organic
matter and grazing intensity determined herbaceous vegetation assemblages,
whereas elevation and soil nitrogen were significant in defining boundaries
between different forest types. On the rarely flooded islands, highly grazed D.
sissoo-A. catechu forests were devoid of understory woody vegetation,
including seedlings and saplings of tree species, but the lightly grazed D.
sissoo-mixed forests had a well-developed second canopy layer, comprising
woody species other than D. sissoo and A. catechu. In grasslands, species
richness and biomass production were highest at moderate disturbance level
represented by the lightly grazed and ungrazed early-burned plots. The
proportion of Imperata cylindrica in
total live biomass showed an increasing trend with the disturbance intensity,
while Vetiveria zizanioides showed an
opposite trend. Ethnicity, educational level and resource utilization were
important in influencing local people’s conservation attitudes.
A succession towards the mixed forests would occur in D. sissoo-dominated floodplain forests, where dams and barrages reduce flooding and associated fluvial processes, and if livestock grazing declines or is stopped, as occasionally suggested by strict nature conservationists. In seasonally flooded grasslands, early burning with moderate grazing would enhance the species diversity and productivity. There is a need to implement a participatory integrated management plan, to include community development, education and off-farm income generation, to assure participatory conservation and management of wetlands in Nepal.
Date: July 25, 2002 Department:
Biological Sciences
Time: 11:00 a.m. Major
Professor: Prof. David W. Lee
Place: University Park, WC130