The study of allelopathy is important in identifying organisms that maybe useful as a herbicide or pesticide in a forestry or agricultural setting. Allelopathy refers to the detrimental effects that an organism has on another organism through the production of chemicals that escape into the environment through their roots or decomposing leaf litter.
Two bioassay methods were used to test the leaves of Rhododendron maximum L. and Pueraria lobata (Willd.) Ohwi, for their allelopathic potential. In the first bioassay, radish seedlings, Raphanus sativus L, were grown in soil and watered with one of seven treatments. In the second bioassay, radish seeds were germinated in Petri dishes containing five milliliters of one of seven treatments. For the plant species, Rhododendron maximum, Pueraria lobata, and Juglans nigra L., two concentrations were made. The high concentration extract contained one gram plant material to 20 milliliters of deionized water (1:20). The low concentration extract contained one gram plant material to 60 milliliters of deionized water (1:60). J. nigra served as a positive control, and the seventh treatment, deionized water, served as a negative control.
When leaf weight, root weight, and seedling
length were compared, the radishes treated with R. maximum 1: 20 and radishes
treated with R. maximum 1: 60 were found to be significantly less (p<.05)
than the H2O control. Radishes treated with P. lobata 1: 20 were
significantly shorter when seedling length was compared. Radishes
treated with P. lobata 1: 20 were significantly larger (p<.05) when
root and leaf weight were compared. These results suggest that Rhododendrons
do have allelopathic compounds within their leaves. The results indicate
that Kudzu may have allelopathic compounds, but the effects of those compounds
may be outweighed by the high nutrient content of the leaves when tested
There has been evidence of stratospheric ozone depletion causing an
increased amount of ultraviolet radiation (UVR) to reach the earth’s surface
in the past couple of decades. This increasing UVR has been shown to have
negative effects on marine organisms making it necessary to do more research
on the effects of UVR on marine ecosystems. There has been much work
with phytoplankton using high-resolution analysis to develop mathematical
functions for determining the effects of specific wavelengths on their
production. These analyses also have strong predictive power to determine
the effects of increased UVR. There has been little work with bacterioplankton
in determining these mathematical functions. With increasing evidence of
the importance of bacterioplankton in marine ecosystems, there is a need
to now develop these high-resolution analyses. Dr. Patrick Neale
at the Smithsonian Environmental Research Center has started working with
bacterioplankton using highly variable controlled indoor incubations to
develop functions. In the summer of 1999 I set out to do outdoor
exposures under natural solar irradiance to see if trends that show up
in indoor incubations were also showing up under natural conditions. Uptake
of radioactive 3H-Thymidine and 3H-Leucine substrates were used to measure
bacterial productivity. Samples were exposed for two and four hours
around solar noon with Schott filters allowing varying amounts of UVR to
pass. The results of this work showed uptake of isotope over the
second two hours of incubation was significantly less than the first two
even in dark control conditions. Many experiments were done to determine
the cause of the slow down. It was finally determined that the isotope
was being sequestered by particulate matter making it unavailable for bacterial
uptake. There will be much further work at the Smithsonian changing
experimental protocol to allow for incubations over two hours and looking
at response of bacteria under natural UVR.
Abstract: Tropical forests are diverse ecosystems that
are being destroyed rapidly. Reforestation attempts are being made
by Tropical Forestry Initiative, but the organization is still in the process
of gaining basic knowledge about the productivity of the tree species
used for reforestation. I participated for one summer in a long term
observational study of five permanent plots. Tree height, diameter
at breast height (dbh) and belt transect measurements were taken. Forest
structure diagrams of the plots were created to visually show growth from
year to year. Amarillon, Sura, and Mayo Blanco are found to have
the significantly (p < 0.05) highest mean height and dbh growth.
There was a positive correlation between mean growth rates of the plots,
and tree species diversity. Higher species diversity may be related
to higher mean growth rates because of the formation of structural layers
in the forest, and more efficient use of resources by the trees.
Beyond my results concerning the growth of the trees, I concluded that
Tropical Forestry Initiative could gain more knowledge about the reforestation
species by creating better communication between its North American and
Costa Rican members.
Abstract: The main objective of this study was to determine what
effect the addition of a 0.86-hectare parking lot had on the stream
that runs behind ANTC and Sutton dormitories. The watershed
for this stream was determined with IDRISI, a Geographical Information
System (GIS) program to be an 11-hectare area. Another program,
Generalized Watershed Loading Function (GWLF) was used to predict
total streamflow from the parking lot for an average year, using
weather data from the Asheville area. The GWLF predictions were backed
up by measurements taken during rain events. These predictions
were used to estimate a yearly loading amount for hydrocarbons and
sediment. The estimate for yearly hydrocarbon loading was taken
from a gas chromatograph/mass spectrophotometer (GC/mass spec) reading
for a sample taken during a December 13 storm event. The calculation
for concentration of hydrocarbons was taken from this sample by comparing
it to a GC/mass spec graph of a 10-ppm standard. The estimate
for yearly sediment loading was taken from the measurements of total
suspended solids taken from three rain events. The oil load
estimated for a one-centimeter rain event was 1.7 grams. The sediment
load was estimated as a range from 9.9 to 3.4 kg for a one-centimeter rain
event. The total yearly oil load was estimated at 168 grams.
The yearly sediment load was estimated to be between
Mentors: Dr. Mark Brenner, Dr. Victoria P. Collins
Abstract: Juglone (5-hydroxy-1,4-naphthoquinone), extracted from black walnut (Juglans nigra), has been shown to inhibit plant growth. Juglone may also inhibit the growth of soil micro organisms, including those beneficial to plants. This study investigated the effects of juglone on nitrifying bacteria by monitoring the conversion of NH4+ to NO3 - in soil. The effects of juglone (3.0 mg /g soil) and sterilization were compared in a 2 X 2 factorial design with 6 replicates/treatment. Each 5 g soil sample was incubated with 2.5 mg N (as (NH4)2SO4) /g soil for 19 days. Nitrate was measured at days 0 and 19 by washing each sample with 30 ml of water and determining the NO3- concentration with an ion-selective electrode. Juglone had no significant effect on soil nitrate levels. Autoclaved soil samples 0.012 + .003 and 0.0040 + .0006 mg nitrate N at days 0 and 19, respectively (mean + S.E.M). Unautoclaved samples contained 0.0040 + 0.0005 and 0.237 + 0.012 mg nitrate N at days 0 and 19, indicating nitrification was occurring in those samples, but the process was unaffected by juglone.
Abstract. Biodiesel is a clean burning mono-alkyl ester-based
oxygenated fuel. It is produced by mixing vegetable oil, lye, and
ethanol or methanol through the process of transesterification. Biodiesel
is less expensive, safer (with a lower flash point), and produces fewer;
less toxic emissions than petrodiesel. It is biodegradable and renewable.
One of the most positive aspects of biodiesel is that it can be prepared
using the twenty-two billion pounds of excess vegetable oils produced in
The objective of this study was to determine if biodiesel produced from used sources would produce a fuel of equitable quality as fuel produced from new sources of vegetable oil based on determinations of kinematic viscosity. I made three subsamples of each of the three new sources (corn, soy, and sunflower) and the three used sources (McDonalds, KFC, and Warren Wilson College Cafeteria).
The oil, sodium hydroxide, and methanol were combined and agitated at 70 degrees Celsius for six and hours and then allowed to settle. I performed viscosity tests on 9 subsamples of each used and new source. I failed to reject the null hypothesis, finding no significant difference between the viscosity new and used oil samples.
Mentor: Dr. Mark Boudreau
Abstract: This experiment is a practical study which
looks at several ways to control predation of soft-bodied insects on lettuce
plants. The research was inspired after an observational on a lettuce farm
on Kauai and was adapted for local pests and conditions. For 31 days, two
cultivars of lettuce were treated with various pest controls, including
neem oil, diatomaceous earth, and increased soil organic matter. Total
numbers of aphids were monitered, as well as fresh and dry biomass of the
shoots and roots. Both neem and diatomaceous earth reduced the number
of predators, while the lettuce grown in compost-amended soil showed an
increase in marketable yield. The results of this study mat be used as
reference information for lettuce growers aiming to control soft-bodied
Abstract: Niche partitioning is a phenomenon that occurs as one of three possible outcomes in the competitive exclusion principle. Gause's principle states that when two organisms occupy the same niche, there are three possible outcomes. Species A will replace species B, species B will replace species A, or the two species will separate niches so that they are exploiting different extremes of the resource (Gause 1934).
The objective of this experiment was to grow beans with and without radishes in a nutrient limited environment. The bean roots were then examined for horizontal and vertical distribution to determine if competition affected the distribution. We wanted to see if niche partitioning was occurring in the bean roots.
Horizontal distribution was analyzed by photographing both sides of each replicate on two different days. Each photograph was superimposed with a standardized grid, and divided into four quadrants. The percent root occupancy was determined for each sample on each day and subjected to a non-parametric two way ANOVA.
Vertical distribution was analyzed by harvesting the root material at 2 cm intervals and drying in an oven. These dry biomass values were subjected to a non-parametric two way ANOVA.
For both horizontal distribution tests, I found no significant difference for the competition factor, or the interaction of competition and quadrant location. Because there was no significant difference between the interaction factors, I was unable to reject my null hypothesis. I did, however, find a significant difference between the quadrant location factors.
For the vertical distribution test, I found no significant difference for the depth factor, or the interaction factors. I was not able to reject the null hypothesis. I did, however, find a semi-significant difference in the competition factor. Overall root biomass for plants grown with competition was higher than plants grown without competition.
Mentors: Dr. William C. Davis, Dr. Lou Weber
Abstract: Studying the soil seed bank can help foresters predict
what may come up in a stand after a disturbance like fire, storm, or harvest.
The soil seed bank is the accumulation of seeds in the soil until suitable
germination conditions occur. In the southern Appalachian mountains,
Liriodendron tulipifera (tulip poplar), Morus rubra (red mulberry), and
Oxydendrum arboreum (sourwood) are major tree components of the soil seed
bank. Ailanthus altissima (tree-of-heaven) is an invasive exotic
tree from China. It is a prolific seeder, stump sprouter, and root
sprouter as well as being allelopathic to competition. The objectives
of this study were to 1) inventory the soil seed bank on Jones mountain,
2) to determine if Ailanthus is present in the soil seed bank, and 3) to
determine the effect of fire on Ailanthus seeds.
In October, 1999, Thirty soil samples were taken on a 12m by 15m grid near a stand of Ailanthus on Jones mountain in Swannanoa, NC. The soil from each sample was sprinkled over flats in a greenhouse. Over several months, the emerging seedlings were identified, counted and removed. In February, 2000 the sampling site was burned. Thirty samples adjacent to each of the previous samples were taken and also put in flats in the greenhouse. Emergent seedlings from these samples were also identified, counted and removed.
In the pre-fire samples, 653,842 Ailanthus seedlings per acre, 159,479 Liriodendron seedlings per acre, 356,170 Phytolacca (pokeweed) seedlings per acre, 177,199 Taxacum (dandelion) seedlings per acre, 124,039 Lychnis (mullein) seedlings per acre, and 17,719 Sassafras seedlings per acre were found. In the post-fire samples, 354,399 Ailanthus seedlings per acre, 17,720 Liriodendron seedlings per acre, 53,160 Phytolacca seedlings per acre, and 17,720 Celastrus orbiculatus (oriental bittersweet) seedlings per acre were found.
Aside from having an inherent competitive advantage over native species
because of its pollution and stress tolerance, its ability to reproduce
both vegetatively and from seed, its allelopathy, and its high growth rate,
it seems that Ailanthus also has a great advantage in that it floods the
soil seed bank. So even if the seed source were eliminated and all
the stumps and root systems were treated, the buried Ailanthus seed would
greatly outnumber all native tree species. Fire may reduce the number
of viable Ailanthus seeds per acre, but not by much and not without reducing
the numbers of all other species as well. It is evident that there
is no feasible method of eliminating Ailanthus, but perhaps with years
of constant attention and treatment with fire and herbicide it can be prevented
from becoming a dominant tree species on the Warren Wilson forest.
Mentor: Dr. Mark V. Brenner
Abstract: The effects of trout farm effluents were determined
on Western North Carolina fish populations. Three trout farms were
sampled in the fall of 1999 using the three-pass DC electrofishing method
upstream and downstream from the trout farms. Salmonid abundance,
length, and weight were determined for each stream reach sampled.
Other fish family biomass was also determined for each stream reach sampled.
The temperature, pH, dissolved oxygen and ammonia content were also analyzed
for each upstream and downstream sampling reach. Rainbow (Oncorhynchus
mykiss), brook (Salvelinus fontinalis), and brown (Salmo trutta) trout
were found in the three streams. Rainbow trout was the only salmonid
found upstream and downstream of all three trout farms. Cyprinidae
and Cottidae were the two other fish families found. Total population
and biomass estimates of rainbow trout alone and all salmonids were not
significantly different upstream and downstream from the trout farms.
No significant difference was found between the pH and dissolved oxygen
levels upstream and downstream from the trout farms. There was a
significant difference in the level of ammonia found upstream and downstream
from the trout farms. There was considerable variability in the data
obtained from the three streams sampled suggesting that more trout farms
should be sampled.