Biomass Essay, Research Paper

Many factors contribute to the diversity of life in an environment. The

availability of nutrients and sunlight, along with other factors that play a

pivotal role in determining what and how much life an area can sustain. While

studying the Second Law of Thermodynamics, it came to my attention that the

classical pyramid shape of the producer, C1, C2, C3, biomass pyramid did little

to take into account the amount of detrital input. I hypothesized that the

amount detrital input greatly effected the number of C1, C2, and C3 consumers

and thus the overall biodiversity of an ecosystem. Further, if you could find a

test-bed where detrital input was the only real difference between two similar

ecosystems you would find that organisms of each ecosystem would be adapted to

the peculiar conditions. This adaptation would lead you to find vast differences

in the taxonomic groups associated with each ecosystem. With this in mind, I

first set out to find two similar ecosystems were I could test this hypothesis.

Second, to sample, categorize and compare the diversity of these ecosystems

along taxonomic lines. Next, I planned to use several of the widely accepted

diversity indexes (Simpson?s Index, Shannon?s Index the Chi-Square Test) to

compare statistically, the diversity of my ecosystems. Scientific Law states

that in order to test the effects of one factor in an equation you must

eliminate all other factors . In order to test the detrital base as the limiting

factor, all other limiting agents must be eliminated. In a field experiment this

is technically impossible; though it is possible to come close by choosing two

ecosystems that are very similar. In order to keep this experiment as simple as

possible the ecosystem chosen had to be nearly self contained and small. The

smaller and more contained the ecosystem the less chance for outside input that

could destroy our results. Alazan and Bernaldo creek provided just the type of

test-bed needed for this experiment. Both are third order creeks in the same

geographic area that are subject to same weather and climate conditions, but

differ considerably in the amount of detritus available. (Fleet) Procedure

Alazan creek is a third order stream that feeds into the Angelina River. It is

bordered by several species of indigenous trees that form a small gallery of

overhanging branches. This gallery consisted of (pine, oak, sweetgum trees) and

was limited to a range of about twenty five feet from the edge of the stream.

These gallery trees are surrounded by open cattle grazing fields covered by

short grasses and an occasional scrub brush. Alazan creek ranged from ten to

fifteen feet wide with a water depth of six inches to two feet. The water was

generally clear, and flowed at a brisk ten to twelve mile per hour pace. The

creek bottom was primarily sand with little or no mud. Turbitity was low to

moderately low and the creek had a high oxygen content. Detrital input was low

and limited to leaves from the gallery trees. Bernaldo creek is a third order

creek that similarly empties into the Angelina River. Bernaldo creek differs

substantially in that it is entirely surrounded by typical east Texas piney

woods. (The particular area that samples were taken from appeared to be

relatively low lying in comparison to the surrounding woods.) It is likewise ten

to fifteen feet wide but, is considerably deeper at four to eight feet than

Alazan creek. Bernaldo creek flows at a much slower pace, approximately six to

eight miles per hour. The bottom of Bernaldo creek consists largely of mud,

which gives the water a darker color. Overall turbitity is high and overall

oxygen content is low. Human disturbance at both creeks was minimal. Although at

Alazan creek the surrounding area was used for grazing animals and at Bernaldo

creek the sight that specimen were actually taken from was a concrete washout

bridge. Both sights appeared to be in a flood plain, one that probably becomes

inundated on a monthly basis during the rainy season. Weather conditions at the

time of the sampling were typical of east Texas in spring, therefore unusual

conditions caused by atypical weather can be eliminated. What it boils down to

is, the only difference between the two creeks was the amount of detrital

material available and the conditions predicated by this difference. Starting

the week of February 8, 1999 daily 1p.m. trips were made by four lab groups to

both Alazan and Bernaldo creeks. During these trips observations were made on

terrain, topography, climate, vegetation and specimens were taken from several

spots along each creek. The specimen were taken by netting at various depths and

locations. The nets used had a pore size of approximately 2 millimeters on four

sides and a canvas bottom (see diagram 1) and were attached to poles 8 feet

long. In order to take a sample, a student placed the scoop nets open end up

stream and allowed the water and it?s contents to be strained. The nets were

then quickly pulled from the water and the samples collected were immediately

taken to opened garbage bags and sorted through. (see diagram 2) When any living

creature was found, it was placed in a collection jar (labeled for the

particular creek it was taken from) to be examined later. The collection jars

contained an organic die known as FAA. FAA is a combination of formalin, ethyl

alcohol, and Rose Bengal and tints most of the small ?bugs? a red/pink

color. The following week each lab examined the specimen jars one by one and

separated the contents by taxonomic groups. Once each creek?s specimens had

been counted and categorized by class period, a list was compiled for the weeks

totals. This list was then used to test by comparison the validity of our

hypothesis. (for the complete list and breakdown see chart 1) Results The

hypothesis I was attempting to prove had three parts. The first and most general

was the creek with the greater detrital base would have greater biodiversity.

This can be proven in several ways. The first is to simply count the number of

species present in each of the two creeks and compare the results. This is

called richness, which is the number of species/taxonomic groups. In that case

Alazan creek contained 13 species/ taxomic groups and Bernaldo creek had 17.

Therefore, Bernaldo creek which had the greater detrital base had 4 more species

than Alazan creek. A second part of counting species is to determine the

evenness of the the creeks. Evenness is the measure of how evenly divided the

individuals are among the taxonomic groups. Bernaldo creek had Next I used

several of the accepted diversity indexes to statically prove which creek had

the greater diversity. Simpson?s Index is the number of times it would take to

pick two individuals of the same species/taxonomic group. Simpson?s index is

calculated by the equation: D = {N(N-1)} / {En(n-1)} Where: N=Total number of

species/taxonomic groups n=Number of individuals of a species. (Cox) In this

case Bernaldo creek had a Simpson?s Index of .017712946 and Alazan creek had a

Simpson?s Index of .0092367032. That?s a difference of .0084762429, or a 91

% greater chance of getting two of the same organisms. This shows a

significantly greater level of diversity for Bernaldo creek than for Alazan.

Shannon?s Index in determined by the equation: H?=3.3219[log N - 1/N E(Ni

log Ni)] With ?N? being the total number of individuals in the sample,

?Ni? being the number of individuals in each species/taxonomic group, and

?E? being the summation of all logs. (Cox) Bernaldo creek had a Shannons

Index of 2349.0908. Alazan creek had a Shannon?s Index of 1876.1630. That?s

a difference of 473.9278, or approximately 40%. The proves that the diversity in

Bernaldo creek is higher than the diversity of Alazan creek. ?The null

hypothesis that the two Shannon diversity indices come from communities equal in

diversity can be tested by a test a ?t? test.? This test is used to

calculate chance of a type one error. The equation for this is: t = (H1 – H2) /

Sd The ?t? value for the above was 3.290 significantly within our accepted

margin of error .0005. (t=3,290P,.0005) Next, the Chi-Square test was performed,

it?s information is given by the equation: X^2=E{(observed-expected)} /

expected Where: expected value is given by {(row total x column total) / grand

total} and ?E? is the summation. (Cox) In this case (X^2 = , P,.005)

Discussion The evidence collected in our study significantly proves the

hypothesis. All of the confidence intervals were met and exceeded in each test

with out exception. This was also the case with each of my peers that performed

this experiment. Although this increases the general knowledge on the impact of

detrital input into a system there is more to be learned. There were three main

sources of potential errors in this experiment. First, there needed to be more

samples taken from more places and at different times of the year. Four

samplings from one spot on the creek are not enough to draw conclusions about

the entire system. What if the area tested was near some source of point

pollution? This could have an effect on the immediate area but cause no down

stream effects due to rapid break down, or simple dilution. What if the area

picked was more diverse during summer? Next, an unforeseen problem occurred when

the crayfish began eating many of the ?bugs? in the collection jars. This

caused many of our species/taxonomic groups to be under represented because they

got eaten before they could be counted! What about animals that were so small

they slipped through the holes in the nets? What about burrowing worms? None of

these animals are represented in the sampling. Had these species/groups been

represented some of the statistics might have been a little different. In the

future this test should be modified in a manner to correct some of the

afore-mentioned problems. With those modifications a person could build an even

stronger case to support the hypothesis.