Ecology

Effects of Leaf Litter Removal on the Abundance and Diversity of Arthropods in Lincoln Parish, LA Fall 2007 By Rachelle Anderson Tuesday Lab Arthropods thrive in the proper environmental conditions. A constant warm temperature, the proper level of humidity, and decent leaf litter and debris for protection and residence are needed. If one of these necessities is not fully met or nonexistent, arthropod occupation declines. A study has been completed in Europe that suggests conclusively that the removal of ground cover eliminates Cameraria ohridella populations in the following spring (Bacher 2003). Another study shows that termites process much on the cellulose contributing to the breakdown of organic matter; they are present where leaf litter is found because they consume it (Collins 1981). The forest floor is a place teaming with diversity and processes involving the surrounding ecosystem (Hansen 2000). There have been numerous studies completed concerning the leaf litter and arthropod relationships; however, there appears to be a void in studies completed in the southern region, primarily northern Louisiana. This case should be a good addition to the knowledge database currently accessed. In this study several plots will be tested for arthropod inhabitation and diversity. A portion of plots will serve as controls by containing original leaf litter. The remaining plots will have the leaf litter removed. In order to gauge frequency of inhabitation and diversity, pit traps will be utilized to capture arthropods that are in the vicinity. The traps will then be collected in a week and analyzed for data. If plots have leaf litter then the arthropod abundance should be higher than the plot that lacks leaf litter. Consequently, if plots have leaf litter then the arthropod diversity should be higher than the plot that lacks leaf litter. The null hypothesis states that arthropod abundance and diversity will be the same in both plots, respectively. Anderson 1

METHODS This study took place in fall 2007 in Ruston, LA in close proximity to Tech Farm. This area is part of the South Central Plains specifically called the Tertiary Uplands which contain a variety of trees and shrubs (Daigle et al. 2006). The forest area is relatively undisturbed and located near a road. Ground cover consisted of general leaf litter and decomposing organic matter. Fallen, dead vegetation randomly accumulated. The plots were arranged in a stratified random treatment, throughout the given area. Seven plots were utilized for leaf litter identification; nine plots were cleared and used for the bare plots. The plots measure 1 meter by 1 meter. The distance from one plot to another varied due to vegetation, ground cover, and natural obstructions (i.e. log). Pit traps were set when the weather was mild and no rain in forecast. The pit traps were placed in the middle of the plots. The plastic cups had 354.882356 cc2 (12 ounces) holding capacity. In order to protect the trap from flooding due to rain, a cover was utilized consisting of an inverted Styrofoam bowl suspended by three nails. 50/50 antifreeze was placed the pit traps to kill and help preserve organisms. Six days later, the pit traps were collected from plots for analysis the following day. The insects were separated from the antifreeze by a screen with spaces of 710 microns. Arthropods were identified by order and information was entered into the Microsoft Excel and JMP IN-4. RESULTS The pit traps were set up on October 2, 2007. On October 8, 2007, the traps were collected. The arthropods were separated from the preserving liquid. They were then divided into portions for identification by order and amount of each. The categorized arthropods allowed information to be combined to create a single central data set. The data set was entered in to Microsoft Excel and a histogram was created; see Figure 1. T-tests were performed on each individual order present to

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determine any significant differences. The means, degrees of freedom, and probability were also recorded. The hypothesis was correct. There was a significant difference in three of the orders collected. T-tests were used to determine the significant differences. The three orders were: Diptera, Isoptera, and Stylomatophora. The mean of 15.2857 Diptera in control plots is significantly greater (t=-4.435, df 14, P=0.0006) then the mean of 4.22 in bare plots. The mean of 0.428571 Isoptera in control plots is significantly greater (t=-2.430, df 14, P=0.0291) then the mean of 0 in bare plots. The mean of 0.714286 Stylomatophora in control plots is significantly greater (t=-2.864, df 14, P=0.0125) then the mean of 0 in bare plots. The null hypothesis was incorrect as shown by the significant differences of inhabitation of the three previously stated orders. DISCUSSION In temperate forests, most organisms live in the soil and litter, decomposing organic matter (Hansen 2000). These are the microorganism that carnivorous macroorganisms feed upon. Herbivorous organisms feed upon cellulose strewn on the forest floor. Consequently, there should be more diversity and abundance in plots containing leaf litter. This was evident for three orders in this case. Diptera lack of existence upon bare plots may be contributed to larval feeding habits. During growth Diptera larvae feed on fungi and specific types of mites (Anderson 1975). The mites that are digested are present in areas of leaf litter, in which they eat. The feeding cycle begins with small organisms that consume organic matter. Diptera larvae also use the leaf litter for protection for the weathering elements and cover from predators. Adult flies, for example, are usually found near the habitat of the larvae (Borror et al.1970). Consequently, a certain species of Diptera would more likely be found in a non-bare plot.

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Isoptera was more existence upon plots containing leaf litter. Termites are very important in the breakdown of lignocelluloses; they are one of the most efficient soil insects (Ohkuma 2003). The norm of the area studied was a place where leaf litter was common. Certain orders exist in a niche that requires this litter for food and protection. Therefore, when litter was removed, the organisms that inhabited it were moved as well or moved on to find an area like the one previously inhabited. Organisms in the order Isoptera would gain little from an area that does not contain the staple food source. In that event, it would be best for the survival of that creature to seek out area with leaf litter. Isoptera is a social creature (Borror et al. 1970), therefore where there is one, there are more. Stylomatophora, contains slugs and snails. There was a significant difference in the number of organisms of this order found in plots with leaf litter. Snails and slugs mucous covered (Wernert 1982). Extreme heat or lack of moisture can be detrimental these organisms. Leaf litter provides a place for moisture to collect and seals out sunlight on lower levels adjacent to soil. Moving from one area to another is more efficient over moist soil and leaves are versus dry, bare dirt. Snails and slugs are a food source of birds and other animals; therefore, being out in the open would not be beneficial. Fallen leaves provide the cover and moisture that the order Stylomatophora needs, in this case. The hypothesis that states, if plots have leaf litter then the arthropod abundance should be higher than the plot that lacks leaf litter, in this case was correct. The null hypothesis that states that arthropod abundance and diversity will be the same in both plots, respectively, was wrong in this case. Via observing the three orders significantly present in plots containing leaf litter, several assumptions can be correlated. The organisms need the leaf litter for shelter. This shelter includes cover from predators and creates an environment suitable for inhabitation via niche requirements for survival. Leaf litter also provides food. Food is provided directly to organisms that consume lignin and cellulose. Leaf Anderson 4

litter also provides food indirectly by creating an area in which microorganism thrive. These microorganisms in turn, provide nourishment for macroorganisms. Areas without leaf litter do not provide of the benefits previously stated in respect to Diptera, Isoptera, and Stylomatophora. Leaf litter is an important part of the North Louisiana forest habitat. Without leaf litter and natural debris, the cycles of food diminish. The smallest organisms provide food for those larger; the larger organisms provide food for birds and other animals, and so on. The leaf litter also provides continual nourishment and replenishment of soil when processed by organisms. This allows plants to grow and in turn, provide more leaf litter and debris. Leaf litter plays an important role in ecosystems.

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Works Cited Anderson, J.M. “Succession, Diversity, and Trophic Relationships of Some Soil Animals in Decomposing Leaf Litter”. The Journal of Animal Ecology. Vol. 44, No. 2 (June, 1975), pp. 475-495. Bacher, S., Kehrli, Patrick. “Date of leaf litter removal to prevent emergences of Cameraria ohridella in the following spring”. Entomalogia Experimentalis et Applicata 107: 159-162, 2003. Borror, Donald J, White, Richard E. 1970. Field Guide To the Insects of America North of Mexico. Houghton Mifflin Company, Boston. Massachusetts. USA. Collins, N.M. “Populations, Age Structure and Survivorship of Colonies of Macrotermes bellicosus (Isoptera: Macrotermitinae)”. The Journal of Animal Ecology. Vol. 50, No 1. (Feb. 1981), pp. 293-311. Daigle, J.J., Griffith, G.E., Omernik, J.M., Faulkner, P.L., McCulloh, R.P., Handley, L.R., Smith, L.M., and Chapman, S.S., 2006, Ecoregions of Louisiana (color poster with map, descriptive text, summary tables, and photographs): Reston, Virginia, U.S.Geological Survey (map scale 1:1,000,000). http://www.epa.gov/wed/pages/ecoregions/la_eco.htm (accessed 10/27/07). Hansen, Randi A. “Effects of Habitat Complexity and Composition on a Diverse Litter Microarthropod Assemblage”. Ecology, Vol. 81, No 4. (April 2000), pp. 1120-1132. Ohkuma, M. “Termite symbiotic systems: efficient bio-recycling of lignocelluloses”. Applied Microbiology and Biotechnology. 61.1 (14 Mar. 2003): pp1-9. Wernert, Susan J. 1982. North American Wildlife. Readers Digest, Pleasantville, N.Y. USA.

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