ECOLOGY OF SOIL BIOTA AND ITS ROLES IN BIODEGRADATION.
ABSTRACT
The effect of the soil biota in ecosystem was carried out by extracting the soil biota from the soil using streaking and pour plate method. By inoculating the different soil samples collected from the school premises. The media used were saboraud and nutrient afar incoperated soil sample to make it selective for the soil organisms only. The culture was incubated at 370C for 48 hours for full growth to appear. Then the isolates were finally inoculated into dead organic matter prepared with soil, just to verify effect. The biota isolated was micro-biota and mesobiota. Among the microbiota the fungi and bacterial and the mesobiota are the protozoas. And fungi was found to have the highest percentage distribution of (63.3%), bacterial (20.9%), mesofauna (32.8%) and protozoa (17.5). This shows that fungi are the predominant soil-biota.
Key words: Biota, Mesobiota, mesofauna
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background of the Study
Soil biota consist of the micro-organisms (bacteria, fungi, archaea and algae), soil animals (protozoa, nematodes, mites, springtails, insects, and earthworms) and plants, living all or part of their lives in or on the soil or pedosphere, Van (2007; 20). Millions of species of soil organisms exist but only a fraction of them have been cultured and identified. Microorganisms (Fungi, archaea, bacteria, algae and cyanobacteria) are members of the soil biota but are not members of soil fauna. The soil fauna is the collection of all the microscopic and macroscopic animals in a given soil. Soil animals can be conventionally grouped by size classes: macrofauna (enchytraeide, earthworms,macroarthropods),mesofauna (microarthropods, mites, and collmbolan), and microfauna (protozoa, nematodes). The size of a soil organism can restrict its location in the soil habitat, Comis, (2007; 10). Smaller members of the microfauna like nematodes are basically aquatic organisms that lives in the thin water films or capillary pores of aggregates preying or grazing on other aquatic microfauna such as amoeba. Soil protozoa are also land – adapted members of aquatic microfauna that can dwell in water films in field moist soils, Tate (2002; 10). Water films are created by adsorption of water to soil particles. Soil has a direct effect on the environmental conditions, habitat and nutrient sources available on the soil biota. The term pedosphere is often used interchangeably with soil and captures the concept that soil is a habitat where the integration of sphere occurs, Simeonson (2009; 150). These spheres include the lithosphere, atmosphere, hydrosphere, and the biosphere, Brady and Weil (2002; 50). Numerous biogeochemical processes regulated by soil biota occur in the pedosphere.
Soil organisms serves numerous roles in the pedospheres. Their most critical function is the regulation of biogeochemical transformations. Five functions mediated by soil biota are (1) the formation and turnover of soil organic matter, that includes mineralization and sequestration of carbon (2) nutrient cycling (3) disease transmission and prevention: for instance many soil microbes like streptomyces are used for production of antibiotic and also most of soil microbes like nematodes such as Ascaris lubricoides causes disease (4) Pollutant degradation and (5) imrpovemnet of soil structure, Alexander (2007; 5). The by products of metabolic oxidation or reduction of C and N compounds in soil microbes. The size and composition of the microbial biomass (the combined mass of micro-organisms in the soil) is dependent upon soil properties and the sources of carbon available for energy and cell synthesis. Carbon inputs to the soil vary in their biochemical composition (e.g their ability to be decomposed) and nutrient content. Carbon turnover, decomposition and microbial activity often lead to increases in organic nutrients and soil aggregation.
Different ecosystems vary in their potential to support soil organisms and organic constitutes, the nutrients such as Nitrogen and phosphorous required by majority of living organisms are the chemical backbone of organic matter and is the energy source for most soil organisms, Madsen (2008; 202). Mineralization of organic Nitrogen to ammonium (NH4+) and additions of Nitrogenous fertilizers that contain NH4+ to nitrate (NO3-), Maier (2009; 200). Soil food is also a member of soil biota that consist of the community of organisms that live all or part of their lives in the pedosphere and mediate the transfer of nutrients among the living (biotic) and non-living (abiotic) components of the pedosphere through a series of conversions of energy and nutrients as one organisms and or substance is consumed by other organisms, Lai (2008; 20). The mesofauna, (collembolan, mites) play a role in nutrient turnover by shedding materials into smaller pieces with higher surface area providing greater access for microfauna (bacteria, fungi, mucorrhizae) that recycle the majority of carbon. All food webs consist of several (trophic levels or feeding positions in a food chain. The term grazing is used when organic carbon is obtained from living things. Soil organisms are part of the detrital food chain if their organism carbon is derived from dead materials. The derital food chain creates new soil organic matter and cycles nutrients from existing organic materials. Biological system and organisms contain fairly constant elemental ratios of carbon nitrogen phosphorus sulfur (C:N: P:S). These ratios and mass balances (net change = input + internal change) allow scientist to determine biochemical shifts between organisms or ecosystem, Lohman (2008; 25).
Most members of the soil biota (fauna) are chemoheterotrophs, meaning that they can obtain carbon and energy by oxidizing (metabolizing) organic compounds. Carbon sequestration limits the process of mineralization mediated by chemotrophs that produce CO2. The by-products of the mineralization process are metabolites, heat and CO2. The production of CO2 can reduce concentrations creating auoxic sites within microaggregates that result micro environments that differs in their content of nutrients and oxygen. These microsites are environments in which CO2 is converted to CH+4 through anaerobic respiration by archaea known as methanogens, Madsen (2008; 202).
Methan can undergo oxidation to CO2 in adjacent microsites. This process is regulated by a group of bacteria known as methanotrophs that transform CH+4 back to CO2 all in the same aggregate, Gupta (2007; 80).
1.2 Significance of the Study
i) This study will help the populace to know what ecology of soil biota is all about.
ii) The role of soil biota in the ecosystem
iii) It will also help people to know the group of micro organisms called soil biota.
iv) It will expose to people how soil biota affect degradation of organic materials in the soil.
1.3 Statement of the Problem
There has been a doubt about the role of soil biota and the particular group of microbes called soil biota in the ecosystem, this lead to the study to find out the actual roles of soil biota and the members of soil microbes regarded as soil biota.
1.4 Statement of Hypothesis
Hi: Soil biota play an important role in the soil.
Ho: Soil biota do not have any role in soil.
1.5 Limitation of Study
The study limits an ecosystem and role soil biota in degradation.
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