Interactions among Soil Abiotic and Biotic Components - Coursework Example

Soil and Urbanization Introduction An ecosystem consists of a community of both living and non-living things. It could be larger as soil or as small as tree. For all the components of an ecosystem to survive, they interact with each other so as to make it balanced. Both living and non-living things have a purpose of keeping the ecosystem healthy and interacting with each other. It is only through the combination of biotic and non-biotic factors that an ecosystem can survive. (Bardgett, 2005) Soil can be defined as an ecosystem that covers our planet and as a place where energy and matter are transformed and transported. The structure of soil consist of both biotic and abiotic factors interacting together. These two components of such an ecosystem provide an equilibrium such that if one side is too heavy, the scale is thrown out of balance. Abiotic components of soil include mineral matter i.e. silt, clay and sand, water, air and organic matter. On the other hand, biotic components include organisms such as nematodes, protozoa, fungi, bacteria, actnomycetes, insects, arthropods and earthworms. (Bardgett, 2005) Project Goal According to Jim (1998), the goal of the project is to establish and interdisciplinary study in order to evaluate interactions among soil abiotic and biotic components and the importance of its physical properties in relation to urbanization. This is in line with the hypotheses: a) Both biotic and abiotic factors affect the flow and export of nutrient within the soil ecosystem b) Urbanization affects soils and their capacity to provide ecosystem services directly through disturbance and management and indirectly through changes in the environment hence leading to a mosaic of soil conditions Objectives The main objective of this study is document, quantify and establish sites for research that will allow the study of the interaction of abiotic and biotic components of the soil and how it relates with urbanization. Experimental Design, Approach and Procedure This involves selecting two sites and preparing them for the experiment i.e. in terms of drainage and installation of utilities. Tanks are placed randomly within the facility and filled with soil substrates which are carefully mixed so as to ensure there is uniformity among mesocosms. Some section of the soil is also filled with nutrient-void granite to allow drainage. Also, a PVC pipe is placed vertically to the bottom of the soil samples and connected to a vacuum extraction system to ensure good drainage. (Byrne, 2007) In order to test the hypotheses interaction, three variables are selected for the study of the soil ecosystem. In this case, two samples of unweathered glacial deposits sand with diverse chemical and physical properties are selected i.e. medium sand with low calcium and coarse sand with high calcium. Blocks of the mesocosms were established at both northern and southern parts of the site. In this case, a multi-species component is critical since it helps in gaining information of individual interactions hence it was advisable that we have orthogonal contrasts done by partioning of the ecosystem. This approach provides a very robust mechanism to help in examining the contribution and interaction of both biotic and abiotic components of the ecosystem. (Byrne, 2007) Results and Response Variables To be able to assess our experimental design and approach, ecosystem-level dependent variables are assessed. These include, the accumulation and distribution of living biomass, organic matter and nutrients. The design of the mesocosms allows for the measurement of such ecosystem-level dependent variables. Figure 1: Chemical and Physical Properties of the Two Soils Figure 2: Total amount of nutrients variation Analysis I. Interaction between abiotic and biotic components of soil Soil mineral matter consist of sand silt and clay particles. Clay particles have a large surface area to volume ratio hence they can hold more water and nutrients than large particles. Therefore, the soil mineral matter holds water and provides nutrients that are required by soil-microorganisms hence the coexistence. Also, these soil particles leads to different chemical and physical properties of soil hence determining the water retention ability, the bulk density, aeration and fertility. The water status and aeration capabilities of soil determines the survival of the biotic components in that soil. For instance, the living things in soil requires water and air to survive and this is determined by the soil mineral composition and structure. (Coleman, Crossley & Hendrix, 2004) According to Byrne, 2007, there are chemical and biological processes occurring in the soil like mineralization of organic matter and fixation of atoms in mineral matter in to organic compounds. These processes include the fixation of ionic mineral forms such as NH4, NO2 and other organic forms such as amino acids, nucleic acids, microbial cell wall and these take place within the ecosystem i.e. involve microorganisms interacting with the abiotic environment. This kind of interaction between abiotic and biotic components is illustrated in Fig. 1 below. Figure 3: Assimilation of ionic forms with organic forms Biotic components such as nematodes carry out the assimilation process. Therefore, the primary productivity is enhanced in the presence of these microorganisms. Figure 4: Nematodes and Bacteria in the fixation process Soil organic matter which is an abiotic component of soil helps in modifying the habitats of soil organisms and provide a source of food for the soil biota. These soil microorganisms feed on the organic matter and in the process releasing inorganic nutrients such as nitrogen, sulfur and phosphorous. This is a decomposition process and is a very important process in any healthy ecosystem hence the organic matter need to be replenished in order to maintain the balance. (Manlay, Cadet, Thioulouse, & Chotte, 2000) The soil ecosystem also serves as a host for microorganisms such as fungi, nematodes, bacteria, arthropods and insects. Decomposers like fungi, earthworms, actnomycetes, bacteria and nematodes mineralize resistant and labile substrates such organic matter in an interaction referred to as first order interaction. In the second order interaction, organisms feed on other organisms involve in the first order interaction. Therefore, interactions in the soil ecosystems function the same way as the second law of thermodynamics which stats that an any process involving energy conversion, the final product usually consist of less usable energy than the original since a lot of energy is lost in form of heat. (Bengtsson, 1998) II. The importance of soil physical properties as it relates to urbanization Soils are the foundation for many ecological processes and interactions, such as distribution of plants and animals, nutrient cycling and the ultimate location of human habitation. However, it was found that soils in urban areas are mostly affected by human activities leading to an ecosystem composed of unaltered soils. With these therefore, the main function of soil in urban areas is mainly to help in the reduction of pollutants, storage of mineral nutrients and carbon and also serving as a host for abiotic components of soil and also regulating the hydrological cycle by absorbing and storage. This is enhanced by the soil texture with consist of either sand, clay or silt which help in this function. (Manlay, Cadet, Thioulouse, & Chotte, 2000) Therefore, in the provision such services, soil plays a unique role as the brown infrastructure of urban ecological systems, much in the same way urban vegetation is thought of as green infrastructure. Whereas green infrastructure provides services attributed to vegetation, such as the moderation of energy fluxes by tree canopies, brown infrastructure provides ecosystem services attributed to soil, such as storm water infiltration and purification, and as a support medium for built. (Bardgett, 2005) Soil has a unique physical property of water infiltration and storage. Typically, urban landscapes consist of a soil drainage that is complex and varies in terms of moisture content and drainage patterns. This result of a combination of urban factors that either increase or decrease the content of water in soils. For instance, urban soils that are highly impacted normally exhibit soil surfaces that are hydrophobic, have surface crust formation coupled with high bulk densities which play a role in restricting infiltration rates. However, in urban environment conditions such as heat stress, soil water is more likely to be depleted through higher rates of evapotranspiration. On the other hand, urban landscapes often have surface drainage features that concentrate water flows. Therefore, the physical property of soil being able to infiltrate water and storage becomes important in such urban environments. (Jim, 1998) The soil bulk density which refers to mass of soil per unit volume, is normally a measure of soil compaction and is a soil physical property that has very important implications for water infiltration, plant growth and storm water runoff. An increase in the soil bulk density is often a prerequisite for building stability, and this reduces the building subsidence. In addition to that, urban activities such as foot and vehicle traffic disturb the soil as well as building and roadway construction result in an increase in bulk density. The presence of soil organic matter, which is normally depleted in urbanized areas, can also help decrease bulk density. Areas that are heavily urbanized, therefore have higher bulk densities than areas such as wetlands and forests. However, vegetation cover cannot be used to predict the bulk density since urban soils are usually covered in turf grass are among the most compacted. (Bengtsson, 1998) References Bardgett, R. D. (2005). The biology of soil: A community and ecosystem approach. New York: Oxford University Press. Bengtsson, J. (1998). Which species? What kind of diversity? Which ecosystem function? Some problems in studies of relations between biodiversity and ecosystem function. Applied Soil Ecology, 10, 191-210. Byrne, L. B. (2007). Habitat structure: A fundamental concept and framework for urban soil ecology. Urban Ecosystems, 10(3), 255-274. Coleman, D. C., Crossley, D. A., & Hendrix, P. F. (2004). Fundamentals of soil ecology. Amsterdam: Elsevier Academic Press. Jim, C. Y. (1998). Urban soil characteristics and limitations for landscape planting in Hong Kong. Landscape and Urban Planning, 40, 235-249. Magdoff, F., Doran, J. W., Coleman, D. C., & Bezdicek, D. F. (1995). Defining Soil Quality for a Sustainable Environment. American Journal of Alternative Agriculture, 35. Doi: 10.1017/S0889189300006123 Manlay, R. J., Cadet, P., Thioulouse, J., & Chotte, J. (2000). Relationships between abiotic and biotic soil properties during fallow periods in the sudanian zone of Senegal. Applied Soil Ecology, 7, 560-570. Read More