Ecosystems in South West Australia - Assignment Example

Ecosystems in South West Australia al Affiliation Ecosystems in South West Australia Question One Projection about the prospect of climate change in South West Australian is a course of concern since the region has become 25% drier over the past few decades (Hughes, 2003). It is predicted that future changes in rainfall patterns and temperature over the next five decades will have significant impacts on the vegetation across the region. The climate change comes as a result of increase in greenhouse gas concentration that has already impacted negatively on the species and the ecosystem. The area is predicted to be drier and warmer as the 21st century progresses which will be characterized by drier seasons and higher rainfall during winter and summer respectively. Litter decomposition rates are predicted to decrease due to reduction in litter nitrogen concentrations (Hughes, 2003). The climate change will affect the quality of liter produced. A higher fuel load is expected due to increased levels of CO2 in the atmosphere that accelerates plant growth and thus increases plant biomass. More root litter that contains more nutrients is produced, and therefore, additional nutrients will be availed upon decomposition. Elevated levels of CO2 result in poor litter quality, hence, the rate of litter decomposition declines. Increased temperature will enhance fuel dryness that will increase the probability of fire outbreaks (Hughes, 2003). Climate change directly influences the rate of NPP and carbon storage. Drier and warmer climate results in undesirable parameters such as UV radiation, tropospheric and biotic factors that result in reduction in carbon storage in plant parts. Shifts in precipitation and temperature result in the conversion of soil carbon to CO2; therefore, carbon storage is decreased. Shifts in the disturbance regime also influence carbon availability in the ecosystem. Disturbances from wildfires, back beetles, and wind reduce carbon availability and t6he net primary production of other nutrients (Bernard, Leadley and Hungate, 2005). Question Two Mineralization is an important process in the long-term manufacture of nutrients required by plants for growth. Elevated levels of CO2 in the atmosphere stimulate biomass production, increased litter fall, and rhizodeposition. The delivery of labile organic matter increases and in turn, influences the deposition of soil microorganisms that enhance nutrient availability and carbon storage. An increase in the net carbon input in the soil causes decreased nitrogen mineralization, and subsequently increases temporarily immobilized nitrogen as well as carbon sequestration. The result of mineralization is the long-term immobilization of atmospheric nitrogen (Bernard, Leadley, and Hungate, 2005). Nutrient cycling is a highly localized process that involves exchanges between plants and soil in ecosystems. The nitrogen cycle is a significant process that involves nitrogen cycling in the ecosystem. It involves a series of processes that include nitrification, ammonification, denitrification, and nitrogen fixation (Bernard, Leadley, and Hungate, 2005). Nitrification is the transformation of ammonium to nitrites then to nitrates through biological oxidation in the rate limiting step. Nitrates are fixed into soil by nitrogen-fixing bacteria such as nitrobacteria and stored in the root nodules of leguminous plants. Amonification refers to a process that recycles organic nitrogen bound to plant, animal, or microbial biomass upon their death. Ammonification breaks down complex ammonium molecules to soluble NO3. Figure 1: illustration of ammonification and nitrification https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcSQeR5_lafvoOfDXbJpGJ26jrv-3qpKalt4vfHtHeVtkxP8uVsfSQ Pasture growing in calcareous soil in a warmer climate that is occasionally waterlogged experiences growth during the wet season as more water is availed to the roots and leaves. When the rain culminates, the plants shed the leaves onto the soil and the process of decomposition begins. The organic matter is broken down to smaller particles by the detrivores. Bacteria and fungi decompose the organic matter to produce nitrogen and phosphorous. These molecules leech into the soil and release CO2(Hughes, 2003). The alpine forest growing on acid clay soil is limited with nutrients because clay soil negatively alters mineralization. Additionally, inability to neutralize the acid reduces mineralization. A sea grassmeadow growing on calcareous residues that are generally anaerobic receives less nutrients due to rapid ammonification than nitrification. Inability to utilize oxygen hinders the conversion of nitrites to nitrates and therefore, most of the nitrogen is stored in immobilized form. Figure 2: illustration of the decomposition process https://www.google.com/images/branding/product/ico/googleg_lodp.ico Question Three When a wetland ecosystem becomes seasonally waterlogged, litter decomposition rate increases. Ammonium nitrogen at the bottom of water that is exposed to nitrogen undergoes nitrification and denitrification. The oxygen present on the water surface causes formation of aerobicsedimentwhere ammonium is transformed to nitrates. The nitrate diffuse into the anaerobic sediment containing N2 and NO2 and serves as an intermediate product in the nitrification-denitrification process. This process stops once the waterlogged region becomes dry and the litter is deposited on the ground where it undergoes decomposition by bacteria and fungi and mineralization by nitrogen-fixing bacteria(Theodose& Bowman, 1997). A sclerophyllus plant growing in low nutrient soil will obtain the deficient nutrient s from the saprophytic nitrogen-fixing shrub that invades it. The shrub will enhance the absorption of nitrates from the soil to the plant since, litter from sites have slower decomposition because of the negative effects of P, N, and high lignin and tannin concentrations. Kikuyu grass s an efficient in utilization of nitrogen containing fertilizers. Additionally, it facilitates soil stability. When land that was initially occupied with Kikuyu grass is irrigated and fertilized, the amount of nutrients increase due to the decomposition and mineralization. The eucalyptus plant is likely to do well due to sufficient nitrogen content.When the grass species is replaced with tall trees, the C: N ratio increases and therefore, the availability of nutrients Is rapid(Vandecaveye, 1923). Question Four Cyanobacteria are green plants that grow in aquatic regions. Although their diversity is limited, they are harmful when they are fed on by the primary consumers and get up the food chain to the upper tropic levels where they either undergo bioaccumulation or are biomagnified. Algal bloom is a symptom of eutrophication that kills fish. The following short-term approaches can be used to curb the spread of algal bloom;increasing oxygen concentration by allowing oxygen flow from upstream is a short-term remedy because cyanobacteria thrive best in anaerobic conditions. In low oxygen concentration, P increases as anaerobic bacteria are poor at retaining it. Ensuring that healthy invertebrate population is present in the water body ensures that algae population is maintained at low levels (Hick, Jernakoff and Hosia, 1998). Another remedy is to increase water flow through the dams or to flash the system and introduce cool water to the system to slow algae productivity. If an algal bloom occurs, physical removal is recommended. The long term remedy to algal bloom involves a change in the land used and reduction of nitrogen inputs such as fertilizer into the river. The land user can increase vegetation around the water body to increase C: N ratio through denitrification. DOM, a complex mixture of organic compounds can be used to kill algae. Increasing the uptake of N and P, and reducing waste disposal and nutrient deposition on the water body are additional remedies to algal bloom(Hick, Jernakoff and Hosja, 1998). N and P enter the waterway and serve as limiting factors to algal growth in aquatic systems. Question Five The diversity in species affects the rate of nutrient uptake in the ecosystem. Dead plants, animals and microbial biomass avail nutrients through decomposition by bacteria and fungi. Decomposers facilitate nutrient availability to the producers that obtain minerals by the action of nitrogen-fixing bacteria. Primary consumers feed on producers. Secondary consumers such as man feed on the primary consumers that are fed on by tertiary consumers like lions. All living organisms die and the nutrients are recycles and reused by existing species Theodose& Bowman, 1997). This cycle ensures constant availability of nutrients in the ecosystem. Species diversity also influences litter quality and hence, the nutrient turnover. The disturbance regime mechanism can be used to determine how species biodiversity influence nutrient availability. For instance, eucalyptus has low C: N ratio and therefore result in decreased mineralization and nutrient availability (Theodose and Bowman, 1997). Question Six P is considered a limiting factor to growth and productivity in many ecosystems, however, the ratio of C: N: P determines the rate of litter decomposition. The mineralization of N and P are tightly coupled and maintain cellular homeostasis of microbial communities. The ratio of C: P negatively correlates with the rate of litter decomposition. High levels of carbon and P reduces the rate of litter decomposition and hence, mineralization decreases. On the other hand, high N and P increase the rate of litter decomposition and hence, mineralization increases. It is for this reason that P is considered a limiting factor to growth (Passel.unl.edu, 2015). Phosphorous is necessary for plant growth. It is a component of nucleic acids that regulate protein synthesis in plants. It is essential in promoting cell division and thus, the development of new plant tissue. It is associated with ADP conversion to ATP, the complex process that catalyzes energy transformations in plants. Presence of P in soil promotes the growth of roots and winter hardiness, stimulates tillering, and speeds maturity. Phosphorous deficiency is characterized by tinted growth and abnormal dark-green color in plants. Extremely low phosphorous levels in soil results in accumulation of sugars which cause formation of anthracyanin colors that lead to reddish-purple coloration of the plant (Passel.unl.edu, 2015). In temperate evergreen eucalypt forest ecosystem, the levels of phosphorous and nitrogen in the roots are relatively high which results in high nutrient content, hence, healthy and evergreen plants. A tropical ecosystem exhibits high biodiversity due to the moderately high temperatures and significant amount of rainfall received. Phosphorous values vary in tropical ecosystems depending on the available P reservoirs. C: N ratio is higher in this ecosystem that P is limited (Passel.unl.edu, 2015). Question Seven Stable isotopes in plants include O, C, N and S. The factors that influence isotopic ratios of primary producers includetemperature, precipitation, and evaporation rate. Consumers also influence the isotopic ratios because they feed on the producers. The concentration of the isotopes in the ecosystem influences that amount present in the organism. For instance, a plant growing in shallow water with high nutrient has high isotope concentration than those growing deep waters with fewer nutrients. The isotopic ratio in consumers depends on the amount present in the preceding tropic levels(Venkiteswaran, Wassenaar& Schiff, 2007) References Barnard, R., Leadley, P., and Hungate, B. (2005). Global change, nitrification, and denitrification: A review. Global Biogeochem. Cycles, 19(1), n/a-n/a. http://dx.doi.org/10.1029/2004gb002282 BRADFORD, J., BIRDSEY, R., JOYCE, L., & RYAN, M. (2008). Tree age, disturbance history, and carbon stocks and fluxes in subalpine Rocky Mountain forests. Global Change Biology, 14(12), 2882-2897. http://dx.doi.org/10.1111/j.1365-2486.2008.01686.x Hughes, L. (2003). Climate change and Australia: Trends, projections and impacts (1st ed., pp. 423–443). New South Wales: North Ryde. Retrieved from http://www.uow.edu.au/content/groups/public/@web/@sci/@biol/documents/doc/uow013530.pdf Hick, P., Jernakoff, P., &Hosja, W. (1998). Algal bloom research using airborne remotely sensed data: Comparison of high spectral resolution and broad bandwidth CASI data with field measurements in the swan river in Western Australia. Geocarto International, 13(3), 19-28. http://dx.doi.org/10.1080/10106049809354649 Passel.unl.edu,. (2015). Plant and Soil Sciences eLibrary. Passel.unl.edu. Retrieved 9 October 2015, from http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=1130447043&topicorder=2 Theodose, T., & Bowman, W. (1997). Nutrient Availability, Plant Abundance, and Species Diversity in Two Alpine Tundra Communities. Ecology, 78(6), 1861. http://dx.doi.org/10.2307/2266107 Venkiteswaran, J., Wassenaar, L., & Schiff, S. (2007). Dynamics of dissolved oxygen isotopic ratios: a transient model to quantify primary production, community respiration, and air–water exchange in aquatic ecosystems. Oecologia, 153(2), 385-398. http://dx.doi.org/10.1007/s00442-007-0744-9 Read More