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Importance of Field Margins to Agro-ecosystems

Field margins are a crucial aspect of agricultural landscapes which occur in different forms next to all agricultural fields (Marshall 1988; Moonen and Marshall 2001). These margins can provide a series of extremely important functions within the landscape which can be divided according to (de Snoo 1995; Udo de Haes 1995) into agronomy and animal husbandry function by defining land ownership, providing stock fencing and shelter, providing windbreak for crops, enhancing pollination and providing wood and wild game (Marshall et al. 2002; Marshall and Moonen 2002a; Marshall 1993, 1995; Zuria and Gates 2006), environmental role by controlling the transport of pesticides, herbicides and nutrients; reducing erosion and runoff (Balzan and Moonen 2014; Bianchi et al. 2006; Crowder et al. 2010; D’Acunto et al. 2014; Haycock et al. 1992; Powell et al. 2004), conservation role by providing species refugia and complementing biodiversity by providing habitat, feeding and breeding locations (Altieri 1999; De Cauwer et al. 2006; Leidner and Kidwell 2000; Ma et al. 2013; Musters et al. 2009; Pfiffner and Luka 2000; Vickery et al. 2009) and recreational and cultural or historical interests by providing field access, and areas for walking, driving, hunting; promote tourism via aesthetics, maintain culture and heritage (Marshall and Moonen 2002a; Pollard et al. 1974; Zuria and Gates 2006).
Currently, there are a lot of studies have been done in Europe on the importance of the field margins to the agro-ecosystems; which varies between studies done on the vegetation of the field margins (Bassa et al. 2012a; Kleijn and Snoeijing 1997; Moonen and Marshall 2001; Tarmi et al. 2009; Tarmi et al. 2011), birds (Vickery et al. 2009), insects (Fuentes-Montemayor et al. 2011; Ó hUallacháin et al. 2013; Olson and Wäckers 2007) and how the field margins biodiversity can react with the landscape (Bassa et al. 2011; Marshall 2009; Poggio et al. 2010) or on the importance of the field margin itself within the ecosystem (Marshall et al. 2002; Marshall 1995; Marshall and Moonen 2002b); even so, we found that there are few studies about this important piece of the ecosystem have been done in South Korea (Kang et al. 2013; Martin et al. 2013).
In South Korea, at the time that they are trying to improve and expand the agriculture best management practices, organic farming and the green growth, there are no laws controlling the field margin’s management schemes, width or length within the agroecosystems which can help improving this remarkable segment of the ecosystem.
Grasping how plant species growing on the field margins respond to different management schemes and how the individual species and the species richness of field margins can be conserved and reestablished will help enriching their functions and roles within the agroecosystem. Currently, it became well known that the field margin plant species are affected by the surrounding landscape (Marshall et al. 2006) and the management practices (Jobin et al. 1997).
In the current study, we examined the plant species richness and the presence of individual plant species growing at the field margins in relation to the different management activities and the surrounding landscape elements in agricultural landscapes of South Korea. To achieve our goal, we addressed three particular questions:
Are the natural field margins associated to higher species richness than the managed ones?
Are the landscape elements and the field margin’s topographic features important for increasing the species richness, if so, which is the most appropriate and at which scale?
Are the field margin’s management activities and the surrounding landscape elements important for the species distribution, if so, which is the most appropriate and to which species?
Effect of field margin management, topographic features and landscape context on the species richness:
The management of the field margin, landscape context and topographic features explained the variations in the species richness of the field margins in the argroecosystems. According to (de Snoo 1999; Hansson and Fogelfors 2000; Maron and Jefferies 2001; Tarmi et al. 2011), applying cutting activities and/or herbicides to the field margins tend to increase species diversity. Some other studies like (Cordeau et al. 2012; Gove et al. 2007; Jobin et al. 1997; José-María et al. 2013; Kleijn and Snoeijing 1997) showed that using herbicides and/or cutting tend to reduce the species richness; while in (Bassa et al. 2012b; Kang et al. 2013; Marshall and Nowakowski 1996) they stated that there is no effect of cutting nor herbicide’s application on the species diversity and species richness. The current study proved that the natural field margins had higher species richness in compare to the managed ones (Figure 4), during our research, we sampled 300 plots covering the entire study area which gave us the opportunity to analyze the effect of the different management activates in details. On the other hand, the applications of cutting and herbicides to the field margins in South Korea are totally unlike than these in Europe, as the farmers apply the management activities regularly for almost the whole season without allowing the vegetation reestablishment, this suggested our idea that due to the uncontrolled management practices, it was too hard for the species to be replaced, and the remaining species cannot spread (Jobin et al. 1997).
Although lots of studies showed that the field margin width has a positive effect on the species richness (Bassa et al. 2012a; Kang et al. 2013; Ma et al. 2002; Tarmi et al. 2009) our study showed that there is a negative relationship between the field margin width and the species richness (Table 2), that is because we sampled our vegetation data in 3 plots/site where these plots added to the middle of the field margin regardless the width of the field margin itself.
Recent research has taken into account the effect of the landscape context (Sosnoskie et al. 2007; Weibull et al. 2003), landscape heterogeneity (Bassa et al. 2011; Bassa et al. 2012a) and landscape complexity (1?Aavik et al. 2008) on the species richness (Bassa et al. 2012a; Weibull et al. 2003), species diversity (Sosnoskie et al. 2007) and species composition (Aavik et al. 2008; Bassa et al. 2011) within the field margins.
The current research agreed with the above mentioned ones, as we found that the plant species richness in field margins was positively affected by landscape context “% of non crop” at different buffer sizes around the sites (Table 2), we found that by increasing the percentage of the non crop areas, especially at 300m and 400m buffers around the sites, the species richness increased, due to the increasing in the landscape heterogeneity and complexity.
Species response to management and landscape context:
Within the studied that have been done to test the species responses to the environmental variable, we found that there are rare studies that have been done on the effect of the landscape context and management on individual plant species. Some of these studies tested the individual species response to the grazing and management intensities (Dorrough et al. 2007; Dorrough et al. 2012; Dorrough et al. 2011; Dorrough and Moxham 2012; Zimmer et al. 2010a; Zimmer et al. 2010b), while some others tested the plant responses to landscape scales, context and grazing and management (Dorrough et al. 2007; Dorrough et al. 2012). Other studies reported the importance of the landscape context and landscape structure to the response of certain species (Kattwinkel et al. 2009; With and Crist 1995).
In agreement with the previously mentioned studies our study showed the importance of the field margin management “natural or managed” activities and the percentage of the landscape context around the study sites on the distribution of individual species within the study area. We found that the annual grass species with a maximum height of 50cm like Cyperus microiria, Persicaria longiseta, Setaria viridis, Setaria sp were related in their distribution but not restricted to the managed field margins because these species are fast growing in compare to the perennial ones (Figure 6 and Appendix A). While the perennial herbaceous and woody species with a height of more than 100cm like Phragmites japonica, Zizania latifolia, Artemisis spwere in their distribution to the natural field margins as these species get the ability to grow with little disturbance and without any cutting or herbicide applications (Figure 6 and Appendix A).
The same trend has been found in the effect of the non crop percentage on the species distribution, as the perennial species like Phragmites japonica, Eupatorium japonicum, Hypericum sp tend to occupy the field margins which has low non crop percentage, these species characterized by its herbaceous nature and height of more than 100cm (Figure 7 and Appendix A). But species like Bidens frondosa, Persicaria nepalensis, Persicaria thunbergii, Conyza canadensis were found to prefer the field margins with high non crop percentage, these species are annual growing species, weedy nature and with short height ~ 50cm (Figure 7 and Appendix A).
According to the results we have got from the effect of field margins’ management and the landscape context on species distribution and the species richness, we can say that the annual species are responsible for increasing the species richness in the field margin, as they are fast growing even under the cutting and herbicide application activities.
In conclusion, our study proved that in areas like South Korea, new laws and strategies should be developed to control the management schemes within the field margins in the Korean agriculture landscapes. These management schemes will help in conserving the biodiversity by providing the suitable habitats for flora and fauna and consequently, will affect the soil quality and stability which will help in controlling the soil erosion happens during the monsoon time in South Korea. The annual species favor but not restricted to the managed field margins while the perennial species prefer the natural ones. The increasing of the species richness is the responsibility of the annual species as they can grow easily in both the natural and managed field margins. Further long-term research should be done on how we can link the ecosystem services provided by the landscape and the plant diversity within the field margins due to its valuable benefit to the whole ecosystem.

Analysis of Stanley Lloyd Miller’s Experiment

“The origin of life is one of the great outstanding mysteries of science.”
Paul Davies
Evolution means an unfolding or unrolling-a gradual orderly change from one form to another. The principle of organic evolution states that all the various plants and animals existing at the present time have descended from other, usually simpler, organisms by gradual modifications which have accumulated in successive generations.
Postulating about the origin of life, in 1855, Virchow stated that ‘omnis cellula a cellula’ implying that new cells can arise only from pre-existing ones, or in other words, life is continuous from the very beginning upto the present day. The continuity of life cannot be disrupted, but at the same time it raises the vexing question that how did the first cell ever appear on Earth? This had two possible answers, namely; panspermia and spontaneous generation. With subsequent reasoning and experiments, these theories were scrapped.
The theory about the birth of the solar system reaped basis for the dawn of life. Scientists like Oparin, Haldane, Bernal etc. postulated theoretically in accordance to, that building blocks of life could be built up by the action of primitive sources of energy upon the ingredients of the primitive Earth.
Their suggestion of the possible steps in chemical evolution which prepared the ground for biological evolution was all theory till now. Experimental proof was to follow.
Calvin’s irradiation set-up of 1951, which gave rise to formaldehyde and formic acid from CO2 solutions, was of one of the first experiments of this kind. Although it holds little importance today since his set-up did not utilize the reducing atmosphere of the primitive Earth. Miller’s publication 2 years later proved the hypothesis that compounds of biochemical importance could be produced in high yields from a mixture of reduced gases.
In 1953, Stanley Lloyd Miller raised the hopes of understanding the origin of life when on 15th May, Science published his paper on the synthesis of amino acids under conditions that simulated primitive Earth’s atmosphere. Miller had applied an electric discharge to a mixture of Methane, Ammonia, Water, and Hydrogen gas-believed at the time to be the atmospheric composition of early Earth. Surprisingly, the products were not a random mixture of organic molecules, but rather a relatively small number of biochemically significant compounds such as amino acids, hydroxy acids, and urea. With the publication of these dramatic results, the modern era in the study of the origin of life began.

The origin of Miller’s experiment can be traced to 1950, when Nobel laureate Harold C. Urey, began to consider the emergence of life in the context of his proposal of a highly reducing terrestrial atmosphere and presented this in a lecture. Almost a year and a half after Urey’s lecture, Miller, a graduate student in the Chemistry Department who had been in the audience, approached Urey about the possibility of doing a prebiotic synthesis experiment using a reducing gas mixture. After overcoming Urey’s initial resistance, they designed three apparatuses meant to simulate the ocean-atmosphere system on primitive Earth. The first experiment used water vapor produced by heating to simulate evaporation from the oceans; as it mixed with the reducing gases, it mimicked a water vapor-saturated primitive atmosphere, which was then subjected to an electric discharge. The second experiment used a higher pressure, which generated a hot water mist similar to that of a water vapor-rich volcanic eruption into the atmosphere, whereas the third used a so-called silent discharge instead of a spark.
Experiments with the second apparatus produced a similar distribution and quantities of amino acids and other organic compounds, whereas the third apparatus with silent discharge showed lower overall yields and much fewer amino acids (primarily sarcosine and glycine).
In the set-up, an apparatus was built to circulate the above mentioned gases past the electric charge. The apparatus used is shown in Fig.(2). Water was boiled in the flask, which mixed with the gases in the flask, circulated past the electrodes, condensed and emptied back into the boiling flask. The formed non-volatile acids and amino acids accumulated in the water phase. The opening in the boiling flask was sealed off after adding 200 mL of water, evacuation of air, addition of 10 cm pressure of H2, 20 cm of CH4 and 20 cm of NH3 . The water was boiled and the discharge was run continuously for a week.

The flask became pink initially and by the end of the week it turned deep red and turbid. Miller stated that most of the turbidity was due to the colloidal silica from the glass and that the red colour was due to the adsorption of the organic compounds onto the silica. Adding to this, he documented that further investigations were being conducted on the yellow organic compounds present, of which only a small fraction could be extracted with ether.
To prevent any microbial growth, after removing the solution from the boiling flask at the end of the run, 1 mL of saturated HgCl2 was added. The ampholytes were then separated by treating with base, acid and then neutralizing and concentrating in vacuo.
It was found that within a week, 15% of the carbon originally present as CH4 had converted into other simple carbon compounds. Among these compounds were formaldehyde (CH2O) and hydrogen cyanide (HCN). These compounds then combined to form simple molecules, such as formic acid (HCOOH) and urea (NH2CONH2), and more complex molecules containing carbon-carbon bonds, which included the amino acids.

The resulting mixture was tested for amino acids using paper chromatography, run in n-butanol-acetic acid-water mixture followed by water-saturated phenol and spraying with ninhydrin. The chromatogram is shown in Fig.(3). Subsequently, the amino acids identified were glycine, α-alanine, β-alanine along with aspartic acid and α-amino-η-butyric acid to some extent. Hence it demonstrated the presence of amino acids, some abundant while others in smaller quantities and the total yield was estimated to be in the milligram range. Furthermore some aldehydes and hydrogen cyanide were also detected.
Contemporary geoscientists tend to doubt that the primitive atmosphere had the highly reducing composition used by Miller in 1953. Many have suggested that the organic compounds needed for the origin of life may have originated from extraterrestrial sources such as meteorites. However, there is evidence that amino acids and other biochemical monomers found in meteorites were synthesized in parent bodies by reactions similar to those in the Miller experiment.
Localized reducing environments may have existed on primitive Earth, especially near volcanic plumes, where electric discharges may have driven prebiotic synthesis.
Miller left behind boxes of experimental samples collected in 1958. The first-ever analysis of some of his old samples has revealed another way that important molecules could have formed on early Earth.
Miller added a potential prebiotic condensation agent, cyanamide, during the course of the experiment. Cyanamide has been suggested to induce polymerization of amino acid into simple peptides which is an important set in chemical evolution and possibly the origin of life. For unknown reasons, Miller had never analyzed the samples. It was verified that the contents of the box of samples were from an electric discharge experiment conducted with cyanamide in 1958.
The latest study is part of an ongoing analysis of Stanley Miller’s old experiments. In 2008, the research team found samples from 1953 that showed a much more efficient synthesis than Stanley published in Science in 1953.

In 2011, the research team discovered and analysed archived samples from a previously unreported 1958 Miller electric discharge experiment containing Hydrogen Sulfide using high-performance liquid chromatography and mass spectrometry. A total of 23 amino acids and 4 amines, including 7 organosulphur compounds, were detected in these samples. The overall abundances of the synthesized amino acids in the presence of H2S were found to be very similar to the abundances found in some carbonaceous meteorites, suggesting that H2S may have played an important role in prebiotic reactions in early solar system environments.
The effect of electric fields on mixtures of simple molecules is presently studied in computer simulations at the quantum level, and Miller results are reproduced in atomistic simulations, as glycine forms spontaneously only in the presence of electric fields. However, this occurs through reaction pathways more complex than believed. The recent method of treatment of aqueous systems under electric fields and on metadynamics analysis of chemical reactions shows that glycine spontaneously forms from mixtures of simple molecules once an electric field is switched on and identifies formic acid and formamide as key intermediate products which are the crucible of formation of complex biological molecules.
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