EEB Group Ecology Report

EEB Group Ecology Report

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  Lisa Tripp UID 303892770 EEB100L Lab 2 Nov. 27, 2013 The Effect of Distance to Water Source on Plant Biodiversity Introduction: The relationship between plant species and water is extremely important for plant survival and diversity. As 70% of the Earth’s surface is covered in water, it is vital for us to understand the effect of water on one of our main food, shelter, and energy sources. Past studies have demonstrated the importance of water for general plant survival, but equally important in the study of water-plant dynamics is the element of biodiversity (Fader et. al. 2010). Studying and understanding this relationship is key to the need to maintain biodiversity, as different plants have different water needs. Plant and water system interactions may also serve as a model to help us as humans understand our own water needs, and understanding of these interactions grow more and more relevant as global climate change may change fresh water source availability (Gerten et. al. 2013). One particularly suited system to study the effect of water on the diversity of plant species is the California Temescal Canyon Gateway Park creek system. A large variety of plants grow in the temperate climate area, and the plants in the area grow wild and are for the most part native (other than few invasive species). Because the creek is the only water source in the area (the area is a non-maintained park), the creek serves as a very controlled water source variable in the ecosystem. To test the effect of water on the biodiversity in the Temescal Canyon creek ecosystem, we measured the degree of biodiversity in reference to distance from the creek. Our hypothesis was that the shorter the distance from the creek, the greater diversity in plant species will be observed. In this observational study, the distance from the creek at which the biodiversity of plant species was measured served as the independent categorical variable, and the degree of biodiversity of plant species measured served as the dependent interval variable (as the amount of biodiversity may depend on distance from water).
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  Experimental Methods: To performthis experiment, we collected data in the Temescal Canyon Gateway Park in the Pacific Palisades of California. We collected our data from alongside a creek at the southernmost end of the canyon, parallel to Temescal Canyon Road, about 30 yards into the trail. The object of the experiment was to collect species biodiversity data, so we did not focus on any one species in particular. Species that we did see included vine-like species and grasses, some of which were crawling, and which grew to an average height of six inches. All evidence of plant life was included, whether dead or alive. We collected data on the number of species rather than the quantity of individuals in the area. Equipment used in this experiment included transects (one for each replicate group, totaling four replicate groups), as well as 0.5m2 quadrats (one for each replicate group, totaling four replicate groups), flags to mark where measurements were already taken, and the human eye to count species within the quadrats. To conduct the experiment, we split our class into four groups. Each of the four groups performed four measurements close to the creek (0m away, with the edge of the quadrat laying on and parallel to the creek edge), and four measurements away from the creek (1m away, with the edge of the quadrat laying on the transect and parallel to the creek edge). Distance from the creek was determined by laying the transect perpendicular to the edge of the creek moving outward. Once we arrived at the location and split into groups, each working at different sections of the creek, we randomly chose four sites per group along the creek (with a plant-presence bias) in our group’s section. We then measured out 0m from the creek and 1m from the creek using the transect, and placed the quadrat at these distances in these four different sites. We then used the human eye to count and record the number of species within the
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  quadrat at thesesites and distances. After measuring the biodiversity at a site and distance, we flagged the area to avoid repeat measurements. In total among the four groups, 16 measurements were taken 0m away from the creek, and 16 measurements were taken 1m away from the creek. To analyze our data, we used the JMP statistical software and performed a T-test, as our variables were a dependent interval variable of number of species and an independent categorical variable of distance from the creek (0m or 1m). Results: The results of this experiment indicate that distance from the creek did significantly affect the degree of biodiversity in the Temescal Canyon creek ecosystem. The T-test ran on the results of this study yielded a p-value of 0.0354, statistically demonstrating the significance of the difference in the degree of biodiversity between the two sets of results (0m from the creek and 1m from the creek) (figure 1). Not only did the T-test reveal a significant difference in the average degree of biodiversity, but also in the range of species richness, with a range of species richness 0m from the creek of 4, and a range 1m from the creek of 3 (figure 1). On average, both the species richness and the range of species richness closer to the creek were greater than away from the creek. Discussion: In this study, areas in close proximity to the Temescal Canyon creek contained on average a greater degree of biodiversity and a greater range of species richness in comparison to areas further away from the creek. From our statistical analysis, we have sufficient evidence in order to reject the null hypothesis that there is no significant difference between the two experimental groups. Our statistical analysis supports the hypothesis that the shorter the distance from the creek, the greater the level of biodiversity.
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  This study wasreliable because it took place in a wild, natural environment in which variables were not manipulated. The reliability of the results of this experiment could have been increased by using a greater number of replicates, data collection at more distance increments from the creek, and elimination of the plant presence bias. A greater number of replicate locations along the creek in this experiment could have eliminated the effects of any outlier locations, and could have served as a better representation of the system as a whole. Data collection at more distance increments along the creek could have indicated more about the possible existence of a biodiversity gradient, and could reveal specific points of significant change. Additionally, eliminating the plant presence bias could have produced more accurate, objective results. Although this experiment did demonstrate an increase in the degree of biodiversity closer to the creek, further studies could be done to both increase the reliability of the study results, and further investigate other possible variables and effects. Such studies could address other possible factors affecting this system such as the presence of invasive species, the presence of sunlight, the temperature close to and away from the water source, and could look at additional systems other than the Temescal creek ecosystem. In summary, areas in closer proximity to the creek exhibit a greater level of biodiversity in comparison to areas away from the creek. In a larger ecological context, it can be deduced that other creek ecosystems may exhibit the same sort of trend, and in even more general terms, this study demonstrates the importance of a water source in the development of species diversity. This study demonstrates commonalities discovered in similar ecosystems, and adds valuable evidence to our overall understanding of plant-water dynamics (Knapp 2002).
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  Figure 1: Speciesrichness sorted by distance from the creek. Species richness was on average higher closer to the creek. The range of species richness was also on higher closer to the creek. Literature Cited: Fader, Marianela, Stefanie Rost, and Christoph Muller. "Virtual Water Content of Temperate Cereals and Maize: Present and Potential Future Patterns." Journal of Hydrology 384.3-4 (2010): 218-31. Gerten, Dieter, Wolfgang Lucht, Sebastian Ostberg, and Jens Heinke. "Asynchronous Exposure to Global Warming: Freshwater Resources and Terrestrial Ecosystems."Environmental Research Letters 8.3 (2013): 18-26. Knapp, Alan, Fay Phillip, John Blair, Scott Colins, Melinda Smith, Jonathan Carlisle, Christopher Harper, Brett Danner, Michelle Lett, and James McCaran. "Rainfall Variability, Carbon Cycling, and Plant Species Diversity in a Mesic Grassland."Science 298.5601 (2002): 2202-205.