practical 1

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James Cook University *

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BS2460

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Computer Science

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Jan 9, 2024

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Practical 1 1. Produce a figure showing the distribution of each species as a function of location along the transect. 2. Examine the distribution of all species. Was there evidence for aggregated occurrence in any species? (Provide a table with the results of the run tests and the conclusions). Species P Value Z Value Run s Occurrence s Conclusion Cyperus.p. 1 0 1 Positive = 50 Negative = 0 As the P – Value is greater than 0.05, we accept the null hypotheses. The Z – Value of 0 is evident as the species was present throughout the entire transect. Ipomea.b. 2.159e-07 -5.1851 4 Positive = 43 Negative = 7 The P – Value is extremely small, so we reject the null hypothesis the at the distribution of the range is random. The Z – Value is negative indicating that there are fewer runs than expected suggesting aggregated distribution. Canavaliar.r. 7.401e-08 -5.3811 4 Positive = 42 Negative = 8 The P – Value is extremely small, so we reject the null hypothesis for the alternative hypothesis that the true number of runs is not equal to the expected number of runs. The negative Z – Value demonstrates that there are fewer runs than what is expected showing aggregation. Pandanus.s. 1 0 3 Positive = 1 Negative = 49 The P – Value is 1 which is greater than 0.05 so we accept the null hypothesis. However, this species was only present 1 time across the transect with 3 runs suggesting a possible outlier. Panicum.m. 1.734e-05 -4.2966 3 Positive = 3 Negative = 47 The P – Value is extremely small, so we reject the null hypothesis that the distribution across the range is random for the alternative. This is further confirmed by the negative Z – Value which indicates fewer runs than what is expected indicating aggregation. Cenchrus.e. 0.0001227 -3.8407 8 Positive = 10 Negative = 40 The P – Value is extremely small, so we reject the null hypothesis for the alternative hypothesis where the negative Z – Value indicates that there are fewer runs than expected indicating an aggregated distribution. Heteropogon.c . 2.267e-09 -5.9774 4 Positive = 15 Negative = 35 The P – Value is extremely small, so we reject the null hypothesis for the alternative that the true number of runs is not equal to the expected. This is further confirmed by the negative Z – Value indicating fewer runs indicating aggregation. Spinifex.s. 2.422e-05 -4.2219 5 Positive = 6 Negative = 44 The P – Value is extremely small, so we reject the null hypothesis for the alternative hypothesis that the true number of runs is not equal to the expected number of runs. The negative Z – Value shows there are fewer runs than what is expected representing aggregation. Unknown 6.613e-07 -4.9724 3 Positive = 4 Negative = 46 The P – Value is extremely small, so we reject the null hypothesis for the alternative hypothesis where the negative Z – Value indicates that there are fewer runs than expected indicating an aggregated distribution. Desmodium.r. 1.56e-10 -6.3994 2 Positive = 7 Negative = 43 The P – Value is extremely small, so we reject the null hypothesis the at the distribution of the range is random. The Z – Value is negative which indicates that there are fewer runs than expected which suggests an aggregated distribution.
3. How might the scale that we used (the length of the transect) influence the pattern detected in species? The length of the transect influences the precision of the data collected as precision increases with longer transects. The 50m transect provides a scale that allows the aggregates of individual species to be analysed however it does not represent the entire region of the dune. By placing the transect parallel to the cline at a random position along the dune system, we were able to get a better description of the gradient compared to a transect that runs across the system. 4. What do these results tell you about the effects of physical parameters in determining plants species occurrence? Physical parameters including temperature, wind and light can vary across the transect due to soil, shade from other plants as well as influence of the sea breeze can determine species occurrence. Plant distribution across the dune is limited by their ecological niche associated with specific physical conditions with a certain level of tolerance. If the physical parameters move to exceed this tolerance such increasing light or temperature, the specie’s distribution or abundance will be impacted. 5. What were the assumptions relating species presence and environment underlying the use of the run tests? What other ecological factors might also need to be considered in attempts to explain species’ presence or absence at a location? Assumptions used for the species presence and underlying environment in the runs test include that the data is a simple random sample, and that each species is independent from each other. In other words, the abundance of one plant species does not influence the abundance or distribution of another. Ecological factors that would impact the presence of plant species along the transect include the influence of human activity as well as the presence of other plants and animals within the system they may increase competition for resources or utilise a certain plant species as a resource for its own survival.
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