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Bio 5C Section 33
Transcript of Bio 5C Section 33
Emilia De La Mora
Fall Quarter 14
Ho: Aspect has no affect on Encelia Farinosa growth rates.
Ha: Aspect has a positive effect on Encelia growth rate
Independent Variable: aspect and rainfall
Dependent Variable: growth
Statistical tests analyzed by looking at P-values and r-squared values for both rainfall vs. growth and aspect vs. growth and determining the relationship between the two
Results - Aspect
Assigned a focused point
Measured a 4 meter radius circle around that point
Used data sheet to record all Encelia that were alive
Instructed to disregard any Encelia that were considered dead
Aspect and slope recorded by pointing compass downhill
How Aspect and Rainfall Affect Encelia Farinosa
Ho: Rainfall has no affect on Encelia Farinosa growth rates
Ha: Rainfall has a positive effect on Encelia growth rate
r-squared : 0.444682
Significant Ho is rejected
Type of Error: no error
r squared: 0.027986
Dont reject null
Type 1 error
Importance of aspect
25 Degrees North East
Maximum sprouting occurred on north-facing slopes. The likelihood of brittle bush recovery from fireby sprouting is greater on cool, less xeric sites where fires are oftenless severe, and less on the hot, xeric sites
The aspect of a slope is very significant on its local climate (microclimate)
Discussion (aspect cont.)
For the aspect graph,the p value of .03 which is less than .o5 indicates that we can reject the null hypotheses and therefore the aspect does have an affect on the encilia growth, a possible explanation being sunlight as a contributor to slope explanation.
The graph shows only that 44.4% of the independent variable affects the dependent variable, therefore the aspect that we studied affects the growth rate with an intensity of 44.4% which is very significant.
Slope or aspect affect micro climate because the west facing slope receives more solar radiation throughout the day, as opposed to east facing slope due to the earth’s axis rotation.Because we rejected out null hypothesis, we conclude that the independent variable (aspect), does have a direct affect on out dependent variable (encelia growth).
Discussion Aspect Cont.
therefore according to the rainfall graph since p value is greater than .05 the null hypothesis is correct and the assumption that the independent variable does not have a significant effect on the dependent variable is therefore correct. Ths is because encilia does not require much rain as a brush plant.
(should be) Contrarily for the aspect graph since the p value higher than .o5 than (should be less than check it) it should indicate that we cannot reject the null hypotheses and therefore the aspect does not have an affect on the encilia growth. Due to sunlight an slope explanation
Our graph results show that rain has an affect on growth but not a significant affect on growth. They need water but with their shallow roots, and tendency to grow in drier climate, an overwhelming about of rain is not suitable to their environment and growth rate in a positive way. Has an affect but not a significant positive direct correlation from which we can conclude that a large amount of rainfall would be positive for the growth rate .
Analyzing the Data
Rsquared: rsquared value is the effect of the independent variable and the p value indicates whether or not the independent variable has or does not have a direct effect (stat.yale.edu)
For this model, because the p value is greater than .05, the null hypothesis is correct and the assumption that the independent variable does not have a significant effect on the dependent variable is therefore correct. This is because encilia does not require much rain as a brush plant.
They need water but with their shallow roots, and tendency to grow in drier climate, an overwhelming amount of rain is not suitable to their environment and growth rate in a positive way.
The rainfall graph shows only that 2.7% of the independent variable affects the dependent variable, therefore the amount of rainfall that we studied only affected the growth rate therefore inconclusive.
While there is an affect, it's just not a significant positive direct correlation from which we can conclude that a large amount of rainfall would be positive for the growth rate of encelia. The graphs don't give us any direct relationship between rain and growth since all the points on the graph are scattered and not in any kind of line.
Because we only used specific years for our graphs, we don't know what results other years got. It is possible that that in other years, there was no correlation between aspect and encelia growth, so since we only checked a specific year for aspect so we don't know if other years had different results.
Other years may have received more sunlight, had different humidity, wind patterns, different soil conditions etc, which could affect how the encelia grew. For rainfall, we only observed a specific plot, so we don’t know if rain affects every plot the way our results show, other plots, could show a correlation between encelia growth and rainfall.
Biome: Chaparral. Wet winter, dry summer, dense shrubs (sage shrubs burn easily and quickly but are able to recover quickly)
Locations: Coastal Sage scrub (CSS) is commonly found in coastal California and North- Western Baja California
1. Within a single year, how does aspect affect Encelia growth between plots?
2. Between years, how does rainfall affect Encelia growth in a single plot?
Density: the amount of Encelia per assigned area
Aspect: refers to the horizontal direction in which a mountain slope faces
South- facing slopes in the northern hemisphere receive more sunlight than north-facing slopes and are therefore warmer and drier. Their physical differences influence species distributions locally (Campbell 1194).
It is hypothesized that chalk grassland swards on steeply sloping ground are more resistant to invasion by competitive grass species than those on flatter sides due to phosphorous limitations in shallow minerogenic redinza soils, and that those with a southerly aspect are more resistant due to increased magnitude and frequency of drought events.
When warm , moist air approaches a mountain, the air rises and cools, releasing moisture on the windward side of the peak. On the leeward side, cooler, dry air descends, absorbing moisture and producing a "rain shadow".
CSS may appear inactive during dry periods, however growth still occurs
Its growth is too sensitive to too much or too little water intake
Rainfall plays a significant factor to Encelia: we receive an average of 10"-20" of rainfall a year.
Plants emerge in winter after winter rains, and most growth is in the rainy season (Tesky 1993).
Data Sheet (containing health status, height (cm), diameter (cm), flowering/nonflowering)
A fitted linear regression model can be used to identify the relationship between a single predictor variable and the response variable when all the other predictor variables in the model are "held fixed". In other words, it is used to determine the extent to which there is a linear relationship between a dependent variable and one or more dependent variables. For example a scatterplot can be a helpful tool in determining the strength of the relationship between two variables. If there appears to be no association between the proposed variables (i.e., the scatterplot does not indicate any increasing or decreasing trends), then fitting a linear regression model to the data probably will not provide a useful model.(duke.edu)
If alpha = 0.05, and the p value from the statistical test is ≤ 0.05, then you would reject Ho and presume the treatment has an effect. If p > 0.05, then you would not reject Ho and presume the treatment has no effect.
In order to receive more accurate results, we would have to check multiple plots and years. something that could affect our data is human activity, people walking up the trails and messing with the plants. Another possibility is animal life, maybe certain plots had more insects, which ate the leave, killing off the plant, which was the actual reason for less plant growth, and had nothing to do with aspect or rainfall.
Other scientific research
It is important to find out correlations between encelia growth, so that we can help its survival rate, and use it for our everyday necessities. Encelia is used in glue, Sealer, Incense, Gum, Toothbrush, and to treat toothaches (Grey). If we know what causes it to grow we can plant more there, moreover if we know that it doesn’t want rain to grow, we will plant it in places that don’t get a lot of rainfall. Knowing these correlations allows you to better use the plant. Scientific research regarding revegetation after a wildfire is seen often tested. Many experiments test if encelia growth could be considered as candidate species for revegetation projects and could represent the types of species in which to invest long-term effort in propagating quantities of plant material ( Abella 2009).