Ecology Lab Final
Know how to interpret (but NOT analyze) invertebrate data collected from pitfall traps and leaf litter bags
Pitfall Abundance Richness Shannon Diversity (sum of (pi times ln (pi)) all times -1 Shannon Evenness - Shannon Diversity/Evenness Leaf Litter Abundance Richness Shannon Diversity Shannon Evenness - Shannon Diversity/Evenness
Know how to calculate % dry mass remaining from a simple leaf breakdown dataset
initial= from handling bag (so not 5g) experimental/ initial times 100%
Major factors affecting soil respiration rate
- Temperature (25 degrees C ideal for decomp) - Soil Moisture (decomp best at semi moist but not flooded) - Soil Organic Matter (texture, density, pH) - Climate Change (soil can hold lots of CO2)
How to run how to run and interpret a simple linear regression
-Determines whether the explanatory variable causes a change in the response variable -Two numeric variables -F-statistic, P-value, R^2-value --------P-value determines whether the relationship between the two variables is significant --------R^2 value shows how much of the variability in the response variable is explained by the explanatory variable
Know what factors affect the rate of leaf breakdown in stream ecosystems.
-The type of leaf being broken down -Current and abrasion levels in the stream -The amount of microbial activity -More simply: type of stream, location in stream, and type of leaf
How to conduct a tree inventory using the point-centered quarter technique
A combination of transect and plotless data collection Uniform points are selected along a line, and then four quarters at that point are established. After that, the DBH of the tree closest to the origin in each quarter is recorded. For our experiment DBH > 5cm
Quadrat sampling method
A frame of known area is used to randomly isolate a subset of a population useful for measuring density of a species because all individuals within a quadrat are counted/measured
How to interpret results from a plant competition experiment.
ANOVA test on Vasserstat comparing results from pairwise comparisons ex. 1C:1R, 1C:5R, 5C:1R Determine what each pairwise comparison is trying to show the effects of What affected the response variables? What had a greater effect?
The advantages and disadvantages of using diversity indices.
Advantages combine richness and evenness into a single value that can be easily compared among communities and tested statistically Disadvantages Diversity indices aren't really meaningful unless they're compared to other communities Not always easy to tell the relative contribution of richness and evenness to the diversity value
How forest edge influences abiotic and biotic factors
Biotic: Stem densities (tree stems/unit area): higher at edges because of more light penetration to promote plant growth Basal area (area of tree stems/unit area): higher in forest interior; interior mostly consists of trees while edges mostly consist of understory plants Species composition: higher in the forest interior because species were better acclimated to interior habitat Animals: variation in bird density, lack of research, different pressures faced by different animals Abiotic: Solar radiation: more solar radiation at the edge than the interior because there are less trees in the canopy Temperature: more temperature fluctuations near the edge Soil Moisture: soil more moist in the interior because less light reaches the forest floor Chemical compounds: more chemical substances at the edges from farming fertilization, pesticides
soil respiration and decomposition relationship
Both processes release CO2 into the soil (as a byproduct of cellular respiration)
How to analyze a tree dataset in which data were measured using quadrat sampling (NOT point-centeredquarter)
Calculate Basal Area (m^2) from Diameter at Breast Height (DBH) (cm) for every tree 0.00007854 times DBH Find the sum of Basal Area for each tree species Calculate Basal Area Per Hectare basal area (m^2/ ha) basal area/0.8 Determine the relative tree dominance Basal area per hectare divided by the total basal area per hectare Rank it and see what trees are most/least dominant
Soil Respiration
Cellular respiration performed by root cells, where carbohydrates from the leaves are metabolized CO2 released into the soil
How to run how to run and interpret a t-test.
Compares a variable between two groups to determine if the variable is significantly different between the groups ----more than two groups: ANOVA One numeric, one categorical T-statistic, P-value -----P-value shows whether variable of interest is different between the two groups
Soil Decomposition
Decomposers feed on dead organic matter and break it down into its inorganic components, which are released into the soil where they can be taken up by plants helps determine the productivity and health of plants
The difference between intraspecific and interspecific competition.
Intraspecific competition: competition within a species/population Interspecific competition: competition between species in a community
How to construct a properly-formatted scientific table and figure.
Just do it I believe in you. Also grades don't define you and you'll end up where you're meant to be no matter what.
Know how leaf breakdown and leaf decomposition are similar and dissimilar.
Leaf Breakdown Physical change Conversion of coarse particulate organic matter into fine particulate organic matter Leaf Decomposition Chemical change Conversion of organic matter into its inorganic components
Know why leaf litter is important source of energy for small streams flowing through forested landscapes
Leaf litter is an important source of energy for small streams in forested landscapes because there is less light available for photosynthesis from shading. Leaves contain carbon-carbon and carbon-hydrogen bonds, so they're a readily available source of organic matter for streams
The appropriate statistical test to analyze an ecological dataset
Look at what variables you have and go from there: -Simple linear regression: determines whether the explanatory variable causes a change in the response variable two continuous -T-test: compares one variable between two groups to determine if it is significantly different one continuous, one categorical -ANOVA: compares one variable between multiple groups to determine if it is significantly different one continuous, one categorical (several groups within that categorical variable) -Multiple Regression Analysis: one continuous response variable, multiple continuous explanatory variables
How interpret (NOT run) results from a multiple regression analysis
Multiple Linear Regression: a multivariate statistic that examines the relationship between multiple explanatory variables and one response variable Potential issues: overfitting: too many explanatory variables multicollinearity: explanatory variables are correlated; may be redundant backward selection method the least significant variable is removed, and this procedure is repeated until all the remaining explanatory variables are significant avoiding multicollinearity If any pairs in the correlation matrix have an R above 0.8, it's probably multicollinearity If the VIF for each variable is greater than 5, it's probably multicollinearity maximize the adjusted R^2 value Remove highly correlated explanatory variables
How to properly cite sources within the text of a scientific paper
One author -(Author, Year) -According to Author (Year), Two authors -(Author and Author, Year) - According to Author and Author (Year), Three or more authors - (Author, et al., Year) -According to Author et al. (Year),
transect sampling method
Randomly or uniformly selects points along lines that are randomly laid useful when an area is zoned can be used to determine an environmental gradient
richness and evenness
Richness: How many species there are Evenness: How many of each species there are
Know how to analyze and interpret results of a plant competition dataset.
Simple linear regression on Vasserstat Record p-value and R^2-value What do these values tell you?
Methods of lime soda and chamber experiment
Soda lime readily absorbs water vapor from the air and removes CO2 from the air in the process. The increase in its mass after it is weighed and dried can be attributed to CO2 A blank is used to account for any CO2 absorbed before the respiration champers are fully set up.
How to calculate soil moisture and soil organic matter from raw data
Soil Moisture -> Determine Soil wet weight by subtracting the weight of the pan -> Determine Soil dry weight by subtracting the weight of the pan -> soil wet weight - soil dry weight = soil moisture -> % soil moisture = Soil Moisture/Soil Wet Weight x 100% Soil Organic Matter -> Determine the soil ash weight by subtracting the weight of the pan -> Soil Organic Matter = soil dry weight - soil ash weight -> % soil organic matter = soil ash weight/soil dry weight x 100%
Know how to determine soil moisture and soil organic matter from a simple dataset
Soil Moisture Determine Soil wet weight by subtracting the weight of the pan Determine Soil dry weight by subtracting the weight of the pan soil wet weight - soil dry weight = soil moisture % soil moisture = Soil Moisture/Soil Wet Weight x 100% Soil Organic Matter Determine the soil ash weight by subtracting the weight of the pan Soil Organic Matter = soil dry weight - soil ash weight % soil organic matter = soil ash weight/soil dry weight x 100%
The difference between descriptive and inferential statistics
Statistics: represent one estimate of the true values random representation of a population Descriptive Statistics describes data --- the middle --- the spread Example: mean, median, standard deviation, variance, standard error Inferential Statistics - help make objective decisions about observed differences between two or more datasets - Begins with a null hypothesis, then data is collected and that data is used in a statistical test - Test calculates a test statistic and then a p-value Example: simple linear regression, t-test, ANOVA, multiple linear regression
Major contributors to soil respiration
The major contributors to soil respiration (i.e., decomposer, plant roots, etc.) Decomposers decomposers of organic matter bacteria, fungi, etc. microbial activity influenced by moisture, soil type, and temperature Plant root cells cellular respiration while metabolizing carbohydrates
How to interpret data from a rank abundance plot
The slope shows evenness The more shallow it is, the more even The more steep/uneven it is, the less even The length of the line shows richness Longer = more species, more rich Shorter = less species, less rich
Ecological matrix
The surrounding area that a fragmented habitat is in—the stuff that causes fragmentation
Ecotone
The transition from one type of habitat or ecosystem to another, such as the transition from a forest to a grassland.
The sections of a scientific paper and what should be included in each section
Title The Influence of ____ on _____ in _____ Abstract summary of experiment one paragraph Problem, Approach, Results, Major Conclusions Introduction Purpose, background information Broad to specific Justification for the experiment Last paragraph: question, hypothesis, basic methods, predictions Citing sources no direct quotes no footnotes either start or end a sentence with citations Materials and Methods Where, when, and how Experimental setup Techniques and why you used them How data was analyzed Paragraph May include subheadings No background info, results, or interpretation past tense no unnecessary details Results What you observed Just the results figures and tables text to illustrate important trends no raw data summary of important trends quantitative refer reader to the table/figure where information you are writing about is summarized ex. (Figure 1) use numbers instead of words when possible decimal always has a zero in front of it DO NOT write "results are in tables and figures" put the information in the table/figures into words Discussion Restate hypothesis and whether results supported or rejected it Compare results to others Explain results, both expected and unexpected State any weaknesses in the experiment End with a conclusion and take home message References Bibliography of sources, APA
Plotless Sampling Method
Uses distances between a point and an individual/between individuals to form a pair of measurements useful where large quadrants would be difficult to manage; good for uniform habitats useful for measuring dispersion
What a null hypothesis is.
no differences exist between two datasets decide whether to reject or accept the null hypothesis
Ecological Fragment
the replacement of large areas of native forest by other ecosystems, leaving isolated forest patches—the area that is fragmented