Lab 2a: Quadrat Sampling (Prelab) PDF

# Lab 2a: Collecting Ecological Data: Quadrat Sampling (PRELAB activity) ## Overview This is a PRELAB activity, instead of a quiz, there is a short sampling simulation to complete and submit over eClass. Next week you will compare this sampling technique with Mark and Recapture sampling. ## Objec...

# Lab 2a: Collecting Ecological Data: Quadrat Sampling (PRELAB activity) ## Overview This is a PRELAB activity, instead of a quiz, there is a short sampling simulation to complete and submit over eClass. Next week you will compare this sampling technique with Mark and Recapture sampling. ## Objectives At the conclusion of this PRELAB activity, participants will be able to: - Perform quadrat sampling to estimate vegetation population sizes - Calculate a cumulative mean - Construct and interpret a performance curve to assess sampling accuracy. ## Review: Samples vs. Populations Connections to the lecture material: - What is a population? - Why is sampling necessary? - How are population sizes estimated? Usually, we cannot measure total populations; instead, we take samples and use statistics to make estimates on the population. It is essential that samples be representative of the whole population if we want good estimates. In this lab, we'll explore how quadrats are used to estimate population sizes of non-motile organisms. ## Sampling Methods Sampling design refers to how you decide which areas to sample. There are three basic types: - Random - Systematic - Combination of random and systematic In this activity, you will use a random number generator and a quadrat grid to randomly sample a simulated landscape. ## Sampling Adequacy: or when is enough, enough? How do you know if you have taken enough samples to accurately reflect the population? The number and size of samples are important for making accurate and precise estimates. In carrying out a sampling program, an ecologist wants to obtain the maximum amount of information for the minimum amount of effort, because sampling is often labor intensive, time-consuming, and/or expensive. However, it's usually not possible to specify ahead of time how large a sample is needed to be adequate. Here are some things that you need to consider when deciding on sampling effort: ### Sample Size: - Many small or medium sized samples will often give you a better estimate (and higher statistical power) than a fewer number of large samples. (ie. It is better to take 10 small samples, than a single large sample). ## Quadrat Sampling Prelab Activity - **Type of area:** A homogeneous area will require less sampling than a heterogeneous one. - **Distribution of population within the area:** Highly clumped populations may require more samples than random or uniform populations. In this activity, we learn how sampling adequacy can be assessed using a Performance Curve. ### Performance Curves A performance curve plots the cumulative mean value of a trait (e.g., in this case, number of species) against the number of samples taken. A cumulative mean is calculated by summing the total number of objects encountered, and then dividing it by the total numbers of samples up to that point (**Table 2-1**). After you have calculated the cumulative mean, you plot the cumulative mean against the number of samples taken up to that point to create a performance curve (**Figure 2-2**). The first few samples probably will not give a very close approximation of the true mean, but as more samples are collected, the true population mean is approached, and the curve flattens out. When the change in the cumulative mean becomes very small with the addition of another sample, we assume that our sample mean has closely approached the true population mean. At this point, conducting additional sampling will not change our estimate by very much. **Table 2-1. Cumulative Mean Calculation Table** | Sample Number | Cumulative Count | Cumulative Mean Calculation | Cumulative Mean Value | | --------------- | ----------------- | --------------------------- | --------------------- | | 1 | 5 | 5/1 | 5 | | 2 | 15 | (5+15)/2 | 10 | | 3 | 0 | (5+15+0)/3 | 6.6 | | 4 | 12 | (5+15+0+12)/4 | 8 | | 5 | 1 | (5+15+0+12+1)/5 | 6.6 | | 6 | 9 | (5+15+0+12+1+9)/6 | 9 | **Figure 2-2. Performance curve showing the cumulative mean against the number of samples taken. Notice how the mean begins to flatten around 8 samples.** Looking at **Figure 2-2**, notice how the variation in cumulative mean decreases as the number of samples increase. After 8 samples, adding further samples does not substantially change the mean. Therefore, from this performance curve, you can estimate that 8 samples is an adequate number of samples to closely approximate the true mean. ## Density estimation Two common methods of estimating absolute population density are: - **The quadrat method:** used for small, sessile or relatively sedentary organisms (non-motile) - **The mark/recapture method (we will do this in a future lab):** used for relatively large and/or mobile organisms. ## Quadrats A quadrat is a (usually square-shaped) sampling area of a known/defined size. To conduct quadrat sampling you need to count all the individuals within a number of sample areas of a known size, and then extrapolate the average density of your samples to the entire area. Using simple proportions, we can estimate the total population size from quadrat samples: $$ \frac{n}{a} = \frac{N}{A} $$ Where: - **n:** average number sampled in the quadrats - **a:** size of quadrat - **N:** total population size - **A:** total area Rearranging this equation, the estimated total population size (called Ñ to symbolize that it is an estimate) is: $$ \hat{N} = A \left( \frac{n}{a} \right) $$ **Ñ** must be a whole number. We will always raise decimals to the next whole number, regardless of mathematical rounding conventions (e.g. 15.2 is rounded up to 16). For example, imagine you measured 5 different quadrats in a forest, and you calculated an average of eight spruce trees in a 10 m² quadrat of forest. If the total forest size was 1000 m², you could estimate population size with this equation: $$ \hat{N} = 1000 \left( \frac{8}{10} \right) = 800 spruce trees in the entire forest $$ In order for density estimates based on quadrats to be accurate: - The number of individuals in each quadrat must be known exactly. - The size of the quadrats must be known. - The quadrats must be representative of the study area as a whole. **Try this one:** You have measured dandelion abundance in ten 1 m² quadrats in the campus quad. You found in these ten quadrats, there was an average of 2 dandelions per 1 m² quadrat. If the size of the quad is 10,000 m², what is the estimated population size of dandelions in the entire quad (remember to round to the next whole number)? **Estimated Population Size: ** # Lab 2b: Scientific Method in the River Valley: Observations & Experimental Design ## Overview **Part 1 (Week 2 of labs):** Observe the biotic and abiotic conditions in the River Valley. Practice sampling techniques. Develop a research question and design a scientific experiment for next week's lab. **Part 2 (Week 4 of labs):** Collect data according to your experimental design. Analyze your data with the appropriate statistical test. Interpret your results. Associated assignment information is on eClass. ## Objectives At the conclusion of this lab, participants will be able to: - Develop a testable question using the scientific method - Construct scientific hypotheses with mechanism and directionality - Distinguish between a hypothesis and a prediction - Apply proper experimental design to test a research question - Apply and interpret statistical tests to collected data, using a t-test and/or Chi-Squared Goodness-of-Fit test - Summarize their results using scientific writing and graphing skills Connections to the lecture material: - How do environments vary and what effect does this have on organisms? - What is the impact of climate on biotic variables? - What types of flora and fauna are associated with the Aspen Parkland Ecoregion? *This lab involves field trips into the Edmonton River Valley. See eClass for more details.* ## Overview of the Scientific Method Science is a philosophical and dynamic approach to examining the world around us. The Scientific Method is at the core of science and can be described as a systematic method of inquiry that involves: - Using observation to develop testable hypotheses - Collecting, analyzing and interpreting empirical data within the framework of a rigorously designed experiment (**Figure 2-1**). The process of science begins with observations, leading us to ask a question. - Why do the trees on the other side of the river look different than on this side? - Why do I see more magpies on campus than any other type of bird? - Are there more mosquitos this year than last year? All these questions can lead to the formation of a research question and a testable hypothesis. ## Scientific Method in the River Valley: Observations and Questions ### Edmonton's River Valley Edmonton is in the Aspen Parkland Ecoregion of Canada. This region is transitional, sharing some of the characteristics of the boreal forest to the north and some of the characteristics of the prairie grassland to the south. The Edmonton River Valley is an important corridor for wildlife and native vegetation along the North Saskatchewan River. There is a wide range of biodiversity in the river valley you may encounter during this lab period. The difference in species at any given site is characterized mainly by the slope, elevation, and moisture level at that site. For example, in the river valley, you may encounter the following types of sites: - **Flat, upland sites:** Undisturbed vegetation dominated by a mixture of white spruce (Picea glauca) and trembling aspen (Populus tremuloides). - **Steepest slopes:** North facing aspect, mainly white spruce forest, lowest insulation, lowest air and soil temperatures, latest snow melt and shortest growing season. Heavily shaded understory. Mosses and occasionally sarsaparilla are found in the needle litter. - **Less steep slopes:** North facing aspect, balsam poplar, aspen and birch are the dominant over-story species, although spruce is still common. Microtopographic diversity is high, resulting in a higher diversity of shrubs, including cherry, red osier dogwood, highbush cranberry, bracted honeysuckle and hazelnut. - **Drier sites:** Open aspen forest, characterized by a well-developed shrub layer dominated by saskatoon, cherry and rose. - **Moist sites:** Young spruce may be found among the shrubs. If conditions are favorable, the spruce may eventually grow up and replace the aspen as the dominant over-story tree. When sampling vegetation: plant communities can be visualized as having a layered structure. Three layers are commonly found in forested areas: - The tree layer - A layer of woody shrubs of an intermediate height - A layer of forbs (smaller non-woody plants - grasses/small herbs) growing close to the ground. There are several abiotic and biotic factors that may have an impact on plant growth in the Edmonton River Valley. Based on observations you make in the river valley this week, you will design your own research project to be completed next week. ### Land Acknowledgment While you may have already heard land acknowledgments during your time on campus, I encourage you to really connect to the landscape around you when you are out in the river valley and think about what these land acknowledgments mean when we say them. The University of Alberta respectfully acknowledges that we are located on Treaty 6 territory, a traditional gathering place for diverse Indigenous peoples including the Cree, Blackfoot, Métis, Nakota Sioux, Iroquois, Dene, Ojibway/ Saulteaux/Anishinaabe, Inuit, and many others whose histories, languages, and cultures continue to influence our vibrant community. ## Scientific Method in the River Valley: Part 1 ### Hypothesis, Prediction, Experimental Design Based on your observations from the river valley and analysis of general trends from the group data set, you will work in pairs (or groups of three) to develop a hypothesis, experimental design, and prediction to test in next week's lab in the river valley. During next week's lab, you will collect your data and analyze your results. After completion of the experiment, you will present your results in a scientific abstract. Because this is an open ended experiment, we have provided several blank pages at the end of the lab for you to use to record your observations. Make sure all partners have copies of all notes after Part 2, as abstracts must be completed individually. There are several abiotic and biotic factors that may have an impact on plant growth in the Edmonton River Valley. - **Example ABIOTIC factors to study:** elevation, slope, light penetration, proximity to disturbance (trails, roads etc.), temperature, moisture level, sunlight - **Example BIOTIC factors to study:** type of species, number of different species present, relative abundance of trees, shrub, grasses, plant height, plant diameter, leaf/needle size, cone size, twig length, twig diameter, etc. ## Assessment of Experimental Design (FINER) - Review by TA **Component** | **Criteria** | **TA feedback** --- | --- | --- **Feasible** | - Research design is adequate - Aims at an achievable sample size - Optimises technical resources - Opts for appropriate and affordable frame time | | **Interesting** | - Engages the interest of the researchers - Attracts the attention of readers/public - Presents a different perspective of the problem | | **Novel** | - Provides novel findings - Generates new hypotheses - Resolves a gap in the existing literature | | **Ethical** | - Complies with local ethical committees - Safeguards the main principles of ethical research | | **Relevant** | - Generates new knowledge - Stimulates further research - Provides an accurate answer to a specific research question | | ## Self Reflection Questions One important step in solidifying learning is to integrate what you learned with what you already know. **Cumulative concept connections:** How does this lab connect to concepts you have learned in lecture or lab so far? Can you use any of these concepts to help support your hypothesis? ## Tools for Making Observations in the River Valley **Available Tools:** - Tape measures - 1m² quadrats - Flag markers - Yard sticks - Plant identification manuals/keys **Sampling equipment:** - Diameter at Breast Height (DBH) tape - Vernier calipers - Clinometers/Compass - Temperature probes - Soil corer **Soil Corer:** Can be used to extract a core sample from the soil. Note the composition of the litter layer and measure the depth of the soil layers. **Vernier calipers:** Are best to use when measuring something very small (e.g., needle length) or to measure the diameter of small branches. **Compass/Clinometer:** You can use the compass to determine the aspect of your slope (which cardinal direction the slope is facing), as well as the degree of the slope. The clinometer is also used to help calculate tree height. **Collecting tree data:** You can measure tree growth by measuring diameter with a DBH tape or by measuring the height of the tree. To measure tree height, you will use the open-reel tape measure, a clinometer/compass (above), and trigonometry. (See Appendix III for directions on how to calculate tree height.)