Techniques for Evolution and Biodiversity Lab: Transects & Quadrats | Lecture notes Literature

Evolution)and)Biodiversity)Laboratory)

Collection)and)Sampling)Techniques)

)

This!section!of!the!manual!provides!some!background!regarding!the!methods!you!will!use.!

You!will!collect!samples!from!two!different!terrestrial!habitats!of!your!team’s!choice.!!

I.))Recording)Data)

Whenever!you!collect!a!sample,!record&pertinent&all&information,!such!as!

• Locality!(Various!GPS!logging!apps!are!available!for!your!phone)!

• Time!of!day!collected!

• Habitat!type!

• Weather!conditions!

• Temperatures!(air,!water)!

• Sample!type!(water!column?!!sediment?!!soil?!!moss?)!

• Other!relevant!details!(depth!of!sample,!volume!of!sample,!etc.)!

Use!a!field) notebook!(spiral!notebook)!to!record! information! about! your! sites! and! your!

samples.!!Since!field!sites!can!be!damp,!pencil!is!often!better!than!pen!for!field!recording!

data.!! (If! you!feel! confident! that!you! won’t! drop!it! in! the!water,! you! could!use! the! notes!

function!on!your!phone.)!

Each!team!should!assign!a!member!to!record!all!data!in!its!notebook.!!!

Each)team)member)should)receive)a)copy)of)all)data,)once)all)samples)are)collected.)

II.))Sampling)Techniques)

Unlike!research!projects!you!may!have!done! in! the! past,! your! survey!of!biodiversity!will!

not!involve!comparing!treatment!and!control!samples!or!manipulating!a!variable.!!Instead,!

you! will! be! performing! a! pilot) study!comparing! the! biodiversity! of! two! naturally!

occurring!ecosystems!that!you!predict!could!differ!for!a!stated,!logical!reason!of!interest.!

The! study! of! biodiversity! often! requires! measurement! of! species! diversity,! species!

richness,! and!other! measures! of! community! composition.! ! There! are! several! different!

ways! to! approach! this! task.! ! The! most! appropriate! method! will! often! depend! on! the!

question!you!are!asking.!

Different!methods!can!be!used!to!estimate!the!number!of!individual!organisms!present!in!

a!study!area!of!interest.!!The!most!obvious,!of!course,!is!simply!to!count!them!all.!!But!this!

is! often! logistically! impossible!in! a! very! large! study! area.! ! Instead,! a! population’s!or!

community’s!parameters! can! be! estimated!by! randomly! sampling! small! subsets! of! the!

entire!study!area.!

Two!commonly! used! methods! that! ensure! random! sampling! transects!and! quadrats.!!

Random! placement! of! transects! or! quadrats! ensures! that! statistical! inferences! from!

collected!data!can!validly!be!applied!to!the!larger!study!area.!

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Evolution and Biodiversity Laboratory

Collection and Sampling Techniques

This section of the manual provides some background regarding the methods you will use. You will collect samples from two different terrestrial habitats of your team’s choice.

I. Recording Data

Whenever you collect a sample, record pertinent all information , such as

Locality (Various GPS logging apps are available for your phone)
Time of day collected
Habitat type
Weather conditions
Temperatures (air, water)
Sample type (water column? sediment? soil? moss?)
Other relevant details (depth of sample, volume of sample, etc.) Use a field notebook (spiral notebook) to record information about your sites and your samples. Since field sites can be damp, pencil is often better than pen for field recording data. (If you feel confident that you won’t drop it in the water, you could use the notes function on your phone.) Each team should assign a member to record all data in its notebook. Each team member should receive a copy of all data, once all samples are collected.

II. Sampling Techniques

Unlike research projects you may have done in the past, your survey of biodiversity will not involve comparing treatment and control samples or manipulating a variable. Instead, you will be performing a pilot study comparing the biodiversity of two naturally occurring ecosystems that you predict could differ for a stated, logical reason of interest. The study of biodiversity often requires measurement of species diversity, species richness, and other measures of community composition. There are several different ways to approach this task. The most appropriate method will often depend on the question you are asking. Different methods can be used to estimate the number of individual organisms present in a study area of interest. The most obvious, of course, is simply to count them all. But this is often logistically impossible in a very large study area. Instead, a population’s or community’s parameters can be estimated by randomly sampling small subsets of the entire study area. Two commonly used methods that ensure random sampling transects and quadrats. Random placement of transects or quadrats ensures that statistical inferences from collected data can validly be applied to the larger study area.

A. Transects

A transect is a straight line (or narrow section) through a habitat, along which observations are made or measurements taken. Ecologists commonly employ transects to randomly sample diversity in natural habitats. A transect line doesn’t have to be high tech. A length of strong twine, marked with distance increments in indelible ink, can serve as well as a measuring tape.

1. Line Transect A line transect (Figure 1a) is a (usually) straight line marked by a measuring tape, string, or other material along which the investigator moves and samples data at known, set intervals. Observed individual organisms of interest are tallied, and their distance from the transect is recorded. A ruler or meter stick can be placed perpendicular to the transect line to measure the distance of an individual organism from the transect line, or to take a sample at a particular distance from the transect line. Several assumptions are made in using a line transect (Buckland, et al., 2001): - A sufficient number of transects are randomly placed, independently of the distribution of - All individuals on the transect line are detected. - Organisms on the transect move more slowly than the investigator. - Distances are accurately measured. A line transect is appropriate for illustrating changes in biodiversity along a gradient of some kind, such as - high to low tide lines - shady to sunny areas - soil moisture levels at various distances from a body of water - pollutant levels at various distances from a particular source - etc. 2. Strip Transect A strip transect (Figure 1b) is a small subsection of known length and width randomly placed in a study area. All organisms of interest that fall within the strip are counted, which limits the practical size of the strip. Multiple, randomly placed strip transects can allow estimation of community characteristics in the larger study area of interest. An estimate of total population density of one or more species can be extrapolated from their densities in multiple, randomly placed strip transects. Strip transects can be useful for examining the overall difference in biodiversity parameters between two habitats that differ in some aspect, such as - recent disturbance - abiotic factors such as light, pH, wind exposure, soil moisture etc.

Figure 2. Quadrats can be constructed of various materials such as twine (a), pvc (b), wood (c), or wire (d) A combination of a line transect with randomly placed quadrats along its length is shown in 2b. Green circles represent individual organisms. An Quadrats are appropriate for addressing questions similar to those one can address with a strip transect. As with a strip transect, and individual organism is counted only if 50% or more of its visible body is inside the quadrat area. 3 a 3 b Figure 3. Randomly placed quadrats alone are shown in 2a. A combination of a line transect with randomly placed quadrats along its length is shown in 2b. Green circles represent individual organisms. An individual marked with a yellow halo is validly included in the survey because > 50% of its visible body is included in the quadrat.

When your team devises a research project, be careful to select the sampling method most appropriate to your overall question and hypotheses.

C. Recording Ancillary Information

At your sampling sites, record all relevant environmental variables, such as

air temperature
water temperature
weather conditions
- soil moisture (subjective scale)
- light condition/quality
- etc. Note whether these are different from one sampling day/locality to the next. Remember that these abiotic variables will NOT necessarily allow you to pinpoint a cause for any differences in biodiversity you see between your habitats. But they may give you a starting point to generate ideas for further research. Your team will survey two different habitats over the course of two days. Both habitats should be sampled on the same day, replicated again on the next day. Each survey should include a minimum of three random samples from each habitat. When you have completed both rounds of data collection, you will have collected a total of TWELVE replicates, SIX from each locality for later analysis.

Literature Cited

Buckland, S.T., D.R. Anderson, K.P. Burnham, J.L. Laake, D.L. Borchers and L. Thomas.

Introduction to Distance Sampling. Oxford University Press, Oxford.

Techniques for Evolution and Biodiversity Lab: Transects & Quadrats, Lecture notes of Literature

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