Part 9: Collecting Monitoring Data

Frequency Method

The Frequency Method is used to collect data about plant frequency, which is a measurement of the presence or absence of a plant species in a quadrat. There are two distinct frequency methods: quadrat frequency and nested frequency. Both are useful for evaluating forbs, grasses, and shrubs, and both use a quadrat for collecting data. This method can be easily coupled with the Dry Weight Rank Method and Comparative Yield since the same quadrat frame can be used for all three methods. If desired, the same quadrat can also be used to evaluate ground cover.

Frequency is expressed as a percentage of total placements (quadrat measurements) and reflects the probability of encountering a particular species within a quadrat at any study site location. Only species within the boundaries of the quadrats are recorded with no regard to plant size or number of individuals. Plant frequency is a function of quadrat size, and if a particular species occurs in over 95% of quadrats, a nested frequency study should be conducted. In this case, plant presence or absence is determined using a much smaller quadrat within the original quadrat. Generally, taking measurements from one- to two-hundred quadrats per site is sufficient to provide adequate data for frequency determination.

Criteria

It is important to establish study criteria. Here are some suggestions:

• Identify the key species based on management goals, or make a list of all plant species encountered in a quadrat frame.
• Determine if annual forbs and grasses are to be included in your evaluation.
• Determine if some species may be combined (such as those that are not easily distinguished, or other groupings as appropriate for the study).
• Decide whether or not seedlings are to be included in data collection, especially seedlings having a low survival rate.
• Shrubs need to be rooted or the canopy needs to overlap within the quadrat.

Try to maintain consistency in species identification and use of criteria

Equipment

• Study location and Documentation Data form pdf, KB
• Frequency form -- option 1 (pdf, 42KB); option 2 (pdf, 105KB)
• Permanent yellow or orange spray paint
• Frequency frame quadrat (40 cm X 40 cm with pin or prong)
• One transect location stake – ¾ to 1 inch angle iron works best.
• Hammer
• Compass
• Steel post and driver
• Tape: 50 -, 100 -, 200-foot delineated in tenths or hundredths

Conducting the Study and Study Sites

• When selecting key areas for setting up these quadrats, be sure site is located within a single plant community within a single ecological site.
• The species selected for evaluation (for instance, key species) should be present in approximately 20% to 80% of the quadrats recorded.
• If the density of the species is high and will exceed 80% of all 40 cm X 40 cm quadrats, then use a nested quadrat (10 cm X 10 cm within the 40 X 40 quadrat).
• If species frequency is low, you may need to use a frame larger than 40 X 40.
• Establish at least one frequency study at each study site (key, critical, and comparison area).
• It is important to have complete general view and close-up photos of the site
• If using GPS, be sure to include NAD 27 or NAD 83 data.

Study Layout

•  Diagram
   Baseline Layout
  Linear layout – Arrange a 100- or 200- foot tape (or metric equivalent) in a line beginning at the site identification marker stake and projecting out toward the end point marker (another stake or a distinct, permanent landmark such as a rock or a butte). Be sure the tape is straight and not forced off-line by the presence of vegetation.
  
  
•  Diagram
  

  Block Layout

  Block technique – From your initial site marker post, step two paces to the right. From here, proceed forward for 25 paces, taking quadrat readings at every other pace. At 25 paces, turn 90 degrees left and walk 25 paces, taking quadrat readings at every pace. At 25 paces, again turn left 90 degrees. Continue in this fashion until the square has been completed, collecting frequency data at every other pace.

Collecting Data

Slide Show

Collecting Data

 

 

Video:

Quadrats

• Begin your transect 3 paces from the site T-post.
• At each pace, place the quadrat on the ground to take a reading. Keep your eyes on the horizon so you do not bias your study by “choosing” a good place to set the quadrat.
• List key species or all species of interest on the Frequency form.
• After the placement of each quadrat, mark the form using the dot-tally system.

Analyzing Data

Make calculations and record results on the Frequency form

• Cover – Ground cover is determined by dividing the total number of hits for all categories except bare ground by the total number of hits (including bare ground).
• Frequency – On the Frequency form total the frequency hits by species that you identified while counting. Calculate the percent frequency for each plant species by dividing the total number of hits for that species by the total number of quadrats sampled along the transect and multiplying the value by 100. Record the percent frequency on the form. For example, if we observed 200 quadrats and found the target species in 139 of those quadrats, frequency would be