The goal of calibration is to ensure that data gatherers are performing the grazing land on-site data collection protocols in a consistent manner to produce quality data. Calibration for on-site protocols is part of the NRI quality assurance process, is designed to promote consistent and precise data collection among data gatherers, and provides a method of comparing data collected by multiple data gatherers.

How often should calibration be conducted?

It is required that calibration be conducted:

• During the training session
• At least twice more during the field season (only once more if fewer than 15 PSUs assigned)

It is recommended that calibration be conducted:

• Between significant changes in ecological sites
• Every two weeks during the field season

What are the calibration steps?

1. Establish a separate transect or set of transects for each protocol.
2. All data gatherers should conduct the same protocol methods on the same transects.
3. Data gatherers should run summary statistics and compare their results.
4. If the results differ more than the specified amount, repeat steps 1-4. Steps 1-4 form a single replicate.

What tools are available for calibration?

• Calibration PSUs may be created on the handheld unit within the CASI.
• CASI On-Site Summary Tool is available from within the CASI to summarize the calibration data collected by individual data gatherers.
• On-Site Calibration Field Worksheet may be printed and used for record keeping during the field calibration exercise.
• Indicator Summary spreadsheet is used to compare indicators among data gatherers.
• Plant Production Double Sampling spreadsheet is used to calculate field weights and conduct calibration for double sampling.

Calibration Exercises designed for On-Site Protocols

These exercises are designed to ensure that data gatherers are performing the grazing land on-site data collection protocols in a consistent manner to produce quality data.

Line-Point Intercept

Data gatherers collect data on the same 150-foot transect with a 3-foot intercept interval. Trainer enters the calibration data for each data gatherer in the Indicator Summary worksheet.

GOAL: Data gatherers should be within 5% (absolute, not relative) cover of one another for:

• % Bare ground
• % Basal cover
• % Rock cover
• % Canopy cover
• % Litter cover

Deviations should be random, not systematic.

Line Intercept Transects: Canopy Gaps

Data gatherers collect data on the same 150-foot transect. Trainer enters the calibration data for each data gatherer in the Indicator Summary worksheet.

GOAL: Data gatherers should be within 5% (absolute, not relative) of one another for percent of transect in gaps of the following sizes:

• Canopy Gaps 1’ - 2’
• Canopy Gaps 2.1’ - 3’
• Canopy Gaps 3.1’ - 6’
• Canopy Gaps > 6’

Plant Height

Data gatherers collect data on the same 150-foot transect for 14 locations. Calculate the average plant heights for each plant height category. Trainer enters the calibration data for each data gatherer in the Indicator Summary worksheet.

GOALS: The average plant heights observed by the data gatherers should not differ by more than:

• 2.5 inches for category 1: (0 – 2’ interval)
• 5 inches for category 2: (2’ 1” to 5.0’ interval)
• 5 feet for category 3: (5’ 1” to 15.0’ interval)
• 15 feet for category 4: (> 15’ 1” interval)

Soil Stability

Data gatherers collect 9 soil stability samples on the same two transects. Samples (peds) should be between 6 x 6 mm and 8 x 8 mm and thickness should be 2 - 3 mm. Trainer enters the calibration data for each data gatherer in the Indicator Summary worksheet.

GOALS: Samples should be within the correct range of sizes and within 1 average soil stability class of each other for

1. Overall average for 9 samples
2. Average for samples with vegetative canopy
3. Average for samples without vegetative canopy

Species Composition by Weight (Double Sampling)

The Double Sampling exercise should only be performed by data gatherers who use double sampling. It is designed to calibrate estimation of species weights by quadrat. Use the Plant Production Double Sampling Spreadsheet to compare the estimated and clipped weights.

1. All data gatherers collect their own weight units from outside the quadrat.
2. Using a single quadrat, all data gatherers estimate the number of weight units, by species, in that quadrat.
3. The quadrat is then completely clipped and species are weighed.
4. Each data gatherer calculates estimated weight, by species.
5. If the data gatherers’ estimates of plant weights (product of weight unit weight and number of weight units) differs from the clipped weight by more than 10%, repeat steps 1-5 on a new quadrat.

Species Composition by Weight (Plant Production)

The Plant Production exercise should be performed by all data gatherers. It is designed to calibrate the estimation of additional factors (e.g. reconstruction factors and similarity index).

1. All data gatherers determine the weight for each species in the same seven quadrats (double sampling or clipping may be used).
2. All data gatherers record reconstruction (correction) factors for each species.
3. Compare the uncorrected (estimated or clipped) weights, by species, using the CASI. The clipped weights should not vary at all; make sure the estimated weights meet the double sampling calibration criteria.
4. Compare the correction (or reconstruction) factors for each species. There should be little to no variation in reconstruction factors.
5. Compare the reconstructed weights, by species, using the CASI.
6. If the reconstructed plant production, by species, differs by more than 10%, compare and discuss differences in species weights and reconstruction factors and repeat steps 1-6.